D7100 'streaking'

Started Apr 7, 2013 | Discussions thread
krikman
Regular MemberPosts: 292
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Re: D7100 'streaking' - doesn't look like blooming or flare
In reply to mosswings, Apr 9, 2013

mosswings wrote:

krikman wrote:

I mean compressian of data to be 12-bit wide, which are image specific. No

in conversion to 12-bit, but coders forgot to cut unusable bits from precise calculations so we got rounding error in green channel.

. From these samples I conclude that these stripe artifacts are no lens defect, no photosites overloading, no sensor errors but round error in data calculations.

Jack

You, Jack, talk about RAW conversion software, but I talk about preprocesses before writing NEF.

An interesting proposition, and definitely true that the D7100 should not normally be operated in 12 bit mode (Mattilla had a D90 previously, which had noise levels high enough to obivate the need for 14 bit recording, so only offered 12 bit recording).  The test definitely needs to be conducted at 14 bits.

My whole point was in-camera ADL work. I can strongly conclude from my D300s behaviour that in-camera ADL works selective. It not just compresses data range but lengthen exposition for darks and somehow restores lights. At levels that impossible for written RAW data. All this required some 'area recognition' for dark and light regions.

From this I supposed that programmers forgot to reset 'pushed down' condition for bright areas setted by in-camera ADL, ant it is for unused or crippled data bits only.

Anyway it is always hard to find where is somebody's algorhytm fails, especially at 0.1% levels.

However, I'm having a hard time ascribing the geometry dependence of the tonality in the deep shadows to strictly truncation sloppiness in the low-level RAW codec.  There would have to be a real change in the sensel charged stored in order for a converson truncation to emphasize any such shifts. Consider this discussion on truncation vs. noise levels from University of Chicago:

Yes, if no ADL 14-bit NEF shows same behaviour all my statements will discarded and we'll blame sensor.

Something else appears to be going on here.  So I agree that the following need be done:

1. Run tests at 14 bit as well as 12 - reduces posterization issues

2. Run tests with the camera in landscape mode, portrait mode, and at 45 degrees to both - reveals directional sensitivities to blooming.

It is clear that in landscape mode and inclined we'll have no stripes at all. But what happens in opposite direction? I presume data reading from left to right in our cameras...

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