Bug #8700

Preview Pictures of photos in lighttable mode are blurry

Added by scotchbonnet - about 8 years ago. Updated almost 2 years ago.

Target version:
Start date:
Due date:
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Estimated time:
Affected Version:
git development version
hardware architecture:


When viewing photos in lighttable mode I noticed that the preview pictures are displayed much more soften than the photos really are. This happens on all zoom levels.
This problem is most noticeably on photos, which got rotated in darktable mode.

lighttable.png (1.18 MB) lighttable.png blurry Anton Keks, 09/29/2012 04:59 PM
darkroom.png (1.5 MB) darkroom.png sharp Anton Keks, 09/29/2012 04:59 PM


#1 Updated by Anton Keks almost 8 years ago

It was blurry before, but after today's update from unstable PPA it got even worse. Now all photos looks like they are out of focus in Lighttable mode, but they instantly get sharp after entering Darkroom mode.

Today I received this version: 1:1.0+1632~g684370a-0pmjdebruijn1~precise
It seems that it was better with previous builds, like 1:1.0+1545~g84773bf-0pmjdebruijn1~precise

#2 Updated by Tobias Ellinghaus almost 8 years ago

  • Affected Version set to git development version
  • % Done changed from 0 to 20
  • Priority changed from High to Medium
  • Status changed from New to Incomplete
  • Category changed from General to Lighttable

Please check both the maximum size in the preferences (this used to determine the thumbnail size, too, right?) and if you are using embedded previews. I never saw anything like that.

#3 Updated by Ivan Korotkov almost 8 years ago

I can confirm this with latest darktable from git (updated Oct 2). Max preview size set to 2400x1400.
Embedded previews are displayed sharp, but previews of processed images (or all images when 'use half-size raw' is selected) are blurred.
My best guess is that this happens due to insufficiently large mipmap level being selected by |dt_mipmap_cache_get_matching_size| (it looks like it tries to find nearest size, not nearest greater or equal size).

#4 Updated by Johannes Hanika almost 8 years ago

can you try to set your preview size to something reasonable (a little smaller than screen resolution)? there's a slight chance you pay to compute that oversized thumb and then we use cairos blurriest resampling mode to bring it back to your screen size.

of course also check the interpolation mode in your preferences.

#5 Updated by Anton Keks over 7 years ago

Johannes, I think you are right. After connecting a bigger monitor, the thumbs now look decently sharp, but making darktable window smaller blurs the image again considerably.
The interpolator is set to lanczos3, but it seems to be irrelevant here.
Today on IRC houz also mentioned that this might be a scaling issue. Would be great to fix it!

#6 Updated by Anton Keks over 7 years ago

And it is important to note that there are no blurring problems with embedded jpeg thumbnails, which are probably not stored to the cache?

#7 Updated by Tobias Ellinghaus almost 7 years ago

  • System set to Ubuntu

IIRC there were some changes to this. Jo, can you comment on it? Can anyone else say if it got better/worse? What I noticed is that the preview is often blurry at first but gets sharp once it got processed in high resolution.

#8 Updated by Simon Spannagel over 6 years ago

  • bitness set to 64-bit
  • Assignee set to Johannes Hanika

#9 Updated by Pedro Côrte-Real almost 6 years ago

I've been noticing this as well. With the image size set to 2000x1200 on a 720p screen the lighttable view is much softer than the darkroom view at the same size. Setting the image size to 1400x800 doesn't help. This is with today's master.

#10 Updated by Pascal de Bruijn almost 6 years ago

As Johannes remarked, changing:

src/views/lighttable.c: cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_NEAREST);

To CAIRO_FILTER_GOOD might help.

#11 Updated by Pascal de Bruijn almost 6 years ago

Actually that should probably be:

src/views/view.c: cairo_pattern_set_filter(cairo_get_source(cr), CAIRO_FILTER_NEAREST);

#12 Updated by Pedro Côrte-Real almost 6 years ago

Setting the view.c line to CAIRO_FILTER_GOOD doesn't seem to have any effect.

#14 Updated by Aurélien PIERRE almost 2 years ago

This should be fixed with the option "high quality thumb processing ", in preferences > GUI options

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