DON'T MISS: Italian conceptual portrait photographer Sara Lando coming to US for two weekends of workshops in August.

Monday, May 05, 2008

Lighting 102: 6.2 - Gelling for Tungsten

In the last L102 post, we talked about some of the problems we have to face when gelling to work under fluorescent light. Gelling for tungsten yields similar, but different problems.

Fortunately, tungsten is easier -- and more forgiving.

First of all, when we gel for tungsten, we use an "CTO" gel, which is orange and converts our daylight-balanced flash to tungsten (or incandescent). This means that our little flash has basically been turned into a normal light bulb, as far as light color is concerned.

As you can imagine, this is gonna be pretty orange. But when you are shooting in a tungsten environment, you need to get your light consistent. And CTO'ing the flash makes the flash orange, so your flash and ambient now match. Setting the camera to the tungsten white balance setting (usually denoted by a little "light bulb" symbol) corrects for all of this and brings all of the lights back to daylight.

Except when it doesn't. And there is the rub.

Like fluorescents, tungstens are not always the "correct" color. In fact, a bulb's color can change radically - even moment to moment.

How? By being dimmed.

If you do not believe me, dim down a tungsten light in an otherwise darkened room. Watch as it gets redder and redder. They go almost pure red right before the dim to "off".


TIP: If shooting in a dimmed tungsten room, try to get the lights cranked all the way up. You will get a higher ambient level -- easier for balancing. And you'll get truer tungsten colors -- easier for gelling to balance.


Knowing this, you should now realize that you cannot perfectly balance for all tungsten lights with just a CTO gel. And even if you could balance for everything, you probably would not want to.

First of all, as with our fluorescents, when color converting we can only gel our flashes for something we can reliably correct with white balance settings. And custom white balance is not very useful, because you would have to match the flash's gel pack with the custom color to complete the process.

If you do shoot regularly in, say, the same room with the same whacked-out color, it might be worth it to test a build a gel pack that matches the room light for your flash. Then you could cancel it all out with a custom white balance. But on a daily basis, this is impractical when shooting flash.

Fortunately, flash and tungsten get along pretty well when not perfectly balanced. The main thing is to get your flash correctly CTO'd and balance that at the camera. Then let the ambient tungsten do what it is gonna do.

It frequently will not be perfect, but it will be much better than if you had not gelled at all. And you can also vary the background color effect by how much ambient you choose to include, remembering that the ambient component is controlled with the shutter speed. Balancing down lower with ambient (more stops underexposed) intensifies the color. So bring it up a little so smooth it out.

Long story short, the bad news is that with tungsten, you have a color problem you might not have previously considered. But the good news is that you do not need to be as exacting with tungsten light, so missing it a little is not a tragedy.

CTO and Window Greens explained, we will jump into some fun stuff next -- color key shifting.

NEXT: Assignment: Work That CTO


__________

Brand new to Strobist, or lighting? Start here.
Or, jump right into our free Lighting 101 course.
Connect: Discussion Threads | Reader Photos | Twitter

18 Comments:

Anonymous Marco said...

Im the first comment, haha. Do you have any advice on what gel package to buy? How many gels should you have etc. Thanks for all you do

May 05, 2008 3:29 AM  
Anonymous Anonymous said...

Hi,

Can you explain how you did the photo http://farm2.static.flickr.com/1433/1439498564_301783b67c_m.jpg that you included in a previous ambient-flash post?

thank you very much,

Miguel Angel

May 05, 2008 5:24 AM  
Blogger LIGHT-SHOOT-PRINT said...

David, I've found that it's very useful to gel for tungsten or fluorescent AND then set a custom white balance in the camera using a neutral shooting target. As you point out, color temperatures for both sources can be all over the place, so you can't rely on just setting your camera to "the little lightbulb" or "the little tube" icons, but you can nail the right color if you take both steps. So often I've gone in to rooms with four different kinds of fluorescent tubes or tungten lights covered with all sorts of colored lampshades, and even with gelling the only way to really get close is to take that one extra step of using the target. The other option is to just shoot the target and then use the neutral grey eyedropper in photoshop or Lightroom after the fact, but you save yourself production work if you do it in the camera.

Hope you're enjoying Dubai.

-Little Tommy G-

May 05, 2008 11:14 AM  
Anonymous Anonymous said...

You can pick up packs of various gels at either http://www.photogels.com or at http://www.flashgels.co.uk. I found that the first site is cheaper since the US $ is so weak.

May 05, 2008 3:27 PM  
Anonymous Luis said...

So....check this situation:
I'm shooting a factory with workers and big machines - 2 kind of lights: daylight coming from big doors and windows and fluorescent lights all over. If i gelled my flash with CTO what wb do i choose on the camera?

thanks.

