I am running RawTherapee 5.8 under Linux. Quite happy with the software so far (I generally get really nice colors from the start , but the RAW preview in the editor window is blurry / unsharp. I have made the following observations:
only RAW files are affected. JPEGs viewed in RT or other software show the same level of sharpness at the same size.
JPEGs exported from RT are fine.
the 1:1 / per pixel preview seems to be fine.
Is there some setting I may have overlooked? Is there a way to activate high quality rendering for the preview?
RawTherapee āforcesā you to go to a 100% (1:1) view to see some of the changes in detail or detail in general.
Those tools are marked with the 1:1 icon.
This from RawPedia:
Note that the effects of some tools are only accurately visible when you are zoomed in to 1:1 (100%) or more. These tools are marked in the interface with a ā1:1ā icon Zoom 1:1 next to the toolās name.
The preview image is downscaled with a ātiledā interpolation. This is a good compromise between speed and quality. There are only a few other ways we could scale: Scaling: GDK-PixBuf Reference Manual
This is a well known feature of the nearest neighbour interpolator. It looks sharper to untrained eyes but it causes a lot of artifacts: the whole point of interpolation is avoiding those artifacts without losing too much sharpness.
Well, from an academic point of view that is certainly true (in the end anything not viewed at pixel level will be interpolated to some extent) but itās not a practical solution to the problem that the preview is definitely blurry. As a user Iād rather trade a few artifacts for a sharp picture.
I wonder how other RAW editors such as darktable manage to provide a sharp preview? To my untrained eye everything looks fine thereā¦
The biggest downside of āNearestā is that it distorts the image depending on the actual size of the preview. This is because entire rows or columns of pixels get left out when performing this type of scaling - it is inherent to the algorithm. You can clearly see this if you compare the text āFIDDLERāSā on the bottle in image 1 and 2.
The only feasible alternative I can think of, is to implement a custom rescaling, such as Lanczos or Sinc rescaling. Thatās not the easiest of tasks and will likely slow down the preview rendering. Hard to judge whether it would be worth itā¦
Lanczos and Sinc are deadly slow if correctly implemented for large reductions in size, very likely to happen for image preview.
FWIW I had good results with a mixed approach. First I reduced the image by half (it is fast, just replace four pixels with their mean value) one or more times until the image was sligthly larger then required, then I used Lanczos for the final reduction.
The algorithm is rather fast and the result is good enough.
Iām late to this discussion, but how did you switch to nearest rendering? I canāt stand editing pictures in this blurry mode, even though the image wonāt be displayed correctly. When being zoomed out I donāt care about 100% image correctness, I care about the overall colors and look. Then after the fact I can zoom into the details. It would be fantastic so you could toggle between the two options so you have the best of both worlds.
Welcome to the forumā¦one caveat is that the software might use a different pipeline to process the image for export, ie more like what you would expect from the 100% view and so your exported images might not match your preview anywayā¦ Darktable now has a toggle to do the full processing for the preview if you like but its very very slow so just good for checking what the full quality export will look likeā¦ I think in RT you can place some small windows to check parts of your image at 100%ā¦this can help to guage your sharpness and other aspects of detail in the imageā¦ you could look at ART. I think there is a mode in the ART preview that will show adjustements at less than 100% zoomā¦
Thank you for the info! I knew of the small zoom windows indeed, I just donāt have as much fun editing looking at a blurry pciture, but your answer certainly provides me with some things to check out!
, but the RAW preview in the editor window is blurry / unsharp. I have made the following observations:
