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scanning advice - almost, but not quite, entirely unlike tea
if I had to explain, you wouldn't understand
dakegra
dakegra
scanning advice
one of K's relatives has dug out a bunch of old photos of K's dad's parents, grandparents and assorted relatives, and has asked me to scan them in for K's dad so he can have digital copies of them.

I've dug out my (very) old scanner (A visioneer 4400, it seems) which it took me a while to sort out, but I found the original CD (me = digital packrat) and got it up and working.

I've done a couple at 600dpi full colour, which seems to give a decent result, output as .TIF files then opened them in Gimp to play around with the balance and settings. TIF files are huuuuuge though.

Some day someone is going to have to explain levels and thresholds in Gimp/photoshop.

Advice please - should I scan them in greyscale (given they're all black & white/sepia), or go for the full colour?
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Comments
pteppic From: pteppic Date: September 30th, 2010 11:17 pm (UTC) (linky)
Full colour.
There is no such thing as greyscale.
Black and white photos are not.
boliviafang From: boliviafang Date: October 1st, 2010 12:03 am (UTC) (linky)
First of all, 600 dpi is WAAAAAY more resolution than you need and that's why the files are huge. I am the pickiest person I know about high res photos and I only insist on 300 dpi. I use 600 if I need to scan in, say a tiny logo from a business card and blow it up to a usable size, then I reduce that new size to 300.

As for grayscale, I hate to limit myself by scanning or saving photos that way, but if file space is at a premium I suppose that's fine for the ones that are b/w. The sepia ones you may wan to keep in "color". I have a heck of a time adding that quality to b/w photos later, so if you have it, keep it.

Also, the program should only remember as much color as the file uses, so a "color" scan of a b/w file would not be as big as a color scan of a full color photo. Although there may still be a significant difference between the color -********* (sorry, my cat typed that) color scan of b/w and the grayscale scan of b/w.

Sorry, too tired to type more. Hope that was informative if not actually helpful.
kaiserdad From: kaiserdad Date: October 1st, 2010 05:45 am (UTC) (linky)
There is no point in scanning at a resolution greater than that of the machine that is going to display them. If you choose to scan at 250DPI Greyscale, you will get 250 tones between black and white, if you do the same in colour, you will get 250 shades between red and indigo plus black, one pixel, one colour or no colour so that uncompressed (Bitmap)they will be exactly the same size, the difference is when you save them in a lossey format (jpeg) when the greyscale will be much smaller than colour. My BMP files are also huge but if they are saved to a CD or stick that is irrelevant.
dakegra From: dakegra Date: October 1st, 2010 07:32 am (UTC) (linky)
I thought that 250DPI was 250 dots per inch - so if you scanned a 6" photo, it'd be 1500 pixels along the long edge?
kaiserdad From: kaiserdad Date: October 1st, 2010 07:38 am (UTC) (linky)
Absolutely correct dear friend.
kaiserdad From: kaiserdad Date: October 1st, 2010 07:47 am (UTC) (linky)

Note

The only advantage of scanning B/W as colour is if you wish to tint them later, you will get more subtly of tonal quality in greyscale but you cannot improve the quality of the original
nalsa From: nalsa Date: October 1st, 2010 08:36 am (UTC) (linky)
I don't particularly want to start an argument on Dave's journal, but some of this is not quite right.

1. You don't know what the future use of your scan will be. Should you scan everything at 72dpi - because that's what monitors display at - then you can't zoom, crop, print, successfully make subtle edits or get any fine detail that may be significant to the end user. To save rescanning the same image again and again, make one scan at the maximum resolution you can and resize it for specific applications.

2. If you scan at 250dpi greyscale you'll get 256 tones between black and white, if your greyscale is set to 256. You can have 2^16 tones of grey if the scanner supports it. DPI is nothing to do with the number of tones you get. Colour is generally set to 2^16 shades, but this is configurable in your scanner settings. Unless you deliberately set your palette to 256 colours you will have considerably more than 250 shades between red & indigo.

3. Scanning B&W images as colour gives you far more scope to edit with, because you have far more information to play with. Using the channel mixer to greyscale a colour image can allow you to make adjustments to simulate different coloured lens filters, for example.
dakegra From: dakegra Date: October 1st, 2010 09:02 am (UTC) (linky)
Thanks Mike, that makes more sense now!
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