Eric Stoner
Eric Stoner

Eric's professional photographic career spans over 25 years specializing in portraits, weddings and commercial photography using everything from simple lighting to very complex.

How to Use Color Correction Filters for Speedlites

March 18, 2014

I just returned from the WPPI (Wedding and Portrait Photographers International) conference in Las Vegas and, naturally, we get all sorts of questions throughout the trade show. One answer I seem to give regularly is, "It depends." You may say to me, "Eric, you didn't even tell us what the question was" and that's okay because in photography, that answer is one that's applicable to thousands of questions! Photography is an art form and so there aren't many hard and fast "rules" because many things are subjective, depending on whom you ask.

Photo by Eric Stoner


Meet my son Alex. I don’t know if he’ll be the next Ansel Adams because, at this point, he says he wants to be an architect! The jury’s still out on that one but he’s got some time to make his mind up. Anyway, I went out with him and my wife to teach them a bit about photography and wound up shooting a few samples to show them about color correcting Speedlites to the existing light. Boring to some, as you will see in the next image of Alex!

One key element in flash photography is learning how to manage mixed or unbalanced lighting. In other words, correcting the balance between the color temperature of the light emitting from the Speedlite and with the background. What do I mean by that? If you look at the image below, we’re unbalanced foreground to background. The color of light from the Speedlite doesn’t match the tungsten lights in the background, thus causing an imbalance.

Photo by Eric Stoner


I'm not saying it's wrong. That's for the person viewing it to decide. However, for the purposes of this article, I'll explain how to color balance foreground and background using color correction filters on Speedlites.

If you look at the image above, the skin tone, illuminated by a Speedlite 600EX-RT, looks natural. The flash is outputting a kelvin temperature of about 5600 degrees kelvin or daylight. The ambient room lights behind him are tungsten bulbs and are roughly 3200 degrees kelvin, causing the background to look very yellow. We have some options here, such as turning the tungsten lights off and using more Speedlites to illuminate the background OR simply adding a CTO (color tone orange) color correction gel to your Speedlites. What this does is that it lowers the color temperature of the 5600 degrees Speedlite to closely match the 3200 degrees temperature of the room lights. One last thing you will need to do is change your white balance to tungsten or set your white balance kelvin temperature manually on your camera. Most Canon cameras have this ability to change the kelvin white balance in increments of 100 degrees, with the exception of Rebel models that will need to be changed to the Tungsten setting on the white balance menu. This is a nice option to have because you can fine-tune the temperature to your liking. CTO color correction gels usually come in different strengths, such as full CTO (deeper amber), 1/2 CTO (medium amber) and 1/4 CTO (light amber). Two of these filters come with the Speedlite 600EX-RT when purchased new along with a filter holder.

Here is the corrected image of Alex using a full CTO on the Speedlite, shooting through an umbrella. You’ll notice the color is much more balanced from foreground to background.

Photo by Eric Stoner

Here are some examples of when to use CTO gels:

One of the most common places photographers use them is in a reception hall for a wedding where there’s usually plenty of tungsten lighting. If we don’t balance the Speedlites to the room lighting using CTO filters, the background will appear very yellow but the skin tone of our subjects illuminated by our flash will look fine. This is an unbalanced lighting situation similar to the first example above.

As I set my lights up, I usually start with a 1/2 CTO gel on all of my Speedlites and do some test shots to see how closely balanced I am. In most cases, they will work just fine but it depends on your taste. One thing to be aware of is this: the more power you push through your Speedlite, the higher the temperature rises. For example, if I use my Speedlite at 1/16 power, the color temperature will be lower or more amber than if I were to use it at full power. Think of it like this: remember that your flash outputs “white” light – if I mix a little white paint into a can of orange paint, the color will lighten slightly and if I add a lot of white paint, the orange paint will lighten substantially. So if I have a large venue and I put a Speedlite in each corner of the room, I'm naturally going to need more power than if I were in a small room. Therefore, I might need to use full CTO filters, which are a deeper amber than the 1/2 CTO I started with. I know it may sound complicated, but once you start playing around with this concept and get comfortable, it will get much easier for you.

