DPChallenge: A Digital Photography Contest You are not logged in. (log in or register) 
 

DPChallenge Forums >> Hardware and Software >> low shutter speed creates noise?
Pages:  
Showing posts 1 - 25 of 25, (reverse)
AuthorThread
 08/22/2004 01:57:51 PM · #1
hi,

i m using sony mavica FD 95 digital camera. when i take night shot at low shutter speed like -2 or -8 it create good picture but huge noise and dots. My lens is clear and everything else is okay. But i dont find how this problems occuring... need comments...

tanveernight shot example

Message edited by author 2004-08-22 14:15:16.
 08/22/2004 02:05:10 PM · #2
Two things. Longer exposure likely means higher ISO, so more noise. Also, longer exposure means that electrical current is applied to the sensor longer resulting in hot pixels. This will show as red, green, or white pixels. Both are perfectly normal. Some cameras handle this better than others. Most newer cameras have some type of noise canceling program built into the camera to handle this.
 08/22/2004 02:05:59 PM · #3
Originally posted by Tanveerhawk:
hi,

i m using sony mavica FD 95 digital camera. when i take night shot at low shutter speed like -2 or -8 it create good picture but huge noise and dots. My lens is clear and everything else is okay. But i dont find how this problems occuring... need comments...

tanveer


Could you post a picture showing us an example of what your discribing?
 08/22/2004 02:10:42 PM · #4
If in-camera adjustments (aperture priority mode?) don't work try this:

> Open image in Photoshop
> Convert to Lab Colour
> In 'Channels' tab select the (a) channel and apply a guassian blur until the noise is reduced to satisfaction
> Do the same with channel (b)
> If desired apply a slight sharpen/USM to the Lightness channel

This will combat most noise problems to some degree and can sometimes create a very pleasing effect provided you don't over cook it.
 08/22/2004 02:19:00 PM · #5
thanks

thats a good idea but blurring the picture and reducing the image details slightly, is there aything i can do with the camera..
 08/22/2004 02:24:49 PM · #6
All image sensors produce thermally generated noise in the image. Longer exposures in low light means:
1. Longer period of time to accumulate noise electrons in the quantum wells (pixels).
2. Low light reduces signal to noise ratio making noise appear more prominent when amplified by the camera's processing electronics.

You can do several things to reduce the effect of noise:
1. Shoot only in well lighted areas.
2. Keep the camera cool to reduce thermally generated electrons.
3. Shoot a 'dark frame' immediately before or after the shot and subtract out the noise using Photoshop or Paint Shop Pro.
4. Buy a better camera. (This is the most effective option.)

Get a copy of Scott Kelby's excellent book on digital image processing!
 08/22/2004 02:44:15 PM · #7
Originally posted by Tanveerhawk:
thats a good idea but blurring the picture and reducing the image details slightly, is there aything i can do with the camera..

This does not blur the image but blurs the colour in the image. The Lightness channel contains the image's definition data. With careful application and masking you should get good results.

If you have ISO control set it to 100.
 08/22/2004 04:44:19 PM · #8
Originally posted by Imagineer:
If you have ISO control set it to 100.


I agree. I usually use ISO 100 when shooting longer exposures at night.


08/22/2004 05:53:29 PM · #9
Originally posted by Tanveerhawk:
But i dont find how this problems occuring... need comments...


You might be interested in knowing how some cameras (including the new Canon EOS 20D announced this week) deal with this issue of "noise" during long exposures.

Some cameras will take the picture then, after the shutter has closed, it will continue to power the sensor for an amount of time equal to your exposure. Then it "subtracts" from the image all of the noise that appeared after the shutter closed.
 08/22/2004 07:27:33 PM · #10
well ours doesnt seem to deal with it very well...


08/22/2004 07:45:19 PM · #11
Originally posted by soup:
well ours doesnt seem to deal with it very well...


I seem to do okay with long exposures ... usually I'm at ISO 100 and most of what I consider long is about 4-8 seconds. But I've taken some 30 second exposures as well and really haven't been disappointed.
 08/22/2004 07:57:47 PM · #12
try like 5-10 minutes
makes me use film for things like that.

08/22/2004 08:00:17 PM · #13
Originally posted by soup:
try like 5-10 minutes
makes me use film for things like that.


