5D mark iii with color irregularities (at high iso?)

[flydoc]

While shooting a football game at night with my 5D markiii I noticed that the color balance seems to be a gradient. In other words it varies between brown and green through out the photo.  I am shooting at 1/800 2.8 or 3.2 with iso at 8000 using a 70-200 2.8L lens.  I wonder if it is a problem with the camera, my shutter, the stadium lights, or just a high iso problem.  I can't really change my white balance in lightroom as the color is gradient and it varies through the image.  Any help would be awesome.  Any ideas? Here are 2 sequential images. Notice the color balance in the top half of one and the bottom of the other.  The grass is green and brown depending on which part you look at. I did a custom white balance and should have changed it as the night progressed, but this is the same whether I use auto white balance or preset or custom.  

[flydoc]

[flydoc]

[flydoc]

Notice the forground grass color in one matches the background grass in the other and vice versa. Virtually all of the photos have this variation within the photo.

[flydoc]

[RobertTheFat]

I'm guessing it's a combination of inadequate stadium lighting and the overall underexposure of the pictures. The high ISO could be involved as well, if it caused a change in the sensor's sensitivity to different colors. I've never used my 5D3 at ISO 8000, but I've seen it handle colors well at ISO 2000 under pretty dodgy light.

It's a high school game, right? The lighting of high school fields is notoriously bad. Your eye corrects for some of it, but the camera doesn't.

If I were in your situation, I think I'd do a click white balance on the stripes in the referee's shirt and go with the result.

[flydoc]

Robert, thank you for the info.  I'm going to try 1/640 shutter and drop the iso to 6400 next week.  I've heard of people underexposing and then "pushing" it in light room so I can drop the iso even more.  Do you think it could be the shutter?

[RobertTheFat]

---

@flydoc wrote:

Robert, thank you for the info.  I'm going to try 1/640 shutter and drop the iso to 6400 next week.  I've heard of people underexposing and then "pushing" it in light room so I can drop the iso even more.  Do you think it could be the shutter?

---

One way the shutter could be involved is that 1/800 of a second is a lot faster than the flicker rate of a bulb operating on alternating current. Even if they do something tricky like using 3-phase current and wiring half the bulbs in a different phase, your exposures will come at random times in the AC cycle. Even an incandescent bulb is likely to have its light output vary enough (in intensity and probably also in color) to be noticeable. The effect is that some of your pictures will be less exposed (and probably redder) than others. That may not be the whole cause of your problem, but it might be a contributor.

In any case, grass, which looks very green in daylight, is not guaranteed to look nearly as green under artificial light. Incandescent light, which is much redder than daylight, is sure to be short of green.

One further point: Focal plane shutters achieve their high speeds by having the two blades form a slot that travels across the sensor. So the actual time the exposure takes is longer than the time that any part of the sensor is illuminated. If the color of the light is varying, it's possible for one side of the sensor to see a color different from what the other side sees. And since I'm pretty sure that the shutter blades travel vertically in a 5D3, that could help explain what you're seeing.

[g8trgirl]

I am so glad you posted this because I am having the SAME issue. Please let me know if you figured it out.