Lighting 101: Using Gels to Correct Light
I would hope that anyone shooting in color and using flash is color correcting their light by now. But this is Lighting 101. So just in case you aren't, we are going to run through it quickly and throw a couple tips out that you may not have considered yet.
First, the basics.
Every flash that you use should have two gels - Window Green and CTO, which stands for Color Temperature Orange (where to get them) nearby and ready to be used at any time. These are your bread-and-butter correction gels.
To attach them to a flash, I cut the gels into strips and put adhesive velcro (very cheap at Home Depot, Wal Mart, etc.) onto the edges. I put hooks on one side and loops on the other, so on very rare occasions you can stack the gels if need be. But mostly it helps to be able to stack them on the side of the flash for easy storage.
You will also be putting the "loop" side of the velcro on the side of your strobe, as shown. This will provide an easy way to attach bounce cards and light shields to keep your flash from causing glare when it is being used as a side/backlight. More on that later.
Back to light color. Florescent light is not white. It is a sickly, putrid green. If you are not gelling your strobe green to match it, objects lit by your flash will be white and the ambient-lit portion of your frame will be green. This is a problem that even Photoshop cannot fix.
The solution is very simple: You place a "Window Green" florescent gel over the strobe head. You color balance your digital camera for shooting in florescent light. You get consistent, reasonably color-correct photos, with both the strobe and ambient light coming out as (again, reasonably) correct color.
I say "reasonably," because all florescent lights are not the same color temperature. And, depending on which part of the 60hz electric sine wave cycle your shutter happens to grab from the florescent ambient lights, they will color shift on you, too.
Don't believe me? Set your camera on an interim shutter speed between 1/60th and 1/125th, such as 1/80th or 1/100th. You are trying to grab a portion of the sine wave here. Motor off ten available light frames in quick succession. See the color shifts between the frames? That's what I am talking about. Not much you can do about it, except to shoot at 1/60th (to get a whole, 60hz wave) or 1/30th (to capture two complete waves.) Not the ideal solution, but it does help.
So, you balance your strobe output level for the ambient light levels when you shoot (just like we talked about earlier) and you should get a smooth, color-corrected photo. If you run into problems, try warming up or cooling down the the florescent setting on your camera. I know my Nikon digital cameras do this very easily, and I would assume the Canon digital cameras do it, too.
Tungsten is the same process, except you use the CTO gel and balance your camera to tungsten. And again, tungsten is not necessarily tungsten. Some lights burn warmer (color-wise) and some light - especially those turned way down on a dimmer, are almost red-orange. But balancing the camera for tungsten and using your CTO gel on the flash will get you acceptably close on most all cases.
Ah, but what about the rooms that have florescent overheads, tungsten desk lamps and big, daylight streaming windows?
No problem. Just shoot black and white.
(Kidding, kidding...)
What you have to do is to choose your dominant light color and go with it. Bear in mind that tungsten and daylight mix much better than do florescent and everything else.
If the room is mostly florescent light but there is window light creeping in, close the blinds/shades/drapes and try to keep the window out of your shot, because some light will creep around whatever is shielding it at the window.
If the windows are large and/or bright (such as in a classroom) I usually just ask if I can turn off the florescent lights "because they make your skin look green in photos." Very few people object to things that keep their skin from looking green. Besides, if the window light was intense enough to be problematic, there should be enough light for people to work by.
After that you just use your flash without gels. Be aware of light levels coming from the the window and, as they say in Great Britain, Bob's your uncle.
I suspect that as our library of photo examples in "On Assignment" grows, we will be getting into using colored gels for effect. But that's for later. If you feel compelled to experiment, just try to remember that (a) that 80's-MTV-Gel-The-Heck-Out-Of-It look is so over and (b) less is more when it comes to color-gelling your photos for effect.
Next: Cereal Box Snoots and GoBo's
First, the basics.
Every flash that you use should have two gels - Window Green and CTO, which stands for Color Temperature Orange (where to get them) nearby and ready to be used at any time. These are your bread-and-butter correction gels. 
To attach them to a flash, I cut the gels into strips and put adhesive velcro (very cheap at Home Depot, Wal Mart, etc.) onto the edges. I put hooks on one side and loops on the other, so on very rare occasions you can stack the gels if need be. But mostly it helps to be able to stack them on the side of the flash for easy storage. You will also be putting the "loop" side of the velcro on the side of your strobe, as shown. This will provide an easy way to attach bounce cards and light shields to keep your flash from causing glare when it is being used as a side/backlight. More on that later.
Back to light color. Florescent light is not white. It is a sickly, putrid green. If you are not gelling your strobe green to match it, objects lit by your flash will be white and the ambient-lit portion of your frame will be green. This is a problem that even Photoshop cannot fix.
