Color casts and lenses - DPChallenge Forums

12/05/2005 11:26:35 PM · #1

Here are two pictures taken with two different lenses on the same camera (Canon 300D) taken at about the same time:

The picture on the left was taken with a Sigma 24-70 f/2.8, at 70mm, ISO 800, f/2.8 and 1/200. The one on the right was taken with a Canon 50 f/1.4, ISO 800, f/1.4 and 1/1000. The 50mm lens looks like it got more of a green cast to the left of the banner. What causes this difference? How can I minimize the effect of the mixed lighting in this gym? (or is the difference just due to the 50mm getting part of the light fixture in the upper left of the picture?)

The lighting in this gym was miserable, here's part of the ceiling:

Message edited by author 2005-12-05 23:28:49.

Canon EF 70-300mm f/4.5-5.6 DO IS USM

12/05/2005 11:36:41 PM · #2

If you were using auto WB that could account for the differnce. It will adjust for each shot, and including a light in one and not the other could do it.

cpanaioti

Canon EOS-40D

12/05/2005 11:39:44 PM · #3

Both have a green cast on the left. The wider angle just appears to show more of it.

Try again with the 24-70 set at 50 and try and get the exact same shot. That would give you a better comparison.

Message edited by author 2005-12-05 23:39:58.

yido

Sigma 20mm f/1.8 EX Aspherical DG DF RF for Canon

12/05/2005 11:40:40 PM · #4

I think the coating makes a difference. You can always adjust the tint in post processing after adjusting the white balance if you shoot in RAW.

12/06/2005 12:02:22 AM · #5

Originally posted by Prof_Fate:

If you were using auto WB that could account for the differnce. It will adjust for each shot, and including a light in one and not the other could do it.

Nope. Set a custom WB and used the same one for both.

12/06/2005 12:04:22 AM · #6

Originally posted by cpanaioti:

Both have a green cast on the left. The wider angle just appears to show more of it.

Try again with the 24-70 set at 50 and try and get the exact same shot. That would give you a better comparison.

Won't be to that gym for a while, if ever again. I'll have to look for another gym with really bad lighting. Unfortunatly, they're not hard to find.

12/06/2005 12:10:38 AM · #7

The one light appears to be flourescent the other (the round one) is something else with a different color spectrum to it. The green light on the far left is...something else entirely?

This mixed light is bound to cause issues.

Also, if you set a custom WB and a lens A, and the coating effects the color the sensor sees then you'll need to do acustom WB for EVERY lens you intend to use under those lights. It's as if you added a colored filter on the lens and expected the WB to remain the same...

12/06/2005 12:25:25 AM · #8

Originally posted by yido:

I think the coating makes a difference. You can always adjust the tint in post processing after adjusting the white balance if you shoot in RAW.

I shot in RAW. The tough thing is that some skin has the same color casts. That is, the same girl will have a magenta face, one arm may be normal and the other may be to green. Due to the restrictions imposed by the school, I can't show recognizable players, etc. But here's a crop that shows some of the problem. If I adjust to correct the green cast, the "normal" flesh tones become to magenta...but I know about using mixed lighting (I learned the hard way). I was just curious to see if some lenses minimize or exagerate the problem.

12/06/2005 12:27:57 AM · #9

And on the Eight day god made black and white film, and it was good. LOL

12/06/2005 12:32:23 AM · #10

Originally posted by Prof_Fate:

Thanks, that explains it. I hadn't thought about the coatings.

Note that its not just the tube fluorescents mixed with one other light--each of the round lights seem to have its own color temperature. (see the third picture).

I also realized that since I was shooting at 1/200 and 1/1000 there could be issues because the lights use AC at 60Hz.

PShizzy

Canon EOS-1D Mark II

12/06/2005 12:37:00 AM · #11

the light on the left is flourescent, which gives off a green tint, while the light on the right is probably a mercury vapor type light which cycles from color to color. even if you were to use a set wb and use the same settings for each shot, the color would change in tint slightly.

where the flourescent may be more green is if the light on the right took a greener hue that mixed with the flourescent, or if it took a color opposite too it, contrasting more with the green and thus allowing the green to come out more.

mercury vapor lighting is horrible, and there are very few ways to overcome it, as usually there are mixed or multiple lights which all cycle differently.

Max

Canon PowerShot Pro 90 IS

12/06/2005 12:40:39 AM · #12

I know shutter speed and flash in ambient light can cause werid colr tinges (the slower the shutter the more ambient light, so the more color cast as flash is daylight in color).

The round ones may be sodium vapor (red i think is their color) like steet lights. I worked one place where the boss had them installed as part of a renovation. once they are warm it looks 'normal', but till then they flicker and cause some hasty shadows and color casts that even the naked eye can see.

