07-18-2010, 01:44 PM
[quote name='Brightcolours' date='18 July 2010 - 02:29 PM' timestamp='1279456196' post='1092']
Some side notes.
Nikon's D3 (and D200, D300/D3s probably, D700, probably all Nikon DSLRs since the D200) appear to apply some NR only (or extra?) when exposure time reaches a certain duration. It can vary from model to model (I have forgotten the exposure time values where you see it kick in with the different models).[/quote]
You can actually switch this feature on and off with Canon, long exposure noise reduction, that is. However, this is not what affects astrophotography. It reduces heated sensor noise, by substracting the pattern noise from a sensor that is hot because of a long exposure. It is the only way to do this, and is different literally from camera to camera, as no individual sensor is the same in this regard. Furthermore, funnily enough, this is a technique borrowed from astrophotography in the first place <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.
With regard to the 5D II: it doesn't affect it. It was creating noise where there isn't any. It is in a way a similar issue to the black pixel syndrome, where in high iso shots with high contrast transitions, the neighbouring pixels got clipped by the A/D converter hardware to 0 values due to the preceived too big difference in eV values. It is a strange phenomenon in that neigbouring signal outputs are somehow interrelated, which is a physics thing as far as I understand (i am no expert on this, BTW, so this is my layman interpretation). The boundaries between two neighbouring well sites is not as clear cut, it seems, as we would expect.
However, Raw is still Raw with the 5D II, as all pixe values are still there. IOW, th eproblem lies in gettign out the real values, not so much trying to get rid of noise, with these issues anyway.
Kind regards, Wim
Some side notes.
Nikon's D3 (and D200, D300/D3s probably, D700, probably all Nikon DSLRs since the D200) appear to apply some NR only (or extra?) when exposure time reaches a certain duration. It can vary from model to model (I have forgotten the exposure time values where you see it kick in with the different models).[/quote]
You can actually switch this feature on and off with Canon, long exposure noise reduction, that is. However, this is not what affects astrophotography. It reduces heated sensor noise, by substracting the pattern noise from a sensor that is hot because of a long exposure. It is the only way to do this, and is different literally from camera to camera, as no individual sensor is the same in this regard. Furthermore, funnily enough, this is a technique borrowed from astrophotography in the first place <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.Quote:With earlier Nikons you could force it to write RAW data by using long exposure NR (black frame subtraction) and then turning the camera off while it was taking the black frame. I wonder if that is still possible with the newer models like the D3 and D3s? That would mean that you can prove exactly which impact the NR on the RAW data has. The Canon 5D mk II got some kind of pattern noise firmware fix. Not sure how that impacts the RAW data integrity.
With regard to the 5D II: it doesn't affect it. It was creating noise where there isn't any. It is in a way a similar issue to the black pixel syndrome, where in high iso shots with high contrast transitions, the neighbouring pixels got clipped by the A/D converter hardware to 0 values due to the preceived too big difference in eV values. It is a strange phenomenon in that neigbouring signal outputs are somehow interrelated, which is a physics thing as far as I understand (i am no expert on this, BTW, so this is my layman interpretation). The boundaries between two neighbouring well sites is not as clear cut, it seems, as we would expect.
However, Raw is still Raw with the 5D II, as all pixe values are still there. IOW, th eproblem lies in gettign out the real values, not so much trying to get rid of noise, with these issues anyway.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....