May 05, 2008 7:40 PM  
Blogger Liquid Air said...

I have had a number experiences where a full CTO gel had a bit more magenta in it than the room lighting which meant after balancing for the gel, the ambient ended up with a slight, but ugly greenish cast. My preference these days is to undercorrect and use a 1/2 CTO gel on the strobe. In my experience leaving some of the orange in the ambient actually looks pretty good in a lot of situations and it is a lot less finiky than trying to match it dead on.

May 05, 2008 9:50 PM  
Blogger Furious said...

David, should the density of the gel change with the brightness of the flash? Would you have to go from say 1/2 to 3/4 *arbitrary numbers* if you turn up your flash?

May 05, 2008 9:57 PM  
Blogger Steve Thurow said...

The picture of the camera was done by zooming the lens during a long exposure and popping a flash or flashes to bring out the detail in the camera.

The ambient exposure on the camera wouldn't leave any detail, thus the flash. Flash triggered front or rear curtain.

May 05, 2008 10:05 PM  
Anonymous Tony said...

Thanks for all the info, keep it up. Your lighting techniques continue to inspire me.

May 06, 2008 10:29 AM  
Blogger masont said...

The darker the gel, the more light power it will eat up so if you are using a 1/2 CTO gel and want to change to a 3/4 CTO gel, you'll need to increase the power of your flash to compensate for the difference.

Mason Trullinger
http://www.photogels.com

May 06, 2008 12:09 PM  
Blogger DaveRe said...

Is there a general guideline on which CTO (or Plus Green) gel to pick? Always start w/ full CTO, or 1/2, or???

Is anyone using a Straw series instead of Orange? They're a little more yellow - possibly less magenta?

May 07, 2008 9:15 AM  
Anonymous Anonymous said...

You can see the color shift with tungsten light in teathrical plays, when fresnel (as an example) lights are dimmed they shift a little their color temperature and also talking with the lighting experts at the theater they say that if the bulb is past half of it life span it will shift even more :).

You can learn a lot about lighting position and setups from theatrical plays :)!!

May 07, 2008 5:57 PM  
Anonymous Anonymous said...

Luis,

If you're shooting with Florescent lights and daylight, you don't want to use a CTO gell. You'll be creating yet another conflicting color cast.

Your CTO flash will be ORANGE
The Daylight will be BLUE
the Florescent will be Greenish/yellow.

Your best bet is to take a look at the site and decide what you're going to be shooting and which light conditions will effect the majority of your shots.

Florescents are a nightmare. What works for me is to check the site by taking some test shots, check what temperature you're going to have to adjust to, and then gell accordingly.

I have run into situations where a Florescent light wasn't putting out greenish light, it was tossing out YELLOW light due to the fact that the light fixtures at the site were horribly stained from smoke.

I broke out my Rosco test book, matched up the closest color to match the lighting, and then picked up the right color to balance my flashes to the site.

May 08, 2008 2:54 AM  
Anonymous scaamanho said...

On trick that works very well for me in studio, where i mix tusteng and flash light is use a coffe filter in the objective and make a wb measure with the tustengs and flash together.
Usually works better that CTO gels

May 15, 2008 6:47 AM  
Blogger DA Photo said...

Hi David,

Totally unrelated question from this recent posting...

Would you be willing to post a suggested equipment list that Strobists should have/get in their Gear Bag? I.e., number of flash units, gels, stands, umbrellas, etc.

Scenario: Photographer gets a call from someone wanting an on-location portrait and a few images of their workplace or home. Photographer needs to travel relatively light, but needs to have the equipment, let's say in two bags (camera bag and one other), to get the job done. What basic and good-to-have equip items would you recommend be "in the bag" at the very least.

Thanks in advance for your comments and recommendations.

May 16, 2008 3:13 PM  
Blogger Petteri said...

Wow! I read all the lightning 102 posts in just a few days time. And I learned sooo much! Now I just have to go and practice all this new stuff. Really loving this blog!

I have tried that Scaamanho's coffee filter thing and it really works! You should try it.

June 12, 2008 5:21 PM  
Anonymous Anonymous said...

I just realized this:
Rosco Light Tough Frost
( or Tough Frost, don't know which'd work better )...
... is a dirt-cheap ExpoDisc!

Therefore, one can balance exactly for ambient, getting that part of the equation controlled, then gel one's strobe for effect exactly.

Fun, huh?

:)

July 15, 2008 2:54 AM  
Blogger phatcamerasandwich said...

Anyone using a flash/ambient color meter to more finely tune flash fill? Seems like it might be useful, although perhaps no so much considering Photoshop capabilities. Thanks.

David

January 24, 2011 12:10 PM  

Post a Comment

<< Home