I shot a wedding under terrible lighting conditions, and without flash or when the flash did not overpower the ambient light the pics wree terrible. When i tried to fix them, well, b&w worked well LOL. PS's auto color corredt worked the best, much to my dismay (i thought i was smarter than the 'auto' modes in ps. Rather humbling i might say)

As to color casts in skin - could be the person. I shot girl for senior pics and her skin tone/color changed with the lighting. All outdoors, all daylight, all the same lens.

coolhar

12/06/2005 01:01:40 AM · #13

Originally posted by hankk:

... I'll have to look for another gym with really bad lighting. Unfortunatly, they're not hard to find.

Ain't that the truth. I've shot in some HS gyms that are absolute dungeons.

I know that using a custom white balance is considered a more advanced photographic technique but using the Auto WB setting has it's place. Gyms almost always have a mixture of different types of lighting fixtures including tungstens, flourescents and mercury or sodium vapor so the color of the light can vary from one section of the floor to another. By using Auto WB in such situations you can at least introduce one constant (the camera's method of measuring and adjusting for light coloration) into the equation.

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

12/06/2005 01:12:00 AM · #14

Originally posted by coolhar:

Originally posted by hankk:
... I'll have to look for another gym with really bad lighting. Unfortunatly, they're not hard to find.

Ain't that the truth. I've shot in some HS gyms that are absolute dungeons.

I know that using a custom white balance is considered a more advanced photographic technique but using the Auto WB setting has it's place. Gyms almost always have a mixture of different types of lighting fixtures including tungstens, flourescents and mercury or sodium vapor so the color of the light can vary from one section of the floor to another. By using Auto WB in such situations you can at least introduce one constant (the camera's method of measuring and adjusting for light coloration) into the equation.

I completely agree with this. Under mixed lighting custom WB is useless unless you do it for every shot. Auto WB is much more consistent. When we were shooting mixed-lighting architectural interiors with 4x5 color transparency, we used a color temperature meter for every single shot, measuring the color temperature at various different spots in the field of view and creating a custom gel filter "sandwich" for each shot that was our best guess at a happy median. We also shot color neg film at the same time, so if we were way off we could burn a transparency from the negative and adjust the colors like we were printing.

Robt.

DjFenzl

12/06/2005 01:51:40 AM · #15

mercury vapor light have been known to throw out a green hue in the room but make skin tones look purple. It's very hard to compensate for that because to correct one you just make the other worse. High school gyms are a nightmare often times.

petrakka

12/06/2005 01:57:14 AM · #16

gyms pretty much suck all of the time. Hell, I just shot a game in the United Center in Chicago and even that light was tough to work with. I don't think a gym will get lit better than an NBA/NHL stadium.

But yeah in my experience just get as good as you can in camera and leave the rest with photoshop. Auto Color actually can do an okay job sometimes, though I wouldn't recommend a reliance on it.

12/06/2005 02:46:09 PM · #17

Originally posted by PShizzy:

Could you explain the cycling more? Is it due to 60Hz AC, or temperature, or the age of the bulb or ...? How big of a range of colors is it?

If it's 60Hz AC cycling, then that explains the different colors of the mercury lights. The gym probably had three phase power, and the lights were on different legs, and so were at different phases.

Canon RF 24-70mm f/2.8 L IS

12/06/2005 02:47:20 PM · #18

Thanks to everyone for the good advice. I'll have to be more careful in the future and check to see if the AWB is better than custom WB.

Would a newer body have better AWB? And since I can't afford a 20D right now, should I raise my standards and "not-get" a 1D Mark IIn? :-)

kirbic

Canon EOS R5

12/06/2005 02:51:58 PM · #19

Originally posted by hankk:

Originally posted by PShizzy:
the light on the left is flourescent, which gives off a green tint, while the light on the right is probably a mercury vapor type light which cycles from color to color. even if you were to use a set wb and use the same settings for each shot, the color would change in tint slightly.

Could you explain the cycling more? Is it due to 60Hz AC, or temperature, or the age of the bulb or ...? How big of a range of colors is it?

If it's 60Hz AC cycling, then that explains the different colors of the mercury lights. The gym probably had three phase power, and the lights were on different legs, and so were at different phases.

The lights in this type of facility do normally run on single-phase legs of three phase sources, so it is definitely possible that you get a different cast at different points in the cycle when different-type sources are involved. In some gyms, you'll notice that though all the lighting is arc lamps, some have visibly different color than others. Either they are randomly mixing different types of lamps (different gases) or they are intentionally mixing them to gain better *visual* color rendering. I suspect the latter. Sure is heck for photography though!