Scanner Talk - 16-bit TIFF Positive - The Something Awful Forums

The Something Awful Forums > The Finer Arts > Creative Convention > The Dorkroom > Scanner Talk - 16-bit TIFF Positive

Cassius Belli: May 22, 2010; horny is prohibited

LargeHadron posted:

Actually no, I'm no quitter. We've been to the loving moon I KNOW there's a way I can trick this stupid scanner using science. I'll report back when I think of something.

Maybe you could take three scans, with the iPad set to backlight the film with #FF0000, #00FF00, and #0000FF, respectively, and then composite them?

# ¿ Feb 14, 2014 07:36

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# ¿ May 22, 2024 10:04

Cassius Belli: May 22, 2010; horny is prohibited

LargeHadron posted:

I'll try the RGB backlight stitch a bit later...I'm curious though what the theory is as to why that would work. Wouldn't comping an image from RGB-backlit components have the same effect as using a white backlight, in "light" of what forums user Geektox explained? Then again, I'm the guy who tried scanning a mirror so I'm pretty stupid.

OK, this is pretty handwavey, but basically:

A CCD scanner can read luminescence values for all three colors at one go, separating them out of white light, so its routine looks like this:

code:

for each pixel;
   scan;
   pixel.red_channel=red_sensor_luminescence;
   pixel.green_channel=green_sensor_luminescence;
   pixel.blue_channel=blue_sensor_luminescence;
done;

A CIS scanner can only read one luminescence value at a time, so its routine looks like this:

code:

for each pixel;
   enable_red_led;
   scan;
   pixel.red_channel=sensor_luminescence;
   disable_red_led;
   enable_green_led;
   scan;
   pixel.green_channel=sensor_luminescence;
   disable_green_led;
   enable_blue_led;
   scan;
   pixel.blue_channel=sensor_luminescence;
   disable_blue_led;
done;

The problem is that, by using the iPad with a white backlight, the various enable_led/disable_led functions don't actually accomplish anything; you're just reading a flat luminescence value, and since R, G, and B are all the same, you get a greyscale image out the other side. If you split the iPad colors up, you're arbitrarily creating three images ("red", "blue", and "green"), flattening them to proper greys, and then importing them as the red channel, blue channel, and green channel for the final image, so you get proper RGB values out the other side.

Make sense?

# ¿ Feb 14, 2014 18:35

Cassius Belli: May 22, 2010; horny is prohibited

LargeHadron posted:

Well drat. That actually worked.

Whoo!

You don't really need an app. You should be fine if you just make some PNG files to the resolution of the screen and put them in full-screen display mode. Then you can get exactly the color balance you want.

# ¿ Feb 15, 2014 04:21

Cassius Belli: May 22, 2010; horny is prohibited

Paul MaudDib posted:

I'd like to get a size-accurate scan of a small object (a rangefinder cam as below). Think it would work if I slapped it on a scanner bed alongside a nickel and using the nickel's diameter to get a relative diameter for the hole in the RF cam?

Probably, but why not just print up a sheet of 1mm graph paper and use that? Put the part on the glass and the sheet face-down over the part, and you can get all the measurements you need, baked right in. It looks close enough to two-dimensional that deformation and perspective changes shouldn't matter.

# ¿ Sep 22, 2016 01:42

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