ICEINSPACE
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Waning Gibbous 55.7%
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03-06-2008, 07:33 AM
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aiming for 2nd Halley's
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Join Date: Oct 2005
Location: Australia
Posts: 2,959
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DSLR in camera noise reduction?
Hi All, I note my Canon 40D has 2 settings for in-camera noise reduction...
what's the feeling out there - do you guys use the in-camera noise reduction for astro work or rely on post-processing to remove noise?
cheers,
Rob
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03-06-2008, 08:17 AM
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Registered User
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Join Date: Apr 2006
Location: Warrnambool
Posts: 12,617
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Rob, ICNR is the way to go, it dose increase your image run, but it is worth the effort, unless you can match the temp's very closely.
Leon
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03-06-2008, 08:29 AM
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aiming for 2nd Halley's
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Join Date: Oct 2005
Location: Australia
Posts: 2,959
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Quote:
Originally Posted by leon
Rob, ICNR is the way to go, it dose increase your image run, but it is worth the effort, unless you can match the temp's very closely.
Leon
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Thanks Leon, pardon my ignorance on this (complete novice), but why does it increase your image run? Also, when you say "unless you can match temp's very closely" are you suggesting that ICNR be used instead of darks which I understand would need to be taken at same temp as the lights?
And one final question can ICNR deal with hot pixels?
Thanks again for your help.
cheers,
Rob
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03-06-2008, 08:41 AM
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Dazzled by the Cosmos.
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Join Date: May 2005
Location: Brisbane
Posts: 11,737
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Rob
ICNR is where the Canon 40D automatically takes “Dark Frames” after each light exposure.
When this is enabled (User sets “C.Fn II–1” to “2=On”) then the 40D will take a Dark for every exposure over 1 second.
So, when you take a 3 minute exposure of say, M83, the 40D will automatically begin a 3 minute “Dark” exposure (ICNR) as soon as the M83 light is completed. This effectively doubles your imaging time, i.e. 3 min M83 + 3 min Dark = 6 mins total.
On my SBIG ST7E, where the cooling temperature is regulated, I have the luxury of taking say, 10 x 3 minute lights of M83 consecutively, followed by say, 5 x 3 minute darks at the end of the imaging run as the chip is at the same temp throughout.
I think that Bert has investigated ICNR on the 5D fairly comprehensively and IIRC, his recommendation was to use ICNR rather than switch it off and try to apply separate Darks later on.
Cheers
Dennis
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03-06-2008, 10:10 AM
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aiming for 2nd Halley's
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Join Date: Oct 2005
Location: Australia
Posts: 2,959
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Thanks Dennis - great info. At the moment (and assuming I will ever be able to image again with this damn weather ) I am using Images plus to control the camera and setting it up to take a range of Lights then a range of darks... do you know if I can use the ICNR with images plus just doing a run of lights or will this over-ride the ICNR?
cheers,
Rob
Quote:
Originally Posted by Dennis
Rob
ICNR is where the Canon 40D automatically takes “Dark Frames” after each light exposure.
When this is enabled (User sets “C.Fn II–1” to “2=On”) then the 40D will take a Dark for every exposure over 1 second.
So, when you take a 3 minute exposure of say, M83, the 40D will automatically begin a 3 minute “Dark” exposure (ICNR) as soon as the M83 light is completed. This effectively doubles your imaging time, i.e. 3 min M83 + 3 min Dark = 6 mins total.
On my SBIG ST7E, where the cooling temperature is regulated, I have the luxury of taking say, 10 x 3 minute lights of M83 consecutively, followed by say, 5 x 3 minute darks at the end of the imaging run as the chip is at the same temp throughout.
I think that Bert has investigated ICNR on the 5D fairly comprehensively and IIRC, his recommendation was to use ICNR rather than switch it off and try to apply separate Darks later on.
Cheers
Dennis
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03-06-2008, 11:41 AM
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Registered User
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Join Date: Apr 2006
Location: Warrnambool
Posts: 12,617
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Rob your camera controls the ICNR, so using Image Plus there is no reason to set it to take the darks at all, just set the camera to ICNR on 2, set Image Plus to take the lights at the desired length, tell Image Plus not to take darks at all, the camera will take care of it.
Just do some flats before hand, and process the lights as they are with the flats, as the darks are already taken care of.
Leon
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03-06-2008, 12:04 PM
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aiming for 2nd Halley's
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Join Date: Oct 2005
Location: Australia
Posts: 2,959
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Thanks Leon
Flats will be my next challenge
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03-06-2008, 12:49 PM
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Registered User
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Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,307
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The Rho complex pic I posted recently had no ICNR and was a stack of 20 10minute subs at iso1600.
http://s231.photobucket.com/albums/e...t=RhoLarge.jpg
Turned out not too badly - I expected loads and loads of noise, but I only applied very minimal NR with the Noise Ninja plug-in which had only a subtle effect.
Noise (and the lack of it) confuses me!!!!!
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03-06-2008, 01:07 PM
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Retired, damn no pension
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Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
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Rob, to expand a bit on what others have replied with.
ICNR = great...but it only deals with REPEATABLE NOISE. It doesn't deal with random noise in the darks (each dark and light will have a certain amount of random noise. Depending on temperature (see below), this may or maynot be an issue
Taking darks after and then applying them = could be great.... but often isn't. Stacking a multiple of Darks will deal with repeatable noise as well as reducing random noise by the sq rt of the number of darks you use to create a master. This is a very desirable thing. UNFORTUNATELY..... your darks, unless taken at the same temperature will have differing amounts of dark current so combining them will not necessarily have the same dark current as your lights. In fact most probably not.
If there was say a 6 degree drop in temp between taking your lights (which will have different amounts of noise 'cos the temp is dropping anyway) and the final dark you taken, then there will be 1/2 the noise in the final dark as in the first light.
what does this all mean....IF you temp is stable (<2 or 3 degree maximum change ) then yes taking darks at the end can be a good thing, especially if you are pushed for light time. If though your temp is dropping (or rising) then consensus seems to be to take ICNR.
HTH
BTW non-random noise is not really noise by definition, it should really be described by something like unwanted signal or detrimental signal or something similar. jmo
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03-06-2008, 03:14 PM
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Registered User
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Join Date: Feb 2005
Location: Monto
Posts: 16,741
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Paul,
Wouldn't the "Random" noise only be a problem if you are taking a single long exposure.
I'd assume that stacking of multiple images would cancel the "random" noise out.
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03-06-2008, 03:33 PM
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Retired, damn no pension
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Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
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That is true for stacking the final lights Jeanette, but the ICNR is only a single dark frame applied to the each image, so the random noise of the dark is also subtracted from the light. This is where multiple darks beat the ICNR as you can reduce the random noise by stacking and creating a master dark. That option isn't available in the ICNR.
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03-06-2008, 04:46 PM
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aiming for 2nd Halley's
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Join Date: Oct 2005
Location: Australia
Posts: 2,959
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AGGGHHHHH.. my head's exploding
but thanks, I appreciate the detailed advice...and I thought planetary imaging was fraught with complexity
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03-06-2008, 05:01 PM
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Retired, damn no pension
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Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
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It's actually pretty straight forward Rob. It's just like baking a cake, you just have to get the ingredients right, in the right order, using the right cake tin (making sure the tin is greased )and baked at the right temperature.
It putting the icing on the cake afterward in photoshop that really that will reeeallly boil your noodle. (don't ask me what noodles have to do with cake baking )
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