Thanks very much for your very thorough explanation re: RAW processing and RawTherapee. I’m not quite certain which approach I’ll be taking, but you’ve given me lots to think about.
Hello @danbob6 and welcome to the RawTherapee forum and from what it seems, also welcome to the world of Open Source. We are all glad you are interested in checking our RawTherapee and do hope that it will bring you much joy as well as efficiency in your workflow.
What I’ll do is I’ll cover the basics of what raw processing entails, which will likely help you understand what can and can not be done in a migration to RawTherapee. Sorry about if I end up going over things you may already know, I am starting from the basics for the sake of proper context.
RawTherapee and Lightroom are both software that are primarily designed to process camera generated RAW files (although they can also do more, this is their primary purpose).
- camera generated RAW files: are not regular images like you’d see on the web, so they are not jpg, or png or tif files. Regular images such as jpg, are made up of a number of pixels, and each pixel has a value for Red, Green and Blue, which together make up the colour, brightness and saturation of that pixel.
Raw files contain unaltered data from the camera’s sensor (if you’d like more details on that, ask me and I can reply with a more detailed explanation on how they work), which on their own are not laid out in the way jpg or tif files are, the data in them has to be processed by a dedicated program and then saved or exported as a regular image in jpg/png/tif format.
This is where programs like RawTherapee and Lightroom come in. They have the knowledge to look through the raw file data and make sense of it and allow you to set the desired brightness, contrast, sharpening and colour intensity of the image you’re working on, and then save it/render it/export it as a resulting jpg you can use on the web or for print.
So for example in RawTherapee, you would open up a raw file such as a Nikon NEF_123.nef and edit it by boosting the brightness a bit, and contrast a bit, and adding some sharpening. In order to post the picture online you have to export it.
That process creates a resulting NEF_123.jpg file (the actual resulting picture that looks the way you want it to), and a secondary file NEF_123.pp3 which contains text, in xml format, that describes which of the RawTherapee settings have been applied to the raw file and at which intensity value. The original raw file, NEF_123.nef remains unchanged. If you go back into RawTherapee and do some more processing only the pp3 text file gets changed. That is the difference between the original file (the raw NEF file) and the processed image (the resulting JPG).
Now comes the more relevant part, the fact that although all of these programs are used to process these files, one program may have a function (like sharpening for example), which may not be found in another program, or if it is found in both, one may do it with different algorithms than the other, resulting in a different look. Now RawTherapee has most of the features that Lightroom has, but due to the fact that Lightroom is closed source (you don’t get access to how the program is written - because they want to keep their secrets to themselves), the people developing RawTherapee have to come up with their own mathematical formulae on how to make each of the features work …and that may actually produce more pleasing visual results, but certainly somewhat different looking.
What that implies is that:
1 there is no program currently that will look at the editing of a raw file in Lightroom and turn that into a RawTherapee edit pp3 file.
2 even if there was such a program, the resulting look in RawTherapee would be different due to the different programming behind each feature in it.
What you cannot do (curently):
You can not simply import the Lightroom Catalog into RawTherapee so that RawTherapee automatically knows what settings you applied in Lightroom.
I am a big fan of RawTherapee but there is also Darktable, a very capable, also open source, raw processor that I can recommend for you to try. If you are comfortable going the commercial route, CaptureOne is an amazing piece of software, which quite honestly gives way better results than Lightroom.
Hope things work out for you and looking forward to hearing more from you on here!