How to take fluorescent pictures

Slow decay

Introduction

One of the most recurrent jobs I’m asked to do as a scientific photographer is fluorescence photography. This is so because fluorescent compounds are usually very eye catching and offer a good picture to illustrate your work. Even, sometimes, the picture itself might have scientific importance. Sometimes the picture depicts different compounds where you want to show the difference in colors or intensities. Other times there is a change and you want to display it, like in the image above, where the sequence shows how the diffusion of ambient oxygen into the solution makes the luminescence turn noticeably off (which means you can see the “invisible” oxygen flowing and mixing into the liquid – the one on the left is completely oxygen free-).

A few days ago I was asked (one more time) how these pictures are taken. For the professionals on low light photography it’s rather simple, but for many amateurs taking pictures in darkness or using invisible light seems to be a very confusing concept. The target of this post is to give some advice to novel photographers on how this kind of pictures can be successfully taken.

 

The scary part made… less scary

  • This kind of photography takes advantage of fluorescence, which is the ability that some chemical compounds have to transform invisible ultraviolet light (usually UVA, sometimes UVB) into visible light. The net effect is that the compound seems to glow in the dark. The key concept to remember is: because you are capturing the light emitted by the compound, any other visible light existing in the scene will compete with the one you want to photograph and will reduce the contrast and glow effect. For this reason you must take this kind of pictures in absolute (or almost absolute) darkness. Even a slight amount of “parasite” light can decrease the sensation of glowing. Even if you don’t see it with your eyes, the camera is especially sensitive to the parasite light, as it will probably be a long exposure picture.
  • Remove any other fluorescent object from the scene. If you are trying to take a picture of something that emits light under ultraviolet radiation, any other object emitting light in the same circumstances will interfere with the picture. This might sound obvious, but sometimes it is not. One mistake I’ve seen many amateurs to make is using a white paper as a base, to put the subject above. It might seem to be a good way to get a clean background t turns out that most papers will glow white under ultraviolet light (so they look whiter under sunlight) and will spoil the result. You can use instead recycled non-bleached paper (as long as it doesn’t glow) or, as I usually prefer, a piece of black cloth. Also, wall paint can be luminescent, or some plastics. The best way to test it taking a picture without the subject: the more light you see, the worse the conditions are.
Fluorescent paper and ink
On the left the text is written using fluorescent pencil over non-fluorescent paper. Only in the full size picture the paper can be slightly seen. On the right a standard A4 paper, glowing in blue. The camera is drawn using a standard pencil (not fluorescent, but can be seen by contrast with the fluorescent paper) and the flash is drawn using the same fluorescent pencil used on the left. The contrast in this case is clearly lower. For both papers the background is a piece of black cloth.
  • A tripod is compulsory. I know cameras nowadays perform really well on high ISO, but still the noise level is important if you go past 1600. Taking into account that your subject is not going to move, using a tripod will allow you to use the lowest sensitivity, take multiple pictures with the exact same composition and focusing precisely, which leads to the next point…
  • Use live view and manual focus. Manual focus may seem a bit from the past, but is very useful in this kind of photography. Once you achieve the focus point in the exact place you want, manual mode will guarantee that the point will remain in focus for the rest of the session. You can take multiple pictures without touching anything, and you won’t need to worry about focusing. Also, the correct focus point is the same under visible light and ultraviolet light (this doesn’t happen in infrared photography), because you are not capturing the ultraviolet light, but the visible light converted by the compound. This means that you can focus with all the lights on and, afterwards, turn them off and use only the black light, instead of doing all the procedure with the black one. For more information on how to focus with precision you can read the post Sharp focus for the sharp eye.
  • Beware the white balance, automatic is not as good as it seems to be. Although the black light is mostly ultraviolet light, it also emits a little amount of violet and blue. This means that the scene will have a blue glow or “haze”. This glow is normal, is part of your light, but the camera doesn’t know that. It believes that this should be neutral grey and will try to compensate, destroying most of the colors. The solution is to accept the blue haze as a part of the picture. I always use automatic white balance (shooting in RAW, of course), so the camera choses the blue/yellow (which is usually wrong) and green/magenta (which is usually correct) balance. Afterwards, when processing the RAW file, I change to “daylight”, and set the green/magenta value to the one calculated by the camera. Finally, if result is not appealing, I slowly modify the blue/yellow balance by hand until it seems natural (which should never destroy the blue part).
  • Regarding the lenses, a wide fast lens will allow shorter exposure times. Although you will be using a tripod, and speed is not limiting, the longer the exposure the more likely to hot spots to appear. Long focal lengths are not advisable, they will yield a very shallow depth of field (which will make focusing and getting sharp images difficult) and you will need more physical space to put everything in frame. The higher focal length I have used is 100mm (on full frame), and only because I could use the macro capabilities of the lens. On the opposite side, a very wide lens will create one out of two problems: it will make our subjects very tiny while it fills the frame with “emptiness”, or it will fill the frame with the subject but deforming size and proportions. Although both cases might have artistic purposes, in scientific photography accuracy is often desired. For those reasons my recommendation is to constrain the focal length to 35-70 mm. 50mm 1.4/1.8 lenses are very common and satisfy both requirements with good sharpness.
  • Finally, about light placement, I usually place light in front of the subject, above the camera, facing the scene (like a hot shoe flash but without touching the camera). As accuracy is desired, the light source should be parallel to the plane of focusing, otherwise some objects will get more ultraviolet light than others, glowing more (the intensity of glowing directly depends on the amount of light received). Placing the light over the camera usually avoids its appearance on the picture (for example, reflecting in glass). If placed behind the scene it must be carefully placed so it doesn’t appear in the frame (it is not only unsightly, as it emits some visible light it will compete with the main subject). Side locations are not recommended if a faithful approach is desired.

