- Emperor of a Minor Galaxy
- Posts: 2288
- Joined: Thu Dec 18, 2008 5:04 pm
- Location: Ironton, Missouri, USA
What DPI should I be scanning at for negatives and slides, and what DPI for photos?
Should I stick to 24 bit color, of use 48 bit?
Should I be targeting max DPI from the originals, or just enough to get them to the size I need?
Thanks in advance for the help.
I use the "advanced" mode of the software.
Paper prints I scan at 600 dpi. there really is not much more even on the sharpest prints. I typically always use 16bit/48 bit. (BW/Color)
For negatives or slides I scan at 4800 dpi and 16bit/48bit.
Important to note is that the actual resolution is equivalent to somewhere around 2400 dpi. (Confirmed by scanning with the 5400 and then downsizing until the finest details were equally sharp) Most scanners that have fixed focus have this issue. It may be possible to raise or lower the image to get a slightly sharper image. Once I have done all my adjustments to the image I downsample to 2400dpi and then convert to 8-bit before saving at the highest JPG quality setting. Hard disk space is cheap so I would rather save at the largest size that retains sharpness than downsize and have to go back and rescan later if I need it bigger. I also save an "internet size" image of everything: After I have saved the full size image I downsize and sharpen the image for screen viewing and then save at a medium compression level
Typically I use the 4490 (or v700) for medium format only. I use the 5400 for 35mm.
Tried hard to find a difference between 24 and 48bit in print, but I could not see any. At 48bit it will add a lot to your file sizes.
I see no discrepancy between Barry and Alan’s statement about bit depth. I scan at 16/48 bits and print at 8/24. The reason is that our scanners have an amazing ability to delineate the most subtle tonal variances and 16/48 allows us to stretch the ‘histogram’ and avoid any sort of posterization. However, like Barry I can’t see any difference when printing at excessively high bit depths…you can do it…you just can’t see the difference. I don’t even think it’s a printer hardware limitation but more of a human limitation when perceiving the constrained dynamic range of a printed surface.
So I scan into PS, crop, straighten if necessary and maybe a slight tweak in tonal adjust and save in the full 48 bit depth, thus keeping a pretty much pristine scan. Then I get to work and do whatever really needs to be done in preparation for print, then save again. Often lots of times. I’m a big believer in redundant saves.
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