The solution is very simple: You place a "Window Green" florescent gel over the strobe head. You color balance your digital camera for shooting in florescent light. You get consistent, reasonably color-correct photos, with both the strobe and ambient light coming out as (again, reasonably) correct color.
I say "reasonably," because all florescent lights are not the same color temperature. And, depending on which part of the 60hz electric sine wave cycle your shutter happens to grab from the florescent ambient lights, they will color shift on you, too.
Don't believe me? Set your camera on an interim shutter speed between 1/60th and 1/125th, such as 1/80th or 1/100th. You are trying to grab a portion of the sine wave here. Motor off ten available light frames in quick succession. See the color shifts between the frames? That's what I am talking about. Not much you can do about it, except to shoot at 1/60th (to get a whole, 60hz wave) or 1/30th (to capture two complete waves.) Not the ideal solution, but it does help.
So, you balance your strobe output level for the ambient light levels when you shoot (just like we talked about earlier) and you should get a smooth, color-corrected photo. If you run into problems, try warming up or cooling down the the florescent setting on your camera. I know my Nikon digital cameras do this very easily, and I would assume the Canon digital cameras do it, too.
Tungsten is the same process, except you use the CTO gel and balance your camera to tungsten. And again, tungsten is not necessarily tungsten. Some lights burn warmer (color-wise) and some light - especially those turned way down on a dimmer, are almost red-orange. But balancing the camera for tungsten and using your CTO gel on the flash will get you acceptably close on most all cases.
Ah, but what about the rooms that have florescent overheads, tungsten desk lamps and big, daylight streaming windows?
No problem. Just shoot black and white.
(Kidding, kidding...)
What you have to do is to choose your dominant light color and go with it. Bear in mind that tungsten and daylight mix much better than do florescent and everything else.
If the room is mostly florescent light but there is window light creeping in, close the blinds/shades/drapes and try to keep the window out of your shot, because some light will creep around whatever is shielding it at the window.
If the windows are large and/or bright (such as in a classroom) I usually just ask if I can turn off the florescent lights "because they make your skin look green in photos." Very few people object to things that keep their skin from looking green. Besides, if the window light was intense enough to be problematic, there should be enough light for people to work by.
After that you just use your flash without gels. Be aware of light levels coming from the the window and, as they say in Great Britain, Bob's your uncle.
I suspect that as our library of photo examples in "On Assignment" grows, we will be getting into using colored gels for effect. But that's for later. If you feel compelled to experiment, just try to remember that (a) that 80's-MTV-Gel-The-Heck-Out-Of-It look is so over and (b) less is more when it comes to color-gelling your photos for effect.
Next: Cereal Box Snoots and GoBo's
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Feed your brain: Great Lighting Books
by David, at 10:36 AM.
36 Comments:
Hello! I saw this link and i was wondering, what materials do you use to make those gels?
Sorry, should have put that info in the post. You can get them at any theater supply store. They are made by Roscoe, or some stores might carry Lee.
If you get one of the free sample packs, the samples are big enough to just cover the heads of the kinds of flashes we use. That'll give you all of the exotic colors. Then you might want to buy a shoot of CTO and Window Green, because you will use those a lot and want to make new ones occasionally.
-D
Don't forget that users of Nikon SB800s get a set of gels supplied with the flash, in that little plastic thing that is usually left in the pouch.
Use these until they wear out, but don't buy the Nikon replacement set - it's way too costly.
Beware of the Nikon tungsten conversion gels. They're not CTO's and are quite strong. Although Nikon offers them as tungsten correction, at the very least, they're something other than a simple 3200k correction.
What about balancing for sunlight? I have both the CTO and window green (thanks for the recommendation) but tried shooting into the sun last night for some balanced portraits.
I'm using a Canon 30D with a 420EX mounted for fill (no PWs yet).
I noticed the unnatural white fill light when shooting the flash bare so I tried adding the CTO to the flash to balance with the setting sunlight. The skin tones came out way too red.
I ended up attaching the CTO so it only covered about 1/3 of the flash and it seemed to have better balance... but it took a bit of playing to get something that looked natural.
What are your recommendations for balancing light shooting into a balcklit scene (sunset) for portraits?
After a little bit of research I've found that you might find the green gel referred to by other companies as CC30 Green, (Rosco) PlusGreen or (Lee) 224 "Lee Plus Green"
CTO (Colour Temperature Orange) is a widely used term across the different companies.
Will CTO and Window Green gels work the same way with color negative film? Thanks.
Please can you give us the links for B&H shop, corresponding to these filters; they have diffrent grade and I don't know which filter is OK. Thank you!
