Re: [ARSCLIST] Large-format scanner redux

[Eric Jacobs <EricJ@xxxxxxxxxxxxxxxxxxx>]

On Monday, August 11, 2008 3:29 AM, Tom Fine wrote:

> Hi Don:
>
> I've tried this but can't get the lighting perfect for 
> LP covers, especially the old-school kind that are actually 
> laminated over a lithograph. Also, scanning results in much 
> sharper text, especially tiny-font text on the back of 
> classical albums. The sharper the text, the easier time the 
> OCR software has.

For digitizing LP covers with a DSLR, we use large polarizing 
filters in front of the lighting (we use four 300 watt halogen
lights) which are at a 45-degree angle to the cover for uniform 
lighting.  In addition, we will sometimes place a polarizer 
on the objective lens of the camera and rotate this until the 
reflections are gone (only an issue with shiniest covers).

Sharpness with a high-res DSLR, high quality lens(es), and good 
lighting will produce an image quite comparable to a flatbed 
scanner - good enough for OCR and even gicle, but hair-splittingly
short of the sharpness of the flatbed scanner.  But if you 
want the ultimate in camera resolution, you'll need a medium
format camera with a digital (line scanning) back - with a 
cost of entry in the $20-35k range for a complete set-up.  Such 
a camera set-up will easily match the flatbed scanner - but the 
line scanning back is slow, just like the flatbed scanner.  The 
flatbed scanner is starting to look a lot more attractive.

Throughput on a copystand with a DSLR is definitely faster
than a flatbed scanner.  But to get comparable results to 
a flatbed scanner with a DSLR, the cost is far more ($10-15k)
because of the cost of the DSLR, lenses, lighting, polarizers, 
and a super sturdy copystand.  We use the Bencher VP-400 
copystand:

http://www.bencher.com/photo/vp400_50050.php

which can hold up to a 40 lb camera (!).  It does not 
vibrate (measurably).  We also use flat field fixed focal 
length lenses (not zoom lenses) to minimize distortion of the 
image.  A right-angle viewing prism is a huge ergonomic help.

A copystand and DSLR only makes sense if you are scanning
many thousands of records.  It also can deal with things
that are bigger than most large flatbed scanners.  If you
are doing less than 5,000 or even 10,000 images, I would
go straight to a flatbed scanner.  If you need to process
far more, then seriously consider looking at a high-end
DSLR set-up.

While on the subject of scanning discs, we've found that 
with 78s that you can get a good scan of the matrix and 
other information in the run-out area of the disc on 
the Epson 10000XL by raising one edge about 1/4-inch.  This
provides a slight raking-light effect - enough to greatly
improve the legibility of this important information.  The
Epson 10000XL has enough depth-of-field to support scanning
of an angled object while keeping everything in focus.

However, for 78s, we do two scans:

   - one 1/4-inch raised edge (raking-light) scan - ideal 
     for run-out area
   - one flat scan - ideal for label

Use a color-calibrated scanner (or DSLR) if you want to get 
the colors right.

Saving high-res scans/images as TIF files or other uncompressed 
format starts eating up storage pretty quickly.  Something 
worth thinking about - are the scans primarily for access 
and research, or are you trying to create preservation 
grade scans that can be correctly reprinted in the future?

Eric Jacobs

The Audio Archive, Inc.
T. 408.221.2128
F. 408.549.9867
mailto:EricJ@xxxxxxxxxxxxxxxxxxx