Hi Julie
The way I'm reading this is that you are taking photos of your completed cards and uploading them to the CUP site using your Crafter Control Panel, but they are not passing validation and re-appear in your quarantine list with the statement "Too Dark" next to them.
Although I don't have the camera you've got I have had used three or four different cameras over the years and I've always set them on "Auto" and let the camera decide on the best setting for what's in front of it.
As it's sometimes difficult to know whether there's enough light on the object being photographed to take a good picture I also put the Flash on automatic. That way, if there isn't enough light the flash goes off and I know straight away that there isn't enough light to take a tidy picture without the flash. I find this preferable to having the flash off and taking lots of pictures of a bad quality and only finding this out when I upload the pictures to my computer. If the flash goes off I either move the card or wait for better light conditions, and don't waste time taking pictures that are not suitable for uploading to CUP.
By experimentation I've found that putting any light cards on a dark or black background helps the camera get its automatic settings right. A light card on a white background doesn't give the camera a range of colours to get its balance right and it takes the whole picture darker. The opposite is true for a very dark card, which I place on a lighter colour background.
I tend to take several photos of each card at slightly different angle of camera to card, and at different angles of card to the light source (
usually a big window for natural light), and take the picture from a bit further away than I need to so that there's a good border of the background around the card.
Once uploaded to my computer I use a piece of software called
IrfanView to crop closer to the card to leave just a fine border, slightly rotate if needed, and also if needed I'll Auto Adjust the colours or Sharpen the image. Nothing too drastic, but it can just help a picture that's slightly off, though a bad picture just needs to be taken again. There are other bits of free software around that other Craftforum members use.
Experiment with things until you get to know your camera and work out what settings and positioning work best for you.
GG