Dalsa sensors, long exposures, dead pixels: Improvement in latest PS ACR

[chrismuc]

I have the impression that PS CS6 with the latest ACR plugin 8.3 handles long exposure files of Dalsa based sensors much better than previous versions: Enclosed an IQ180 ISO50 4 s exposure and a crop: No colored hot pixels. I also opened old Leaf Aptus 7 files with 4-8s exposure time and they show only very few hot pixels compered to "thousands" before.
Btw: The pic was shot with the Hasselblad Zeiss 50f4 FLE lens at f11 at 16mm shift upwards (+ Mirex shift adapter on FPS) and Alpa lens correction in PS applied to correct the slight linear distortion. Works nicely.

[atulshoots]

adapter on FPS
what is FPS?

[alifatemi]

adapter on FPS
what is FPS?

FPS abbreviation
Fellow of the Pharmaceutical Society of Great Britain!

[dchew]

adapter on FPS
what is FPS?

Focal Plane Shutter. A camera made by Alpa:
FPS_body

Dave

[Ken R]

I have the impression that PS CS6 with the latest ACR plugin 8.3 handles long exposure files of Dalsa based sensors much better than previous versions: Enclosed an IQ180 ISO50 4 s exposure and a crop: No colored hot pixels. I also opened old Leaf Aptus 7 files with 4-8s exposure time and they show only very few hot pixels compered to "thousands" before.
Btw: The pic was shot with the Hasselblad Zeiss 50f4 FLE lens at f11 at 16mm shift upwards (+ Mirex shift adapter on FPS) and Alpa lens correction in PS applied to correct the slight linear distortion. Works nicely.

Looks quite clean, very nice. Thx for posting.

[Paul2660]

At iso 50 and a 4 second exposure on an IQ180 were you seeing a lot of stuck pixels before?  I would feel that something was wrong as the IQ180 should easily get 4 seconds probably up to 20 seconds or 30 before extreme noise such as stuck pixels show up at that low an iso.  The 3 times I worked with a IQ180 I was able to get 10 second to 15 second shots with no problems.  This was with a DF body and Mamiya 35mm F3.5 lens and a Arca rm3di and Rodenstock 28mm.  You shouldn't have problems until around 1 minute I would think with the 180 at 35 or 50 iso.    Plus the mandatory dark frame the 180 takes on exposures over at 1 second or longer should remove all "normal" stuck pixels.  That's one of the main reasons for the dark frame as normal chroma and luminance  noise really can't be removed with a dark frame as I understand it.  It shouldn't matter on this if you were using CS LR or Capture One as the Dark frame is done at the back level. 

The IQ160 I normally used (which had gone back to Phase One which is how I ended up with a 180) easily did 10 second exposures at iso 50 and really only started to get noisy ( no stuck pixels) after around 30 seconds. 

Can't speak to the Aptus back as I have never shot one. 

With non Phase Back shots, in Capture One i.e Canon 6D and Nikon D800 where I am doing 30 sec to 5 minute work, I always use the "single pixel noise" reduction slider in Capture 1.  This helps to remove the stuck pixels.  I don't allow the camera to take the "dark frame" since I am stacking and don't want the gaps in between shots.  LR sometimes will see stuck pixels when I open a D800 raw other times it won't, I have never figured out what is queuing the software to see/remove the stuck pixels.   I have not tried LR 5.x on any Phase files that were longer exposures. 

Paul Caldwell

[Doug Peterson]

At iso 50 and a 4 second exposure on an IQ180 were you seeing a lot of stuck pixels before?  I would feel that something was wrong as the IQ180 should easily get 4 seconds probably up to 20 seconds or 30 before extreme noise such as stuck pixels show up at that low an iso.  The 3 times I worked with a IQ180 I was able to get 10 second to 15 second shots with no problems.  This was with a DF body and Mamiya 35mm F3.5 lens and a Arca rm3di and Rodenstock 28mm.  You shouldn't have problems until around 1 minute I would think with the 180 at 35 or 50 iso.    Plus the mandatory dark frame the 180 takes on exposures over at 1 second or longer should remove all "normal" stuck pixels.  That's one of the main reasons for the dark frame as normal chroma and luminance  noise really can't be removed with a dark frame as I understand it.  It shouldn't matter on this if you were using CS LR or Capture One as the Dark frame is done at the back level. 

The IQ160 I normally used (which had gone back to Phase One which is how I ended up with a 180) easily did 10 second exposures at iso 50 and really only started to get noisy ( no stuck pixels) after around 30 seconds. 

It matters a great deal actually.

The dark frame is captured at the back level, but is stored in the raw file as separate data. It is then analyzed and used by the software, assuming the software is programmed to look at it and use it.

This is done very purposefully, as the math to incorporate dark frame data to create a better final image has improved year-over-year since they started doing it. So hard-wiring correction into the firmware of the back would mean that a file captured several years ago would not benefit from the advances they've made in the math since then.

Always glad to see ACR catch up a bit to C1 in image quality .

[ondebanks]

Doug,

Which Phase One backs subtract the dark frame before writing out corrected RAW values, and which store the dark frame in parallel with the "actual" unmodified image in the RAW format?

Ray

[ondebanks]

That's one of the main reasons for the dark frame as normal chroma and luminance  noise really can't be removed with a dark frame as I understand it. 

Indeed, employing a dark frame actually makes chroma and luminance noise worse. At every pixel where a dark value is subtracted, you are adding a second readout noise component. This type of noise adds in quadrature, thus 2 frames (original and dark) leads to sqrt(2) = 1.4x the readout noise of the original frame alone. You are also left with the residual shot noise of the dark currents, as the dark frame can only subtract an estimate of the dark noise. That can be even worse than the combined readout noise.

Of course, there's no doubt that being left with lots of random noise is still far better than leaving the image with tonnes of uncorrected systematic dark current.

Bottom line is, a clean image not requiring a dark frame is always best of all!

Ray

[chrismuc]

I did another test: Night shot, 64 s exposure time at ISO 35. Open in ACR 8.3, lift shadows 100%.
Result: Pretty few hot pixels and acceptable amount of noise in dark areas.

[Chris Livsey]

FPS abbreviation
Fellow of the Pharmaceutical Society of Great Britain!

Pedant mode on;

The Queen agreed that the title "Royal" should be granted to the Pharmaceutical Society in 1988. From that date the abbreviated title was FRPS.

Pedant mode off:

I am a member, but not a fellow 

[Wayne Fox]

I had an email exchange with Eric Chan about the hot pixel issue when trying to pull detail out of shadows with my IQ180 a while back, something which C1 handled no problem, and he was aware of it. Maybe he found time to work it into this release.  (I'm sure it was a long way from the top of his list considering the last two versions of LR's involved complete raw engine rebuilds, and all the new cameras that the camera raw team have to manage each year).