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Photography Question 
Michele Wassell
 

Long Exposure Noise, etc


 
 
Hi,
I was at Yellowstone NP photographing lower Yellowstone Falls in June of this year. I had on an ND and a Polarizer filter on my Canon 20D, 70-300mm DO IS lens using a tripod and mirror lock-up. I was shooting at iso 100 and my shutter was anywhere between 20-30" seconds long. I did have the custom function enabled for long exposure noise, but my image still came out with a lot of noise.

I am trying to understand why things happen and don't happen. I have had a very difficult time with the 20D and understanding results.

Any help/suggestions/opinions, etc would be greatly appreciated.

Thank you so much.

Regards,
Michele


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8/1/2007 12:35:26 PM

 
Ariel Lepor
BetterPhoto Member Since: 9/8/2005
  Yes, long exposures make noise like this. What you could do is get rid of the polarizer, use a wider aperture, and cut the image noise to like 5 seconds.


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8/2/2007 11:31:19 AM

 
Michele Wassell   Thank you.. However, I even see noise on my images with 1/30th of a second in darker areas of the photo (ex: shadows, dark green, etc) to the point that the image can't be printed.

Sunsets and photos with dark shadows, can't be printed because the noise is so bad.

How do people get rid of that kind of noise?

Thanks again..

I really appreciate your response.

Michele


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8/2/2007 12:29:12 PM

 
Ariel Lepor
BetterPhoto Member Since: 9/8/2005
  For those photos, are you using a low ISO?

I'm surprised that you would get such high noise levels, since SLRs are usually pretty good at that. Does your camera have an anti-noise function you could use?

Anyway, to get rid of existing noise, my favorite program is Helicon Filter (see en.wikipedia.org/wiki/Helicon_Filter and heliconsoft.com) (which is excellent at removing noise and correcting other elements of the picture). If you buy a license for the program, you also get a noise-reduction brush and more advanced options.


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8/2/2007 12:57:44 PM

 
Michele Wassell   Yes, at iso 100 all the time except action which I don't have very much noise even at iso 1600.

I have Noise Ninja, but when used on some of these photos, it doesn't make it better, just splotchy. Not all areas need it in a lot of photos, just the darker areas.

Thanks!! I will look into the Helicon Filter.


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8/2/2007 1:05:56 PM

 
Alan N. Marcus   Hi Michele,

Noise, O my, back to engineering tutoring:
Noise is a key limiting factor that diminishes the fidelity of a reproduction system. Noise in a digital system is the counterpart of flare in a film based system. Sorry to report that a digital system is afflicted by both. To explain these systems we are forced to swap back and forth between wave theory and the particle of light. Lenses are best explained by wave theory, film and chip by particle (corpuscular) theory.

In the case of noise we resort to particle theory. The heart of the digital camera is the imaging chip with its surface covered by millions of light sensitive sites. During the picture taking deed, photons stream through the lens and shutter and smack the surface of the chip. A specific site is smacked repeatedly and it needs multiple hits to become tripped off. More hits are needed if the ISO (sensitive) setting is low, less hits if the ISO is high. Tripped off means that each hit has generates a tiny voltage and the voltage accumulates until the threshold of the site is reached and a voltage is measurable.

While a specific site is waiting to be hit by a photon, it may be hit by other radiant energies such as x-ray or gamma ray or heat rays. These stray energies can cause the site to trip thus a false signal (noise) results.

In a normal picture taking condition the photons stream in quickly and the site receives it quota in short order. If the scene is dimly light i.e. natural density filter is mounted, the exposure duration is abnormally long. During a long exposure the light sensitive site is more likely to be bombarded with stray energy thus the resulting image suffers degradation due to noise. Noise is always present but most desirable in mundane, uniform areas. Busy areas hide image noise.

Alan Marcus (caution often dispenses marginal technical advice)
ammarcus@earthlink.net


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8/2/2007 1:26:11 PM

 
Ariel Lepor
BetterPhoto Member Since: 9/8/2005
  Alan is the one with the technical info. ;)

With Helicon, in the free version, you can do everything that I'm about to say during a one month trial. After that, you will only be able to use a single noise reduction slider, or, it costs like $30 to $75 dollars for a license.

Anyway, here are the ways you can specify which areas of the image to apply noise to: the light or dark areas, different colors, different color ranges, how much/what type of reduction, and you can also view a noise map to see which areas of an image are affected. You can also use a brush (with edge detection and feathering) to apply noise reduction, or another brush to erase changes made in certain areas of the picture.

Can Noise Ninja do that?


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8/2/2007 1:58:03 PM

 
Suzanne Colson
BetterPhoto Member Since: 7/31/2006
  On any of these images did you adjust the exposure after the fact? I have taken several images, inside, with 30 second exposure and am not seeing unacceptable amounts of noise with both a Rebel XT and a 30D. WHen I do see noise it is generally when the picture was underexposed and I am bumping up the exposure in Bridge or Lightroom. Just a thought...

If I do have an issue with noise I have been have some good results with Noiseware.


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8/2/2007 3:45:38 PM

 
Ariel Lepor
BetterPhoto Member Since: 9/8/2005
  Yeah, underexposing any shot and then correcting that later will certainly result in increased noise levels.

But a 25 second exposure was underexposed? Was this at night?


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8/2/2007 5:55:52 PM

 
Irene Troy
BetterPhoto Member Since: 5/27/2004
  I am going to throw something out that may be totally off the mark; however, it may just provide some help. I’ve photographed the scene that you captured many times and I have to tell you that it can be a difficult scene to capture well. First: because of the way in which the sun can reflect off the “gold” cliffs and because of the volume and speed of the water falling (which comes as white) you are forced to deal with a lot of light reflection and bounce. Couple this with the fact that the vantage point that you selected (Artist’s Point, right?) is quite some distance from the actual falls, and you have a setup for image making trouble. To cut glare you used the ND and polarizer. Both cause light refraction even as they cut glare. All of this adds up to light causing all sorts of exposure issues.

Most visitors to the park stop at Artist’s Point to make their images. Of-course, it is a terrific view! But, as I said, there are several factors that make it hard to capture a good image in this situation. Keep in mind that noise is an exposure issue. Here is what I have tried successfully in this same situation: whenever possible try to make such an image on a cloudy/overcast day or either very early or very late in the day. Think of clouds as a giant diffusion disk that will soften light and reduce the need for longer exposures – hence greater risk of noise. Because you are trying to achieve that lovely silk water effect, you need the long exposure. However, in direct sun light you will have glare and too much light – again, forcing an even longer exposure. Time of day and amount of sunlight play a huge role in determining the quality of any image and the more reflection and bounced light that you have, the greater the risk of noise and a poor exposure. The brighter/ the more direct the light the greater the problem of attaining a proper exposure without unwanted noise.

Incidentally, I looked at your gallery and you have some terrific images! I love your travel philosophy. I left my “real” job a few years ago to follow my dream of writing and learning to express my passion for travel and nature with my camera. Like you, I continue to struggle with the image making part, but I love it!

Irene


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8/3/2007 11:37:17 AM

 
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