 

OK… I think it’s cool. How can I do that?

Probably, you won’t be a scientist with access to professional ultraviolet lighting or fluorescent compounds, but that doesn’t mean you won’t be allowed to have some fun with it.

Amateur ultraviolet lights are nowadays very cheap, and can be found in almost all lamp shops or internet. If you think about it, if many pubs and clubs have this kind of illumination, there must be a place where they buy it.

I got my ultraviolet fluorescescent lamp on a local shop (in a small city) for around 20 euros (22.50 USD) a few years ago. It included not only the lamp itself, but also the ballast, starter and 2 meter wire to plug it. Taking into account the amount of light it can provide (similar to a typical fluorescent lamp, but in the ultraviolet range) I think it’s quite cheap. It has been in service sporadically for 14 years, and still working.

On the other side, you can get hand lamps based on ultraviolet LEDs on internet with a very low budget. I fond mine on Amazon for about 7 euros (8 USD). The official price was 20 euros too, but it was in one of those sales that last for many many months. The advantage is portability (it works with AA batteries, not plugged), but it’s much less powerful. Which one best suits you is your choice.

 

UV lamps OFF

UV lamps ON
Top: My fluorescent black light setup and my handheld LED-based UV light. Bottom: Both of them turned ON. Although the fluorescent tube has more intensity, the LED lamp emits more in the visible spectrum (which is bad in this case), so it appears brighter.

 

About fluorescent substances, there are many ways to get them. Some are natural. For example, chlorophyll, the green pigment in leaves, fluoresces in red. This means that taking the picture with ultraviolet light will render all the green parts deep red. Also, extracting the pigment is easy, just smashing some leaves in alcohol and filtering the liquid afterwards. This way you can isolate it and use it for any other purpose.

 

Clorofila
This is a standard bush, with green leaves. The picture was taken using only ultraviolet light, so the leaves appear red because the chlorophill in the leaves fluoresce in red. This effect can be achieved in many vegetal species.

 

Other source of fluorescent pigments is fluorescent paint. Some of them are used to paint on paper (like pencils or markers). If the paper is not fluorescent (many are), you will see the annotations glow while all the rest is dark. This can yield to interesting pictures, for example, a composition of a book with fluorescent annotations. Other paints are made to be used in the skin (e.g. make up). This way you can paint a model and get nice pictures where only a few parts or patterns are seen. As an example you can see the work of John Poppleton.

In general, if you see something that reacts to this kind of light there is a chance of using it for fluorescent photography. Sometimes you can use the item itself as an element in a more complex composition, and sometimes isolated and used in a completely different way. As in many other aspects of art the limit is your imagination.

For another example of this kind of photography you can read my other post The fluor rainbow.

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Tricks for concert photography (II)

In the previous post I gave some technical tips for taking pictures in concerts. The post came from a conversation I had with a colleague a few days ago, and it included about half of the things we talked about. In this second part we we’ll see other recommendations, less related to the technical part and more related with the artistic way of taking those pictures.

 

Spot metering and ETTR (advanced)

One of the problems that you’ll surely have during the event is the variable amount of light, which will change along the scenario. The camera has a built-in photometer to measure light and controlling the exposure parameters (on guiding you on the adjustment if you are using manual mode). But if the measure is wrong you will end with a poorly exposed picture.

When using evaluative or center weighted metering, the camera will take into account a lot of information in the scene and will average it. This means that if you have a big area poorly lit or with an excess of light, the measure will be wrong. The best way of dealing with it is using spot metering. In this mode the camera will measure the light only using the central point. This way you can point it to the place of interest, measure it and be sure that the subject you are interested in will be correctly exposed (but you have no guarantee on the other parts of the picture).

Anyway, if you still need to use one of the wider modes, stick to evaluative, as it gives more importance to the point closest to your focus point and less to the further areas of the image.

For more information about the metering modes you can see this resources for Canon or Nikon (in other brands modes are similar).

A concept related to spot metering is exposing to the right (ETTR), where you take the pictures as overexposed as possible without blowing up any important areas. This allows storing a higher amount of information in the area with less noise (highlights). In concerts, many of the information is in the dark area of the histogram, and the highlights are usually empty, so storing the picture in the highlights (overexposing) and correcting afterwards in the post-processing can help to decrease the noise levels. This technique, however, is advanced, and the photographer should be confident with it in simpler circumstances before trying it in a concert. If any part of the picture is blown up (pure white) you won’t be able to recover it.

