Nagging questions

"Alfred Molon" wrote in message
...
In article ,
lid says...
most dslr sensors are capable of over 12 stops, limited by the d/a
converter.

Not true. Most DSLRs have less than 9 stops of dynamic range, according
to the tests of dpreview. See for instance the Nikon D300s:
http://www.dpreview.com/reviews/nikond300s/page17.asp

The best it achieves is 8.6 EV. Even the D3, with its bigger pixels is
not better:
http://www.dpreview.com/reviews/NikonD3/page20.asp

Also here the maximum is 8.6EV.

Reading all the way down to "RAW headroom" on the D3 link, 2nd paragraph:

"As usual the default Adobe Camera RAW conversion delivers less dynamic
range than JPEG from the camera (a more contrasty tone curve and very little
noise reduction in shadows). Simply switching to 'Auto' in the ACR
conversion dialog reaps huge rewards (we measured the result to have exactly
12 stops of dynamic range), and in our tests with real world shots produced
superb results with images that seemed to be over exposed beyond
redemption."

-Jim

In article , Alfred
Molon wrote:

most dslr sensors are capable of over 12 stops, limited by the d/a
converter.

Not true. Most DSLRs have less than 9 stops of dynamic range, according
to the tests of dpreview. See for instance the Nikon D300s:
http://www.dpreview.com/reviews/nikond300s/page17.asp

dpreview tests dynamic range by comparing jpegs which is bogus, to say
the least.

The best it achieves is 8.6 EV. Even the D3, with its bigger pixels is
not better:
http://www.dpreview.com/reviews/NikonD3/page20.asp

Also here the maximum is 8.6EV.

scroll to the bottom where they measured 12 stops with raw.

dxo labs measured it at 12.2 he
http://www.dxomark.com/index.php/eng/Image-Quality-Database/Nikon/D3

and roger clark measured 13.7 here, but he measures the capability of
the sensor itself, not the rest of the system.
http://www.clarkvision.com/imagedeta...formance.summa
ry/

nospam wrote:
In article , Eric Miller
wrote:

Just some random, mostly resolution-related questions. I fully accept
that the questions themselves may be misguided, so feel free to interpret.

Chip size, noise and other stuff.

All other things being equal, will a larger sensor have more noise?

no. for a given sensor technology and pixel count, a larger sensor will
have larger pixels, and therefore have less noise.

http://www.clarkvision.com/imagedeta...formance.summa
ry/


Okay, but if the larger sensor has pixels of the same size, will it have
more noise?

Eric Miller
www.dyesscreek.com

In article , Eric Miller
wrote:

Okay, but if the larger sensor has pixels of the same size, will it have
more noise?

if the pixels are the same size, the larger sensor will have more of
them, which is also beneficial.

Peter Chant wrote:
nospam wrote:


most dslr sensors are capable of over 12 stops, limited by the d/a
converter.

Is this the limit? Then why did Fuji have their fancy "super" sensor with
differing sizes of sites? I wonder why someone does not come out with a 16
bit a/d chip?

Pete


Adding more bits makes sense only if you get meaningful data, i.e., if
the low bits are still above noise level. IIRC each bit earned requires
6dB more signal/noise power ratio. For 14 bits, the electronics should
be as quiet as those of an audio device with 84db of signal/noise ratio,
and for 16 bits if goes to 96dB. Not undoable, but not that easy.

--
Bertrand

Alan Browne wrote:
Peter Chant wrote:
nospam wrote:


most dslr sensors are capable of over 12 stops, limited by the d/a
converter.

Is this the limit? Then why did Fuji have their fancy "super" sensor
with differing sizes of sites? I wonder why someone does not come out
with a 16 bit a/d chip?

The fuji sensor solved the highlights issue, not the shadow issue that
"deeper" a/d should help with.

Several of the MF cameras use 16 bit a/d. It's diminishing returns
after 12 or 14 bits.

I should even add, that IIRC, DXO tests of Hasselblad sensors at 16 bit
a/d show them to not be as good as Nikon, Canon and Sony cameras in
noise terms.

In article , Alfred
Molon wrote:

He is writing that with RAW usually you have one more stop of headroom.
The D3 achieves up to 12, but it is also a full-frame camera, pretty
much the best performing one at the moment. Most DSLRs use smaller
sensors and have therefore less dynamic range. You claimed that "most
dslr sensors are capable of over 12 stops" which is simply not true.

yes it is.

http://www.clarkvision.com/imagedeta...formance.summa
ry/

Alfred Molon wrote:

Most DSLRs use smaller
sensors and have therefore less dynamic range.

Bzzzt.
Sensor size *as such* has nothing to do with dynamic range.
Pixel size, however ...
Small sensors tend to have smaller pixels, that's all.

You claimed that "most
dslr sensors are capable of over 12 stops" which is simply not true.

http://clarkvision.com/articles/digi...ndex.html#data
indicates that the sensors are perfectly capable of 12+ stops,
based on their full well capacity and read noise, but excluding
A/D noise (which is not really tied to the sensor, anyway).
The rest of the page makes it clear that the camera performance
is limited by
a) 12 bit A/D converters,
b) noise in A/D converters,
c) *much* less improvement for A/D converters of 14 bit than would
be assumed by the additional bits. High megaherz speeds seem
to do that, at least for now.

-Wolfgang