RawTherapee starting up times

Just wondering is there a way to improve the starting up time of RawTherapee. Currently using a local compile dev version in MSYS2 on windows 11 my start up time is around 20 sec vs ART of around 10 sec

on WSL2 RawTherapee dev starts around 10 seconds while Art is fast at 5 seconds

i have a i7-7700hq with 32gb of ram and apps starts from a nvme ssd

Start RT in a folder with few photos in it and make sure you don’t have any network shares attached.

I tried it. created an empty folder and started a few times with that folder as default starting time is around 17 sec. There are no networks shares attach. I don’t think that is the issue. Thanks @paperdigits.

How about a lot of LUTs in the luts folder?

its clean compile i have delete the even the cache files. no luts. What’s your start up time on Linux or windows @paperdigits. My ART dev build on linux via WSL2 is really fast it starts up in less than 5 sec even on a folder that has around 700 files. and lut folder with lots of luts

@eyedear I know this is quite annoying and does not seem very logical. Some time ago I tried to investigate what was taking so long. Having a flat field or dark frame directory slows things down, but there was also an unusually large period for simply instancing the GUI with its many elements iirc.

Something to look into for RT6 for sure… it takes time.

i see so its due to the gui. The weird thing is that the start up time in windows is twice that of Linux and art seem to be twice as fast as rawtherapee maybe due to a smaller set of features.

For example, for me the startup times of darktable on Windows and Linux are also noticeably different. GTK certainly plays a role in this…


I just timed my startup times and from hitting enter until the program is loaded (my base directory does not conain any images) takes 3 seconds. I tried with a filled cache and an empty one, same result.

Having a small cache size might come into play as well I think. If you start inside a directory that contains many images and your Maximum number of cache entries is set lower then the amount of images in that directory you will see a performance hit.

darktable takes about the same time to load here and “a lot” longer when it needs to do some db cleaning/updating.

This is on a Linux machine (Debian) and my machine isn’t a powerhouse (rough specs)

wow 3 sec is really good. my machine has only 4 core and the base speed is much slower so a 8-10 sec start up time on wsl2 linux might be correct. I am just trying to figure out how to make it start up faster anything less than 5 sec is superb.

You noticed “slowness” when using RawTherapee, but is this an issue in general on your machine and also seen when using other, graphical programs that demand a lot from it? Did you notice this after using a newer RT version? Those are some things to consider.

I’m mentioning this because a lot depends on the machine you have, more precisely: If components work well together and are balanced (and at times set up for specific tasks).

I’m not saying that RawTherapee can’t be improved, it certainly can (I want opencl, and I want it now! :rofl: ), but troubleshooting performance issues isn’t all that easy to do and is often a combination of many factors.

Oh, the specs I linked to are out-of-date in one category: I have 32Gb RAM now instead of 16Gb.

I seem to remember that the difference of starting time between RT and ART is mainly due to the batch edit function in the RT file browser.
On W10, ART takes a little more than 2s to start on empty folder. I6700K, 16 GB, skylake build.

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Since its likely the GUI initialisation taking its time it makes sense that art is twice faster.

RT probably has more than twice the amount of sliders compares to Art.

I’m no dev but it sort of makes sense to me.


Hm… @eyedear I wonder whether it might be due to the graphics processor?
Do you have a separate graphics card , or…?

Have fun!
Claes in Lund, Sweden

yeah, it’s a notebook with intel as the integrated and nvidia 1060 as the discreet. if i remember correctly RT does not use any gpu acceleration. should the graphics card cause this?

i also realized on some different devices, that the starting time but also the processing time of RT differs a lot even on a single device.
Without having any idea, what could be the reason, i started to switch to the Windows “ultimate performance mode” before starting RT. Since then i am fine with the performance of RT.

On a 7 years old low-end pc with a 4-core AMD cpu, 8GB ram and a ssd, I get the following times, starting RT and Art from a terminal. I wait until all the thumbs are loaded (same folder, 196 photos), then I kill the programs with Alt+F4.

paul@graveyron:~$ time rt
real 0m6,420s
user 0m6,896s
sys 0m0,534s
paul@graveyron:~$ time art
real 0m2,988s
user 0m3,172s
sys 0m1,629s

On an old 8-core from 2013 I get this when starting RT on a folder with 1118 files:

~ 11 seconds

Edit: that was on a windows machine with 32 GB RAM, so most likely all thumbs were in OS filesystem cache when I started RT.

wow on native linux system its surely very fast.

I forgot to mention that the photos in that folder were all in the cache, because used before with RT and Art. With a fresh folder (that is: new photos) it takes of course a bit longer because the thumbs must be generated.