Originally posted by Oldbayrunner I know others will not agree with this but your camera came with a capable software, Digital Camera Utility 5, that's free and calibrated for processing your cameras raw or jpeg files. So if you don't want to spend a lot of time on your photo processing it has a lot of automated features designed to match Pentax camera output for quick processing.
I agree with this as far as RAW conversion. I really like the output from PDCU. I've never been a big fan of the PDCU interface however.
This topic has been hashed out many times in this forum. Much depends on your preferred workflow. Some software will likely mesh better with the way you like to manage and work with your images than others.
Software praised by one person will be anathema to another.
I personally don't want my software to manage my images. If the software has to "load" an entire folder before it allows me to look at an image in the folder that's an instant deal breaker.
My own recommendation would be to get FastStone Image Viewer ( free/donation ) as a very lightweight image browser and simple editor. Use it to invoke your RAW converter of choice when you need to do RAW conversion ( eg. PDCU ).
Because this program is my default starting point, I have a hard requirement that any RAW converter I try must work in such a way that when I invoke it for an image I'm viewing in FastStone, that converter must come up with ONLY the image
in question loaded. If it attempts to render or catalogue the entire folder, it gets uninstalled.
In this way, I'm only doing RAW conversion on an as needed basis. For simple cropping/resizing and other minor editing, FastStone rocks. If you need to do more complicated edits, involving layers, etc., then you can use Gimp ( free )
or Photo Shop Elements ( inexpensive ).
I've tried RAWtherapee, but I found it has so many options, it ends up being a bit of a rabbit hole. 4 hrs later you come up for air and you're still not sure you've got the best results from the one image you started with.
I do like the Silkypix interface ( after acclimatizing to it ), but I found that in A/B comparisons, I preferred the output from PDCU and DxO. I don't think there's a free version that will work for K3 images.
Summary:
Browsing/culling/simple editing = FastStone ( free/donation )
RAW converter = PDCU, Rawtherapee ( free ) or DxO ( potentially free )
Complex editor = Gimp ( free ), PSE ( cheap )