Exposure and color temp difference between AF100 and 5Dm2?

S

stevedocmaker

Well-known member
I know this crosses over a couple of other threads, but read to the end to see the new finding/discussion.

I've been testing my AF100 along side my 5Dm2. I'll be doing a two camera shoot and I want to get the images as close to each other as possible. I've attached two frame grabs. I'm a little disappointed with the results, see for yourself.

I've been shooting with the 5D in with the following setup:

Neutral setting
sharpness: 1
contrast: -2
color: -2

I found this gets me very close on the AF100:
Detail: -2
Vdetail: -2
Chroma: -2
Master Ped: -2
Gamma: HDNORM
Knee: LOW
Matrix: NORM2

Another user found that the auto color balance was noticeably cooler on the AF100. I used a color meter in my shoot, and I found that I had to set the AF100 400 degrees COOLER than the 5D, which I think gets tehm pretty close. I can live with this difference, but it's big enough that I think something's off in one or both cameras. There's no way to know which without more cameras to compare, but in my work with the 5D I've always found that the color meter gets me right on target.

I also found that to get images with identical exposure, I have to set the AF100 two thirds to one full stop down from the 5D! The images below are from clips with the 5D set to f5.0 and the AF100 set to f6.0 (same ISO, 50 fps on the 5D and 180.od/24p on the AF100).

Can anyone explain this??? Is this a glitch in the AF100? Is it a glitch in my AF100? Shouldn't f5.0, same ISO, virtually same shutter speed yield identically exposed images? Or can this difference really be explained by the 2 frame difference in shutter speed?

Also, Look at the white paper in the scene. It's noticeably hotter in the AF100 frame. I will continue tweaking to see if I can't get this blow-out tamed, any suggestions?

Also there is a slight magenta tint to the shadow on the paper in the AF100 shot. I may try shifting the color phase -1 or -2 and see what happens, but the mid-tones of the AF100 already appear slightly greener to my eye.

The only other major difference to my eye in the two clips when viewed full frame is that the AF100 footage is a bit noisier, but that is to be expected given the difference in sensor size. (Of course the 5D clip is ooozing with moire - no surprise there).

Camera Comparison.jpg
 
The Canon has a predisposition towards redder images; you can compensate by setting the color temp setting in the AF100 lower. The AF100 colors are spot-on, especially when using norm1 matrix and HD NORM gamma -- it renders colors exactly as the eye sees them in that circumstance. The Canon look isn't about accuracy, it's about a "look", and the warmer/redder tones make caucasian flesh stand out. You can match that on the AF100 if you want to.

For sensitivity -- the Canons are notorious for being quite optimistic in their sensitivity ratings. The AF100, again, is spot-on. use a light meter and a gray card, you'll find out that 400 ISO is exactly 400 ISO on the AF100, but it might be more like 320 on the Canon. That's why, when you set them at the same ISO, you have to stop the AF100 down further -- because the Canon isn't truly at that ISO.

As for a magenta tint -- how are you white-balancing? I find manual white balance is more accurate than the daylight preset, which does have a bit of a magenta tint to it. Teh AF100's tungsten preset is pretty much spot-on though. But if you can, execute a manual white balance.
 
Thanks for the insight, it's reassuring. Especially in reference to the exposure difference.

As I said, I'm white balancing from a color meter. I don't know of any way to calibrate a color meter, but one would think that 4600 degrees in one camera would be identical to 4600 degrees in another. I use a color meter because the Canon is such a pain to white balance with a card. I'll try the card method though and see if it gets any closer.

That pinkish shadow on the paper is what bothers me. Overall, the AF100 image is a bit greener than that of the 5D, which is falls in line with what you have said about the Canon color. And the rest of the items in the AF100 image are more accurate than the 5D clip, which again supports what you said. But, that shadow on the paper just jumps out as magenta. if I try to adjust color phase for the shadow, it looks like the rest of my image will get ugly. You can see from the two shots that the Canon image is much better in regards to the white paper. So to me it looks like there's just a quirky glitch in the shadow's density range, which for some reason has a slight magenta shift. Probably not noticeable unless you're shooting snow on a sunny day, or perhaps someone lecturing at a white board.
 
I hate to have to say it, but -- no, I wouldn't expect the results to look similar just because you WB'd to the same rating on the meter. Different cameras, different color profiles, it just doesn't usually work out that way. Just like you found with the exposure... it doesn't line up that way.

If you want the best results from the AF100, I do highly recommend a proper white balance off of a white card placed in the light that you're intending to shoot under.

Also, look into the scene file thread for Editman's 5D Mark II emulation scene file, it might help you get the two units closer in color and shadows and gamma. Good luck!
 
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