ThomasH wrote:
We all became used to the Web sited with tests of equipment. They are
often much better and more thorough than what we can read in the
printed press. What we see on these pages influences our purchasing
decisions and as it is in business: meanwhile Manufacturers "sponsor"
these sits often to bias the tests just a bit...

While looking at the web sites with tests of digital cameras for
several years already I never stopped to wonder: Why they still
fail to include all essential characteristics of the sensor and
of the image processor. For me not just the megapixels count.
I would like to know what is the bit depth per pixel. Or I would
like to see a warning: "manufacturer does not disclose bit depth
of a pixel."

Just look at the dpreview review of Canon G6, what is considered
a prosumer camera. Page 2 (Specifications) lists RAW mode, but
does not specify the bit depth. It makes me angry. Same Steve
Digicams (he mentions however that the digic processor processes
12bit signal) and you can go on so along all review sites of rank.
Same with (say) Nikon 8800. It has NEF and RAW modes, it says.
And? How many bits per pixel does it deliver???

This feature is so fundamental, so decisive. And yet is being
mentioned only in DSLR or middle format digital back reviews.
Why? More bits per pixel provide the so important richness of
detail in highlight and in shadow, allows to manipulate image to
a far larger extend. Of course, whoever ignores RAW or tiff mode
and shoots *.jpeg, has always already lost and obtains 8bit per
color in pixel, regardless the used gear! But the raw data and the
tiffs support bigger depth per pixel and can deliver much richer
image detail. Just a reminder to all who do not deal with data
processing: Obvious calculation shows that 12bit can hold 4096
levels of luminance, 8bit merely 256, it's 16 times more!! Even
mere 10bit per pixel allows already for 4 times more levels of
luminance.

I would suggest to *always* calculate as an additional technical
spec "image data" in megapixels. As an example lets compare two
cameras. I took in both cases Pentax to escape the usual
Canon/Nikon bashing. I used factor of 1024 to calculate Kbyes
and Mbytes.
camera A has camera B has
6Mpix 7Mpix
sensor 3008 x 2008 3056 x 2296
depth 12bits per color. 8bit per color
raw data 69.12Mbytes 53.53MBytes
converted tiff 207.37MBytes 160.6Mbytes

And there is the extra megapixel gone... Why everybody puts
cameras in "megapixel categories," but never not in "image data"
categories?

Of course higher resolution has its merits, but I would always
weight it against more dynamic range! If the smaller resolution
is big enough to match the quality of my glass and to achieve
the largest size of prints which I can do, I will rather always
go for a camera which has better dynamic range and less pixels!
I just would like to know... what is it!!! If not provided,
I assume its mere 8bit per color.

Thomas

Personally I find looking at actual results is a much better comparison
than stats.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math