The best way to perform this operation is using spot metering, pointing it to the brightest place of the scene that we want to be correctly exposed (e.g. we might want the white shirt of the singer to be well exposed but we don’t care if the bulbs of the lights are blown up or not, so we will measure in the shirt). We will adjust the camera’s parameters in this point so the photometer shows the indicator as right as possible (usually +2 o +3), but still inside the scale (it’s better to not reach the final line than getting slightly too far outside the scale, usually marked with a right pointing arrow). Finally, once taken, if the picture is overexposed we compensate it while processing the raw file.

Always Late
The dark areas on the right will confuse the camera on average metering, leading to overexposure to compensate them, and rendering the important area (on the top left) overexposed and probably blown. Spot metering on the area of interest allows to adjust the correct exposure on the desired point.

RAW format and processing

Shooting in JPEG will allow you to take more pictures in the same card, but at the price of poorer quality if you need to touch anything later. And have for granted that you’ll need to touch things… many things. This is the reason why you should always use RAW format. Using RAW means that you will be in charge of processing it to get the final image (instead of the automatic process the camera does). Think about it: Who knows better how the picture should look like, your camera or you? If you are opposed to photographic retouching you are lucky: standard processing of the RAW usually doesn’t count as retouch. You are just making an interpretation of the information the sensor stored. The camera also does that, the only difference is that the camera just applies default values blindly and you can decide the optimum ones while you see the result. It is the digital equivalent of choosing the brand of film, choosing the times and amounts of liquids or the times used with photographic paper. In the era of film cameras nobody opposed for that.

When adjusting the parameters, you should take care that the main subject is correctly exposed by adjusting exposition controller. After that you can recover the highlights and control the shadows with the respective controllers. Blacks and whites should be used in a way that both are just at the limits where you won’t see any pure black or white area (of interest) in your picture. Also, take a look at the noise levels and adjust the color noise value (as much as needed) and luminance (a good balance between noise and sharpness).

Finally, if you are going to process it further in other software, don’t do any sharpening and wait to the final step to do it, as quality quickly degrade if modifications are made after a sharpening process (even resizing!).

 

Get the best place you can (or allowed)

In a concert there are a lot of people. We want to make the best possible pictures, but sometimes somebody’s head will challenge our ability (and patience) as photographers. If we are taking the pictures for ourselves a rogue head in the middle of the picture can be annoying, but if the pictures are for professional use this can render them completely unacceptable and without any chance of recovering.

If it is possible, try to talk with the organization to get a favorable position. Sometimes the first line is reserved for press and photographers, or at least you will get a reserved place near the stage. If that is not an option try to arrive with enough time and position yourself in the best spot you can. Sometimes, if you have in mind the kind of pictures you want to take you will see that some places are more adequate for them than others.

Also, try to analyze the public and the “sweet spots” during the show. Sometimes people may get more concentrated in some areas than in others, or you might find some higher spots where people won’t interfere. Analyzing the space around you is a necessity if you will be surrounded by the rest of the public.

Also, if you have confidence with the performers, try to get some pictures before the concert, when there are no people around. Those pictures will not replace the ones you will do during the act, but might help as a failsafe in the case that something unexpected happens. The pictures before, taken with a calmer mood, will probably be sharper and with more quality than the ones taken in the hot moment.

 

Take advantage of eventualities

Finally, one last piece of advice. During a concert, many unexpected things may happen. I’m not talking about UFO abductions or Superman appearing to save the day. But sometimes the singer might adopt the exact position where the light creates a mystic halo around his head, a burst of smoke might create a great effect, or the performers might do some nice movement that they won’t repeat (like rising a fist to the air or jumping).

Always be ready for those eventualities, and be sure to catch them with your camera. In the worst case you’ll have the most iconic picture of the event instead of a lot of cliché pictures. In the best case, if more photographers are present, you might be the only one to have the best picture of the event. And this opens a lot of opportunities.

It's time to kick some aces
During this carnival parade, the girl stopped a couple of seconds to adjust her cape. This can be seen looking at the complete series of pictures. But taking the picture in this exact moment led to a different interpretation, where she looks like she is preparing for some kind of fight (Hollywood style).

Tricks for concert photography (I)

A few days ago I had an interesting conversation with a photographer colleague. She was starting taking pictures in concerts and she was asking for advice to improve her results. At the end, we concluded some tips that could help getting a more interesting outcome from a concert session. I thought they could help other people, so I’ve decided to post it here for everyone.

As a summary, all the tips are directed towards taking pictures in low light conditions. This means that, even if you are not going to take pictures in a concert, it may be worth knowing for other kinds of photography, like street photography at night (if you live in a catholic country you can find them useful now that Easter is close), nightscapes, or a portraiture session using natural dim light (candles, perhaps in a basement). Nevertheless, I’m assuming that you already know how to take pictures in those situations, and that you expect to improve them. If that’s not the case, there are many tutorial where you can learn how to expose correctly (or focusing) in those conditions.

Love the burst

One of the first thing I learnt (the hard way) taking pictures in events, talks and speeches is that people make a lot of funny expression with the face when they talk. If you want to take a decent picture of an orator you must be either very lucky or very patient to catch him while he’s not speaking. In most cases if you take only one picture, you will end up with a grin. And of course singing has a lot in common with speaking. The only difference is… well… that the singer will usually be more expressive, increasing the ratio of bad pictures.

