Collectible Stocks and Bonds from North American Railroads     by Terry Cox

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Brightness is the single easiest concept to understand and see. All image manipulation programs make it is easy to adjust brightness.

Why do most certificate scans appear dreadfully dark?

Part of the reason lies in the nature of certificates. They are printed with black ink and very dark, saturated colors. Ink is concentrated within very narrow engraved lines separated by light areas of paper. The human eye evens out these large differences and constructs shades or grays and shades of colors. Depending on resolution, scanners measure the fine lines as light grays instead of blacks, and therefore darken the scans to what it thinks should be average documents.

The mind behind the human eye has an uncanny ability to artificially construct images that don't really exist.

When we see a certificate, we see it with bright printing and brilliant colors, even though the paper may be gray and the colors dull.

Scanners do not have such ability. Unless instructed differently, scanners try to report reality.

In order to deliver accurate and repeatable information about appearances of documents, scanners attempt to illuminate documents uniformly. Since the amount and color of light is accurately known, software designers can accurately calculate the amount of light that should bounce back from normal documents and photographs. They then use that knowledge to design routines into their software that measure the amount of light being reflected and then adjust exposure to properly scan normal documents and photographs.

And therein lies the problem of scanning certificates.

Certificates are neither normal documents nor normal photographs. Here is a scan of a thoroughly ordinary certificate. There is handwriting on the back that shows through to the front. The certificate is a little distressed with a water stain. The right end is lighter than the left.

The problem of non-normalcy can be exacerbated by the fact that many certificates are printed on thin paper. There is often show-through from printing on the backs of certificates. Many people think they should place black or colored paper behind certificates to show paper edges. Those dark backgrounds often cause additional problems. I have prepared a couple pages that show and explain exposure problems when scanning documents against colored backgrounds.

I think the natures of certificates and scanners are only parts of the problem, however.

I believe the bulk of brightness problems come from our own behavior and perceptions. When we look at certificates, we normally place them on a desk or against a dark background. Rarely, if ever, do we place them against a perfectly white background. In those situations, our brain makes dark certificates look lighter and better than they really are.

Another reason certificates almost always appear too dark is because we trust our equipment too much. We think our scanners are designed to scan everything well. They are not. They are designed to scan ordinary photographs and documents. Most users tend to use default settings and never make any adjustments.

Using scanned images

How do we normally use our scans? We print them or view them on computer monitors.

Both inkjet printers and offset presses ALWAYS make images darker. Pros understand this phenomena and know that they need to lighten images rather dramatically before printing. Amateurs generally print images the way they come out of their scanners and they generally get dreadful results. Then they give up or blame their printers.

Backgrounds matter

The scan above looks fairly bad because I am displaying it against a white background. If I hold the original certificate near the screen and compare it with the image, the scanned image looks a little dark, but not horribly so. In other words, background matters.

To show the difference, here are two examples of the same image as it came from my scanner. One is surrounded by white and one is surrounded by black.

Which image do you think looks better? Probably the one with the black background. Even though they are identical, most people perceive that one as lighter than it really is.

So what to do?

Brighten the image with image software. Almost every scanner comes with software that gives you the capability to alter images after the fact. Here is what you get if you do nothing except brighten the image.

You can see that the certificate has problems that no amount of brightening can fix. But this image is much, much closer to what we think we see when we look at this particular certificate. Rarely do I see unaltered images of certificates that cannot be helped simply by brightening.

Try it with any image you have. Oftentimes, you only need to brighten your image a little to make dramatic improvements.

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(Last updated July 16, 2011)


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