# Digital Noise Problem (long exposure)



## fishingnotcatching (May 30, 2007)

How does one reduce the noise when shooting a long exposure with a DSLR? I have been trying different iso's (100 - 3200) and aperatures (1.8 - 22), but at a 30 second shot, I can't get rid of it. What's worse, it seems to change from frame to frame when I keep everything the same. Is it just a matter of light? and if so, what kind of light - in other words, can I change the character of the light to reduce noise (i.e. different direction, etc. ) See below shot at F22 I think, maybe 16, and ISO 400, thirty seconds. Any one know how to combat the issue?


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## Pocketfisherman (May 30, 2005)

The amount of chroma noise is a function of the ISO setting. Higher ISO, more noise. However, there is also noise generated by current leakage within the sensor photosite cells themselves. Higher end cameras have the ability to take a long exposure dark frame shot and overlay that data with the actual shot, then null out the noisy photosites where there is a birght pixel in both frames at the same location. So, shoot at the lowest ISO you can, try whatever built in noise reduction your camera has specific for long exposure situations. Then, deal with what is left with post processing like Photoshop's noise reduction filter, or with a third party package like Noise Ninja. You can also selective apply a slight gaussian blur in post processing to the background to make the noise a lot less obtrusive. Lastly, it is best to expose to the right side of the histogram just short of blowing the highlights. Then, restore the shadow with a post processing curves adjustment. That will minimize noise in the shadow areas.


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## ssminnow355 (Oct 26, 2007)

Long exposures allow the dark current "electrical noise" within the system to build up and is what gives you the noisy background. Cooling the camera chip is the only effective way to get around it past 30 sec exposures.


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## sandybottom (Jun 1, 2005)

I think your FStop is too high. Try this--

F9
1/60 sec. 
ISO 400
Flash
Anyone think this is wrong please correct me.
I just want to see if that works for you. Let me know.


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## Arlon (Feb 8, 2005)

I shoot at iso 100, f32 and 15-30 seconds with no noise that I can detect. Are you in manual mode or shooting some priority mode? I don't have exif reader here so no clue what you where shooting.

Keep ISO at the LOWEST possible setting. Period. LITTLE OR NO SHARPENING either. Sharpening does a wonderful job of sharpening noise too..

I also have noise reduction set to "normal" on my d200. 
Sandy, if we're trying to light paint your numbers don't work at all especially if you're trying for extreme DOF like this:

This is a 30 second exposure at f32 and ISO 100. There is no noticeable noise even at original scale and DOF is deep....

Click the image for a larger version..


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## sandybottom (Jun 1, 2005)

Arlon, I'm speechless. I know I don't know enough to give advice but you know me I try to help anyway I can. I'm just that kind of person.
I guess I was waiting for a nice example like the one above to help this guy out.


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## Arlon (Feb 8, 2005)

sandybottom said:


> Arlon, I'm speechless. I know I don't know enough to give advice but you know me I try to help anyway I can. I'm just that kind of person.
> I guess I was waiting for a nice example like the one above to help this guy out.


Sandy, that shot was thinking outside the box a little. No way you would have guessed that one! Shooting "normal" methods you here right on.

Another "slow" shutter was the orchid I posted a few days ago. That was at 8 seconds and F32 (TV was on so I couldn't o slower without getting TV exposure).


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## sandybottom (Jun 1, 2005)

I've been thinking about setting up a photo box and trying some nick nacks/ flowers in it. At least being inside the house with the AC on will be nice. 
I hear you, Arlon. Well, maybe now that he has a few examples he can post another one for us.
I don't think I've messed with F32 too much. I know its super slow and a tripod is a must.


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## Arlon (Feb 8, 2005)

light box is super easy to set up and very useful.. I do a lot of "nick nacks" in the light box.

my "custom" light box is out here: http://www.pbase.com/arlon/image/92124056/large


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## fishingnotcatching (May 30, 2007)

I was shooting manual, F22 is the most I can stop the lense I was using down. I needto switch to my other that gets to 32. OK, so 100 will give less noise that 400. I have to admit I was "piggybacking" your light painting technique from an earlier post, though obviously not to the same success. I also threw a strobe in for good measure. I'm also starting to fear that the 20D gets worse noise than you nikoners. 

Will try again tonight and post results tomorrow.


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## Arlon (Feb 8, 2005)

You should be good with the 100 ISO and be sure to turn on the "long exposure" noise reduction in the camera. I don't use any flash at all, just the flash light. I'm also really careful to put my background as far back as possible. I use a black blanket I got at a resale store for a few bucks as backdrop. Keeping the backdrop far enogh back helps to keep it out of the exposure also just using the light and NO flash helps too.

I have used flash remotely, handheld on lowest power and just tripped with the test button to paint. It works but usually leaves shadows.

F22 should work fine, I was just using f32 for the added DOF and a little more exposure time to play with. I also intentionally underexpose a few stops in the camera so I can increase contrast in photoshop later without blowing the highlights (look closely at the orchid picture). That helps darken any stray light spots in the background. Keep playing, once you get one right it will be like the first time you got your balance right on a bicycle. It was a lot easier after that!

This one was painted with about 10 flashes (handheld the flash unit).


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## BPitcher (Aug 23, 2004)

try noise ninja http://www.picturecode.com/


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## RustyBrown (May 29, 2004)

Keys to minimizing noise from my still unpublished book...


Keep ISO as low as possible
Expose correctly
Minimize shutter speed to reduce sensor heat noise
Use Noise Ninja
Earlier sensors like my 7D and your 20D will be more sensitive to the heat build up issue. My camera actually overheated at Kemah in the winter shooting with MT and Captain Mike one night and shutdown until it cooled off.


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