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Old November 27th 07, 11:51 AM posted to rec.photo.digital
Thomas Richter
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Posts: 52
Default NEWS: HD Photo to become JPEG XR

John Navas schrieb:

For first, this news is old news. It dates back to the JPEG meeting in Lausanne this
summer.

Why JPEG XR is badly needed:

The problem is 8-bit (per channel) JPEG. Although non-linearity gives it
roughly 11 stop dynamic range, 8-bit luminosity resolution is more
limited than many camera sensors (often 10-12 bits). While 8-bit JPEG is
fine for scenes with lower luminosity range, more bits are needed for
best results with higher luminosity range. This is a major, if not the
major, reason to shoot RAW.


Probably, probably not. Another issue is - at least in my understanding - that
photographers feel that they "loose" possibilities by lossy compression, i.e.
image content is gone forever. I wouldn't say "badly" either. There are lots
of proper alternatives that just wait to be used, you mentioned them.

* An alternative would be 12-bit JPEG, but there's too little support
for that to be practical.


That goes, however, for all alternatives as well. Actually, the IJG seems
to support 12bit by now.

* Another alternative is JPEG 2000, which also has a useful lossless
mode, but it's still not widely supported, has EXIF issues, has
potential patent issues, and puts a higher computational burden on the
camera processor than JPEG.


The EXIF issues are currently addressed. Actually, the issue can be solved
rather easily as JPEG2000 has more than enough room to include meta-data.
You are correct when saying that it has complexity issues, though. The
second major error made during its standardization.

* Yet another alternative would be Adobe DNG as an alternative to
proprietary camera RAW, but major camera manufacturers seem resultant to
adopt it.


That's not too unlikely to happen with any new format. Actually, Japanese
camera vendors don't seem - in my reception - feel too hot about JPEG-XR
either.

* Lastly there's Microsoft's JPEG XR (HD Photo), which is more like JPEG
than JPEG 2000 in terms of computational burden with compression
efficiency comparable to JPEG 2000, but is not yet standardized.


It's currently undergoing standardization, however, saying that it can compete with
JPEG2000 in terms of compression performance is IMHO highly overstating its powers. In
fact, from the tests performed, I somewhere sort it near or sometimes even below
baseline JPEG, depending on image content. Note that JPEG-XR is not yet final,
so things will hopefully change to the better, and that for proper tests, one
also has to check with HDR images from the market JPEG-XR actually targets at,
so beware - this is just the status quo. On the other hand, being more critical to
MS press releases won't hurt, either. The best you can do is test yourself.

Until this is sorted out, RAW remains an important tool for scenes with
higher luminosity range, despite its drawbacks. I personally don't use
RAW often, but I do sometimes use it.


The major drawback is its lack of standardization. The problem seems that camera
vendors prefer to bind their customers instead of making images interchangeable.
I don't see why JPEG-XR would change their position, but that's all my guesswork.
Otherwise, it would have been easy just to approach the JPEG to standardize *some*
type of raw format - it is IMHO just not desirable for the vendors.

So long,
Thomas