Portrait shots, How to keep my background the same color?

[Robert Forester]

I have a new job and part of my responsibility is taking shot of my fellow employees head shots. I purchased a professional photo background in order to have the consistency in the background. I use LED lights, so that is pretty controlled. The problem I am having is sometimes this gray background color is way off. The subject usually looks really good, but I want the background to remain gray... it usually turns brown. I think that it has something to do with the outfit color of the subject. I have really noticed this with blue outfits. How do I need to set my camera where the color does not change. I am using a Sony Cybershot DSC-HX400V, which is a fixed lens. I have been using the camera in the program mode. Thanks for the help!

 

[Designer]

Don't use "auto white balance".

You are correct in assuming that the camera is trying to white-balance the entire frame, including the subject's attire and the backdrop.

Shoot in Raw, set the WB to "Custom", and shoot a blank frame at the backdrop for reference.

When you edit your session, adjust the backdrop to be correct, and then match all of the portraits to those same settings. The colors then should be correct.

Also make sure that there are no other lights in the room to confuse your color editing.

If you have a good color eye, (and if your computer display is properly calibrated) you should be able to match the backdrop fairly closely, but if not, shoot a white target and let the editing software make the WB adjustment.

 

[JonA_CT]

To add to what Designer said, blue is probably worse than other outfits because I’d imagine that your LED lights are probably cool-colored too, so the camera is trying to overcompensate.

 

[TCampbell]

It sounds like you are using "auto white balance" in your camera. Auto-white balance tries to "guess" at the correct white balance adjustment based on what it sees in the scene. But there are so many factors that can effect it's guess that it isn't very reliable.

If your lighting isn't changing then you should be able to set manual white balance based on the "kelvin" value of your lighting.

All color is derived from the light shining on your subject. If you are in a completely black room and shine a "red" light on a piece of perfectly "white" paper, that paper will appear "red". Is it really red? You know it's really "white" -- it's the light that is red.

The mid-day sun pumps out the color of light we tend to think of as "white". At sunset, that same sun appears to be pumping out "orange". Incandescent lights and candles also pump out a light that looks a bit yellow/orange. Many LEDs put out a light that looks a touch blue (although modern LEDs are often engineered to try to replicate the soft & slightly yellow color of incandescent (tungsten filaments) lights.)

Changing the light source and the color of your subject will change along with it. This is the whole point of "white" balance is to try to detect the true color of the light source so that the camera (or computer) can produce an accurate color result regardless of the color cast of your light bulbs.

Ordinarily I might do this by having a subject hold a photographic "gray card" but even a white sheet of paper might do. The card is color-neutral. It's "gray" but it doesn't favor any color (sometimes gray looks just slightly blue (cool), or just slightly "brown" (warm), etc. etc. The gray card is perfectly neutral.)

Digitally, color is represented by the amount of additive values of light -- specifically it describes how much "red", "green", and "blue" must be added to arrive at the correct blended color.

If we imagine these intensities on a scale of 0 to 99 (100 possible values) then "0" means no light on that color channel and "0, 0, 0" means it's completely black (no light on any color channel) and "99, 99, 99" means pure white (maximum light value on every color channel). But "50, 50, 50" would mean it's neutral gray. (in truth your camera is probably using 14-bit color depth which really means the values are from 0 to 65535 and if you save them as JPEG images then those are 8-bit color depth which has values from 0 to 255. I'll just use 0 to 99 to make things easy in the example.)

So suppose you take a photo of something that SHOULD photography at "50, 50, 50" (our neutral gray card) and what we actually get reads "60, 53, 40" (that means it's got noticeably more red, slightly more green, but less blue) and that would result in a slightly orange color cast in the background.

It turns out that since you took a photo of a known perfectly neutral color source (and you must be able to know that it is, in fact, perfectly neutral -- if you just grab anything that looks gray to you (but technically isn't) then it can result in slightly inaccurate color balance.) THEN the computer can auto-adjust every pixel in the image (if I know the red value of "50" actually red as "60" then that means it's reading 20% too much red. If my "green" channel reads 53 but should read 50, then I have 6% too much green. If my blue value reads 40 but should have read 50 then it means I am lacking 25% of my blue.

Knowing this, the computer will mathematically tweak every pixel in your image and the result is spot on color balance.

Most cameras have a custom white balance that will let you take the photo of a gray card and use that to apply white balance. BUT... if you are in a situation where you know the color temperature of your lighting... then you can also usually just enter that value in the camera by doing white balance by kelvin value.

Since you aren't changing your lighting conditions (unless you have a window nearby in which case you are getting "mixed" light sources ... which creates a new problem) you should be able to set a manually selected white-balance level and the images should be consistent day in and day out for weeks and months on end. Some lights do shift their color slightly as they age... so I can't say the color will always be the same... but it should hold for quite a while.

 

[Robert Forester]

It's seems I can't shoot raw with this camera, but I can set the camera to P. In the P mode It will cut set aperture and shutter speed and I can manually set the temp on the lights. I played around 5000K and I think it might work good. Any other suggestions or thoughts on this? Thanks guys!

 

[Robert Forester]

Great info by the way!

 

[Designer]

It's seems I can't shoot raw with this camera, but I can set the camera to P. In the P mode It will cut set aperture and shutter speed and I can manually set the temp on the lights. I played around 5000K and I think it might work good. Any other suggestions or thoughts on this? Thanks guys!

I've been able to make pretty good adjustments using the JPEG files. If you can't capture the Raw files, then use the JPEGs.

I wouldn't try setting the WB by using the stated color temperature of those lights. More complicated than it needs to be.

Just shoot a target and go with that. If you don't mind interacting with each subject, shoot one shot with them holding a styrofoam plate or take-out box. That ought to break some ice!

If you do that for each one, you will have a WB target with the exact same light as your portrait shot. Easy-Peasy, and good for a few grins as well.