Sony Aplha a7R II S-Log2 Color Match with Sony FS7

The Sony a7Rii has been out for a few weeks now and I’ve been curious about its potential to be used as a B-Cam with the Sony PXW-FS7 which has been a very popular camera in the last few months.  In theory the cameras should be pretty compatible color and performance wise.  Both cameras have the same lens mounting system, the same Sony color science in their processors, both can shoot in slog2 gamma, and another big feature that they share is the ability to record 4k UHD internally.

All the theory in the world only goes so far however, I wanted to see how that theory applied to the “real world”.  I set up the cameras with a DSC chip chart and rolled the cameras for a couple of minutes.  Unfortunately I was only able to shoot in HD AVCHD codec on the a7Rii because our SDXC U3 cards haven’t arrived yet, but for the purposes of this post that should not greatly effect the captured image.  To match as best I could I set the FS7 to MPEG422.

Camera Settings:
a7Rii
AVCHD 1920×1080 24p
ISO 2000
Sony SLEP 28-135 E-mount lens set at f/5.6
1/50sec shutter speed
slog2 (PP7)
3200K
Super35 Crop mode

FS7
MPEG422 1920×1080 24p
Sony SLEP 28-135 E-mount lens set at f/5.6
1/48sec shutter speed
Custom Mode slog2
3200K

 

The proof in the pudding.
slog2Color Compare Slog2As you can see the two cameras were very similar to each other in slog2 right out of the camera.  The a7Rii exposed just a tiny bit brighter than the FS7 but well within workable range.  Depending on how well your monitor is calibrated you might also see that the a7Rii is a little bit less saturated, but again definitely within an acceptable margin of the FS7.

 

CorrectedColor Compare Corrected

To correct the images I used Pixel Film Studio’s LUT Loader for Final Cut Pro X, which I talked about in a previous post, to load up a slog2 to REC709A 3D LUT.  I did a little tweaking with the saturation and brightness features of the LUT Loader plug in to match levels and then used a color corrector to massage them into the state you see in the image.  The largest challenge was working with the red values.  As you can see in the waveform, the largest difference between the two is how each camera handled the red values.  The a7Rii has a much higher luminosity in red than the FS7.  I am by no means a colorist and I would wager that the difference could be corrected for easily by someone who knows their way around color.  It might also be possible to correct it in camera on the FS7 using the paint menus, but that is a post for another day.

Verdict
I would be very confident in my ability to use the to cameras together and achieve a seamless result for any client.  With a little bit of practice I bet it wouldn’t even add much time to the overall process, once you knew what adjustments needed to be made for the match, much like a LUT you could have some presets made up that you apply off the bat and then make minor adjustments as needed.

 



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