Scanning the Pictures

By Thomas F Abrahamsson

Scanners

Today, inexpensive but very good USB based Flatbed scanners dominate the consumer market. Every modern scanner support a bitdepth of 24 bits, that is 16.7 million colours, or even more like 48 bits. This is what you should get your hands on!
I can't teach you how to use your scanner, or how to handle the scanner software. However, I often get the question: 'How many DPI's should I scan my pictures in?'

Well, A standard monitor usually has roughly 72 DPI resolution - but this depends on the monitor's size and 'Dot Pitch'. This of 72 as a good estimate though...
This means that if you scan a drawing of yours that is 10 inches wide, it will be 10 inches wide on your monitor as well if you scan it in 72 DPI. DPI stands for dots per inch, but a monitor and the computer work with pixels. If you run at 72 dpi, each dot will exactly match a pixel on screen... well.. roughly....

I usually scan my pictures at a somwhat higher resolution though (200-300 DPI). If you want to publish your material on the web, you have to resize your pictures to fit within a web page, so experiment with different picture sizes and DPI's to get it all right. If you plan to publish your work in some printed material, you should go for much higher resolution to avoid jagged edges and big, visible squared, a minimum of 300 DPI is what I recommend.

If you plan to scan for you web page, I recommend that you scan your pictures at about 200 DPI and then you use a paint program to scale down the large picture to the amount of pixels that fit on a web page (about 600-1000 pixels wide at most).

Scanning...

First of all, remember to scan the picture in true-color (also called colour photo or 24 bits, or planes). Never user the predefined 'black/white' or 'clipart' profiles that comes with some scan program packages! These usually defaults to 2 colors and the result is horrible - see below!

Max Bertuzzi has a few tips to share on this topic:

'I have to tell you a photoshop trick that works very well for B&W images ( line art drawings ) I've learned it by trying and trying ( in fact the first images I sent you aren't scanned that good ) At present, I usually scan the pics in B&W ( 2 colors ) in a high resolution ( 400 dpi or more ). Once scanned, I tell photoshop to make 'em grayscales. Photoshop will automatically ask if you want to scale the image. I choose yes, and give my ratio (1:x). Then I change it from grayscale to indexed colors ( 8 or less colors ) and voilà! There will come out a perfect clean black and white line art, optimized for the web! Of course I save it in GIF format.'

Ok, Then, avoid the scan program when resizing images. Most scan programs are made for scanning pictures, not to work with them. Many scan program have horrible resize algoritms which totally destroys an otherwise nicely scanned picture.

Some examples

	This picture was scanned as in two color mode (ie, clipart, line drawing or black&white). It doesn't look very good with hard edges...
	Zooming it up reveals why it looks so bad!

	This is much better! This one was probably scanned in a 256 gray scale mode, or in true-color mode! You can see that the edges are smoother...
	Zooming it up reveals why it looks better!

So, How do I resize images?

Yet again, this Depends on your paint program. Generally speaking, I can't give a good answer to this one. Below I show you how it looks if you resize an image the right, or the wrong, way. When using photoshop, you have to go to RGB mode (ie, true color mode) before you resize. Then let the program resize the image, and finally go back to 'Indexed colour' mode again (ie, less bitplanes to be able to save as a GIF).

	To the left is the original sized 362 x 300 pixels.
	This picture was reduced to 100 pixel wide when in 'indexed' mode.
	..while this one was reduced in RGB mode, then converted back to 'indexed' mode. Note how much smoother this one is.

FARP Article Guestbook Date Name Comment   5 Apr 2003 Lottie *Kunzai* Burnett Loading... What if your scanner thinks it's clever and over-exposes one side of the image while making the rest dark? I think I know the answer to that actually, but scanners are kind of expensive... thanks though, useful page =] 28 Jun 2004 Anonymous Loading... thanks, this really helps. But what i need now is how to scan with out the black background. mayby it was there and i just skipped it. 20 Oct 2004 Anonymous Loading... I was wondering as my scanner has stopped working, is it ok to use a digital camera? I have already taken pictures of my drawings and the image is very good quality and has no edges, it just has the drawing. 3 May 2005 Anonymous Loading... öh.... what? man, I won't understand computers evereverever... okay. have to try these things. I hope I'm able to get my pics smaller... *gets crazy over these &%$&§%$&&%$% computers* grrrrrrrrrrr 23 Oct 2005 Saint Jimmy Loading... uhhhhhh..... Usualy i understand computers being the nerd i am but noone will awnser my question... HOW DO I SEND A PICTURE IN!!! I mean, do you have to be a member or what? Do I need a certain type of scanner? Does it cost anything? Someone please S.O.S 1 Nov 2005 Tamara 'Tamapaa' Hardwidge Loading... Yay! My scanner is my best friend! 20 Sep 2006 Gothgirl Loading... um.....my mom won't let me by photoshop. But i have that lame Paint program. Will that work? 9 Oct 2006 Anonymous Loading... I am new to scanning and am a scrapbooker trying to post layouts on the web. My pages are mostly 12x12. My scanner scans up to 8 1/2 by 11. Please help me! Is there anyway for me to be able to scan my whole pages! Anxiously Waiting, Thanks 26 Jan 2007 Mr_MR Loading... I'd also disagree with this text in as much as moniters DONT HAVE A DPI. That's right. If you don't believe it, ask yourself if there are the same number of pixels per inch in a 1280x1024 resolution as there are in a 400x300 resolution. The answer? Of course not. DPI is the resolution of the scanner, and the printer. It determines how high definition the items are scanned in, and printed out. Think of it as the real-world equivalent of the screen's resolution, or "real-life pixel size", if you will. If you scan a 8" wide document at 72 DPI, then the computer needs 576 pixels(8x72) to display the images entire width. OK, rant over, sorry about that 26 Jan 2007 Mr_MR Loading... In reply to the previous AP, scan your pages in in two parts, use an image editor to make an image of the same size as your original page, and copy the two scanned pictures into it,moving them around until they line up. Page: [1] 2 Not signed in... Sorry, Thomas F Abrahamsson does not allow anonymous comments. Please sign in to write on this Guestbook... Post Message!    Private message?

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