Most dSLR are capable of capturing images at ISO 800 and higher. ISO 1600 and ISO 3200 are normal settings on higher end dSLR. Some professional dSLR have unrated high ISO similar to ISO 6400. You may be interested in reading High ISO Capable Compact Digital Camera (Pns) . An introduction to ISO is introduced here.

High ISO is important is you do a lot of low light photographing. This includes concerts, weddings and indoor events. Landscape photographers and enthusiasts would need good performing ISO so that images will be clean.

Most dSLRs produce “close to” noise free and noise free images at ISO 400 and lower. How much noise is there when we use higher ISO settings? Is my upcoming dSLR or my current dSLR able to produce clean high ISO images? We will look into this.

Here is a list of dSLR cameras with at least ISO 1600 setting (Having these settings does not guarantee the output is acceptable):

Why Compare High-ISO Noise Between Cameras? @ Darrell Young

Unless one really needs the ability to take images in very low light situations, and most of us don't, then what is the big concern if one camera has better extreme ISO noise? This issue is one of those silly things that seem to come up from time-to-time.

Unless you are doing something rather odd, it is not normal to shoot at ISO values above 800. Why degrade the quality of your image unless you absolutely must have the extra speed. If i were in a dark parking lot and an alien spaceship landed, I suppose.

For the VAST MAJORITY of us, extreme ISO noise is NOT an issue. Today's DSLR cameras are so good at getting rid of noise, that it really is a moot point. The D2x simply has no noise at 100 ISO. And up to 800 ISO has very little.

Here’s some sample of high ISO comparison of the above listed dSLR:

 

Canon EOS 5D, Canon EOS-1Ds Mark II and Nikon D2X at ISO 1600 and ISO 3200 Details

 

 

 

Fujifilm s3pro and Nikon D70 at ISO 800 and ISO 1600. Details

 

 

 

Panasonic DMC-L1, Olympus E330 and Canon EOS 30D at ISO 1600. Details

 

 

 

Pentax K10D, Nikon D80 and Canon EOS 30D at ISO 1600. Details

 

 

 

Nikon D200, Canon EOS 5D and Nikon D2X at ISO 1600 and ISO 3200. Details

This article is about the comparison of dSLRs' high ISO performance, it does not state which camera is the best in noise control, it serves as guideline for those who are interested in how these dSLRs perform. You are encouraged to go through the sample images of each dSLR and the reviews.

Further reading
Nikon D2Hs DSLR High ISO Noise Test Comparison vs Nikon D2H

Compare 17 different dSLR noise. ISO 800 and ISO 1600

17 Examples of dSLR noise

D2X Noise User Report. (Includes D2H, D100 and D70)

D200 Noise Performance

High ISO Comparisons Nikon vs. Canon & Digicam vs. SLR

DSLR Resolution and Noise Comparison

Why Compare High-ISO Noise Between Cameras?

Nikon D2x - Understanding ISO and Noise Reduction Settings

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