Is there a specific way to force kdenlive to use, say in the case of 2 seconds worth of images at 24 fps, the supplied 1920x1080 image 48 times with no compression (or the 48 supplied images if they are all different)? Or is this determined by resolution/format & sampling rate? I don't care about the file size.

Another feature that would interest me is precise control of frame rates, on many projects I simply don't need more than about 10 fps or even 5.

Drop the image on the timeline and stretch to suit duration required or RMB edit duration, or if you have a lot of these to do then you could change the default image duration in kdenlive -> environment.

48 images all different then set the default image duration as mentioned above to suit.

You can create a Project Template with the frame rate to whatever you want in the Manage Project Profiles kdenlive menu.

For 'lossless' rendering look in the Render -> Lossless HQ options. Lossless h264 444 for RGB images might be suitable.

I've done the edit duration and also the set default duration for images. For the video can you make it simpler? I don't understand how a project setting like QCIF at 15 fps 176x144 will affect the rendering of 1920x1080, etc. For a specific example, what would I need to select and where to make a lossless 1920x1080 mpg video at 10 fps from a single 1920x1080 image that I pull out to the desired duration?

If your delivery requirement is 10fps at 1920x1080, then you could create a project profile to suit.

Start a new project using that template.

Drop an image on the timeline and set its duration as discussed.

Save the project.

Then for rendering either set the start end end points in the project monitor to select just that image with duration in order to render just the selected area or you can just render the project as a whole.

Render using an option from the Lossless HQ render tab, I'd suggest a x264 lossless choice.