D7100 'streaking'

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

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.

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:

http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html

The essential figure is #18.

Clearly delineated steps emerge when the noise level is less than the quantization level, but there has to be a change in the average signal level to generate a change in the recorded data.

Note also that the transition region tonalities are not constant on either side of the step - which is not what I see in the pushed images.

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.

 mosswings's gear list:mosswings's gear list
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