Using the burst mode on the camera will not solve this problem, but will increase drastically your chances of getting a nice picture. Nowadays cameras allow taking between 3 to 9 pictures every second. This way, if some of them go wrong, there is a chance the next one will result in a more appealing result. Because of this, every time you take a picture, allow 3-5 pictures to be taken, so afterwards you have enough material to choose from.

The most obvious disadvantage of this method is the increase in storage. After the concert you will need to select and remove the invalid pictures. During the concert this should be not a big issue. Sure you will need more cards, but storage is really cheap (especially SD cards), and you can get 32 Gb of space (enough for more than 1000 RAW pictures) for less than 15 dollars/euros. Very fast cards will be more expensive, of course, but in concerts you don’t need a lot of speed in the burst, just enough pictures of every moment to have the option of choosing.

Big sensor and bigger ISO

When the singer is on the stage, you can expect a lot of movement (especially in the climax, just the moment when you should be taking more pictures). This means that you should use a fast shutter speed to be able to capture more than just a blurred shadow. If you have a stabilized lens don’t make the mistake of thinking that it will compensate the lack of speed: the stabilizer will compensate your movement, not the one of the target… And you won’t be the one moving.

On the other side, you might have a very fast lens with a very wide aperture. This, of course, can help sometimes, but it also implies a risk: If you are using a telephoto wide open, the depth of field will be very thin. In the stage there is a lot of movement, and it’s easy that the performers will move fast out of those precious centimeters where the focus is. This means that your focusing engine should be very precise (not easy in low light conditions) and you must be very skilled in focusing (if you are reading this, it might not be the case). Also, lenses wide open tend to be a little bit soft, which might be (or not) the effect you want. Closing aperture to around f/5 will increase the depth of field enough to make your picture crisper and your life easier. On wide angle lenses you can open wider, up to f/3, as the depth of field widens with lesser focal lengths.

This leads us to the third parameter used in composition: ISO sensitivity. If you need to use a fast shutter speed and also a narrow aperture, you have no other option. Yes, it is widely known that increasing ISO also increases the noise levels and decrease overall quality. Or… maybe it doesn’t?

It turns out, by the way cameras and sensors work, that noise is always present in the darker areas of the picture. This leads to a curious effect: If you take an underexposed picture with low ISO, and afterwards you correct the exposure, it will probably have more noise that the same picture correctly exposed using a higher ISO level (this is a good post about this topic, in a great astrophotography blog, in case you want to know more). Controlling the noise is a little bit trickier than this but, as an starting rule, don’t be afraid of rising the ISO as much as you need, if the pictures are correctly exposed you won’t find the noise too annoying.

And finally, because you will need to use a high ISO level (it’s uncommon to be lower than ISO 800, and is easy to reach up to ISO 3600), a full frame camera will help to control the noise levels a little bit (the bigger the sensor, the better the yield in low light conditions). Of course, full frame cameras are expensive and not everybody has a budget for that, but if you are thinking on this kind of photography in a professional way, the investment will be worth.

Above the Clouds
This picture was taken using ISO 1250, f/4 and 1/100s. The musicians are not moving from their positions, which allows having a narrow depth of field and using a relatively slow shutter speed. Notice that the image is sharp and clear even with a ISO over 1000.

Av mode for an easy life

If you like to have the control in all situations, you will probably use manual mode all the time. This way you can control exposure in a precise way and get the exact result you want. The problem is that, in many cases, the lighting in the stage is not fixed and you will have a mixture of changing lights moving around all the time. The values you used a few seconds ago might not be useful now.

If you are an experienced photographer, you will know when to shoot and get the lights in the position you expect. But if it is not the case letting the camera expose for you is a good way of securing some “average” pictures. In Av mode you can set the aperture and ISO to the desired values, and let the camera choose a good shutter speed. This way you can focus your mind on deciding the right moment and not on changing the parameters all the time.

It might happen that the pictures seem overexposed and blurred, or too dark. The camera thinks on an average illuminated scene, not the chaotic mess you have in front of you (ok, it’s pretty and charming, but for your camera’s photometer is like D-Day in Normandy). In the first case, the camera will try to compensate the darkness allowing too much light to pass, using a low shutter speed and blurring the image. On the second case, it will measure only on the brighter part of the scene and use a very fast speed. The solution to this eventuality is called Exposure Compensation, and it’s the equivalent of telling to the camera: OK, you are too short/long, compensate that always. A few test shoots will allow you to get the correct value.

Enough information for a day. It’s time to think about it and practicing the concepts. In the second part of this post we will see more tricks, this time less technically oriented but still important.

Tricks and tips for a first session with models

A couple of days ago I was browsing a subreddit where someone asked for advice when photographing a model for the first time. One day afterwards, another person asked mostly the same, tricks to make the model feel comfortable. This has made me think that perhaps there are many people around here who would like to start taking pictures about models and do portraiture, but they don’t feel able to manage a session and the responsibilities that it implies.

In my opinion, most of the insecurity a photographer suffers before doing his/er first session is just a consequence of not knowing what to expect, and disappears soon after the beginning of the session. Besides, I thought that the advice I provided could be useful for many people beginning to take portraiture pictures, so I decided to share them here too.

 

Know your ene… your friend!

