[Leica] Yet another surprising fact about the M (240)

[Herbert Kanner]

Yew, I know. I was just surprised at first that it could be a factor of two. Then I stopped being surprised after I thought about it for a few minutes.

Herbert Kanner
kanner at acm.org
650-326-8204

Question authority and the authorities will question you.




> On Jul 14, 2015, at 7:28 PM, Richard Man <richard at richardmanphoto.com> wrote:
> 
> Lossless compression is not new or difficult, even Huffman did it in 1952
> as a term paper project :-)
> 
> On Tue, Jul 14, 2015 at 6:55 PM, Herbert Kanner <kanner at acm.org> wrote:
> 
>> I was surprised to see in the manual that there was lossless compression
>> of the DNG. So I thought I'd try it out by taking two shots, one compressed
>> and one uncompressed. When I looked at my DNG file, I was astounded to find
>> a DNG of over 40 MB and a compressed one of about half that size. (I
>> deleted the negatives before thinking of writing this, so I can't give you
>> exact numbers.
>> 
>> Well, I was at first astounded that lossless compression could be that
>> effective. Then I thought about the details of an image. Except where there
>> is really fine structure in the image, there will be areas where the data
>> does not change. A simple number triple, one giving a value for, say the
>> red pixel, the second giving a starting location in the file, and the the
>> third the number of consecutively stored pixels having the same value,
>> could easily result in a factor of two compression for lots of pictures.
>> And what I just described is a very unsophisticated compression method. If
>> anyone knows more about how this might have been done, I'd be very
>> interested.
>> 
>> kanner at acm.org
>> 650-326-8204
>> 
>> Question authority and the authorities will question you.
>> 
>> 
>> 
>> 
>> 
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> 
> 
> 
> 
> -- 
> // richard <http://www.richardmanphoto.com>
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> 
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