Now ya got me curious... what are you shooting for 5-10 minutes? Have any examples to show?
 08/22/2004 08:56:29 PM · #14
I rarely put my ISO above 50 ... my G5 creates tons of noise otherwise. So for night shots .. I just have a very long exposure time at 50 iso .. the noise isn't too bad like this.

Message edited by author 2004-08-22 20:56:37.
 08/22/2004 09:09:27 PM · #15
Originally posted by Imagineer:
Originally posted by Tanveerhawk:
thats a good idea but blurring the picture and reducing the image details slightly, is there aything i can do with the camera..

This does not blur the image but blurs the colour in the image. The Lightness channel contains the image's definition data. With careful application and masking you should get good results.

If you have ISO control set it to 100.
08/22/2004 09:11:35 PM · #16
Originally posted by Imagineer:
If in-camera adjustments (aperture priority mode?) don't work try this:

> Open image in Photoshop
> Convert to Lab Colour
> In 'Channels' tab select the (a) channel and apply a guassian blur until the noise is reduced to satisfaction
> Do the same with channel (b)
> If desired apply a slight sharpen/USM to the Lightness channel

This will combat most noise problems to some degree and can sometimes create a very pleasing effect provided you don't over cook it.


************************************************************************

Above is best advise to correct. I would simply add that you space out the long exposore shots. In short, start with a cool sensor. Do not shoot one after the other.
 08/22/2004 09:16:42 PM · #17
Originally posted by ElGordo:
All image sensors produce thermally generated noise in the image. Longer exposures in low light means:
1. Longer period of time to accumulate noise electrons in the quantum wells (pixels).
2. Low light reduces signal to noise ratio making noise appear more prominent when amplified by the camera's processing electronics.

You can do several things to reduce the effect of noise:
1. Shoot only in well lighted areas.
2. Keep the camera cool to reduce thermally generated electrons.

*********************************************************************
3. Shoot a 'dark frame' immediately before or after the shot and subtract out the noise using Photoshop or Paint Shop Pro.
4. Buy a better camera. (This is the most effective option.)

Get a copy of Scott Kelby's excellent book on digital image processing!


***********************************************************************

Elgordo is also right in this tip, however, this is the system that 90 percent of camera's use to reduce the hot pixels in their internal software. Any extended exposure should be done at the lowest ISO and like I said, let the sensor cool between shots.
08/23/2004 01:56:16 PM · #18
well i think that noise of exposer is natural in digital camera , so i have nothing to say of it, rather i have to take better shot with out any noise... but what if i take shot under sunlight, will it affect the sensor? as someone said keep the camrea cool place before taking shot...

tanveer
 08/23/2004 02:11:12 PM · #19
Originally posted by soup:
try like 5-10 minutes
makes me use film for things like that.


5- 10 minutes shot, impossible, whats the benefit of it

tanveer
 08/23/2004 02:14:17 PM · #20
Originally posted by Tanveerhawk:
Originally posted by soup:
try like 5-10 minutes
makes me use film for things like that.


5- 10 minutes shot, impossible, whats the benefit of it

tanveer


startrails
 08/23/2004 02:28:20 PM · #21
humm great idea, star trails but how it will look like can u show me an example?

tanveer
 08/23/2004 02:36:17 PM · #22
08/23/2004 02:42:57 PM · #23
humm, but not that much impressive... picture is blurry.. isn't it,,, which camera u used for shot...

tanveer
 08/23/2004 02:47:45 PM · #24
not my shot, just an example. and it probably got blurry from some wind shaking the camera
 08/23/2004 02:51:12 PM · #25
i shoot the night sky sometimes, trying to get star trails with different types of silouttes ( trees, buildings, whatever looks interesting. ) and what not. but with the 300d i haven't been to pleased with the results - not too many stars i know are bright blue, red, yellow and perfectly square...

i've shot film shots upwards of a couple hours in the past.
i have a bulb bubble thing, that i can lock, and leave - come back later.


Pages:  
Current Server Time: 04/19/2024 08:46:58 PM

Please log in or register to post to the forums.


Home - Challenges - Community - League - Photos - Cameras - Lenses - Learn - Prints! - Help - Terms of Use - Privacy - Top ^
DPChallenge, and website content and design, Copyright © 2001-2024 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 04/19/2024 08:46:58 PM EDT.