Advice on Auto ISO please

[stevegaskin]

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Trying to work out the best solution for ensuring a optimum shutter speed to avoid possible camera shake (e.g maximum exposure time of 1/125 sec).

My initial thought was to set Auto ISO to 1600 (don’t really want to extend this in order to minimise noise), then set maximum exposure time to 1/125 in Auto ISO. However, if I set shutter control to Auto exposure, and the light is too low based on whatever aperture I’ve set, the camera overrides Auto ISO in order to attempt to provide a correct exposure; this can result in the exposure time increasing beyond 1/125 sec.

As an alternative. If I set the shutter speed manually to 1/125 will Auto ISO adjust to provide the correct exposure for any given aperture?  Would I need to increase the Auto ISO parameter beyond 1600?

Other suggestions are welcome.

Thanks

 

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[M11 for me]

You have to set the speed manually. On the other hand I would advise you to go higher with the ISO than 1600. 

[evikne]

I think you are way to careful with the ISO. When you have manually set the aperture and exposure time to the maximum you can tolerate, there is nothing left to adjust other than the ISO. And then you have the choice between raising the ISO or not getting any picture at all. So I don't see any good reason to limit the auto ISO very much.

On the other hand, the M10 sensor is quite ISO invariant: If you lock the aperture and exposure time and use a too low ISO (manually or auto) so the picture gets underexposed, you can raise the exposure in post processing and get more or less the same result as if you used a higher ISO.

Edited December 20, 2019 by evikne

[adan]

As already mentioned - the only way to absolutely command a specific minimum shutter speed with Auto-ISO is to use the manual shutter dial. You set, say, 1/250th on the dial, and the camera will ramp the ISO up and down to match the light it sees coming through the aperture, but the shutter speed will never change on you.

(It's one of the signature features of Leicas - they still have a nice, dedicated, labelled, easy to set manual shutter dial. )

BTW - with a manually-set shutter speed, the camera will still warn you if you are exceeding the range of ISOs you've chosen. The manual metering symbols are always visible in the viewfinder, and if you see a > or < in the finder, that is the warning that you'll get underexposure or overexposure, unless you increase the upper Auto limit, or go to a higher ISO manually, or dial the shutter to a slower/faster speed.

But as evikne says - if you do get underexposure, raising the brightness/exposure in post-processing is about equivalent to having used a higher ISO anyway. In fact it can be better, since processing tricks like adding brightness and contrast and dropping the blacks a lot, but not trying to save the shadows, can get a decent "ISO 50000" picture out of an ISO 10000 underexposure. (see below. Looks about like Tri-X pushed to 3200.)

Personally, my upper limit is ISO 10000-12500 - where banding starts to appear. (I like dark places!) And I like shutter speeds higher than 1/125 - my subjects are often moving even if I can hold the camera steady.

But the camera will still always use the lowest possible ISO if there is enough light, so I still get ISO 200 in sunlight, or 800-1600 in moderate light. I only get the higher ISOs when there is just not enough light otherwise (which is what I would set manually anyway).

_______

Under streetlights, 1/180 at f/2, ISO 10000 "push-processed" to ISO 50000 in post-processing.

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Edited December 20, 2019 by adan

[M11 for me]

Another aspect comes to my mind: I normally - in darker surroundings - I set the aperture and the exposure time manually and set the ISO knob to A (which is set to a max of 25'000; why should I limit that variable? Always assuming that I shoot handheld and do not use a stand.). In the case of automatic ISO the brightness of the pictures taken is often too light. As an example the ISO went to 12500 when 6400 would have been enough. The scene appears then lighter than I would like it or lighter than what I see with my eyes. The meter tries to place the peak of the histogram into the middle. In that case I use the compensation wheel and it is the only case that I use that wheel. I set it to minus 1 or something that I  have to test a bit in a given situation. 

A last point: Even when I do nightshots (in towns as an example) my ISOs go never above 10000 as I need light to shoot. When there is no artificial light around then I can not shoot handheld anyway. Then I have to move to long exposures on a stand which I very rarely do.