Scanner calibration

Jun 23, 2018 16:22:47 GMT @falshung said:

The scans are dark and out of focus

 

Causes

1. The white background plastic in the lid that normally comes with scanners should be replaced with a matte black card stock
2. Check the scanner's calibration directory - a google will let you know how
3. See if you have a backlight adjustment in the software

4. Unless you plan to print, the above right scan was at 300DPI and produced a 800px wide image - more than enough for TSF or any other posts. Scan time under 5secs

Most Important
5. The software that came with the scanner is not adequate . This is the NO 1 issue and the solution has been noted

Spectral reflectance, colorimetrics, calibration - the right software is the solution

Sorry to have been gone for a bit.

I have to think the scans are dark mostly because the stamps are dark - I do use black matte when scanning stamps. But that may just be a function of my monitor versus yours. They look like the stamps I scanned on mine... .

BTW, people should use black backgrounds even when you're displaying your stamps. Vision (including color interpretation) is contrast-sensitive (as opposed to luminance sensitive) so yes, colors really do stand out more against a black background than a white one. It's the whole blue/black or white/gold dress thing, if you saw that when it passed through the internet a couple years ago. If not, here:

Use a color-picker on the 2 images. The 'yellow' squares on the left side are actually the same color as the 'blue' squares on the right. The background (and background light source) matters.

They are out of focus because both versions of the stamp were originally scanned at 1200dpi to 48bit .tiffs, then downscaled to 300dpi and 24bit .pngs so they wouldn't be absurdly large files for the post. The first (old) scanner has a 600dpi optical limit (interpolated up to 1200), so that one should appear much more out of focus than the other (4800 x 9600 optical). Both images, however, lost resolution in the downscaling through software interpretation, and again in the format switch (I saved the converted images at the default compression - read that as 'whatever resolution loss the program decided was good'). Focus is almost certainly both a hardware and software problem.

Right now, in the end, the scanning process you use depends on why you're doing it. Vuescan is awesome in that it re-interprets your old scanner driver so it'll keep making the same quality scans no matter how much Windows or Apple 'adjust' their operating systems, but the same images will still be different from monitor to monitor. If you're scanning to keep a record of what you have, great. Use the same scanner at the same settings for all your stamps, and you have pretty good information for an insurance adjuster should anything ever happen to your stamps.

But if you're scanning to determine color variety, I don't think it can be done. At best, a scanner can give you 'relative' color (you need to have a similarly scanned 'known'), but not the 'actual' color. Right now, there's just way too many unaccounted-for variables and not enough standardization (in hardware or software). You'd need something built for the specific purpose, and a whole lot of processing power.