Possible Cause of D200 "Banding" Issue

http://www.imaging-resource.com/PRODS/D200/D200A.HTM

Enjoy,
RiceHigh
http://www.geocities.com/ricehigh

Rita Ä Berkowitz wrote:
RiceHigh wrote:

http://www.imaging-resource.com/PRODS/D200/D200A.HTM


Thanks, good article. I haven't noticed this "banding" with my D200 so I
guess I'm the lucky one? It seems this problem happens under certain
conditions and not with all cameras. He did a great job outlining the
highpoints of the camera and this "banding" issue. I agree with him
when he
concluded the article by saying, "The relatively minor (in my view)
issue of
the "corduroy" streaking aside, the Nikon D200 is simply a fantastic camera
to shoot with, and its other image-quality parameters are absolutely
first-rate."

Rita

The D200 is certainly a very elegant looking camera, Rita. Vrey nice indeed!

In message .com,
"RiceHigh" wrote:

http://www.imaging-resource.com/PRODS/D200/D200A.HTM

I don't think it could have anything to do with sensor overload, as the
effect would then be greatest at the lowest ISO. Looking over the RAW
data in the ISO 400 .nef of the lightbulb, I see that the every other
column of red/green is brighter than the ones in-between, but the
blue/green columns look homogenous. I would suspect some kind of
blackpoint calibration error.

Now I've looked at the ISO 100, 1600, and 3200, also. 3200 is all odd
numbers in the RAW data, meaning that it is an arithmetic push in the
camera, like most other DSLRs. 1600 had a similar level of banding as
400; it's just masked by the higher random noise of the 1600. 100 has
banding also, but it is intermittent; visible in some successive
columns, more subtly, but almost invisible in some areas. A shot of a
grey wedge might be more useful, as you can then see if the bands are
offsets or scalars more clearly.


--


John P Sheehy

The Imagining Resource article suggests that it is sensor overloading
specific to the interlaced addressing and data retrieval of the D200
Sony sensor. Your suggestion of black point calibration errors might be
possible. However, both the IR article and your explanaton cannot
exactly explain why the patterns appeared to be in corduroy line form
which each of the darker and brighter lines I think is thicker than one
pixel.

Anyway, I hope this problem can be overcomed very soon so that I can
consider the D200 again.

RiceHigh
http://www.geocities.com/ricehigh

wrote in message
...
In message .com,
"RiceHigh" wrote:

http://www.imaging-resource.com/PRODS/D200/D200A.HTM

I don't think it could have anything to do with sensor overload, as
the effect would then be greatest at the lowest ISO.

In the Pixmantec forums/fora I read that they only see some evidence
of the artifact after White balancing. As usual, Raw converters will
make a difference.
http://forum.pixmantec.com/showflat.php/Cat/0/Number/22268/an/0/page/0#22268

As White balancing is a post-processing step, it apparently is a
hidden (hardware) S/N issue. I believe it is stated (FWIW) that Nikon
can adjust with a hardware+firmware upgrade to "address" the issue.

Bart

In message ,
"Bart van der Wolf" wrote:


wrote in message
.. .
In message .com,
"RiceHigh" wrote:

http://www.imaging-resource.com/PRODS/D200/D200A.HTM

I don't think it could have anything to do with sensor overload, as
the effect would then be greatest at the lowest ISO.

In the Pixmantec forums/fora I read that they only see some evidence
of the artifact after White balancing. As usual, Raw converters will
make a difference.
http://forum.pixmantec.com/showflat.php/Cat/0/Number/22268/an/0/page/0#22268

As White balancing is a post-processing step, it apparently is a
hidden (hardware) S/N issue. I believe it is stated (FWIW) that Nikon
can adjust with a hardware+firmware upgrade to "address" the issue.

The vertical banding in the light bulb sample exists before white
balancing. Every fourth column (every other R/G column) is slightly
brighter than the rest.
--


John P Sheehy

In message , I,
wrote:

The vertical banding in the light bulb sample exists before white
balancing. Every fourth column (every other R/G column) is slightly
brighter than the rest.

I also noted some other things about the D200 RAW data looking at the
light bulb files.

The clipping value is only 4095 in every other column of pixels; in the
remainder, they alternate at something like 4000 and 4016, which means
that any value above 4000 really should be clipped, as clipping at
different levels creates false detail in the highlights. I didn't think
to make a correlation between this and the shadow banding, but if the
issue is an offset, they are probably both symptoms of the same problem.

The Canon 10D does this variable-clipping point also, in a more
random-looking pattern, but the stretch is only over about 9 levels
(3997 - 4006 at ISO 100, with the range sliding up at higher ISOs). RAW
converters should ideally clip all this data at the lowest clipping
value (after optimally blackpointing, of course).

The RAW data is already blackpointed in the NEF. This allow more
potential headroom, but as seen above, it is mostly wasted, as compared
to a camera that outputs RAW data to 4095, with a positive blackpoint.
I believe that keeping the positive blackpoint offsets in the data makes
it easier for future converters to eliminate noise at the RAW source.
On the 20D, where the blackpoint is generally 128 in the RAW data,
binning the RAW data for downsampling can bring the average noise close
to the linear blackpoint (128); binning already-black-clipped data does
not make the average black level approach linear black, as all of the
binned elements are 0 or greater.

The DNG 3.3 converter apparently not only drops the masked, black pixels
from D200 NEFs (maybe the NEFs don't even contain them, as they are
useless if the data is already blackpointed), but the DNG converter
crops the exposed RAW image by 4 pixels horizontally (3900 instead of
3904, as output by IRIS).

--


John P Sheehy