D200 file Compression questions

Started Mar 8, 2006 | Discussions thread
Kaj E Veteran Member • Posts: 9,440
Re: D200 file Compression questions

gnet158 wrote:

JPEG Compression lists two options,
1 Size Priority
2 Optimal Quality

The size of a JPEG file typically increase with detail in the image. An image with little detail (for instance one with plenty of blue sky is typically small).

The "size priority" tries to limit the file size, so it applies more compression to an image with much detail to keep the file size fairly constant for all scenes. This setting tries to limit the max. file size.

The "optimal quality" setting keeps the compression constant and allows the the file size to increase with more detail.

As implied by the names Size priority keeps the file size smaller at the expense of quality, whereas the "optimal quality" keeps the quality good at the expense of larger files.

What’s the real difference aside from being able to fit more JPEG’s
on your CF card when using option 1?

RAW NEF Compression
1 NEF (RAW) no compression
2 Comp NEF (RAW) – compresses files 40-50% with little drop in
quality. Is that true?

Uncompressed RAW records all the information available in the RAW file 12-bits throughout the image. In an uncompressed RAW file the darker tones have fewer steps of information than the light ones.

The compressed file compresses the lightest tones in the RAW file by limiting the many available steps in the highlights. The dark tones are untouched because they have fewer tones to start with. This results in a file with an average of about 9.3 bits. The philosophy is apparently to discard some of the "unnecessarily" numerous steps in the highlight area. The highlight area will in this way lose data and be of lower quality but the overall quality will still be quite good.

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Kind regards
Kaj
http://www.pbase.com/kaj_e
WSSA member

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