RE: Compressed Raw

[herschel mair <herschelmair@xxxxxxxxx>]

Raw files are actually black and white files with data about which cell relates to which colour. All this makes a much smaller file that a Tiff file so I guess you could call it compressed. However the data is all there and nothing is lost in the process. Once you open that file on a computer it converts all the black and white data into a colour image via a process called

DE-MOSAICING using rather complicated algorithms (Each manufacturer of camera and software have thier own version of this sofware) so depending on whether you open the image in Photoshop or Phase One or the maufacturers software, you could end up with quite different images. these images are now uncompressed, bitmap-type images. They can then be saved as uncompressed TIFF Files or even compressed TIFF files without any loss. Or you can compress them into JPEG files and choose how much quality you want to lose. Either way you should convert your raw images into the universal DNG format for posterity.

 

herschel

Llorenç Herrera <lha@xxxxxxxxxxxxx> wrote:

Hi, this is correct about Nikon D-70, it compresses de RAW files. But it?s a non-degrading compression, nothing related to JPEG compression. It means that those RAW compression does not affects in any way the final image quality.

 

JPG, MPEG, MP3, OOG ? etc. are all degrading-type compression techniques. The final result shows imperfections when looked very near (or heard paying lot of attention)

LZW, ZIP, RAR, Compressed-TIFF ? etc are all NON-degrading-type compressiong techniques. The final result shows EXACTLY the same digital data you can see if it weren?t compressed.

 

I don?t know exactly, but I bet that the kind of internal compression Nikon uses on its RAW files is one kind of LZW.

 

I don?t know anything about Nikon D100

 

__________________

Llorenç Herrera Aznar

http://www.lorenzoherrera.com

http://www.fotopunto.com

 

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De: owner-photoforum@xxxxxxxxxxxxxxxxxxxxxx [mailto:owner-photoforum@xxxxxxxxxxxxxxxxxxxxxx] En nombre de Jerry McCown
Enviado el: viernes, 29 de abril de 2005 0:02
Para: List for Photo/Imaging Educators - Professionals - Students
Asunto: Compressed Raw

 

My D100 default setting is compressed raw and I had to go in and turn the compression off as it was taking WAY too long to save the file.

LScottPht@xxxxxxx wrote:

With the Nikon D70, the RAW images are compressed RAW images. I will have to go back and look at my manual, but I think it even says so in the manual. I'm not sure why the camera shoots compressed RAW images, perhaps others here could answer that.

 

Leslie

 

I don't think this is correct, RAW files are not compressed from what I understand

Herschel Mair

H.O.D. Photography Dept, Higher College of Technology
Al Khuwair
Sultinate of Oman
9899673

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