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, <nhr...@gmail.com > > > > <mailto:nhr...@gmail.com>> 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 ____________________________________________________________________________ darktable user mailing list to unsubscribe send a mail to darktable-user+unsubscr...@lists.darktable.org
