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Auto ISO
As the name suggests, Auto ISO allows automatic control of ISO as a parameter in the shutter speed / aperture / ISO triad. However, does Auto ISO work well in wildlife photography or is it a gimmick? Kaleel Zibe shares his experience

When I first came across the setting on the Nikon D3, I dismissed it as rather a gimmick. My initial experiments were using my most common exposure mode: aperture priority, and I disliked the camera changing the ISO value as well as the shutter speed. This felt too much out of control to me.

The only time I felt comfortable using this automation was when leaving the D3 in a forest in a camera trap for several days. The camera needed to take pictures in wildly changing light conditions, requiring flexibility of ISO. By definition I could not change the ISO at the camera trap, so the camera needed to be able to do this itself.

Recently, whilst photographing gannets with friends at Bempton Cliffs in North Yorkshire in England, the issue of Auto ISO cropped up again. I felt I should probably give it another go, and the aspect that finally won me around was the discovery that Auto ISO works extremely well in manual exposure mode.

Having never previously considered this combination, being able to fix the aperture and shutter speed while the ISO value follows on automatically was something of a revelation. I like to take control of the look and feel of a photograph, and to be able to set both aperture and shutter speed, leaves me completely in charge creatively. For example, I knew I needed a certain shutter speed to avoid camera shake with a 600mm lens and a moving gannet, but I also wanted to use the aperture to control the depth of field for sharpness across the bird's head while still blurring the background.

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Out of interest, under normal circumstances, exposure compensation does not work in manual mode because it has no counterpart control to modify in order to adjust the exposure: aperture and shutter speed are fixed in manual mode. However, in Auto ISO with manual mode, exposure compensation alters the ISO value, so you still get a quick way of over- and underexposing when the metering system is being confused.

ISO affects how much noise is present in the image and the total dynamic range available, but it is not a creative control. If the camera is able to automatically adjust the ISO value, it is very liberating to be able to control the true creative parameters of aperture and shutter speed while retaining the ability to balance exposure with exposure compensation.

At this point I should introduce a couple of health warnings: firstly, not all cameras have a linear noise response at intermediate ISO settings (i.e., half and third stops). ISO is essentially an amplification of the visual signal. Full stops like ISO 400 and 800 are amplified using the camera's hardware, which gives the cleanest signal. However, some cameras use software amplification for half and third stop values like 560 and 640, which introduces more noise than is simply within the light itself. Most Nikons and high-end Canons use hardware for all ISO values, but it is worth checking which amplification method your camera uses for intermediate ISO values. Take a series of photos at whole and partial ISO stops. If the camera uses a mix of amplification methods, it is likely that intermediate ISO values will produce significantly more noisy images than at full stops.

The second thing to consider is to limit the maximum ISO that Auto ISO can use. This will depend on the camera's noise performance at high ISO values and what you consider too noisy.

I am now a true convert to Auto ISO, particularly in manual exposure mode.

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About Author

Kaleel Zibe

Kaleel is an award-winning filmmaker and photographer and runs wildlife photography safaris in Kenya and Uganda. He films and shoots for clients such as the BBC, RSPB and Montane and wrote the critically acclaimed book, ‘Wildlife of the Farne Islands’

4 Comments

  1. Avatar

    I’ve mostly shot wildlife in manual mode with auto ISO for a long time now – it makes sense to me that if you’re going to automate one of the exposure parameters then it should be the one which doesn’t really make a ‘creative’ input to the shot. Not to mention that to some degree you can fix things in post if the camera chose a higher ISO, but you can’t really salvage a shot blurred due to the shutter speed being too slow or one where the depth of field is too shallow. My first couple of cameras with auto ISO didn’t allow exposure comp in manual with it though, which was a pain, as being able to quickly override the camera’s ISO choice is indeed extremely handy!

    • Kaleel Zibe

      Thanks for the comment, Steve. Glad you found the article useful. Yeah it’s definitely good now most cameras offer exposure compensation in manual mode.

  2. Avatar

    I’m a hobbyist, but my go to settings for a lot of my wildlife photography is manual mode and auto ISO, to manage ever changing backdrops, eg sky, then green grass etc. I limit the max the ISO can go to. Most of the time I find this pretty effective, unless needing a lot of exposure compensation, when I use shutter priority mode instead.

    • Kaleel Zibe

      Hi Claire, yeah exposure compensation is a big thing for me and having enough control with that (the iso changing when the shutter speed and aperture remain constant) is important. I’m interested that you switch to shutter priority to gain more compensation. Do you find you hit a max compensation when using manual mode?

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