Catch light, that is. The life of the portrait.
They say it is all in the eyes. And in portraits the eyes come alive with the presence of a catch light. But before we talk specifically about catch lights, a refresher on reflections. After all, we don’t photograph people, places, or things. We photograph the light that reflects off of those people, places, and things. There are two basic types of reflections. Diffuse reflections define the subject and its texture. We base our exposure on the diffuse reflections, whether that be skin, a tree, a flower, etc. Specular reflections are direct reflections of the light source, like a mirror. We also have shadows, which are areas that don’t get lit.
As you change the distance between your light and your subject the diffuse reflections get brighter or darker. Move them closer together and you have to lower your exposure to maintain the correct exposure. Move them farther apart and you need to provide more exposure. Pretty simple and intuitive. The diffuse reflections loosely follow the Inverse Square Law of physics. I am going to skip the math and science part here, but basically it tells us that changing the distance between the light and the subject will have a bigger effect on the exposure than you might expect. Light falls off rapidly as you move the light farther away.
Then we have the mirror-like specular reflections. Specular reflections are the same brightness as the light source, no matter the distance. You can easily see this by pointing a flashlight (torch) at a mirror and observing the brightness as you move the light closer or farther away. At this point you might start to ask why these highlights don’t follow Inverse Square. The answer is that they do! But in a different way. As you move the light source farther away from your subject the specular reflections get smaller, as you move the light closer the specular reflections get bigger.
Once you have an understanding of this you can start to consciously control the relationship between the various highlights. And that is where we come to discussing the catchlights in the eyes of our subjects. This stems from a question I recently received, “Can I make the catchlights less noticeable by moving the light farther away from my subject?” And the answer is, No. Moving the light farther away will make the catchlights MORE noticeable. They will be smaller, yes, but they will also be brighter in comparison to the diffuse reflections. The followup question was if dimming the light would reduce the brightness of the catchlight. Again, the answer is no. Dimming the light lower both the diffuse and specular reflections and you will need to increase the exposure, leading to the same relationship between them.
Let’s look at what is happening. Start with a light in a softbox at about 36-inches from our subject. We meter the light and find that the proper exposure is at f/8. Now move the light back to 48-inches from the subject. To maintain the same f/8 exposure we have to raise the power of the flash up about 1 stop. Now the face is still at the same exposure level (moving the light back and raising the power level compensated for each other). But the light is 1 stop (2X) brighter and because the catchlight is a mirror reflection, it is now twice as bright than it was before, making it much brighter than the diffuse reflection.
We can also look at this going in the opposite direction, bringing the light in closer to our subject. If we bring our light in 3 times closer, say it was originally at 9 feet away and now we move it in to 3 feet away, what happens? We have to stop down (change aperture or lower the flash power) by 3 stops to maintain the proper exposure. That makes the specular highlights 9 times darker than they were. Let’s see that that looks like in pictures.
In the top image the lights are set 36-inches away from the subject. In the lower image the lights have been moved back to 48-inches from the subject. In doing so I had to increase the flash power by one stop to maintain the correct exposure on the “skin.” This in turn made the catchlights one stop brighter in the lower image. So even though the catchlights are smaller in the lower image, they are brighter in comparison to the rest of the face.
For this next example I attached a small mirror to the mannequin’s forehead and made two photos lit with a 2x3 softbox being reflected directly back to the camera. The one on the left had the light 9 feet away from the subject. The one on the right had the light 3 feet away. You can see how bright the softbox reflection is on the left, causing a lot of lens flare and haze, compared to on the right. The exposure on the face, though remains approximately the same. The reflection in the mirror on the right is 9x less bright by bringing the light in to 1/3 the distance. You can also see the difference in the highlight on the tip of the nose, small and bright when the light is far away, larger and more translucent when the light is in closer. The catchlight in the eyes on the right gives away one of my little signatures, the black bars of tape across the front of the softbox to simulate a multi-plane window.
Let’s look at a different example, this time a still life/product photo. This shiny can was lit with one 60-inch octabank. On the left the light is about 48-inches (120cm) away from the can. On the right the light was moved in to 12-inches (30cm) away. There are a few things to observe here. On the left there is a strong highlight that you can see in the red cap and behind the text on the label. While you can read the label text, it is a bit washed out by the highlight. On the right, with the light in closer, the highlight looks much nicer on the red cap and the text on the label is much easier to read. You might also note that on the right the overall look of the text and the can is lower in contrast and color saturation. That is one of the downsides of using a large soft light in close. A set of soft grids on the octa might have helped bring back the contrast, but at the cost of seeing the grids in the highlights. Below is another series of photographs of this can. This time lit with a 2x3 softbox. On the left the light is 48-inches from the can and we see the bright highlight making the text hard to read. In the middle the softbox is set 12 inches from the can and the text is more readable. Over on the right I added a soft grid to the softbox. I think I see a bit more contrast and saturation, but you can see the cells of the grid in the highlight, especially in the red cap and at the shoulder of the can (see my post about grids for more info).
And now for the controversial question about what shape catchlights are preferred. My preference is for rectangular catchlights. That is the shape you get inside from a window, a doorway, or a skylight. It is also what you get from a wide open sky outdoors. So many people talk about, and advertisements for lighting modifiers mention, “natural” round catchlights. I have to assume they are referring to the shape of the sun. But when we photograph people out in the sun we don’t usually get a round catchlight as they are either squinting, or turning away from the sun. Sure, in many animal photos we see small round dot catchlights, but rarely with people. And they remind me of department store family portraits from the 1960s. It comes down to personal taste. It is a rare client who comments on or requests a specific shape to the catchlights in their eyes. Dare I bring up the topic of pupil size? Maybe next time.
Until then, if you have any questions about this or any other lighting questions please comment below or join my studio lighting group on Facebook.