Yes, you definitely need a better slide to establish your baseline color. I also notice that your image is soft on the right side, possibly out of focus due to an alignment issue. Are you using a mirror for alignment? A couple years ago I started a thread here about a DIY copy stand for digitizing film which you might find useful. Since then I’ve modified the system a bit, using a Benro GD3WH geared head and eliminating the Super Clamp. For a light source, a lot of people now are using a Raleno video light, which I’m considering getting myself. DIY copy stand for DSLR scanning