B&H Links:
CTO 3407
Green 3304
Dave
Here you go:
Rosco Cinegel Green 3304
Rosco Cinegel CTO 3407
Dave
Anybody have any idea about my previous post? Isn't anybody finding that using the CTO for outdoor portraits produces too much colour in the flash?
Are you mounting the gel all the way over the flash or do you adjust how much it covers?
Richard-
You may want to ask in Flickr. Many people have worked their way through this area when it was first published back in April.
-Matt
Richard,
You can buy CTOs in half and quarter strengths. CTO 1/4 makes natural-looking, warm skin tones when balanced with daylight or warmish ambient. Half might do what you need. Also, for natural outdoor portraits use a large (4' x 6') white foamcore board bouncing sunlight onto the subject's face while the direct sunlight rim lights the head and shoulders and background is semi-shaded. Ratios and color balance are automatic.
John
Here's a wedding image shot in daylight with gels.
I don't have a problem using gels in daylight. Its a nice effect. I do have a problem with CTO being WAY to red to match tungsten settings on my canon system, and most tungsten burns colder than intended anyway. In my experience that hue shifts it to yellow I use Roscoe Straw 3441 and a couple other variants with more yellow to get the right tone for tunsten matching.
Mike L. - a professional wedding photographer from Toronto - noted that CTS gel is a better match as it does not produce magenta casts on Canon EOS. He switched from CTO to CTS. See this ROSCOE page for more info on CTO vs. CTS: http://www.rosco.com/us/filters/cinegel.asp
Why not just purchase the Rosco sampler swatchbook at a penny for swatchbook. I purchased 5 of these this morning, with shipping, it will run me just under $6.
Swatchbook
Question..
I realize the Strobist is "aimed" at Digital shooters.. However, I still enjoy using film.
I recently had a shoot where I used daylight-balanced film (Fuji Velvia), indoors. My subject was lit by light coming through a window. In the background was ambient light from an incandescent lamp.
I'd like to be able to reproduce this scenario, but using a strobe instead of daylight.
Would I need to apply any color gels to my strobe in order to achieve these results? Or is a flash already a close match to daylight?
Question..
I realize the Strobist is "aimed" at Digital shooters.. However, I still enjoy using film.
I recently had a shoot where I used daylight-balanced film (Fuji Velvia), indoors. My subject was lit by light coming through a window. In the background was ambient light from an incandescent lamp.
I'd like to be able to reproduce this scenario, but using a strobe instead of daylight.
Would I need to apply any color gels to my strobe in order to achieve these results? Or is a flash already a close match to daylight?
FYI B&H has the swatchbooks back in stock for 1 penny ($0.01).
http://www.bhphotovideo.com/sitem/sku=45184&is=REG&bi=E15
Tampa Bay Photographer -- Tom Moore Fine Art Photography
I have a couple boxes of old color darkroom filters. These are Cyan Magenta Yellow filters that are 6 inches square... I picked them up at a garage sale for a quarter. I'm wondering if anyone has CTO and Window Green equivalents to these filters. CTO is (guessing) somewhere around 20M and 40Y?? Anyone know the location of this reference material?
Hi, everyone.
Okay, I guess I'm missing something here...why not use a small grey card (whibal, or the like) and shoot a test shot for the lighting conditions. Later in Camera Raw/Lightroom, adjust the white balance by selecting the card in the test shot with the eyedropper. Is this approach insufficient? I would think it would cut through the difficulty of dealing with mixed lighting, but maybe I'm off-base here.
Thanks,
Pete.
Pete, the point of the gels is creating a single color of light from multiple types of light sources. If you simply used a gray card, you would only be balancing for a single light source, or a mix of both, giving inaccurate colors.
In the US, the fastest shutter speed to use under fluorescent light to capture a full light cycle is 1/125 second, and not 1/60s as mentioned in the text.
That's because a period of the power sine is itself divided into two sub-periods which are identical except for the fact that the current changes direction. However the sense of the current does not have an effect of the light emitted by a fluorescent light. In other words, that light has a 120 Hz cycle, and a shutter speed of 1/125 s is close enough from 1/120 s.
Use manual or shutter priority modes if you shoot under fluoresent light at 1/125. This is critical because if you shutter speed changes by as little as 1/3 stop, the impact on the lighting color will be significant. The issue lessens as you capture more cycles in one shot and at 1/30s or slower this becomes an non-issue.
In other countries with power cycling at 50 Hz, the fastest shutter speed is 1/100 s.
I suggest that you modify the text, there is no need to post this comment.
