The problem is that the image I see on the Profia is still much darker than the one on the Crown Graphic in the same conditions.
It sounds like you might need to clean your screen. It’s not too difficult. I can’t tell you how to remove it but it’s usually pretty simple for most cameras.
Once you have the glass separated from the frame you can clean it in a solution of water with dish soap and some q-tips or a cotton ball, something that won’t scratch glass. I find it best to submerge the glass in the solution and slowly work over every cm bit by bit in small circles.
Once you’ve cleaned both sides with soap you can rinse the glass. I always use distilled water to rinse the glass so that I don’t get drying spots. Actually I always use distilled water for the entire cleaning process just in case but I’m not certain it’s necessary. You need to rinse it very thoroughly. It’s easy to get all the soap off if you rinse it properly but if you let soap residue dry on the ground surface it’s going to be a lot more work to get it back off.
The final step is to dry the glass. This can be difficult because if you use the wrong material you will rub lint into the ground surface and you’ll have to start all over. I use pec pads as they don’t scratch and are completely lint free but if you don’t have anything like that you can always let the glass air dry, but it will take longer.
If after a thorough cleaning you don’t see the improvement in image brightness you’re looking for, you might need to replace the ground glass. Some manufacturers produce better quality ground glass than others, some are brighter and produce a clearer image.
If your current glass isn’t up to the task you’ll have to find a replacement that will outperform it. I can’t help you there. I’ve never had to replace a ground glass screen. There is a vendor on ebay that makes custom ones. I don’t know how good they are but it might be possible to get one that fits your camera from them. There might be other options out there. I’m not sure.