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CODE4LIB  May 2009

CODE4LIB May 2009

Subject:

Re: Recommend book scanner?

From:

"Han, Yan" <[log in to unmask]>

Reply-To:

Code for Libraries <[log in to unmask]>

Date:

Fri, 1 May 2009 15:22:49 -0700

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (85 lines)

That is right. 
In addition, for certain printing (gold seal), digital camera delivers better result than scanners. 

-----Original Message-----
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of Jonathan Rochkind
Sent: Friday, May 01, 2009 2:38 PM
To: [log in to unmask]
Subject: Re: [CODE4LIB] Recommend book scanner?

Yeah, I don't think people use cameras instead of flatbed scanners 
because they produce superior results, or are cheaper: They use them 
because they're _faster_ for large-scale digitization, and also make it 
possible to capture pages from rare/fragile materials with less damage 
to the materials. (Flatbeds are not good on bindings, if you want to get 
a good image).

If these things don't apply, is there any reason not to use a flatbed 
scanner? Not that I know of?

Jonathan

Randy Stern wrote:
> My understanding is that a flatbed or sheetfed document scanner that 
> produces 300 dpi will produce much better OCR results than a cheap digital 
> camera that produces 300 dpi. The reasons have to do with the resolution 
> and distortion of the resulting image, where resolution is defined as the 
> number of line pairs per mm can be resolved (for example when scanning a 
> test chart) - in other words the details that will show up for character 
> images, and distortion is image aberration that can appear at the edges of 
> the page image areas, particularly when illumination is not even. A scanner 
> has much more even illumination.
>
> At 11:21 AM 5/1/2009 -0700, Erik Hetzner wrote:
>   
>> At Fri, 1 May 2009 09:51:19 -0500,
>> Amanda P wrote:
>>     
>>> "On the other hand, there are projects like bkrpr [2] and [3],
>>> home-brew scanning stations build for marginally more than the cost of
>>> a pair of $100 cameras."
>>>
>>> Cameras around $100 dollars are very low quality. You could get no where
>>> near the dpi recommended for materials that need to be OCRed. The 
>>>       
>> quality of
>>     
>>> images from cameras would be not only low, but the OCR (even with the best
>>> software) would probably have many errors. For someone scanning items at
>>> home this might be ok, but for archival quality, I would not recommend
>>> cameras. If you are grant funded and the grant provider requires a certain
>>> level of quality, you need to make sure the scanning mechanism you use can
>>> scan at that quality.
>>>       
>> I know very little about digital cameras, so I hope I get this right.
>>
>> According to Wikipedia, Google uses (or used) an 11MP camera (Elphel
>> 323). You can get a 12MP camera for about $200.
>>
>> With a 12MP camera you should easily be able to get 300 DPI images of
>> book pages and letter size archival documents. For a $100 camera you
>> can get more or less 300 DPI images of book pages. *
>>
>> The problems I have always seen with OCR had much to do with alignment
>> and artifacts than with DPI. 300 DPI is fine for OCR as far as my
>> (limited) experience goes - as long as you have quality images.
>>
>> If your intention is to scan items for preservation, then, yes, you
>> want higher quality - but I can’t imagine any setup for archival
>> quality costing anywhere near $1000. If you just want to make scans &
>> full text OCR available, these setups seem worth looking at -
>> especially if the software & workflow can be improved.
>>
>> best,
>> Erik
>>
>> * 12 MP seems to equal 4256 x 2848 pixels. To take a ‘scan’ (photo) of
>> a page at 300 DPI, that page would need to be 14.18" x 9.49" (dividing
>> pixels / 300). As long as you can get the camera close enough to the
>> image to not waste much space you will be getting in the close to 300
>> DPI range for images of size 8.5" x 11" or less.
>> ;; Erik Hetzner, California Digital Library
>> ;; gnupg key id: 1024D/01DB07E3
>>     
>
>   

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