M-Raw and S-Raw - a really bad idea.

Started Sep 19, 2009 | Discussions thread
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Steen Bay
Veteran MemberPosts: 6,792
Re: An example of what could be done
In reply to ejmartin, Sep 24, 2009

ejmartin wrote:

mmullen wrote:

ejmartin wrote:

For reference, the original NEF file is 23.2MB. Granted, some of the NEF filesize is taken up by metadata and an embedded fullsize JPG. But not so much that the filesize could not be reduced by a substantially larger factor than that achieved by sRAW, with much less loss in resolution.

sRAW and mRAW are not about retaining maximum resolution, these formats are provided for those who do not need maximum resolution but still wish to retain the full tonality and editing abilty of the RAW file.

One does not have the full editing ability and tonality of the RAW file. One has a downsampled, aliased truncation of the RAW data. I will agree that one has the full tonality and editing ability of a quarter of the original image data for a savings of only half the storage space (in the case of sRAW; mRAW is similarly inefficient).

Until you understand that, you will not understand why Canon offers these additional formats.

My understanding is not deficient. How much do you know about image data compression? There are many ways of throwing away image information, and demosaicing and downsampling throws away about the most for the least return in data compression. Canon made a rather poor choice.

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I'm sure it's correct that a full size RAW file can be compressed by a considerable amount, almost without any loss of important information, but what I'm after is a bit different though. When I find M-RAW interesting it's not so much because of the lower file size (MBs), but more because I see downsampling as a method to 'optimize' per pixel sharpness and noise.

It's quite possible that for example a 80mp RAW file only (in best case scenario) would contain, let's say 21mp 'worth of detail', and then I'd rather have a 20mp M-RAW file with lower noise and maybe 18mp worth of detail, with so good per pixel sharpness that sharpening wouldn't be necessary. (And such a M-RAW file could probably also be compressed..)

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