Why do scanners always cut off one edge of the image?

[scs0]

I've owned several scanners over the course of 10 years or so and I've
noticed that every single one will cut off about a half inch or so
from one side of the image. It seems like scanners aren't designed to
scan to the edge of the scanning bed. Why is that? By using the
corner of the scanning bed you can guarantee that you've aligned the
image properly, but then the scanner will happily cut off part of the
image.

Why do all scanners have this design bug?

 

[Charlie Hoffpauir]

I've owned several scanners over the course of 10 years or so and I've
noticed that every single one will cut off about a half inch or so
from one side of the image. It seems like scanners aren't designed to
scan to the edge of the scanning bed. Why is that? By using the
corner of the scanning bed you can guarantee that you've aligned the
image properly, but then the scanner will happily cut off part of the
image.

Why do all scanners have this design bug?

I've had three flat bed scanners, and none had that problem. Maybe you
bought poor scanners?

 

[CSM1]

I've owned several scanners over the course of 10 years or so and I've
noticed that every single one will cut off about a half inch or so
from one side of the image. It seems like scanners aren't designed to
scan to the edge of the scanning bed. Why is that? By using the
corner of the scanning bed you can guarantee that you've aligned the
image properly, but then the scanner will happily cut off part of the
image.

Why do all scanners have this design bug?

They don't.

My Cannon 8400F does not see 5/100 inch of the sides. In decimal = 0.05
inch.
I know that because I scanned a 6 inch ruler that is scaled in 1/100th of an
inch.

That is a long way from 1/2 inch.

 

[CSM1]

The 5 flatbeds that I have had haven't had that problem to any great
extent, of the two I have now,
to have the problem, but only cuts off a small amount (<.02 inches on
one side only)

However the hp LaserJet 3030 automatic document feeder seems to loose
some on all sides even though it shouldn't miss anything. For
example, when scanning something x long it only see x minus a bit
and looses about .13 on each side. This may be a software problem
since the flatbed doesn't have the issue. However I've tried the
software that came with it and VueScan (8.4.56) and both
loose stuff with the ADF. (Scans 8.50 wide with flatbed and
either software, but I'm not sure how wide the flatbed glass
or scanning element is. Some options even say it is scanning 8.5 wide
from the ADF, but it is narrower than what the flatbed sees.)

Epsom Perfection 3200 Photo says it only wants to scan 8.49 wide.
(The glass is definitely wider than 8.5, but I don't know wide it
actually is.)


More questions:
. why isn't the scanning element wide enough so that everything
on the glass is scanned? If tolerances mean that .02 to .1 inch
is black due to the wider scanning element, it is not a big deal.

. why are the beds 8.5 inches or some other standard width?
They need to be .25 wider so that we can see the covers of
magazines that are folder, stapled, and cut so that the innermost
pages are the standard width.

Scanners are 8.5 inches wide because in the United States 8.5 inch wide X 11
inches is a standard letter size paper.

In Europe and other countries, the standard paper is A4 and is 210x297
millimeters, which translates to 8.26 inches x 11.7 inches.

If you were using A4 metric paper the scanner bed would be 1/4 inch wider
that the paper.