Mottling in dark areas in Lightzone on Mac


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bburchsted
Mottling in dark areas in Lightzone on Mac

Dark areas show up noisy and mottled in Lightzone on a Mac, but when viewed with Preview, the tiff files are smoother. The file is a scan of a negative, scanned at about 1200 dpi on an Epson V750 scanner, 16 bit grayscale.

I would attach two screen shots, one of the file in Lightzone, the other in Preview, but I am not permitted to attach files, apparently. Nevertheless, the Preview is 'smoother'.

(Is there a way to attach files?)

The mottling effect gets exaggerated with 'developing' in LightZone, and is transferred to the prints. That is, it is not only a render issue on the screen.

Is there some setting I have wrong that causes this mottling affect in dark areas?

Thank you.

Bob Burchsted

Jacal
Attachments are currently

Attachments are currently disabled because of some security issues. Upload your files to filebin.net and post a link here. (You can also use Dropbox or something similar.)

Make sure to also include one of your scans, tiff files come in many forms.

Have a nice day!

- Mart

bburchsted
Attachments uploaded

https://filebin.net/fzff6kw9jwxbwvhu

Contains screen shot of Preview, screen shot of Lightzone (just the lower left corner in both cases), and the original scanned tiff file.

Thank you.
Bob

Jacal
I can see, what you mean.

I'm not at home currently and don't have all my tools and toys at hand. I thought, LightZone might not properly support greyscale colour space, but it looks the same with this image, converted to 16-bit rgb.

I'll see, if I can find out something sensible at the end of the week. Other forum members are invited, of course.

Be well!

 

- Mart

bburchsted
I had tried another profile

I had previously tried converting the grayscale profile from the Epson scanner to Adobe RGB (1998). It seemed to 'brighten' the whites a bit, but the dark areas still had the noise. The noise gets excarbated when processing the picture. My wife has Photoshop on her computer, and she did not see the noise there.

Thank you for taking the time to look at this. I don't know if it is a problem for other people - I'm not sure how many Lightzone readers are scanning (black and white) film.

Best Regards

Bob

 

Jacal
For comparison,

screenshots of the bottom-left part of the image at 50 % in four programs. On Windows, darktable running in a Linux virtual machine.

link

 

- Mart

bburchsted
Interesting comparison

Interesting. It almost looks like the LightZone is using 8 bits instead of 16 (the Epson scanner 'supposedly' uses 16 bits), but even the Gimp (which I believe is still 8 bit) shows a better gradation. I'm not familiar with the other programs (heard of RawTherapee, but never used it).

Thank you, again, for your time in this matter.

Bob

Jacal
I have used Gimp 2.9,

which does support 16-bit and more, and will become the stable 2.10 some day, some year.

But the  gradation is better also in IrfanView, that is only 8-bit capable.

I remember I have noticed unpleasant transitions from black to (dark) grey also with some raw photos, blaming LightZone's demosaicing algorithm for them. It might be something completely different, like Python would say, but it is out of my humble abilities to diagnose it.

Mart