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The new Nikon D7000 is out, and a lot of previews has touted the "native iso" of D7000 to be 100.

What does this actually mean? I'm assuming it means it performs at its best at iso 100, which means if you're ok to sacrifice light sensitivity, you'll get really great images...?

15

As I understand it the "native" or "base" ISO is the sensitivity you get without amplifying the analogue signal you get from the sensor. It becomes important when the native ISO is higher than the lowest available on a camera (e.g. the base ISO is 140 and the lowest setting is 100). In this case the camera is likely to overexpose the image (as you can't unamplify the signal to recover the highlights) and the non-amplified signal is more likely to be affected by the read noise of the electronics (then read noise of the electronics is roughly constant so if you have a small signal the read noise is higher by comparison).

As already stated it's unlikely to actually be noticeable in images however if you always strive to use the lowest ISO the camera offers whenever possible, you may be wasting your efforts as the image quality may be just as high/slightly better one setting up.

For further reading:

  • 2
    I think it's important to point out that 'native' ISO is not always synonymous with 'base' ISO. 'Base' ISO is generally the lowest ISO setting in the set of 'native' ISO settings, which set may or may not be composed of more than one ISO setting. – Tex Dec 2 '14 at 13:45
12

From what I gather, it appears to be yet another silly measurement for gear-heads to obsess over.

Here is a pretty good overview that I found regarding both Native Iso and Base Iso.

Obviously from the tone of my answer, I'm not really keen on such qualitative measurements. I suppose if you need a way to stack-rank compare bodies it might be valuable, but in my opinion it needlessly complicates things with criteria that aren't really that important.

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    I saw that posting too, seems as reasonable an explanation as any. Anyways, I tend to agree with you, it's generally not really meaningful in actual practice, it's something for measurebators to argue over. – John Cavan Sep 16 '10 at 21:45
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    I have to agree. The more I learn about photography gear, the more I realize how little all the micro-measurements matter. Distortion, slight vignetting, base/native ISO, etc. are all pretty meaningless in the real world. Those that do have a visible effect can usually be corrected in post-processing these days, often automatically with the advent of lens profiles for various software. They may matter for scientific purposes, but its unlikely any scientific project would use any commercial grade equipment. – jrista Sep 17 '10 at 16:15
  • Knowing what the native ISO of your camera is only marginally useful, yes, but knowing what determines native ISO is important to understanding how sensors work, which is worthwhile IMO – Matt Grum Apr 30 '11 at 20:24
2

ISO is changed by applying gain at the analog stage of the signal (which, incidentally, is why you can't change the ISO in raw), and the base ISO is the amount of gain at which the signal-to-noise ratio is the maximum.

In practice, the one at which the image is the cleanest. But that part is already obvious to everyone.

1

There is a noticeable difference if you are shooting in a wide light range. An example would be a bright sunny day with high contrast. I have a sony a7r. The native iso is 100 but I can shoot the iso at 50. I started shooting most photos at 50 to have as little grain in my images as possible and have that crystal clear image. On most photos I didn't notice a problem until I shot in an extreme condition. I found that my extreme lights and darks were clipped when I shot under 100 iso. A good way to test this is to go out on a bright sunny day and shoot the sky and land together. You'll notice the brighteset parts of the clouds are clipped when using an iso of 50 or 80. When I went to an iso of 100 I had no clipping in my images

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    I can't quite see how this answers the question. It talks about your experience with ISO settings, but not what (if anything) the industry means when they talk up "native ISO". – user31502 Apr 18 '16 at 18:06
  • @jdv - I don't really agree. It backs up and compliments the answer from Matt and has some additional value as a result. – John Cavan Apr 19 '16 at 2:45
  • This isn't a forum. Answers ideally stand on their own. If this is meant to augment another answer it needs to say that, and show how. As things stand, it is a wall of text that does not answer the question posed. – user31502 Apr 19 '16 at 5:06
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Steve is right. His experience pretty much summarizes what a non-native ISO can do to our images. Native ISO is 100, 200, 400, 800, 1600, ETC the little numbers in between are not native and what they do is to digitally process our files to mimic the results of those ISO numbers (ISO 125, 160, 250, 320, 500, 640 etc) but the results generally aren't good and clipping and other artifacts may occur.

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