I get reasonably good results photographing negatives with a slide copier attachment and a macro lens (vs using a flatbed scanner). However, if you plan to scan many frames of film, you should consider a dedicated film scanner with batch feeder. Depending on your lens and camera, image quality from a film scanner may or may not be better, but it would be much more convenient.
Flatbed (or film) scanner
Advantages:
- Scanning negatives is an anticipated use case. Software usually include ability to invert and color correct negatives, often with single click.
- Scanner may have automated dust removal features (via additional infrared channel).
- No demosaicing.
- When image doesn't turn out well, it's most likely a problem with the film. (Don't have to constantly second guess scanner and settings.)
- Light source is built into the scanner. Results are consistent.
Disadvantages:
- Capture process can be slow. Scanning is done line-by-line.
- Focus and resolution of some scanners may not be optimal.
- Scanner takes up desk space.
- Scanner likely cannot extract "all" information from film (grain structure and dynamic range).
- Software usually automatically crops frame. May have difficulty capturing sprocket hole images. (More problem with film scanners than flatbeds.)
Other:
- Convenience, if using a film scanner with an automated feeder.
- Flatbed with transparency adapter is best (and most affordable) option for medium format.
Digital camera with slide copier
Advantages:
- Capture is fast (about the same as taking a picture).
- With good macro lens, can focus on image grain.
- With increased magnification ratio, can extract more information from image (grain and dynamic range).
- No scanner to occupy desk space.
- Reasonably affordable if you already own the camera and lens. (Slide copier attachments are ~$35-50.)
- Depending on attachment, can capture images that extend into sprocket holes.
Disadvantages:
- More time is spent post-processing images.
- Have to demosaic. Reduces resolution and may introduce artifacts.
- No automated dust removal.
- Photographing negatives is not a normal use case.
- Camera may not meter properly.
- White balance won't work properly.
- Software is not designed to invert and color correct negatives. May have to spend lots of time tweaking curves.
- When image doesn't turn out well, is it a problem with the film or camera or software? (Constantly have to second guess whether camera or software is at fault.)
- Focusing on grain can be difficult (depending on lens, magnification, and eyesight).
Other:
- Need to purchase a slide copier attachment.
- May need to purchase a suitable lens.
- Aberrations and distortions depend on lens.
Contrast, sharpness, dynamic range depend on lens.
For best results, have to use reproduction ratio greater than 1:1 and stitch.
Depending on how careful you are, lighting may not be consistent across the frame.
Medium format...
- Difficult to find suitable slide copiers.
- If using a lightbox, will likely have alignment problems.
- Will likely have to stitch several images.
