Quick question on setting CWB in Gym

[Hydro]

Going out in a few hours to try some basketball shots for the first time. I got a gray card (actually a pop-open fabric with white on one side and gray on the other) but would like some input on how to set up correctly at the gym. Should I take the CWB photo shooting down on it, or should it be facing the lighting from the floor, or what? Does it matter?
Any advice greatly appreciated.

[tbfoto]

Hi Hydro, I'm getting ready to do a shoot tonight in a gym that has VERY yellow lights. Here's what I do...I lay my gray card on the gym floor in good light. Sometimes the light isnt as bright on the sidlines so I do it on the floor out in the good light. Make sure that your body does not cast a shadow and then shoot the gray card. This works well for me. Have fun.


Tbfoto

[gramps]

This makes three of us shooting in a gym/arena tonight! I still haven't played with the CWB yet. The arena our team uses is AWB freindly.

[tbfoto]

I shoot in alot of different gyms but this one is by far the worst. I work with other photographers who have shot in this same gym and they all complain about it. Even when they do a WB they have a problem. I know that there is a difference between shooting your gray card from the floor facing up and shooting it standing up. Try it both ways but I'm sure you will prefer to shoot it facing up towards the light sorce.

BTW...High school varsity basketball + Homecoming


tbfoto

[Hydro]

Thanks, TBfoto. But I should use the gray side?

[tbfoto]

Yes. You can shoot a white card but using a 18% gray card is best.

Good luck

[maderito]

Gym lighting is mixed lighting. There is no single correct WB setting. Players are illuminated by direct overhead lighting and strong reflections from the polished yellow floors. You can correct for the overhead lighting or the floor reflection - but not both.

My suggestion: decide on your the average exposure you will use and shoot a white card with this exposure dialed in for manual mode. The card should thus turn out closer to white than mid-gray (e.g. RGB=180-200).

Since you are mostly interested in getting faces and uniforms to look right, shoot the card as it reflects the overhead lighting. Your floors and shadow areas may off - but you can correct that with hue/saturation adjustments in Photoshop if you're inclined to fine tune your images.

If you're shooting games in which the players have white uniforms, use the uniform as your white card during RAW processing for white balance. Just remember that you'll get different WB settings depending on what light is hitting the uniform. Aim for white uniform parts that are not in shadows.

Remember that the power in mercury vapor lights cycles rapidly as does the color temperature. So there is no one right setting for all shots. Also - the lighting is closer to flourescent than tungsten - so fluorescent white balance setting often gets you close (as does AWB).

Your experience may vary from mine. ;)

[ron chappel]

Wow,you mean the orange one is the one with CWB??..or am i confused by your description?
If the lower one really is the CWB version then you are using a blue'ish 'grey' object to set the ballance!

Woody thanks for the seriously good explanation!
Most people assume that -with the right settings- any colour problems can be fixed,but it's alot more subtle than that as you explain.

[Illegally_Alive]

tbfoto- For a WB you want to shoot a pure white card. The 18% gray card is just to make sure you're getting proper exposure.

-B

[gramps]

this was shot in raw with AWB. The AWB has been great for the different gyms/arenas I have been in.
http://www.pbase.com/sjh/image/39418464.jpg

[mbze430]

tbfoto- For a WB you want to shoot a pure white card. The 18% gray card is just to make sure you're getting proper exposure.

-B

This is true, you can shoot a 18% gray to get the appropriate exposure, but this will also give you a good mid-tone(Zone 5) in your lighting situation.

Shooting a white card works too, but it doesn't tell you your correct exposure, because the AE system takes white and tries to bring it to 18% gray. That is why you need to add 2/3 stop to get a white-white instead of a gray-white. Same goes for Black. Decreasing 2/3 stop will give you black-black instead of gray-black.

I personally shoot against a 18% gray reflecting the main source of light.

BTW, if your gray card is glossy, it will NOT give you a consistance WB.

[Jon]

tbfoto- For a WB you want to shoot a pure white card. The 18% gray card is just to make sure you're getting proper exposure.

-B

Canon specifically recommends (20D manual, p. 52) that "Instead of a white object, an 18% gray card (commercially available) can produce a more accurate white balance."

[maderito]

Canon specifically recommends (20D manual, p. 52) that "Instead of a white object, an 18% gray card (commercially available) can produce a more accurate white balance."
Jon -

I don't think the Canon recommendation covers the problem here. The mercury vapor light found in gyms, like flourescent light, has a spectrum entirely different from daylight and much narrower than tungsten. It is very hard to correct for, and any custom white balance technique can at best get you close - but not right on target.

The only real solution would be to develop a custom camera profile for each gym using a standard target, e.g. a GretagMacbeth color chart shot under the prevailing light and working exposure conditions.

RGB color models assume daylight (of different color temperatures) which form the coordinates for a color system where R=G=B=gray for all color values. Gym lighting probably fits a very warped and nonlinear color space compared to standard lighting.

See this thread for some useful info:
http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00ApI5&unified_p=1

[Jon]

I know, and have frequently said here, mercury and sodium lights are a bear because they have a discontinuous spectrum, like fluorescents. If you'll note, my post was in specific response to Illegally_Alive's recommendation of using a white subject rather than a grey card. And I'd certainly rather start from close than from who knows where.

[maderito]

I know, and have frequently said here, mercury and sodium lights are a bear because they have a discontinuous spectrum, like fluorescents. If you'll note, my post was in specific response to Illegally_Alive's recommendation of using a white subject rather than a grey card. And I'd certainly rather start from close than from who knows where.
Agreed ... close works for me too. ;)

[cecilc]

Something that has worked really well for me in setting a custom white balance is the ol' coffee filter trick .....

I just place two coffee filters over the end of the lens and expose a frame pointing directly at the overhead lights, then set the custom white balance off of that frame.

http://www.awesomehouse.com/images/girlsbball.jpg http://www.awesomehouse.com/images/walton1.jpg

Hey, it may not be perfect .... but it's the best solution that I've found so far.