What could be the cause of this?

Macro_Cosmos · Post by **Macro_Cosmos** » Wed Jun 17, 2020 10:16 pm

Larger here: https://flic.kr/p/2jcHUM8

This is really weird. While the Laowa 25mm can barely resolve 400lp/mm at 5x, the Z6 gives me something funny and also worrying, despite the crisper more contrasty images (somehow, Z6 is 24MP and D810 is 36, at ISO 64! 8 years and BSI makes such a difference, or maybe Nikon is baking their raw files? Or maybe it's both).

I also cannot explain why the dust isn't rendered totally black anymore. I think I turned on the lights above my optical bench, but I really don't think it would cause the banding.

That said, this never shows up in normal shooting.

What should the next step be? I'm thinking about using a 10x objective, and also a 5x one to compare to the Laowa. Unfortunately, the D810 I no longer have.

rjlittlefield · Post by **rjlittlefield** » Thu Jun 18, 2020 8:02 am

Have you tried shooting the chart multiple times, with a slight shift between shots?

I would be interested to know if the odd checkerboard problem moves around the image, or if it always appears around the same pixel coordinates.

--Rik

Macro_Cosmos · Post by **Macro_Cosmos** » Thu Jun 18, 2020 10:47 am

rjlittlefield wrote:Have you tried shooting the chart multiple times, with a slight shift between shots?

I would be interested to know if the odd checkerboard problem moves around the image, or if it always appears around the same pixel coordinates.

--Rik

I have one shot in my catelogue, but from memory, I took a series of images using my stackshot. Each "good focus" one had this problem.

As for shifting the chart, haven't done that yet. Great suggestion, I shall give that a go.

- shift target slightly between shots
- try using 5x objective
- try using 10x objective
- try using 2x objective
- speedlight illumination

Current plan in an attempt to replicate the issue. My money's on Nikon's processing (debayering error).

chris_ma · Post by **chris_ma** » Thu Jun 18, 2020 11:47 am

does this happen with both, jpeg and RAW files?
and in different RAW processors?

Macro_Cosmos · Post by **Macro_Cosmos** » Fri Jun 19, 2020 6:44 am

chris_ma wrote:does this happen with both, jpeg and RAW files?
and in different RAW processors?

Didn't shoot jpeg.
It shows up regardless the processor used for raw images, it even shows up as desaturated pixels when using rawdigger.

I'll make sure to have in-camera jpeg setup when I try to reproduce this problem.

chris_ma · Post by **chris_ma** » Fri Jun 19, 2020 7:33 am

hmm, interesting...

could be a result of some in camera RAW preprocessing, like if they had to map out some dead pixels (too many pixels for that, but something similar)

or it's simply a bug in the camera.

Pau · Post by **Pau** » Fri Jun 19, 2020 8:09 am

Just a maybe stupid guess, but its periodicity and wavy aspect suggest me an electromagnetic interference.
I would try changing the camera position, and to turn off or change distance of computers, transformers, phones, LED light electronics, etc

Macro_Cosmos · Post by **Macro_Cosmos** » Fri Jun 19, 2020 1:52 pm

Pau wrote:Just a maybe stupid guess, but its periodicity and wavy aspect suggest me an electromagnetic interference.
I would try changing the camera position, and to turn off or change distance of computers, transformers, phones, LED light electronics, etc

The waves aren't present in the vertical or 45deg line-pair patches though, so this shouldn't be the case at all.

chris_ma wrote:hmm, interesting...

could be a result of some in camera RAW preprocessing, like if they had to map out some dead pixels (too many pixels for that, but something similar)

or it's simply a bug in the camera.

Yeah it's pretty... I don't know a good word, esoteric?
That would be a worrying amount of dead pixels to map out. It could be the OLPF doing something stupid. The weirdness isn't present in any other patches. There's horizontal ones and 45 degree ones at both directions, none display such banding.

This is pretty annoying though. 400lp/mm is perfect for testing 5x objectives.

Lou Jost · Post by **Lou Jost** » Fri Jun 19, 2020 2:31 pm

To me the periodicity suggests moire

Lou Jost · Post by **Lou Jost** » Fri Jun 19, 2020 3:22 pm

Alos I see some clear color moire in the pattern.

Macro_Cosmos · Post by **Macro_Cosmos** » Sat Jun 20, 2020 2:22 am

Lou Jost wrote:To me the periodicity suggests moire

Yeah this is the same suggestion as what a friend of mine in photonics claims.
"Camera probably tried to algorithmically fix moire, which backfired because Nikon (implying that Nikon's software can be funky)".

D810 is free from the issue because of the higher resolution.

This isn't good news. It means that Nikon compensates for aberrations in-camera, and it can't be turned off to preserve the purist raw file.

Of course, this isn't to say Sony or Canon isn't guilty, but multiple wrongs isn't a right. I don't mind pre-baking, just let me turn it off if I want to.

Beatsy · Post by **Beatsy** » Sat Jun 20, 2020 4:50 am

Macro_Cosmos wrote:...Of course, this isn't to say Sony or Canon isn't guilty, but multiple wrongs isn't a right. I don't mind pre-baking, just let me turn it off if I want to.

Amen to that. Sony "star-eater" is an infamous, continuing example of the trend. RAW isn't anywhere near as RAW as it used to be. Marketroids are probably scared of the masses seeing the *actual* sensor output and stopped the engineers from making it available. Hmm. That last was penned as a jokey conspiracy theory, but now I've said it...

Lou Jost · Post by **Lou Jost** » Sat Jun 20, 2020 6:13 am

Yes, Beatsy, it is a spreading and terrible trend that makes things very hard for those of us who need to do something non-standard with our photos. Pentax went the same route with the K-1 Mark 2, which is why I chose the Mark 1. Panasonic's S1R lossy-compresses its RAW files and that can't be turened off either. That's another related despicable trend.

Duke · Post by **Duke** » Sat Jun 20, 2020 7:06 am

For a just moire artifact looks too irregular in it's shape. Why would it have such wavy form? It looks more like a cleaning stains from detergent on the IR-filter.
The image processing chip does some funky stuff with the contrast enhancing as well, but it doesn't explain particular reason for that type of wavy shape.

Lou Jost · Post by **Lou Jost** » Sat Jun 20, 2020 7:21 am

For a just moire artifact looks too irregular in it's shape. Why would it have such wavy form?

Each transverse band has exactly the same shape, the same waves in the same places. This suggests to me that the iregularity is due to surface waviness of the target.