Question : Pixelpipeline for culling and preview in EDIT: _lighttable_ compared to darkroom

Software darktable
1

I have a couple of questions regarding comparing pictures and how they are rendered in darktable

I can compare pictures in many ways:

  1. Comparing exported output from darktable using an external file viewer.

  2. Stay inside darktable and change files to view in EDIT: darkroom, back and forth.

  3. Using darktable snapshots and compare inside EDIT: darkroom.

However, I can also use Lighttable:

  1. Lighttable Culling.

  2. Lighttable Preview.

If I use 1,2 and 3, then I assume that the full pixelpipeline is used and all details are rendered, except for special cases like raw chromatic aberrations, which will not render depending on zoom level.

If I use alternatives 4 or 5, Lighttable Culling and Lighttable Preview, what kind of rendering is used, the full pixelpipeline or a simplified lighter version? If it is simplified, then how? Lighttable Culling and Lighttable Preview clearly respects changes done to the raw files, at first glance, so many changes are rendered as per normal.

2

From what i gathered you will always see the result of the full pixel pipeline.
One exception being the thumbs with some combo of preferences, at least with my setup.

3

Hello @grubernd and all,

I see some differences, at least indirectly. What I have noticed is that Lighttable > preview seem to respond faster when switching between pictures compared to the same switching of pictures in darkroom. Another finding is that if I zoom and move around Lighttable > preview then I consume less GPU power than doing the same thing in darkroom ($ watch -n 2 nvidia-smi). I interpreted this as Lighttable > preview rendering in a ‘simpler’ way. I have not been able to trace this to any documentation or other discussion though. My setting is ‘very fast GPU’ so both pixelpipes, ‘preview’ and ‘full pixelpipe’ render on my GPU.

The only indication, so far, are the names ‘preview’ and ‘full pixelpipe’ in preferences > processing > OpenCL scheduling profile > help text. They seem to indicate some difference.

4

By full pipeline you mean “fullsize aka every pixel ever” or “all the selected pixels through all the tools”?

I mean the latter…

So yes, rendering and display speed according to required size and available cache sizes. e.g. you can make lighttable culling switch images at 100% size without noticable delay on any hardware by pre-rendering the fullsize images using the commandline processor…

5

I also mean the latter, “all the selected pixels through all the tools”. I wonder if I miss some very fine structure changes if I compare in lighttable culling/preview compared to if I compare inside darkroom.

6

Once you zoom to 100% you see “everything”.
The difference is that in culling mode the whole image gets rendered and then displayed,
while in darkroom only the currently visible part is rendered and displayed.

In culling you can pan around, in darkroom every pan will result in new parts being rendered.

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