Unacceptable delay if RT is being launched via the Windows Explorer via the WE's context menu in a folder with many images


I have a folder with RAW and JPEG files, altogether more than 1200 files. When I try to open any file via the context menu of the Windows explorer (“Open with RawTherapee”) the fan goes into overdrive but RT doesn’t open (or maybe it does after more than 20 minutes; I killed RT via the Task Manager). Is it possible that RT tries to create thumbnails of every image in the background in the folder?


Don’t know about RT but Windows Explorer is known to choke when it has a multitude of files in one folder. The Desktop has the same problem. The general solution is to have many folders with fewer files rather than one big folder with many.

PS Always remember to specify your OS and RT versions.

(Pat David) #3

This sounds like what may be happening? I’ll get a delay navigating into folders with many images sometimes as well (not from the windows context menu, but just navigating files in RT directly).

(Morgan Hardwood) #4

@christoph_s http://rawpedia.rawtherapee.com/How_to_write_useful_bug_reports


@afre Windows Explorer (in v. 7 and 10) works just fine and displays both JPEG and RAW files as thumbnails very quickly. The problem is RT 5.5.


@afre Also, if I open a RAW file with an image viewer like IrfanView, it happens immediately. I also tried Krita and Lightzone: No problem at all (apart from longer launch times, because the programmes are more complex than just a viewer).


@ patdavid Yes, I also noticed that. RT is extremely slow with directories that contain many large images, independent of the file system. Photivo is much faster in that regard.

(Ingo Weyrich) #8

Some time ago, when rt got a file name on start, it started without file browser (for reasons),
Then users complained about having no file browser in this case.
So the behaviour was changed (after discussing the issue). Of course having a file browser in rt in this case needs to process the thumbs, which takes time, especially if you open a folder in rt the first time.

Possible solution for Windows rt builders: Allow Open with rt with and without file browser by passing or not passing -R as argument to RT


Since processing the thumbnails can take veeery long with lots of images in a directory, I really think RT should simply open the image without the file browser open. Users can switch it on later if they want to.

The main reason is that if you open a file via the Explorer context menu, which already is file browser, you decide to open a single image, not a directory. Hence, delays of 20 minutes or more not only don’t make sense, they are also counter-intuitive.


I can confirm - with RT 5.5 opening a directory with many .nef files in the File Browser may take loooong time. During that time RT becomes totally unresponsive. Maybe thumbnails generation can be done in background, in a separate thread or something?


More details. The first opening a directory and showing thumbnails is actually quite fast. But then I think RT starts loading existing .pp3 and adjusting the thumbnails accordingly and that’s what is slow and moreover RT becomes unresponsive. I’m on FreeBSD 12 if that matters.


No appreciable delay opening image in giant folder on macOS via context menu. Image opens right up, then file browser processes in the background, with percentage shown on the side tab.

RT 5.5 & RT 5.5-dev
MacOS 10.14.3β18D32a


Windows10, RT5.5 and last dev. RT cache on SSD

  • test with a folder containing 986 nef files
    I deleted the cache, then opened a raw with “open with rawtherapee”
    I wait about 7s before being able to change a processing parameter. Thumbnails are created in backgroud.

  • I added about 500 jpeg. Waiting time 9s

  • if you want to avoid opening the browser, associate the file type with rawtherapee

@christoph_s Have a lot of raw files been already processed and then have a pp3 file?
are you on a network drive?


@gaaned92: No. I tried again on a directory with no PP3 files at all, only RW2, JPEG and TIFF. Same result.


@gaaned92: Additional info: Directories are on a 1 TB external hard drive, NTFS, connected via USB3.

(Morgan Hardwood) #16

@christoph_s try on a folder with only raw files, no TIFF.


@Morgan_Hardwood Why should I do this? A programme needs to be confronted with real-world scenarios to be improved, not just lab conditions. (Unless you mean to eliminate potential error sources.)

(Morgan Hardwood) #18

@christoph_s I do mean the latter. I am quite aware what a program should do, and you can help by testing whether removing TIFF from the equation changes anything.


@Morgan_Hardwood I tried again with a folder that only included RW2 files. Same result. I also did a cross-check with Darktable in the “Lighttable” view. Opening a directory with only RAW files, as well as a mix of RAW and JPEG/TIFF is acceptaply quick, even though DT creates additional XMP files while opening the folder.

Also, opening a file with DT via the Windows Explorer using the context menu option “Open with” is almost immediate. It’s the same with Photivo, so the problem definitely seems to be RT.

(Morgan Hardwood) #20

Thanks for testing.