One of the key advice I can give for this kind of session is: know the person you are going to photograph. It can be very uncomfortable and cold to take pictures of someone while both stay silent not knowing what to say. Confidence is important, as it gets reflected in the expression of the model.

I only photograph people I know, friends, people I’m confident with. This way there is no problem in finding a topic to talk about during the session and conversation will flow naturally. But, of course, you also want to photograph people you have never seen before. What I do is to convert them in “friends” before the shooting. A couple of days before the session I like to meet them to take a coffee (or tea if they are English gentlemen) and explain some details of the session. In this meeting (around 30 minutes, but it can be longer if the feeling is good) I explain the idea I have about the session so they can think about it. If they know what to expect and have a couple of days to think about it, they will feel more confident as all the process will sound familiar to them. I explain what pictures I plan to take, some details about the material, why I chose the place or any tips about posing that may be useful.

But I also use this meeting for another thing: knowing the model. The model is the center of the shooting, everything moves and evolves around him/er. This means that knowing how s/he thinks, what does s/he expects from the session and other personality features will help to design and adapt better the session. The meaning of a portraiture session is to show the person as it really is, capturing the essence. Also, knowing a little bit about the model allows to find topics in common to talk about during the session. This way is harder to get to a dead silent point where no one knows what to talk about.

A famous photographer once said that you cannot take a good portrait of someone without falling in love with them a little bit. Once you get to that point, you start to see the real subtle aspects of the person that make him/er unique, and you can use photography to share them with the rest of the world in a way that when people see the picture will exclaim: “wow, this picture is really him/er”.

You know... Just hiding

Even if your model is shy, you can use it as an advantage to take some pictures that show the personality. It’s important to adapt to the model, not making the model adapt your ideas of the session.

 

Have I ever told you about the weather in Madagascar?

This is another of the golden topics, so important that has already appeared in the previous one. You should never stop talking for more than a minute. It might seem hard at first, but it is really important.

In order to achieve a connection and complicity a good flow of ideas needs to be present. It doesn’t matter about what you talk as long as you keep a natural an fluid conversation. Use what you learnt about the model to bring those topics to the conversation. In the worst case make the model talk about himself. People like to talk about their lives and will bring up some conversation for a while.

Also, you can use some time to explain what you are doing, why you do it, and teach a little of basic photography. Knowing a little bit about the process will make the model feel more involved in the shooting, and by extension more confident about posing.

If the model gives you some ideas, never discard them. Even if it sounds dumb, you never know how well an idea will perform until you try it, and you might find it provides a good picture at the end that you would have never got if you hadn’t considered it. This will also make the model feel a part of the process, and feel his/er ideas valued and respected. Even if the idea doesn’t fit with the theme you had in mind for the session, taking a few more pictures is not expensive in time and money nowadays, and the model will be happy to have them. If you don’t like them, you are not forced to publish them in your social networks or blog.

 

Use props to distract the attention

Holy Week V
The prop the girl is using provides more interest and context to the picture than a picture just of her face. Her gaze from behind the prop is what gives strength to the composition

Another trick that I read some time ago and worked very well for me is bringing a small prop to the session. Sometimes the object is related to the theme of the shoot or something related to the model. Other times it is just something innocent that doesn’t hurt the image, like a lollipop, a small ball, a ring, or a bell. The point is that when the model has something to fiddle with, gets distracted with it and feels less nervous. It works as an axiety release valve and helps the model to feet attached to something. If the prop doesn’t belong to the session and is cheap, you can give it to her as a present, so she has a nice memento of the shooting.

If the object is related to the shooting theme, you can also use it artistically to show a new perspective of the model’s personality. For example, if the model plays a musical instrument, you can make some pictures using it. If s/he likes an sport, you can use clothes and a ball related to that sport or the favourite team. This way the model has a familiar object to distract with, and it can add a new dimension to the portrait and what you want to show.

 

Respect the space of the model

This is a so important advice that takes a paragraph only for it. Give the model space to move and act without interfering with him/er. The minimum distance should be the one that, even if you extend your arm completely to the front, you won’t be close to touch him/er. And also never touch the model to correct the posing. If you need to give indications, do it by voice, or do it yourself and let the model mimic you. Touching a model is usually one of the fastest ways to incommode him/er and make the session unpleasant.

 

Technical advice, because I’m never too much technical

Also some technical advice can help to obtain better pictures and feel better about the result of the session:

  • Use a short tele for portraiture. Between 70-200mm is recommended. Take into account the crop factor of your camera. In APS-C format, for example, a 50mm works like an 80mm, which is a good focal for this kind of photography. A zoom adds versatility, a prime lens allows you to take pictures with lower illumination level and take more advantage of the ambient light. Wide angle lenses might give a good portrait if you know how to use them artistically, but they tend to distort the face proportions, so use them with care. More than 200mm should not be used, as it compresses so much, yielding flat faces with low attraction.
  • Some people claim that for wide faces a narrow lighting should be used, and for a narrow face a broad lighting is the correct one. I believe it’s not a strict rule, and you can use both creatively, but taking this advice in mind gives you a good starting point for the session. This rules are made by experience and usually work well, but can also be broken if the creativity allows a better picture. Never avoid trying new approaches and experimenting a little bit, as you will be expending just a little bit of time in exchange for the possibility of achieving a great picture; but keep the rules at hand, as an average they will work very well.
  • If you do a close-up, you can cut slightly the forehead, but never cut over the neck. In case of doubt it’s better if you take the picture a little bit wider capturing everything and you recompose afterwards on the computer cutting on the right place.
  • If you feel that the model is appearing in the pictures with the face wider that what it should, make him/er to move the forehead slightly to the front. This will change the perspective and will help to dissimulate some defects. This Youtube video explains it very graphically.

