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

[John McMaster]

It varies in size depending on the scene  (unlike a Sony which is always the
same size so shows lossy compression), my S2 shots are usually smaller files
than the Monochrom (which cannot be compressed).

john

-----Original Message-----

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.
>>