Nikon Auto ISO

Started Sep 19, 2012 | Discussions thread
mosswings Veteran Member • Posts: 8,926
Re: Nikon Auto ISO

Graystar wrote:

The other setting is Maximum Sensitivity. Here, you tell the camera the max ISO to use. I don't really understand why this is needed. Lets say that a person doesn't want to go beyond ISO 1600 because of noise. So he sets a Max. Sen. of 1600. Now, when AutoISO reaches ISO 1600, the camera will go back to reducing shutter speed to get standard exposure. So you don't get the noise, but now you get blur from subject motion. That doesn't make sense to me. A sharp image with more noise is better than a blurry image with less noise. For this reason, I always keep the Max. Sen. to the highest ISO in the list...which is "Hi 1" for my D90.


I concur with Graystar's thorough and thoughtful tutorial, but want to add a couple of comments - the first on where to set maximum sensitivity, and the second on a slightly off-topic concern, minimum shutter speed.

Upping ISO is not without its costs. The costs for me are reduced dynamic range capability and lowered image acutance/color fidelity. There is a range over which you won't notice its symptoms, but it's significantly less than the limits of the ISO setting knob and is dependent upon scene and your intents. For my D90, I will generally not use an ISO higher than 650 or 800, and most commonly limit it to 400. Only in quite low light and with limited dynamic range scenes will I let the ISO exceed 800. Newer cameras like the D5100 extend this limit by about a stop or so. With this small of a range Auto-ISO becomes less useful. With a 3-stop increase from base ISO you are effectively turning a D90 into an S100 or XZ-1. I don't like the consequences. Bottom line, watch that Maximum Sensitivity.

You're running a very slow minimum shutter speed. Perhaps you've steady enough hands to get decent keepers from this at short focal lengths, but you will be moving from a 6MP to a 16MP camera, and your handholding technique and steadiness will need to get much better to obtain the same pixel-level sharpness. If you view your images at the same final size, you may not see the blur, but it will be there. My rule of thumb nowadays is to use 1/(2*FX equiv focal length) for all shots, and no lower than 1/250 for moving subjects. That suggests a better min shutter speed of about 1/30-1/60. This means that you may find yourself kicking the ISO up a stop to obtain sufficient shutter speeds if you're trying to extract all of the camera's resolution potential while handholding. Somewhat of a "red queen" problem, running ever faster to stay in the same place. Sort of. Of course, tripods free you from the minimum shutter speed curse.

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Olympus XZ-1 Olympus Stylus 1 Nikon D90 Nikon D7100 Nikon AF-S DX Nikkor 18-105mm f/3.5-5.6G ED VR +5 more
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