 

The Pearl of Japan (Reprise)

This picture, taken using a focal length of 67 mm (full frame) shows the face keeping the proportions natural, providing a natural appeal.

 

With all this advice in mind, I think any first session with models will go slightly better. Do you have any other tip or trick you use in your sessions? Share it in the comments.

Warm light filter

If you look through the internet you will see that many popular pictures are characterized for having a very warm and catchy light, which makes the picture very appealing. If you take the time to analyze the pictures you see you will realize that many times the illumination they are depicting is not possible in the real life. It is easy to find thousands of very red dawns and sunsets on the internet but… When was the last time you saw a sunset so intense with your bare eyes? Probably never.

Many of those pictures have the light enhanced by filters or other photo-artistic means. Sometimes is on purpose, by adjusting parameters as the contrast, vibrancy or hue. Others, is just by chance: many mobile devices tend to modify colors in automatic mode to make the pictures more appealing to the viewer. Some of those modifications may be drastic and easy to detect, but in many cases the modifications are subtle and faint, and only the trained eye can detect them. In all those cases, the modifications were made not to get a faithful picture, but an artistic one, a picture able to impress us with its beauty and to transport us to a magical place.

This process I’m explaining here is not in the subtle category, but it can be made as subtle as needed and combined in different ways to get amazing atmospheres. The following procedure creates a global warm light atmosphere for the entire picture, but with a little of patience it can be adjusted for only some areas of the picture, and applied selectively to the appropriate sections. Anyways, even in its global form, it can be useful to enhance a sunset landscape, or, like in this example, to include some artistic warmness into a cold atmosphere picture.

Base: For this example, I’m using a picture of two friends of mine. The base picture is already processed, the color is reliably adjusted and all sharpness modifications have already been done. It’s what it can be considered a faithful finished picture. As the copy is stored in a lossless format in 16 bits, working with it doesn’t mean losing any quality.

00 Base
This is the starting picture. The atmosphere is extremely gelid for such warm gazes.

Step 1: In order to adjust the atmosphere, I’m going to separate it into two parts: highlights and shadows. This separation will allow me to adjust hue and relative brightness considering those two important parts of the image. To adjust the tone of the highlights we will create an adjustment layer using the mode Gradient Map. We have to create a gradient using white for the light part of the gradient, and in this picture I’m using a pale orange / sepia color for the dark part. To get the magic done, set the blending mode of the layer to Multiply. This mode will add the hue of the dark parts of the gradient to the  dark parts of the image but won’t affect (almost) the bright parts. This way we will get a dim painting of the light parts, that will be more evident as the color of the picture gets further from pure white. Of course, we can adjust afterwards the gradient parameters to obtain a better result for our picture. Just play with the controls until you are satisfied.

01 lights parameters
Conditional blending values for highlights.

The problem in this step is that the layer is also modifying our shadows. To avoid it we need to modify the blending options (double click on the layer, to open the blending options box). In the section of “Blend if” we will use the Grey option, and pressing the Alt key we will move the dark triangle of the “Underlying layer” to a middle point, around 128. This way what we are doing is deactivating the light modification gradually as the image gets darker, but without using any drastic cutout that can leave artifacts in the picture.

 

01 lights
The cold light got a little bit warmer. Still, the dark parts of the picture didn’t realized that the temperature is raising.

 

02 shadows parameters
Conditional blending values for shadows.

Step 2: We repeat the same procedure as in step 1, but this time we will use a color for the gradient a little bit reddish and darker. To affect the darker areas, we will use the “Linear Burn” blending mode and, because the effect is very intense for this mode, we will reduce opacity under the 50%, to a point where we are satisfied with the result. Again, this method affects also the highlights part of the picture, so we have to modify the “Blend If” controls. This time we will move (pressing the Alt key) the white triangle of the underlying layer to a satisfying middle point.

 

Of course, this is a coarse adjustment. We can add any other adjustment layer over each one of those, like levels or curves, and using the “Clip to layer” option it will modify only the gradient layer effect, not the entire picture.

02 shadows
The overall tone now is more adequate, according to the situation. Also, the light now blends well with the girl’s hair, which is an incentive for using this processing on this picture.

Step 3: To refine the process, we will add a global warming effect (in this case it is not environmentally dangerous, as it doesn’t require CO2). This will allow fine adjusting the global tone of the image. We have to create a Solid Color adjustment layer, and choosing a color. As we are moving in the warm area of the spectrum, I used a golden color. For a subtle effect, use Linear burn blending mode with an opacity of 20%. For a more drastic effect, use Soft Light with a 5-10% opacity. The first one will tune the color focusing on the dark or more saturated parts while the second one will focus on clarifying the picture and increasing contrast. The decision is up to you. In this case, I used the first one.