That's one example of how to use CTO's. Here's another example that is intentionally used to unbalance an image. In the last scenario, we were correcting for tungsten lights indoors. Now, let's take them outdoors under daylight conditions and change it up.

Usually, when using flash in an outdoor environment, we set our white balance to daylight or similar, as in the example below. This is balanced because the Speedlite is emitting light roughly 5600 degrees kelvin or daylight conditions.

Photo by Eric Stoner


Let's see what happens when we add a CTO filter to the Speedlite and set the white balance to tungsten.

Photo by Eric Stoner

The background looks very blue, doesn't it? So by adding the CTO gel on the Speedlite and the white balance set to tungsten, we will be balanced for a proper skin tone and the background will render a colder blue as in the example above. It can take on the look of evening or twilight.

It's not a technique you will use everyday, but it's nice to have it in your bag of tricks when you're looking to create something interesting or dramatic. Now, try going out on a sunny day and turn High Speed Sync on your Speedlite while underexposing the background by one or two stops, then watch the sky or background go much darker. Your Speedlite must remain close to your subject while using High Speed Sync and then you can control how deep the background renders by choosing a faster or slower shutter speed – another tool in the arsenal to use with your Speedlites.

CTO gels are the most commonly used, but let me share with you some of the other types of color correction gels that exist and when to use them. The next one I'll cover is the CTB (Color Tone Blue). They are often used in cinema to raise the temperature of tungsten lights (3200 degrees kelvin) to daylight balance (5600 degrees kelvin). I occasionally use these filters outdoors to intentionally warm the background up – the exact opposite of what we did in the last example. Here's how it works:

By adding a CTB filter to my Speedlite, I'm adding blue light to the subject from my flash. I have to shoot at a kelvin temperature higher than 5600 degrees or daylight because I must balance out the blue light coming from my flash. By setting the kelvin temperature on my camera to about 8000 degrees kelvin, the subject’s skin tone will appear correct and the background will have a warmer tone to it. I often use this technique if I'm working with a subject on a dreary day when the background looks uninviting and cold. So, basically we're using a color correction filter on the Speedlite and changing the white balance until we get a good skin tone. And then the background, in this example, goes very warm.

Photo by Eric Stoner

The last color correction filter I'll talk about is one I use often in fluorescent lighting environments, such as an office building. Fluorescent lights emit a green hue to the camera's "eye," however our brain corrects for it and we see it as white light. Green is a horrific color to introduce when photographing people. Look at Frankenstein, for crying out loud! It's certainly not the most flattering light there is, however if you're armed with the right filters, it can easily be corrected. I've done my fair share of executive portraiture in office buildings and introducing green color-casts in an otherwise nice portrait is enough to make any executive jump off a ledge! Simply add a Plus Green (cc30 Green) Filter to your Speedlite and set your white balance to fluorescent and you're done! The green color-cast is gone! The first example below is a Speedlite with no correction filter and white balance set to daylight. Notice how green the background looks?

Photo by Eric Stoner


Now, here is the corrected image with the Plus Green (cc30 Green) added to the Speedlite and the white balance set to fluorescent.

Photo by Eric Stoner


I should be clear that the gels I've mentioned in this article are specifically designed for color correction, not to be confused with theatrical gels that come in just about all the colors of the rainbow. That's a topic for a future article. One other thing worth mentioning is that I always shoot using RAW format, which allows me the benefit of adjusting my files in post-production. If you wish to shoot JPEG only, you need to make sure your color is spot-on accurate because JPEGs are “finished” files and processed in the camera, leaving you very little room for corrections in post without doing damage to the file.

So get out there to your local dealer and invest in these filters. They can save you a ton of agony trying to fix it in post!

Until next time, get it right in the camera!

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