YiM1, Panasonic 12-42 F3.5-5.6 zoom (version 1)
Before I got the colour checking card, I did not have a really accurate way of evaluating how my cameras were treating exposure. As time went on, I was developing a general idea, but it was a slow process of trial and error. My previous conclusion was that the contrast and "dynamic range" of the three colour profiles of the Yi-M1 were very close. I did notice that the "Portrait" seemed to give a bit more shadow detail, so I thought it probably had a bit more dynamic range. I had little experience at all with the "Vivid" profile because it seemed too saturated for what I was recording. Now that I have the colour checking card, the first thing I wanted to find out was what differences if any there were.
I used the pixel reading ability of Corel Paint Shop Pro to read five pixels in each of the six grey squares of the captures ("Standard" w/EV = +0.0 and "Portrait" w/EV = +0.0". For convenience, I will call these colours (in order from darkest to lightest) "Black", "Black + 1", "Black + 2", "White - 2", "White - 1" and "White".
Graph Data:
The following are the brightness "[luma"] values in 8-bit form for some of the sample images:
[All JPEGs compressed level 1]
"YiM1-P4250002-Standard-ev0_0-12h42m50s970.jpg"
"Black" = 17.5 (below 20)
"Black + 1" = 60.9
"Black + 2" = 130.2
"White - 2" = 184.9
"White - 1" = 223.8
"White" = 246.0
"YiM1-P4250005-Portrait-ev0_0-12h55m21s883.jpg"
"Black" = 30.8
"Black + 1" = 78.2
"Black + 2" = 144.2
"White - 2" = 198.3
"White - 1" = 232.0
"White" = 254.4 (clipped)
"YiM1-P4250009-Vivid-ev0_0-15h00m51s788"
"Black" = 13.6 (below 20)
"Black + 1" = 59.6
"Black + 2" = 132.6
"White - 2" = 193.6
"White - 1" = 234.1
"White" = 254.8 (clipped)
"G85-00010-Standard-ev0_0-13h26m54s730"
"Black" = 54.9
"Black + 1" = 104.5
"Black + 2" = 163.0
"White - 2" = 207.3
"White - 1" = 235.3
"White" = 253.5 (clipped)
[2020-05-09 19:41 reformatted the above for consistency]
Special Cases:
There are three "special cases" I should explain. All have to do with the "White" or "Black" values. The far limit values are "0" and "255" If even 1 of the values of red, green or blue component values for any of the pixels tested is equal to either "0" or "255", then I have marked the resulting Luma value as "clipped". Since I only tested five pixels for each colour, it can be assumed that more pixels had such values. For such a case, I would prefer to adjust my exposure to better "contain" the exposure of that brightness level if it can be practically done. So if I see clipping, then I will probably adjust to eliminate it.
The "under 20" values are not as urgent. "Under 20" is a broadcast standard for "black" That is to say that any value under "20" can be presumed to be "black" for the purposes of North American television. That is all it means. It is commonly called "legal black", but that is a misconception. There is no "law" being violated. However, values below 20 can be "noisier" and are thus less reliable. But there is no guarantee that a value higher than 20 will be free of noise. One needs to study one's camera(s) to know how much of "under 20" can be recovered in post.
The Graph:
I graphed some of the values as "reciprocity curves" and there are a few things that can be said about the results.
First, the contrast situation was a bit worst than I thought -- not much, but definiitely worse. The reciprocity curves for the Yi-M1 are almost identical. Yes, there is slightly less contrast in "Portrait" profile, but only around a half stop less than the "Standard" profile. The exposure of of the "Portrait" profile appears to be about 1/3 stop lighter than "Standard". This accounts for part of the increased shadow detail. Unfortunately, to make use of the full dynamic range in "Portrait", I would need to expose at at about "EV = -1/3", which gives up some of that shadow detail.
In the "Standard" profile, the "Black" sample brightness is entirely below 20, which is "legal black". It was not clipped, but recovery is unreliable. I have recovered shadows in some cases, but my experience confirms this limitation.
The contrast for "Vivid" is even worse than "Standard". I did not bother to graph it. Now that I know how limited its dynamic range is, I don't intend to use it again.
The "G85 Standard" profile is included as a control (for comparison).
Finally, to find a single number value to compare the reciprocity for each profile I subtracted the "black + 1" value from the "white - 1" value. For these values, the lower results indicate less contrast. It is not necessarily true that one always wants less contrast, but for most of what I do, that would be my general goal.
In fact, I probably will not even use the G85 "Standard" profile very much. The G85 has profiles with even less contrast, which I will probably use more often. I doubt if I will use the Yi-M1 for video much in the future, but if I do, from now on, I will probably only use the "Portrait" profile. Since I use the "Histogram" function on that camera when chosing my exposure, I generally set it to "protect" my highlights that way. If I didn't, then I would probably try to reduce the exposure by "EV = -1/3" from now on.
Yi-M1 Standard 223.8 - 60.9 = 162.9
Yi-M1 Portrait 232.0 - 78.2 = 153.8
Yi-M1 Vivid 234.1 - 59.6 = 174.5
G85 Standard 235.3 - 104.5 = 130.8
But again I have purchased these on Amazon and they are rated better than the OEM and the bundled charger is a boon too.
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