In the picture you can see the final result. What do you think? Do you know any other way to add a magic light to a picture? If so, please comment and share your “secret”.

03 Highlights final
A subtle golden glow tone finishes the atmosphere. No more cold white light!

Frequency separation

In portraiture photography, probably one of the most widespread and important processing techniques is frequency separation. This technique allows us to separate the picture information into two layers, one that contains the color information and other that contains the texture information. Once the separation is achieved, you can modify, for example, the color of the skin without altering the texture it has. And on the contrary, you can modify little imperfections as blemishes, scars or pimples without having to take care of the color of the skin. It is an advanced technique that requires some practice to exploit everything it offers, but the truth is that, once dominated, allows for a great flexibility on processing and spectacular effects correcting the face of the model.

 

Why two frequencies?

When we analyze a picture, there are two kinds of information you can focus on. On one side you have colors. Colors usually are uniform areas that remain the same or contain very little variation along the image. If you imagine the picture of a leaf flying against the sky, you can coarsely describe it as a huge blue background with a green spot in the middle (you can add a second white irregular spot if you want to consider a cloud also in the picture). Perhaps the blue background is not uniform, but it changes softly along its area. The same happens with the leaf and the cloud, might be irregular, but are well confined and the hue and luminosity is usually similar along all the spot.

Of course, the former description is a bit too much coarse to describe a great picture, but it is obvious that contains a lot of information about the picture; vague and “soft” information, but useful to describe it anyways. That is what is called a low frequency. If you imagine music waves, they are composed of many waves of different frequencies. If you look at the low frequency ones, the have a very broad shape, uniform, that changes slowly with space or time. By similitude with these waves this first layer gets the name.

Leaf
According to color, all the picture is mostly green (and variations). What conforms the picture is the abrupt variations of contrast on the borders. Picture by Mitya.

If we focus again on our low frequency picture, we notice that something is missing to achieve a high quality picture: details. The details such as the lines of the nerves in the leaf or perhaps a very small bird in the background have the characteristic that they are not wide and extensive, but instead are very small regions that change abruptly in very few pixels. The nerve of the leaf is also green, with the same hue that the rest of it, but on the side it gets darker because of the lighting shadow, while on the other side it gets lighter green. This information compose the high frequency layer, by similitude with the homologous sound waves: changing fast with time and space, acute and well defined. In this case the high frequency layer is coded as a grey layer (where grey means “do nothing to the low frequency layer”) that contains borders, lines and other shapes in darker or brighter tones (with the information on how to modify these parts on the low key image).

Those two layers are combined using the linear light mode. This mode is contained in the contrast group, which means that its main purpose is to modify the contrast of an underlying image. As we have our low frequency layer behind and out high frequency layer on top, the latter one will modify the contrast in the designed parts of the image to provide. Linear light works leaving the pure-grey tones of the high layer exactly the same as in the low frequency. If we have a light grey or white on the high layer, we will get a linear dodge, meaning that will brighten the luminosity of the lower layer adding the value of the upper layer. This leads to an increase in luminosity but a decrease on saturation and intensity of color. On the other side if the upper layer is dark-grey or black, it will apply the same as with the white part, but inverting the brightness after that, so we get a darker effect with colors more saturated.

 

That sounds difficult! How can I do it?

It is simpler that it looks to achieve the frequency separation. You don’t really need to know how it works to use it, although knowing what parts are implied in the process allows us to twitch it sometimes a little bit, allowing us to achieve some interesting effect. If you want to experiment is a whole world right in front of you, but if you want a fast and ease result, here is the recipe for success:

1- Create a new empty group.

2- Duplicate the base image twice inside the group. Rename the upper one as “High frequency” and the lower one as “Low frequency”. If you are lazy, remember that renaming them takes less than a minute and will avoid a ot of confusion when you work with more layers.

3- Turn off visibility of the upper layer and in the lower layer apply a Gaussian blur. 4 px is a good starting value, but you should choose a value that blurs all the fine details of the image but still makes all the overall image clean. Finally, turn on again the visibility of the upper layer.

capture1
Parameters for 16 bits/channel.

4- Select the high frequency layer and go Image > Apply Image. As a layer you should select the “Low frequency” one, channel in RGB, Opacity at 100%, scale with value 2 and Preserve Transparency and Mask… unchecked.

If you are working on 8 bits/channel mode (and I don’t know any reason why you should be doing this): Use Subtract as the blending mode and set the offset to 128. Invert should be unchecked.

If you are working on 16 bits/channel mode: Set the blending mode to Add and the offset to 0. Invert should be checked.

5- Change the blending mode of the upper layer to Linear Light.

If everything went well, you should now have an image that looks exactly the same as the initial, but separated into two layers, one that provides the color information and other that provides the texture information.

 

Why bothering doing all this?

So… I followed all the steps and I got an image that looks exactly the same as the initial one. Why should I bother to follow all this procedure?

The fact is that every photographer chooses what to do now. The separation allows you to modify those two parts of the image in different ways as needed. Do you want to correct the color of a part of the image without altering the texture? Just modify the lower layer until it fits your necessities. Do you want to get rid of some skin imperfection? Apply the healing brush or the cloning tool on the upper layer and voilá… it’s gone!

