Sony skin tones

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wwc Forum Member • Posts: 51
Sony skin tones
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This is a follow-on to this thread by AlphaPhotography, where he supplied a raw file from his A7RII which demonstrated (in his opinion and others') the yellow-greenish tint that seems to affect the skin coloration of light-complexioned people when taken with a Sony cameras.

In that thread, I suggested using the hue and saturation adjustments in Lightroom's Camera Calibration panel.

I couldn't find much information out there about what exactly these adjustments do, but my theory is this: that panel controls where the red, green, and blue values from the sensor are mapped into the color space. They determine where the corners of the gamut triangle are, like the one shown below. This picture is a screenshot from my Mac's monitor calibration, and it shows where the red, green, and blue phosphors are in a CIE chromaticity diagram. The triangle represents the gamut of the display.

The camera's gamut is similarly, except that instead of the phosphors, the triangle's corners represent the colors detected by the RGB pixels in the sensor. My theory is that changing a hue slider moves the point in a manner that "rotates" around the (central) white point, and that changing a saturation slider moves the point toward or away from the white point.

By moving these points, you change how the RGB values from the raw file are mapped to the space of colors.

OK, so that's the speculative part. Here's the more practical part. I took two photos with two different cameras:

  • Sony A7 with FE 50 f/1.8, at ISO 1250, f/1.8, 1/125 sec
  • Olympus OM-D E-M10 II with Olympus 25 f/1.8, at ISO 1250, f/1.8, 1/125 sec

The ISO, f value, and shutter speed were the same for both cameras.

Here's the picture from the Sony, processed in Lightroom with all default settings except white balance (I set the color temperature 3150 and tint to +3) :

And the Olympus (using the same white balance settings):

These were snapshots taken in difficult lighting conditions: a mix of window light and indoor LED lights. But even though the light wasn't ideal, these pictures still serve to illustrate the issue.

Not surprisingly, the picture from the Sony has yellower-looking skin. The skin color from the Olympus looks better, in my opinion. My impression is that I usually prefer skin colors from the Olympus to those from the Sony.

I then modified the Sony picture by adjusting the sliders in the Camera Calibration panel, to try to make the skin color look as close to the Olympus as I could. Here's the result:

And here are the settings I used:

This isn't to say that the colors are perfect, just that it is possible to make the colors from the Sony look closer to the colors from the Olympus. And since a lot of people like Canon skin colors, it's probably possible to make colors from the Sony look more like Canon colors as well.

There's a limit to how much you can do with this. If you look closely, you'll see that the blue from the shirt is more saturated in the Olympus photo than it is in either of the Sony versions -- even though we had to desaturate the colors from original Sony picture in order to get the skin to look like the Olympus. The sensors probably have different spectral responses for their RGB sensors, and so it wouldn't be possible to make the pictures look exactly alike.

In Lightroom, these adjustments can be saved as a preset and I think they can be automatically applied when importing photos from a specific camera, which would completely automate the process.

If you have a color checker target and more controlled conditions, you would probably be able to do a better job making one camera's output look like another's. I think this is just a starting point.

Olympus OM-D E-M10 Sony Alpha a7
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