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03-22-2008, 01:40 PM   #1
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slow shutter speed noise reduction

there is an option on my camera that reads "reduce noise at slow shutter speeds" does this need to be on ? I found with my last camera that actually the slower the shutter the less noise, infact I knew that shooting faster than 1/500 was not a good idea. what should I do ?

03-22-2008, 01:49 PM   #2
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QuoteOriginally posted by simons-photography Quote
there is an option on my camera that reads "reduce noise at slow shutter speeds" does this need to be on ? I found with my last camera that actually the slower the shutter the less noise, infact I knew that shooting faster than 1/500 was not a good idea. what should I do ?
The reference is to digital noise, not sound waves. A sensor warms up as it is in use, and as it warms up it can send spurious signals, called "Noise". It is equivalent to the film term "grain". The noise reduction takes another exposure of the same length with the shutter closed, and subtracts any pixels that show up from the original image. This has the effect of producing a cleaner image, but taking twice as long between shots as the camera saves the dark image.
03-22-2008, 01:58 PM   #3
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aha thats a clever way of resolving it. yes I know what "digital noise" or "electrical noise" is its just that from past experience a slow shutter speed meant less noise but that was on a fuji digicam faster than 1/500 sec was visibly grainy. its really a similar process used to reduce noise in sound (crackling on LPs or tape hiss).

so is the CCD in use whilst the camera is on ? its obviously not used for previewing like on a digicam or compact, so if its kept off and only used to take a picture that is a great step in the right direction of noise reduction.

at what speed would this noise reduction kick in ?
03-22-2008, 02:11 PM   #4
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QuoteOriginally posted by simons-photography Quote
aha thats a clever way of resolving it. yes I know what "digital noise" or "electrical noise" is its just that from past experience a slow shutter speed meant less noise but that was on a fuji digicam faster than 1/500 sec was visibly grainy. its really a similar process used to reduce noise in sound (crackling on LPs or tape hiss).

so is the CCD in use whilst the camera is on ? its obviously not used for previewing like on a digicam or compact, so if its kept off and only used to take a picture that is a great step in the right direction of noise reduction.

at what speed would this noise reduction kick in ?
I think the K10D noise reduction cuts in on exposures longer than 2 seconds. I cannot find it in the manual and the camera menu doesn't tell me either.

03-22-2008, 02:14 PM   #5
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yea I tried looking it up as well but you gave me more info in the previous post than the flipping manual, I'd bet you guys on here know more about the specifics than what the manul has to say on many things
03-22-2008, 06:11 PM   #6
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To make a complicated story short:

Set "long exposure noise reduction" to ON if you don't plan to take a dark frame exposure manually yourself (and you sound like you really don't plan to do so . So, ON, not OFF.
03-22-2008, 06:16 PM   #7
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QuoteOriginally posted by simons-photography Quote
aha thats a clever way of resolving it. yes I know what "digital noise" or "electrical noise" is its just that from past experience a slow shutter speed meant less noise but that was on a fuji digicam faster than 1/500 sec was visibly grainy.
I would guess that was a result of the camera automatically boosting the ISO in order to allow you to use the faster shutter speeds in less-than-adequate lighting situations.
03-22-2008, 07:47 PM   #8
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QuoteOriginally posted by simons-photography Quote
yea I tried looking it up as well but you gave me more info in the previous post than the flipping manual, I'd bet you guys on here know more about the specifics than what the manul has to say on many things
There are lots of things the experts on this forum know that are not in the manual. Internal camera operation not listed in the manual is often an educated guess unless it can clearly be measured. I just read the debate on what the new K20D "D" mode does and the opinions often conflict. Unless Pentax comes out and defines that mode there will be many debates.

I've asked more than once what the Scene modes do beyond the K100D manual's: "Portrait = Optimal for capturing portraits." No one seems to know what specific changes the camera makes for each scene mode and I've given up waiting for Pentax to tell us!

You asked about the shutter speed that NR kicks in, but that may depend on the model. I know from the delay after the shutter closing to display appearing that my K100D has NR in effect at 1 second. I turn off NR and the delay is noticeably shorter. I >think< I can detect the delay at 0.5 seconds, but that is a guess. The manual does not specify.

Canada Rockies mentions longer than 2 seconds (as in 3 seconds?), but he has a K10D.

There are times you may want NR off and fireworks are a good example. People write in complaining when they shoot 2 second exposures the shutter "jams" for a few seconds. The shutter is blocked during NR. Fortunately a bright flash on a dark background does not need NR. A dim subject on a dark background with a multisecond exposure does need NR (or dark frame subtraction as falconeye mentions).

03-23-2008, 01:41 AM   #9
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QuoteOriginally posted by Mike Cash Quote
I would guess that was a result of the camera automatically boosting the ISO in order to allow you to use the faster shutter speeds in less-than-adequate lighting situations.
nope I was in manual mode at iso 100 and broad daylight I never used anything more than ISO 100 because it just was not worth it

Leo I have the K10D as well I'm not that rich ya know hehe
03-23-2008, 10:08 AM   #10
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QuoteQuote:
I've asked more than once what the Scene modes do beyond the K100D manual's: "Portrait = Optimal for capturing portraits." No one seems to know what specific changes the camera makes for each scene mode and I've given up waiting for Pentax to tell us!

You can take a set of test shots in all the modes manual and compare exif.
03-23-2008, 10:25 AM   #11
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portrait modes normally open up the shutter so that the background blurs

firework setting puts the shuter between 2 and 4 seconds and uses aperture and iso to control exsposure
03-23-2008, 05:00 PM   #12
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QuoteOriginally posted by SpecialK Quote
You can take a set of test shots in all the modes manual and compare exif.
That is an interesting suggestion. I'm not sure subtle things like color correction values are displayed in PhotoMe. I presume some modes like candlelight compensate for the color of the lighting. The Pentax Manual says Candlelight = "For capturing scenes in candlelight." It may require manyshots in each mode to quantify the change in such things as aperture where the effect of the scene mode will depend on several factors.

More people might use the scene modes if Pentax "came clean" and specified exactly what they do. I tend to avoid, "un-specified behavior." Perhaps it goes back to my days in precision test equipment where companies were expected to specify exactly what the equipment does.

Anyway, I'm happy setting most of the parameters myself. I'm just lousy at judging color and suspect the camera's scene modes might do color adjustment better than I can!
03-24-2008, 05:53 AM   #13
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Do you mean the aperture? BIG difference between the aperture and the shutter.
The shutter always opens up (or you'd have no picture ) The aperture/f-stop determines the DOF for the shot.

QuoteOriginally posted by simons-photography Quote
portrait modes normally open up the shutter so that the background blurs

firework setting puts the shuter between 2 and 4 seconds and uses aperture and iso to control exsposure
03-24-2008, 06:20 AM   #14
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QuoteOriginally posted by egordon99 Quote
Do you mean the aperture? BIG difference between the aperture and the shutter.
The shutter always opens up (or you'd have no picture ) The aperture/f-stop determines the DOF for the shot.
yes you are correct it was my bed time...
04-27-2017, 04:30 AM   #15
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Does slow shutter speed NR work for higher ISOs (about 3200) and for RAW files?
I've read on RawTherapee's user manual that dark frame subtraction doesnt really work well for high ISO files.

here's the read:
Dark Frame - RawPedia
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