As an example, I present a picture of a portrait in the phases before and after using this technique, so you can compare the differences.

Comparison Freq. separation
She is Icxiuh, a nice Mexican chemist I worked with a few months ago. On the left, the picture has gone trough a RAW development and minor brightness and color corrections. On the right is the same picture after applying frequency separation and corrections. The skin in the forehead, cheek and the part above the lips was corrected using the cloning tool, mostly on the low freq. layer but also sometimes in the high freq. layer. To unify the color of skin afterwards the skin was softened using a gaussian blur with 8 px only in the low freq. layer. Finally, the cornea was whitened softly in that layer. I needed to work on the high freq. layer for the nails, due to their high contrast with the surroundings.

What do you think? Do you know any variation or trick related to this technique that you want to share? If so, the comments section is open to you.

Live view to adjust white balance

One of the parameters that determine the quality of a picture is white balance. A good adjustment lead to pictures that conserve the nice and bright colors the original scene had, while a bad adjustment usually tints all colors with an orange or blue mist. This mist not only distorts all the colors but also gives the sensation of a really poor quality picture. This adjustment is especially important in the fields of photography that requite a great purity in color, e.g., when photographing a painting or in scientific photography. The correct adjustment of the white balance is very important when saving the file in JPEG format, as it will be difficult to modify it afterwards. Besides, that doesn’t mean that when shooting in RAW format we can avoid adjusting it. A good white balance will allow us to measure light in a more effective way and to predict better which exposure values are the best for our composition, without the risk of “burning” any of the color channels by mistake.

White balance arises from the fact that white light we see is not usually pure white. Some light, like the one produced by candles or incandescent bulbs, have a dominant in the red color. The scattered light by the clouds in a cloudy day tends to be tinted with blue, and fluorescent light usually has an excess of light in the green part of the visible spectrum. This dominant color tints the object we are photographing, more noticeably the whiter ones, as they are the ones which reflect a higher amount of light (i.e. if you are absorbing all incident light it doesn’t matter which color was originally, as the object is returning none to the camera). The brain is very good in correcting this tint, so you can always identify a white object as white regardless the light used to illuminate it. But the sensor doesn’t correct anything, it just collect photons of different colors and count them to produce an intensity level for each of the primary colors. The white balance adjusts the offset of the three channels to the point that a known neutral color appears without any predominant component.

In the film era, you had to know in advance what kind of light you were going to use, and load the corresponding film. The worst part is that there only existed a couple of temperature colors: tungsten for warmer lights and daylight for neutral. With the appearance of the digital world, cameras allowed more adjustments, as it was an easy operation to implement on the camera. Still, in many cameras, you still had to adjust in advance the values because the picture was saved in JPEG. Even nowadays, using RAW format, a good adjustment on the spot is desirable. It happens that when you decide to adjust the color temperature for a picture a few days after taking it, it is very difficult to remember the true color the scene was at that moment. The only solution for getting reliable colors is to adjust it before taking the picture and getting sure that the value is correct before leaving the place.

Live view supposes a great advance for adjusting this parameter. Instead of having to guess the correct value, you can simply point your camera to the subject, adjust the values and see how each value modifies the overall aspect of the picture in the screen. The target is to stick to the value that provides an image in the screen as similar as possible to the scene that you are just watching with your eyes. This way, the scene will be saved with its true color and, afterwards, you can modify it if artistically needed without losing the original correct value. In low-end cameras a fine adjustment is not possible, and usually you have to stay with the closest profile the camera allows. On higher-end cameras, usually a color temperature dial is available, where you can select an exact value. The use of this mode is preferred to the predetermined ones, as it offers more control and the possibility of choosing values between the predefined.

So, the next time you visit a museum, a church or an art gallery and you want to take a picture, try this method to get the correct value. You will notice how simple and fast is, and how great the results are.

Example:

This morning, when Mr. Leprechaunius Smith and Mr. Brainsqueezer woke up, they found a new visitor near their house: Ms. Little Salmon. Amazed by such discovery they hired their favorite photographer to take a picture of the event.

The mixed lightning makes taking the picture complicated. From the left side the scene is illuminated by the sun, with a warm yellowish light. From the right side the still-deep-bluish-sky provides a cold blue fill light. The composite illumination produces a complex mix that the photographer wants to capture.

JT5D5861_CL

If the photographer uses the Shadow white balance the effect of the blue fill is neutralized, increasing the effect of the warm sunlight. This is not the desired effect. Although the sun is an important factor on the picture, here it monopolizes the light destroying the desired mix of lights characteristic of the moment.

JT5D5861_TU

On the other side, if the photographer uses the Tungsten white balance the effect of the sunlight is neutralized, covering the entire scene with the blue diffuse light. Sunlight is transformed into a neutral “white” light that lacks of the expressive power desired.

JT5D5861_MAN

Using the Live View, the photographer can adjust the temperature parameter of the white balance to the exact point where both lights are seen exactly as in the scene that is in front on him. There is enough blue fill light from the sky at the same time that the sun keeps enough warmness to imbue character to the picture.

Now all three of them will have a nice memento of their first meeting!

Do you have another trick to adjust white balance? If so, share it in the comments section so we can all learn something useful.