Originally Posted by Hugo Zhang
Yes, you can lay the 5x7 negatives on the scanner, emulsion side down facing the glass. Then, put Anti-Newton Ring glass on top (mat side down on to top of negative) to hold the negative flat. I found that worked well enough with Epson Scan up to 2400 dpi, but the makeshift 5x7 film holder worked somewhat better with Epson Scan and much better with VueScan. I would urge you to do some consistent, documented scanning tests before deciding upon your final workflow specs. Epson Scan is a good start because it produces decent results without a lot of fiddling.
If you lay your negatives directly on the glass, then use the setting for film guide and try to center negatives on the scanner glass. The Epson Scan software that comes with the scanner is best for this setup. If all you're doing is digitizing old photo negatives or prints, then those minimum quality settings that you mention will work but not very well. You'll likely be better off at 1200 dpi or 2400 dpi and 48-bit color for two reasons:
You extract much more data from the higher resolution and higher bit depth negative scans, and that data may be of value some day to others - if you don't get that data when you can, then you've precluded any higher level use that may be desired in the future, either by you and by those to come; and,
Even if you just print same size, the downsizing and higher bit depth will result in a better print. When digitizing an analog process like a negative or paper print, a higher sampling rate ( higher resolution and bit depth) than the intended final output will minimize the inevitable loss of information in the final digitized result, resulting in better apparent sharpness and less banding.
Disk storage is now very cheap and inexpensive, so there's no practical reason to do tiny scans unless you 1.) don't have the time, or 2. ) store everything "in the cloud".
Scanning an analog item like a negative or a paper print at 300 dpi will result in effective resolution that's lower than 300 dpi. I've forgotten most of the math to calculate the actual loss of effective resolution but higher sampling rates result in much less loss. I've found that 1200 is good enough for a lot of 5x7 negatives on a flat bed scanner and that 2400 dpi high bit rate scans seem optimum. ( As I mentioned in my original post, higher than 2400 dpi scans don't seem to capture any additional real resolution, tend to reduce micro-contrast somewhat and quickly result in excessive file size.)
When I started doing large format photography back at MIT with Minor White back in the early 1970s using the Zone System, we had to go through a lengthy series of camera, lens, and exposure meter calibrations and then calibrations of our film and print exposure and development. These were, and remain, fairly tedious and time-consuming but are unavoidable if you want to do high quality film photography.
Digitizing analog film and paper prints introduces into the final workflow yet another step requiring careful calibration of your monitor, of your scanner settings and technique, and of your printer in addition to the same equipment and film developing calibration tests required for Zone System.
These are just optimized starting points and if you're after the highest quality output, you'll still need to make tweaks for different images and also in your digital post-processing with Lightroom or a similar program. Ideally, a scanned film negative image will have a full and well-differentiated tonal range without being too contrasty. That allows you to optimize afterwards in post.
However, once you have your complete system dialed in, digitized storage and final printing is much easier and more consistent than making a final wet print and you only have to spot the print once, digitally. It's ultimately worth the effort when you're intent upon exhibition quality results.
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