Auto ISO…Why?

Quite recently I was asked whether auto ISO was something I used regularly. And the simple answer is…hardly ever. In fact I really can’t remember the last time I did. So why? Well I guess the the best way I can explain my reasoning is to say that I mainly shoot in Manual Mode.

Because I try to envisage the image that I want before I depress the shutter I dial-in the settings that I need before I take the shot. As photographers we’re all working with a blank canvas and it’s what we want to eventually ‘paint’ that should determine what our settings are…not the other way round. I mean that we should not allow the camera to dictate what the final image will look like. It might be that depth of field is our number one priority or it might be shutter speed etc. but if we rely solely on the camera to make our choices then we relegate ourselves to ‘button pushers’. So let’s suppose I’m shooting in manual mode and I’ve already envisioned the image I want of a bird taking off into the wind. Shutter speed is important because I want to freeze wing movement but, depending on the size of the bird I may not need a very fast speed…especially if it’s a raptor. Depth of field is important if I want front-to-back clarity of the bird, say from wing tip to wing tip. But I’ve already metered for the image I want and the ISO is already determined. So if I need to change any of the variables because of a slight change in light then it’s simply a matter of quickly changing one or more of the settings without taking the my eye from the viewfinder (because I’m totally familiar with the ergonomics of the camera). Therefore, I still maintain the same exposure that I metered for in the first place. If I need to change the shutter speed then I know that I have to change the aperture to maintain the same exposure – equal clicks in opposite directions. If I need the image brightening then I can also change the ISO by equally clicking in the same direction. The exposure will be maintained.

So I saw a presentation given by a fellow photographer who was championing Auto ISO in Manual mode. His reasoning was based on shooting a dappled bird moving in and out of dappled shade. Now you might think that by setting auto ISO any light change is compensated for as the bird moves too and fro. And, sure, it might well do but I have to ask the question, ‘Why would you want to do such a thing?’. This seems crazy to me: either shoot the bird in the light or shoot the bird in the dappled shade…don’t try to do both. To me it’s pointless. I’d rather take a lunch break and wait for the conditions and light that I want because I want total control of the canvas, the brushes and the paints. I’m not saying that you shouldn’t shoot in ‘auto anything’…it’s your choice. But if you choose to shoot in manual then why shoot auto ISO? It doesn’t make sense to me. Take control of everything you can. As photographers we have enough trouble waiting for the light to be as we want it, so why leave ISO in the lap of the gods? Paint the picture you want not what the camera wants.

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