Why does the Nikon D40 start at ISO 200 instead of ISO 100?

Asked 8/19/2010

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My Nikon D40 offers ISO 200 to 1600, with no ISO 100 option. Why would a camera’s lowest ISO be 200 rather than 100? Is this normal for some cameras, and does having ISO 200 as the minimum create any real disadvantage in practice?

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Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

16y ago

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The camera is a bit 'elderly' these days, but the ISO range is usually determined by the native base of the sensor itself. However, most current cameras will do ISO 100 (and the odd one even less), but the limits are usually based on the technology at the time, cost factors, etc.

For a more technical description, the ISO of a digital sensor is determined by the signal gain of the sensor and these are matched up to be similar to film. At the low end of the gain, you get low ISO, so the lowest gain of the sensor matched up to film determines that end as well as the far end. ISO 12232:2006 gives guidance to camera makers on how to actually line these up, and the options vary quite a bit.

Now, if you want a really detailed article on film speed that covers film through digital, Wikipedia has it. It's an interesting read.

Originally by user472. Source · Licensed CC BY-SA 4.0

user472

16y ago

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A camera’s minimum ISO is usually its sensor’s native base sensitivity. On the Nikon D40, that base is ISO 200, so there isn’t a true ISO 100 setting available.

This is normal: the available ISO range depends on the sensor design, electronics, and the technology and cost constraints at the time the camera was made. Many newer cameras offer ISO 100, and some go lower, but not all sensors are designed that way.

In digital cameras, ISO is tied to sensor gain and how the manufacturer maps that response to standardized ISO behavior. So the lowest available ISO is basically the lowest practical gain setting the sensor supports while meeting the camera maker’s design goals.

Is ISO 200 a problem? Usually not. The main downside is just having one stop less flexibility in very bright light or when you want the longest possible shutter speed / widest aperture without overexposure. In most everyday photography, ISO 200 as the minimum is not a significant issue.

Why does the Nikon D40 start at ISO 200 instead of ISO 100?

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