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The picture below is a crop (at 1:1 scale) of a photo I just took. It was taken with a Canon 7D and the 24-105mm F4 lens (RAW, F4, ISO 2500, 1/160s).

It looks properly exposed to me, so where is all this noise coming from? What I am trying to figure out is:

  1. Is this an acceptable amount of noise?
  2. Do photographers just correct this in post, or could I have done something else in camera?
  3. Would it even matter if it was printed at something around 16X20?

enter image description here

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After uploading the image, it doesn't look as bad here as it does in Lightroom. Maybe compression was done somewhere? –  Joe Oct 25 '13 at 22:12
    
If the difference is flagrant, can you be a bit more descriptive of what you see in Lightroom ? –  Emile Oct 26 '13 at 0:09
    
Hard to explain, but the noise stands out more in lightroom. Maybe like 1px bigger if that makes sense. –  Joe Oct 26 '13 at 4:25
1  
Turning it into Jpeg has probably taken the worst of it out. –  Esa Paulasto Oct 27 '13 at 6:22

5 Answers 5

up vote 7 down vote accepted

This is normal considering the high ISO you are using on that camera. If you look at samples for each ISO with the Canon 7D, yours show more noise than the ISO 1600, similar to the ISO 3200 crop.

Notice that I only shot full-stop ISO which is important with Canon DSLRs because the gain to obtain the 1/3 stops in between is applied in software by the processor which amplifies noise more than the on-sensor gain which is used to get the full stops.

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2  
That's very interesting about full-stop ISOs - is this true for Nikons also? –  Kaushik Ghose Oct 26 '13 at 3:36
3  
No. That's why I said Canon. Sony sensors work differently and they are found in all other DSLRs and most mirrorless cameras. Nikon mirrorless cameras use Aptina sensors which work yet another way. –  Itai Oct 26 '13 at 3:42
    
the gain to obtain the 1/3 stops in between is applied in software by the processor Im curious as to where you learned that. I believe you, but never heard it before –  Joe Oct 27 '13 at 15:49
1  
The +1/3 stop ISO settings amplify the noise, the -1/3 stop ISO settings reduce the noise. E.g. ISO 2500 is ISO 3200 compensated by -1/3 stop, not ISO 1600 compensated by +2/3 stop. –  Michael Clark Oct 27 '13 at 23:41

Every photo has more or less noise. We beat it in post-processing of the RAW image, or then it is done automatically for in-camera JPEGs.

My camera is a very entry level Sony A37. Some time ago I forgot to dial ISO down after a night-time shooting, so I accidentally had it up at 3200 when taking a photo of my daughter the next day.

un-cropped image ^^uncropped image

Normally I use Sony's own Image Data Converter software to convert my RAW files, but as this applies some basic denoising already at import I usually don't see very noisy photos to begin with. So I'll skip Sony's converter for this one.

Opening this same photo in another software, the RAW-Therapee in this case, shows a very different image. The whole photo is nothing but separate dots of color plus some "hot pixels" and whatnot. This somehow reminds me of the sample photo in your question:

as-shot version as seen in RAW-Therapee software

I don't really know how to use RAW-Therapee, so I can't show you the best example here. Even so I could easily remove the noise almost altogether. Actually I must have taken some detail away too, softening the photo unnecessarily. Anyway, I was not trying to properly process my photo but instead only wanted to see how the de-noising works. This is what I got:

de-noised with RAW-Therapee conversion tool

See how smooth it now looks. Somebody with proper skills and experience would undoubtedly do better job with RAW-Therapee, or using altogether another software, like Lightroom or suchalike. So far I'm committed to using Sony's own conversion tool until I find it limiting myself, already I feel this moment is nearing.

My answer to your question #1: From what I've heard of Canon 7D this looks normal enough.

And to your question #2: Yes, noise is dealt with in post. I would not hesitate to use even the highest ISO levels if the alternative was not taking the photo at all.

I am not sure with answer #3, because I rarely print my photos. Small prints of high-resolution photos should make noise invisible in most cases.

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The high iso (2500 !) is surely responsible of that noise ! Looking at studio samples from dpreview, this noise matches with the supposed noise : canon 7d @ISO3200. Just play with the ISO setting in this application to see the impact of ISO on noise (example : ISO100).

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"The high iso (2500 !) is surely responsible of that noise" no its not –  Michael Nielsen Nov 1 '13 at 17:10

My opinion on noise is that chroma noise should be dealt with and the natural looking grains like you have in your example looks better than digital NR artifacts (like those you can see in Esa's reply). The best way to deal with noise after the fact (see below why I say "after the fact") is to use it at a downscaled medium. Resize (down) is the best denoise algorithm you can find. Pixel peeping can always disappoint us (looking at 100% crops), but once you show the entire image on the screen or print it to a fitting size, it will look just fine, and it may look more organic than the result of a denoise would. You might also see that the NR artifacts disappear after the resize, or sometimes it has a glossy look or plastic prism look. See below, I resized your image, boosted contrast a bit and even sharpened it.

resize is the best denoiser

if you need a bigger medium for the image, you need to add more light. Noise comes from the lack of light (not high iso) and possibly a larger sensor as well (if you need it really large), but you should always aim for shooting at least twice the resolution of your desired output for really clear photos to overcome read noise and bayer pattern artifacts.

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It is not fair play against NR tools if you use my sample photo as an example of poor noise reduction results. As I said in my answer: I don't know RAWTherapee and how to work with it. I only had to use it, because Sony's RAW-converter can not show the effect I wanted to show in my answer. –  Esa Paulasto Nov 2 '13 at 10:07
    
it is not based on the result you got. I tried all the fancy tools like Topaz denoise plugin and fractal based "perfect resize" as well as teh more normal ones Lightroom, PS, and noiseninja. it is a general impression that the results have the chracteristic processsed look I dont like. –  Michael Nielsen Nov 2 '13 at 10:17

You need a much lower ISO, which means you need much more light. Off camera flash is the key. The Strobist 101 series will teach you how for very little money. http://strobist.blogspot.com/2006/03/lighting-101.html

It changed everything about how I use my 50D.

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