Sony’s Shading Compensation (Vignetting Correction) Whacks Raw Files Hard—Turn it Off When Shooting RAW
Related: optics, Samuel Chia, Sony, Sony A7R, Sony A7R II, Sony A7R III, Sony A7R IV, Sony mirrorless, vignetting
See my Sony mirrorless wishlist.
Ouch. I thought I had nailed down all nasty behaviors with Sony mirrorless years ago. Actually, I did note this issue way back in 2013 (and that it doesn’t even work properly at some apertures), but while I have long disabled , I had forgotten the details as to why.
I was re-alerted to this behavior by Samuel Chia: enabling Shading Comp whacks the raw file data—totally different raw file. But the other lens corrections do not alter the raw data. Who though that clusterf*ck up?
Fortunately, I have made it a habit for years to always turn it off. See my several pages of recommended settings and button programming for Sony mirrorless.
Samuel Chia writes:
Shading Comp actually applies to raw files. It was a big shock when I discovered it. ZZZ was very angry, it affected many of his tests and virtually every image he shot on this Sony to date. And it doesn't work well, often causing non-monotonic results, sometimes weird colour shifting and incomplete correction of falloff.
Usually this doesn't matter unless one does extreme 'stretching' as astro-imagers tend to call it. Sony and Nikon and Canon mess around with raw data too much for their mirrorless line up. They should all give us a button that lets us have unmolested raw data, regardless of how 'dirty' that data is. ZZZ joked about making T-shirts which say 'Don't molest my raw data!'
Below, RawDigger histograms overlaid show the very large change that Shading Comp makes to the raw file, whether in Compressed or Uncompressed mode. Perhaps pixel shift does not adjust at all (?), but I neglected to check that.
