...a Flat PS can be useful but a Log PS will typically throw away more information when there is only just enough to start with. Snake Oil - probably yes! BUT when there are more than 10bits to play with things get flipped and a 10bit log encoding is a much better way to store the information.
If you mean Snake Oil as in, "a remedy for all diseases" then yeah, I totally agree.
I think we should define what a "Log" picture style is because technically all picture styles are log. What I think would be an accurate definition is a picture style that is designed to capture as much of the camera sensor's dynamic range as possible without regard to how the image appears aesthetically and allowing as much latitude as possible for color grading in post production. The log settings in professional cameras that record 8-bit, like the Canon C100, are hardwired into the firmware and probably don't work the same as downloadable "log" picture styles. What is interesting with the C100 is that most of the posts I've seen on the subject show that users seem to prefer shooting Wide DR Gamma which is a "flat" picture style rather than the Canon Log Gamma setting.
We should also define what a "flat" picture style is. It is basically a gamma (contrast) adjustment of the Rec. 709 mode.
When I first learned photography, my college professor had us shoot what seemed like endless tests of classmates holding Kodak gray cards in every conceivable lighting situation. Then he would have us plot the H&D curve of our negatives.
H&D stands for Hurter and Driffield who were the 18th century photographic scientists that discovered an interesting phenomena which is that when plotted on a graph using density as the y axis and the log of exposure on the x axis instead of getting a straight line they got an S-shaped curve. There were three parts to the curve, in the shadows there's the toe, the majority of the curve is more or less a straight line and the angle of the slope is called the gamma and finally the highlights fall on the shoulder where the curve flattens out and adding exposure has no effect--well sometimes adding a lot more exposure will reverse that part of the curve and is known as solarization. Ever seen a black sun in a photo? When shooting black and white we learned to expose so that important shadow detail is above the base + fog level and develop for the highlights so that important highlight detail isn't compressed into the flat shoulder part of the curve.
Well that was a whole semester's class in one paragraph. I like to see pictures and graphs so here's one that illustrates what an H&D curve looks like:
The base of film isn't completely transparent and the maximum density doesn't block all light so the usable area between base plus fog density and D-max is what we've got to work with when shooting film. Likewise, with 8-bit digital we have between 0-255 bits to play with and in 10-bit we've got 0-1023. That's a big difference but--most color displays are only 8-bit. Wait, you say, but my monitor is marketed as a 24-bit display! Yes, it is an RBG display, 8-bits per channel, so the maximum range is still just 0-255 per channel or --
256 shades of red, green, and blue, for a total of 224 or 16,777,216 color variations. A 10-bit display can theoretically show up to 1.07 billion color variations. I say "theoretically" because I've worked with both 8-bit and 10-bit displays and 99% of the time I couldn't tell the difference. About the only time that it really matters on a display is when you have subtle color gradations like in soft clouds then you can clearly see "banding" in 8-bit displays.
Back to the film lesson, we don't look at negatives we look at a print, either on paper or on film projected on a screen. Prints are usually higher in contrast than negatives and print emulsions show brighter whites and darker blacks than negative emulsions. Properly exposing a negative involves measuring light and making calculations while make a print is more of an art. Likewise when grading log and flat picture styles we're looking at it aesthetically, not scientifically. The more you have to work with in your original the better be it a film negative or a flat or log (preferably 10-bit and up).
Can you mix flat, log, H.264, 4:2:2, 4:2:0, etc.? Sure, it is done all the time. Will it match in a multi-camera setting? Depends--it is often hard to match cameras that are the same make and model. It is best if you have the chance to do some testing before the shoot. Which takes us back to that college photography class--shoot someone holding a gray card (or color chart) in every lighting situation you are likely going to encounter.
[EDIT] Sorry, got a little wordy there and forgot to point out this post about picture styles. Seems like most of this was worked out in 2011 and there hasn't really been any breakthrough flat picture styles for DSLR's since then.
http://philipbloom.net/blog/pictureprofiles/
