Tried PNG export and it does not show any artifacts. Tried JPEG with 95%
quality and it still shows the artifacts. It shows artifacts at 100%
quality too. Should I be try changing something else?
I don't recall making any changes, but that does not mean I did not
accidentally made changes. Laptop touch pad is acting up and many times
moves the pointer at most unexpected place automagically. This is why I
wanted to try restoring to defaults.
I don't care about size as much. But kind of scratching my head as
settings show max size 0 for both fields. This should export to original
image dimensions as I understand it.
Thanks for the help, hopefully we can get to the bottom of it.
Regards,
Niranjan
On 11/25/19 11:16 PM, Remco Viëtor wrote:
On mardi 26 novembre 2019 07:18:29 CET Niranjan Rao wrote:
Ubuntu 18.04, darktable 2.6.2
More and more research I do, I am getting convinced that this is a
problem with one of the updates of darktable or somehow my settings are
screwed up.
I have photos from same raw exported at different times. Please check
the photos of two giraffes at
https://photos.app.goo.gl/K35BT8X5HGhSzwQj6. One was exported back in
August. I don't know if I got a darktable update since then or not.
Exported same photo with same style today and it shows artifacts. None
of the older images show these geometric patterns and same image
exported today shows it, no style changes since then.
I can start with scratch, but afraid of loosing all my tags and edits.
What will be easiest way to restore darktable to it's default values
without loosing my edits and tag information.
I notice you didn't answer Kofa's question (cited below). <250k filesize for a
16 megapixel image means that the image is strongly compressed, and that can
induce artifacts. You have basically 1 byte to encode 64 pixels, that's 1 bit
for 8 pixels (or 24 bytes)... And I know that that's not how jpeg compression
works, but it indicates the amount of information that is lost.
I'd suggest trying less compression and/or enable dithering on export. Notice
how the 1.6 MB jpeg file of the giraffes does *not* show the banding in the
sky.
If I load that file in darktable and reexport to a smaller size (~250kb) I do
get the same banding you see, at a quality setting of 25-30%. Those are not
geometric patterns, btw, the bands follow intensity levels in the original
image.
If you need the small filesize, ask yourself if you really *need* a 16M image
for the exported version. For screen display, 1960*1080 (~3.5M pixels) is
usually enough, and that in itself is less than 25% of the original image. An
image reduced in size to 1080 height (full screen for me) at a quality setting
of 85% shows no banding, and the file size is ~160 kB (so less than your bad
jpg).
Remco.
On 11/13/19 10:24 PM, KOVÁCS István wrote:
On Wed, 13 Nov 2019, 17:23 Niranjan Rao, <[email protected]
<mailto:[email protected]>> wrote:
Darktable version: 2.6.2 on Ubuntu 18.04
I am seeing patterns in the sky
To me, it looks like Jpeg compression artifact. It's a high-res photo,
yet only about 200 kB. Have you tried exporting into png or tiff to
see what the image actually looks like before compression? If you are
no artifacts in lossless files, try exporting at a higher Jpeg quality
setting, and, if you really need small files, use a lower resolution
instead of increasing compression (lowering quality).
Kofa
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