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01-02-2013, 03:21 AM   #1
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Time Exposure

Hi,

My K20D takes as long to write to the memory card as the length of time that the shutter is open for, eg., five second photograph = five seconds writing.
Is there any way that I can speed this up?

Regards.

01-02-2013, 04:15 AM   #2
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That's...peculiar, to say the least. Perhaps invest in a better memory card?
01-02-2013, 05:40 AM   #3
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It might be worth having a look at your noise reduction settings in the Custom Menu, as these can slow down your write to speeds.
01-02-2013, 05:44 AM   #4
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yep, what kerrowdown said...dark frame subtraction

01-02-2013, 01:07 PM   #5
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QuoteOriginally posted by kerrowdown Quote
It might be worth having a look at your noise reduction settings in the Custom Menu, as these can slow down your write to speeds.
Hi,

What would reducing the noise reduction setting do to picture detail?

Regards.
01-02-2013, 01:22 PM   #6
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QuoteOriginally posted by gordon_l34 Quote
Hi,

What would reducing the noise reduction setting do to picture detail?

Regards.
If you have noise reduction on, after the exposure ends, the camera takes another exposure (with the shutter closed) and is a record of the noise characteristics of the sensor. Before saving the original exposure, the camera will then subtract the dark frame from it and then save it. If you want to turn NR off, you will have to deal with the noise in post processing but the upside is that you don't have wait for the camera to do the NR thing after exposure. Astrophotographers usually make up libraries of dark frames (various exposure times and ISO's) and use these to reduce noise in pp.
When doing exposures running into minutes, it is a better use of imaging time.
01-02-2013, 01:41 PM   #7
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QuoteOriginally posted by pixelsaurus Quote
If you have noise reduction on, after the exposure ends, the camera takes another exposure (with the shutter closed) and is a record of the noise characteristics of the sensor. Before saving the original exposure, the camera will then subtract the dark frame from it and then save it. If you want to turn NR off, you will have to deal with the noise in post processing but the upside is that you don't have wait for the camera to do the NR thing after exposure. Astrophotographers usually make up libraries of dark frames (various exposure times and ISO's) and use these to reduce noise in pp.
When doing exposures running into minutes, it is a better use of imaging time.
Hi,

Happy New Year to one and all.

Yes I do have NR turned on to the maximum. What you are saying is that I am going to have to learn post processing, which is something that I have been trying to avoid by getting the photograph right in the camera in the first place.

Thanks and Regards.
01-02-2013, 09:20 PM   #8
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QuoteOriginally posted by gordon_l34 Quote
Hi,

Happy New Year to one and all.

Yes I do have NR turned on to the maximum. What you are saying is that I am going to have to learn post processing, which is something that I have been trying to avoid by getting the photograph right in the camera in the first place.

Thanks and Regards.
I do feel your pain. My feeling is that you only have 2 options.
Firstly you leave NR on and effectively double your time between successive exposures.
Secondly you turn NR off and deal with the noise issue in software. As well as doing the dark frame subtraction method, there are also software available for dealing with noise eg NeatImage and Topaz DeNoise. Topaz does a pretty fair job and I am happy to use it. However for the night shots I take, I do find the Dark subtraction is more consistent. DeNoise does a great job at removing residual noise left after subtraction. I am not a fan of extensive PP preferring to get right in the camera (a hangover from my film days), however sometimes circumstances and equipment conspire against me. The following shot is pretty much the type of thing I have to deal with. It was shot with a Pentax *ist DS some 6 years ago of Comet McNaught. It was 30 sec @ ISO3200 and all I can say is the noise is horrific. There is also severe horizontal banding and despite my best efforts using PSE6 (with Carboni Actions installed) and NeatImage, I was never able to reduce the noise satisfactorily and extract all the detail in the the PEF file.
I'm still on the learning curve but using dark frame subtraction several months ago, I obtained better results in an afternoon than 6 years of slugging it out in PSE6.

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01-03-2013, 04:20 AM   #9
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QuoteOriginally posted by gordon_l34 Quote
Hi,

Happy New Year to one and all.

Yes I do have NR turned on to the maximum. What you are saying is that I am going to have to learn post processing, which is something that I have been trying to avoid by getting the photograph right in the camera in the first place.

Thanks and Regards.
A Happy New Year to you too,

"NR turned on to the maximum" is probably the High ISO Noise Reduction, (HI-NR) which doesn't take any measurable time. The time lag that you observe comes from Slow Shutter Speed Noise Reduction (SSS-NR) where the Dark Frame subtraction discussed above comes into play.

SSS-NR is for dealing with hot pixels and the soft glow that the sensor may produce when it consumes power for an extended time. With your application (no post-processing intended) and exposure times as short as 5 seconds I would confidently turn the SSS-NR off and keeping the HI-NR on.

It is only when you shoot very dark scenes and in particular if you apply some rather aggressive image enhancement in the post-processing that hot pixels and amplifier glow can become a real problem. What you could do, and should do, is to take a few dark shots after each session. It is easy to subtract these from your images in software afterwards, just in case that you should have problems with hot pixels and/or sensor glow after all.....

Your K20D is somewhat older than my K-5 but, anyway, here is a sample of what I am talking about: Dark Frames shot at 5, 30 and 139 seconds and ISO 400 without any processing at the top and very aggressively contrast enhanced in the lower row:
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