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 Jack Hogan, Apr 8, 2013

Jack Hogan wrote:

Jussi Mattila wrote:

I put the images available at: D7100 streaking NEFs

Hi Jussi,

A few observations:

1) All images were taken at the very same exposure, 12 bits, compressed Raw
2) The ISO 100 image has perceivable streaking even without pushing, and its maximum Raw values are at less than 1/4 of full scale - this would exclude blooming
3) The ISO 1600 image has no streaking even when pushed several stops - this would exclude most input related sensor issues including flare (same lens, same exposure)
4) The difference in the mean raw values from the darker and lighter streaks to the top right of the window in the ISO100 image is less than 1 ADU (on average about 0.6), Raw values 12.6 stdev 1.3 next to the bright light, 11.9 stdev 1.2 next to the blind at an SNR of about 10 - this corresponds to a difference of about 5 electrons
5) The mean raw values from the same spots at the top right of the window in the ISO1600 image are around 195 with stdev around 20, also with an SNR of about 10.  If there is a slight difference it is too difficult to measure/see.
6) One can also see streaks at ISO100 in the slightly brighter vertical riser just to the right of the measurements in 4), with mean values around 18/19 and differences of about 0.7-1 ADU between the brighter and darker streaks.

It could be something in the processing (row specific dynamic offset, gain, ADC parameter or ?).  Suggestion: take the same 5 shots at 14 bit lossless compressed to see if it makes any difference (more noise might dither things out) just to eliminate one more variable.

Jack

To put Jack's suggestion into context a little bit, the D5200 writes files ONLY in 14 bit visually lossless compressed format.  Just as the D5100 before it.  This is apparently to avoid posterization in the lowest levels.  The D7100's default is 14 bit "uncompressed". High DR scenes should always use 14 bit formats. The question is now whether Horshack's test shots were shot in 14 or 12 bit format. He had to resort to a 5-stop pull to reveal the streaks, so the answer may be yes.

I'd also note that Lightroom doesn't just do anything simply even though it uses a simple name to describe it.  I raised the "exposure" knob to reveal the streaks, but it may be playing games with the tonal balance in the shadows as it does so. YRMV.

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