In-camera processing of long-exposure RAW data

Started Jan 21, 2010 | Discussions thread
Bernard Delley Senior Member • Posts: 1,310
Re: HPS threshold-speed change?

The new D7000 HPS algorithm isn't quite the Moon Maid algorithm, though. In the presentation material for Nikon that I gave to Thom, I tried to emphasize the importance of including a headroom factor, but apparently Nikon didn't think it was necessary - or perhaps it wasn't straightforward enough to implement.

Are you sure about HPS activating at 1/4-sec. shutter speed? My D7000 (at original firmware version) doesn't use HPS until exposure time reaches 1 sec., which is the same threshold as the D3x.

I missed seeing the headroom part of the algorithm in your posts. -- Maybe Nikon wants the more aggressive straight clip for general noise reduction. I strongly feel that Nikon should make it a user controlled option something like 'Long exp Noise Clipping'.

My D7000 (6073683) says firmware A 1.01 B 1.01 L 1.002.
from 1/4 sec on it does clipping, and it cannot be intercepted in "mode 3"
(Long exp NR on , time 10s up, power off during 'job nr' blinking)

Below is other evidence that a set of 16 is used in clipping. For the full set (-border 3) of 16 M pixels I (my little program) checked if a pixel value is topped in its neighborhood, if yes disregard, else if it is solitary increase count at center of matrix. If there is an equal value increase the count at the corresponding relative position in the matrix. The result for 1/4 s shows 0 at center (its never top alone) and the pattern shows the 16 sites used for clipping (+ some accidentally equals at the other sites).

A riddle about the sensor properties shows up in the numbers below:

Why are the two top value pixels particularly frequently vertical neighbors in the Bayer square rg/gb ? This little mystery also shows up in the frequency of accidental equals at 1/5 sec.

dsc_0310.nef evidence that clipping was active: 0 solitary top values
ISO2 : 6400
Exposure Time : 1/4
threshold for analysis 180 :
counts for top equaled in neighborhood
counts for solitary top value at center
r1
1 0 2 2 2 1 4
0 156 4 173 2 169 2
4 4 179 98 198 5 1
2 168 133 0 126 168 2
3 4 165 1046 179 1 3
1 172 3 176 2 156 0
0 4 1 0 3 4 1
g2
1 1 1 3 0 0 0
0 92 2 94 3 68 1
1 5 56 146 86 1 0
2 104 126 0 133 104 2
0 3 91 1162 76 5 0
2 71 2 94 5 92 0
1 2 4 2 1 3 1
g3
1 4 1 0 4 4 1
1 68 4 55 4 67 0
0 1 75 1040 92 4 0
2 63 106 0 80 63 1
0 5 86 99 56 4 1
0 68 2 56 2 68 2
0 1 0 2 1 0 1
b4
1 3 3 2 1 2 0
2 180 2 202 2 190 0
3 5 179 1159 163 3 3
1 181 80 0 106 179 2
1 1 198 146 180 5 4
0 192 4 202 4 181 1
4 0 2 3 2 1 1

dsc_0311.nef evidence of no clipping: lots of solitary top values
ISO2 : 6400
Exposure Time : 1/5
threshold for analysis 200
counts for top equaled in neighborhood
counts for solitary top value at center
r1
1 1 3 3 5 2 4
2 3 4 4 2 3 2
6 1 8 1 3 0 8
1 5 2 15260 0 5 0
4 2 0 37 3 4 8
3 3 2 4 2 3 3
7 2 2 3 4 1 5
g2
6 4 2 3 4 2 2
3 0 3 1 2 2 3
0 4 3 3 0 1 1
0 1 0 12036 2 2 1
4 1 2 28 2 3 2
2 2 2 1 3 0 1
0 3 2 3 1 5 3
g3
3 1 1 3 2 2 0
5 1 2 3 2 0 3
3 4 2 37 3 2 2
5 0 1 9932 5 0 2
1 0 0 1 3 1 0
5 0 4 3 4 0 1
2 2 4 3 2 3 5
b4
5 3 3 3 2 2 7
1 11 5 3 4 4 2
6 3 2 28 0 1 3
2 3 4 16307 1 3 5
8 2 3 3 6 4 6
3 4 2 3 2 12 5
4 1 5 3 3 3 1

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