A reader saw something that looked like amp glow on dark-field photographs with his new GFX 50S II. I asked for raw files in the three mains shutter modes: mechanical shutter (MS), electronic first-curtain shutter (EFCS), and electronic shutter (ES). At my request, the exposures were made at ISO 1600 at 1/10 second. I had asked for the exposures to be made with a body cap on the camera, but the reader was confused and made them with the new 35-70 GF zoom and a lens cap. I’ll post his images, and mine with a GFX 50S I, all images with a 5-stop Exposure push in Lightroom.
There is a small amount of purple amp glow in the bottom of the images both cameras with MS and EFCS. For some reason that I don’t understand, the glow is less with ES.
Looking at the GFX 50S Mk II raw file in RawDigger shows what’s goong on:
The set of data on the left is for the whole image The set on the right is for a small square near the bottom. Note that all the channels of the area near the bottom have higher average. The change is greatest for the B and G2 channels.
I don’t think this is much of anything to worry about, but there could be some situations where it might be a problem.
I imagine that with proper application of dark frame subtraction this could be mostly eliminated.
You are probably right, but it would take a lot of averaging of the dark frames because the noise level is high compared to the systematic errors.
What is the pattern that shows in the GFX 50 S II images?
I’m guessing that has to do with distortion correction. The guy with the GFX 50S II didn’t test with a body cap, but with the 35-70 zoom and a lens cap.
Thanks, mystery solved! Now I’m tempted to see if my own camera (a Fuji X-T4) can make a similar beautiful pattern.
Given these findings, I think it’s reasonable to recommend using ES for long exposures in low light scenes, or with an infrared pass filter. I sure will going forward.