Thierry aka "TOF guy"
Hey Strobist, thank you so much for this site! I've been behind the camera for almost ten years, but the use of strobe has always eluded me. Unfortunately one of the first things I learned from Strobist is that I bought the wrong kind of flash last year. (It can't be dialed down.) Oh well, back to the B&H used dept for a trade in.
ps Do you know Andy Cook?
Free sampler kit from Rosco...
http://www.rosco.com/us/filters/swatchBookRequest.asp?type=cinegel
I wanted to correct your spelling of the word "fluorescent."
This isn't an attack; I am really enjoying your blog.
Dmitriy
If you don't want to spend too much for your gels, just go to Staples and buy some colored Poly repport holders. I know lots of thech guys would be ready to hammer me for this idea (it's not the same color tone - way off of being "calibrated" too and not the same material) but hey! you pay $0.65 and it's much better than nothing. And if you're ready to pay a few bucks more, I just bought them on e-bay too: LightingelStore ($3.89 each).
Dave Honi has a gel kit that works with his speed strip.
A great collection of Rosco gels, cut to fit 99% of the speedlites out there and the Speedstrip make is super simple to attach them
His web site: http://www.honlphoto.com/servlet/the-21/HonlPhoto-Rosco-Gel-Kit/Detail
Hello,
for anyone interested in gels. Just send an email to lee filters and ask for a free filter sample pack. I orded one some time ago, had it in two or three day's, from the UK to the Netherlands, there are more collors than you will ever use, its just fantastic. Good luck.
After a bit of research I’ve figured out the filter number for those of us who use Lee filters.
The numbers are: 204 Full C.T. Orange (Daylight to Tungsten 3200K) and 244 Lee Plus Green (Green cast to match fluorescent).
I am working my way through this blog and love it. Thanks!
On the subject of fluorescent lights I notice you don't mention electronic ballasts. These are worth mentioning mainly because of the lack of flicker - the frequency is from about 20 to 50 KHz which is quite a jump from 60 Hz.
Here is something else: what about fluorescent bulbs with a decent CRI? (ie over 80). I can buy GE T8 (standard 4' fixture) SPX50's for $2.6 ea and they have a CRI of 86 at 5000K. Shooting a friend's wedding I actually advised the replacement of the ballasts and bulbs in all the fixtures of the hall. During the process I snapped a few shots showing the contrast between the old and the new - quite remarkable. (The motion got approved on the basis of efficiency - not only are the new bulbs brighter but they'll pay for themselves in about 2 years...)
So... sure you have to be able to deal with old fixtures/bulbs - but it seems like there are (and will be more) many situations when you would automatically be gel-ing your flash green and that would be the wrong thing to do?
Finally, regarding gel-ing your flash to match the green: worse than a color cast is the fact that parts of the color spectrum are plain LEFT OUT by mediocre fluorescents = some colors are unrecoverable (ie, not there in the photo) - unless you make sure your flash gives the lion's share of the light!
I'd like to hear more on this!
For anyone who is in the UK, you can give Lee a call and request swatch books, which they will sent to you free, along with an information-packed brochure. See here: http://www.leefilters.com/lighting/contact/
Apparently their US-based site is coming soon, but if you have a look at the holding page, they have posted contact details already: http://www.leefiltersusa.com/
Hope this helps.
Hi David,
Looks like a bit of a folow-up to my last post on this page! Anyway...
I know you are always on the lookout, as we all are, for sources of lighting goodies...
For CTB & CTO filters (as well as others) you might want to check out this page. The price quoted is for a 24"x24" sheet, so imagine how many gels you could get out of it for your SB-800s (the fresnel only measures about 2 1/4"x1 1/4"!
Ok, so they list 'Europe' as the post-to destination, but I don't see why they couldn't help you guys out over there in the States.
For what it's worth, I just ordered some larger kit from these people (I'm in the UK, as you know) and it arrived next day, following a really polite and professional service.
A quick update to my last post...
Having been in touch again with that same company, I'm told they have now released dedicated Lee Filter strobist sets which contain 20 filters, designed for use on speedlights etc here
Oh, and they have also confirmed that they are more than happy to dispatch to you guys in the US (as they frequently do).
Again, hope this helps.
Strangely enough - I have been using different colours of Post-It notes to do this - works great!!!
There may be a source for cheap or free gels, provided you only need to gel the flash itself, and can use a small piece. Most theatres have huge bins of scrap gel - gel too small for any of their lights (meaning you can't get a 5.25" square out of it). The staff typically use it to gel their flashlights and such. If you talk nice and/or bring beer, there's a good chance you'll walk away with 20 pounds of gel. Having said that, you'll never find CTO or any other color correction that way.
Also, theatrical lighting companies are probably a far better choice for getting sample books... most around here have a large bin of them by the door, and don't really care what you want them for.
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