Df Auto ISO and the ISO Dial - Observations (long post)

Started Dec 18, 2013 | Discussions thread
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Kent J
Kent J Senior Member • Posts: 2,378
Df Auto ISO and the ISO Dial - Observations (long post)

This is a repeat of a post I made in another forum, but that was on a for-pay thread, so I thought I would repost here:

There have been a few negative statements in various forums regarding the Df Auto ISO implementation, particularly in regards to the ISO dial. I’ve found it a very good way to shoot with the Df, so I thought I’d share my findings.

First of all, don’t even bother going to the manual. The section on Auto ISO is useless.

The key to understanding how the ISO dial is used for Auto ISO is based on how the value the user sets in the menu for Maximum Sensitivity (ShootingMenu>Auto ISO sensitivity Control>Maximum Sensitivity) interacts with the value set on the ISO dial. The camera uses the greater of these two values for Maximum Sensitivity. This seems somewhat confusing and as I stated the manual is no help at all. However, it is actually a very useful and clever implementation.

Example: M Mode with Auto ISO:

The camera selects the ISO needed for correct exposure until it needs to get lower than ISO 100 or greater than the Maximum Sensitivity value. Beyond that, over or under exposure occurs. If the desired Maximum Sensitivity is set with the menu (say, ISO 6400), the ISO dial serves no real purpose (as long as it is below ISO 6400). The dial selected value means nothing and changing it does nothing. This is why (I think) some folks see this as a flawed implementation.

BUT, if you set the menu value of Maximum Sensitivity to it’s lowest value (ISO 200), the ISO dial will have the greater value (as long as it is above ISO 200) and you can adjust the maximum ISO sensitivity with the dial (ISO 1600, 3200, 6400, whatever you want without going in the menu). This is how I have my Df set up.

Example: A, S or P Mode With Auto ISO:

The user selects the desired ISO with the ISO dial - sounds logical. The camera will use that ISO value until the meter says it needs to reduce the minimum shutter speed the user has set in the Auto ISO menu (A Mode), exceed the lens’ maximum aperture (S Mode) or both (P Mode). Then it will start to boost ISO as needed until it reaches the Maximum Sensitivity set in the menu. This will be a very different setting than used in the previous M Mode example - it may be ISO 1600 or more. This is pretty much like previous Nikon DSLRs.

So, what happens when you change the ISO dial in this example? The camera will use the new dial setting as your new desired ISO (still reserving the right to boost ISO if needed) until the ISO dial setting exceeds the menu Maximum Sensitivity. From then on, the desired ISO and the Maximum Sensitivity are the same (the dial setting), and you are just specifying which ISO you want to use and are essentially back in manual ISO.

This is fairly logical from an ISO dial standpoint, the only thing being you need to remember the menu setting for Maximum Sensitivity to know when you transition into and out of manual ISO (if you care).

So in summary, the ISO dial can be used in three ways:

P, A, S or M mode with Auto ISO Off: the ISO dial setting is the shooting ISO

P, A or S mode with Auto ISO On: the ISO dial setting is the desired shooting ISO but the actual shooting ISO can be altered by the camera. When the dial setting exceeds the menu value for Maximum Sensitivity, it is essentially the shooting ISO.

M Mode with Auto ISO On: the ISO dial setting is the maximum ISO sensitivity the camera can use (as long as the menu value for Maximum Sensitivity has been set to its lowest value - ISO 200).

These are my own observations from playing with the Df. I got nothing useful from the manual on this. I emphatically reserve the right to be wrong and welcome any additions or corrections to these observations.

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Life is too short for slow glass.

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Nikon Df Nikon AF-S Nikkor 300mm f/4D ED-IF Nikon AF-S Nikkor 14-24mm f/2.8G ED Nikon AF-S Nikkor 50mm f/1.4G Nikon AF-S Nikkor 85mm f/1.4G +15 more
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