UPDATE: what is seen here looks to be one and the same problem as the horizontal white stripes; see Fujifilm GFX100S: Horizontal Bright Stripes in Blue Sky with Monochrome Conversions (aka PDAF Banding).
While evaluating image quality in Pine Creek Valley view to Freshly-Dusted High Peaks, my eye caught on horizontal dotted-line patterns. I wasn’t looking for defects, but the human brain is an incredibly good pattern recognition machine. And once seen, they are hard to unsee.
For lack of a better term, and because of the probable genesis, for now I am calling this defect PDAF pimples, as I suspect they stem from PDAF focusing pixels.
- Pimples are seen even without any unusual raw processing parameters. They may be faint but they are there with the right subject matter. Using perfectly reasonable adjustments can make them much more obvious.
- Pimples interact with the underlying subject matter, becoming visible or not, depending (see snow below, where they are absent). I have not determined what condition(s) are required for them to manifest.
- Pimples contaminate the entire frame; it is only a matter of whether they are obvious or not.
- Pimples are seen only along lines that are 36 pixels apart (not in-between the lines). There are 242 such lines on the GFX100S sensor.
- It’s not feasible to spot them out as they number in the tens of thousands, at least.
- I don’t know if they are related to Adobe Camera Raw (choice of raw converter). But they surely are in the raw data capture and so it should only be a question of raw processing accentuating or masking them.
So in addition to being a problematic camera for monochrome conversions, the GFX100S has an additional image quality problem with at least some color images under some conditions. On the flip side, all other aspects of the GFX100S are superb. Balance that 'equation' to suit. I have not seen such defects with my Sony A7R IV or Sony A1.
Why didn’t I see the pimples at home with work so far? Maybe subject matter and lighting. But up in the mountains literally the first day of shooting and the first image I chose, this issue cropped up. I think these pimples are also in the Fujifilm GFX100, because I ran into similar manifestations with aggressive monochrome conversions. But this is color.
They remind me of the Leica M10 Monochrome pimples except that in this case they occur only along/on straight lines and they definitely involve particular subject matter.
Below, “pimples” can be seen along horizontal lines, those lines being 36 pixels apart. They are more visible with green luminance being boosted, but also still there without doing so. They seem to all have a black interior single-pixel dot with a surround of green. 2X linear enlargement for ease of viewing.