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I'm a beginning photographer who recently invested in the following setup:

Nikon D7000 camera body, 15-105mm Nikor kit lens, 150-500mm Sigma lens.

We recently made a trip to the Pantanal, Brazil where we made heavy use of the Sigma lens. Upon returning home, we noticed that those photos contain an excessive amount of noise. Below is an example of an unprocessed photo:

enter image description here

As you can see, even without zooming in particularly the unsharp areas have serious noise. And as I usually up the contrast of such an image, the noise gets even worse. I shoot mostly in aperture mode, and in this case the ISO was at 640, in order to be able to have a shutter speed that allows me to shoot without a tripod (other meta: F6.3, focal 500mm, 1/320s). Still, the D7000 is known to be able to handle high ISOs quite well, so I'm surprised to see this kind of noise at this ISO already.

I know how to get rid of noise, using both Lightroom and Noise Ninja, but the amount is so excessive that via luminance I'm losing too much detail. So my question is what the source of this noise is. Is it a natural limitation of my lens? Too little light available? Is it due to the 640 ISO? Is it due to me or some setting I'm overlooking?

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Is this straight out of camera? or have you put this through LR first, if you have gone through LR sometimes it is set to increase the sharpen to 30 automatically. –  Graeme Hutchison Dec 13 '11 at 8:36
    
Doesn't look that noisy to me. Sure, if I look at the picture zoomed 100%, then it's noisy, but who would want to look at a picture at 100%? As displayed on the browser, it's also noisy, but that's only because my browser fails to antialias. If I donwload the picture and downscale it with proper antialiasing, it looks fine, at least to me... –  Edgar Bonet Dec 13 '11 at 9:14
    
@Graeme, this is exported from Lightroom with no manual adjustments but indeed by default it sharpens it by an amount of 25. –  Ferdy Dec 13 '11 at 10:07
    
@Edgar: So you're saying this is the kind of noise one can expect given the circumstances, and that it is not a failure of my lens or me? –  Ferdy Dec 13 '11 at 10:08
1  
@Ferdy: Certainly not a failure of your lens: the lens cannot do that. A failure of you? Well, you probably can have less noise if you avoid the automatic sharpening. Try also to increase the JPEG quality: on looking closer, the noise actually looks a little like JPEG compression artifacts. –  Edgar Bonet Dec 13 '11 at 10:54

2 Answers 2

up vote 4 down vote accepted

I think that image is somewhat underexposed and that's half the problem. You might do better to use a higher ISO, and move the histogram to the right. Most of that image is in the lower half of the histogram.

I've read assertions that multiples of the base ISO, so 200, 400, 800 and so on are less noisy than intermediate values like 320 or 640. I don't know if that's true or not, perhaps a myth.

Even with a a camera like the D7000, dark areas are going to contain some noise, even between 400 and 800, especially if you try to lighten them in post processing.

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Thanks. Interesting advise to up the ISO, I would have expected the opposite. Will definitely try this. Agreed on that images will contain some noise, but don't you think this amount is quite excessive? Or would you consider this is in the average or acceptable range? –  Ferdy Dec 13 '11 at 10:09
    
I agree with taking the full stops in ISO, I find using something like 250 is not as good in quality as say 400. That is using D300.Using a D3 this difference is unnoticeable –  Graeme Hutchison Dec 13 '11 at 10:34
    
More recently I've been using auto ISO where I'm setting a minimal shutter speed and the camera figures out a ISO to match it. This allows me to shoot by hand, but I think this would go against your advise of controlling ISO through full stops only? –  Ferdy Dec 13 '11 at 10:53
    
In order to fully understand why Higher Iso = Less Noise (this equation is not completely true though) please read this answer: photo.stackexchange.com/a/21654/6977 –  liquidity Oct 31 '12 at 3:49

I personally can't see much noise in the photo. I think you are confusing the blur of the background and foreground, or bokeh, with noise.

The long focal length of the lens and the distance you have taken the subject at has caused some nice blur before and after the subject. I am not personally familiar with the aperture of that lens, but if it has fewer aperture blades (5 or so) then any blur will be slightly less smooth than if it had 7 or more blades. When you have point light sources in the background this can look like hexagonal lights instead of smoother rounder ones, but when you have complicated backgrounds like the foliage in yours, this will make the blur ever so slightly more 'jagged' that it could be.

I think it is this 'jaggedness' to the blur of your photo that is making it look to you like the out of focus bits have noise, when really it is just an affect of the distances and background blur of that lens.

EDIT: I also think this may have been amplified a little by the other suggestions people have made on the not so low ISO and maybe a touch of auto sharpening added to the pictures

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Good point. Very true, my L series lens with more blades yields a silky smooth bokeh whereas my kit lens with less blades produces a harsher/noisier bokeh. –  Jakub Dec 13 '11 at 15:19
    
There is definitely some sort of noise or JPG artifact in there, if you zoom in on the image. Only the poster will know how it compares to the original I guess. –  MikeW Dec 13 '11 at 17:44

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