Auto ISO

RMH wrote in post #16533996
I think what he'as saying is it's better to have the right ISO than set a limit and then need to push it 3 stops in post

Well, that's not exactly what I meant; what I meant was that you will not save yourself from noise just by keeping the ISO at a limit, in M mode (it will keep noise down in Av or Tv mode, by compromising Tv or Av values). There are advantages and disadvantages to using the limit in M-autoISO.

I must admit, I don't really understand the need to shoot in M in this way - I've never really encountered a sitution where I wanted a speciffic shutter speed and still needed to adjust quickly, just a minimum shutter speed, so Av makes more sense to me, but that doesn't mean it doesn't exist - I only shoot photos of more or less stationary people, so my needs are not your needs

I started out shooting birds in Tv mode, with fixed ISO. I quickly got annoyed at having to adjust ISO to control the aperture. I switched to Av mode, with fixed ISO, and got annoyed with the way that the shutter speed dropped to unusable levels if the lighting suddenly lowered, or the bird jumped into the shade. So, I started using all-manual, but still wound up with exposure problems when the lighting changes. All through this, I was dreaming of auto-ISO in M mode, as a reasonable wish (as it would seem like nothing for Canon to provide this), and as a more distant wish, the ability to make my own program modes where I make a table of ISO settings, Tv values, and Av values for a range of metered EV levels offset by the EC control.

Canon seems to either be dead from the corporate neck up, or they are intentionally holding us back to guarantee upgrade purchases in the future, as they announce their original new features that users had already thought of over a decade ago.

John Sheehy wrote in post #16534352
I started out shooting birds in Tv mode, with fixed ISO. I quickly got annoyed at having to adjust ISO to control the aperture. I switched to Av mode, with fixed ISO, and got annoyed with the way that the shutter speed dropped to unusable levels if the lighting suddenly lowered, or the bird jumped into the shade. So, I started using all-manual, but still wound up with exposure problems when the lighting changes. All through this, I was dreaming of auto-ISO in M mode, as a reasonable wish (as it would seem like nothing for Canon to provide this), and as a more distant wish, the ability to make my own program modes where I make a table of ISO settings, Tv values, and Av values for a range of metered EV levels offset by the EC control.

I still don't quite get it; there's limits at both ends of the ISO range and surely you'd rather have the sutter speed go up rather than overexpose an image because ISO can't go any lower?

Sounds to me like you really want a 1/1000 second (or whatever) min shutter speed in Av mode. Then if we get down to ISO 100, the shutter speed can go up to 1/2000 or 1/4000 or whaever if the ligth increases, and stay at 1/1000, but with higher ISO if light decreases....?

John Sheehy wrote in post #16534352
Canon seems to either be dead from the corporate neck up, or they are intentionally holding us back to guarantee upgrade purchases in the future, as they announce their original new features that users had already thought of over a decade ago.

No arguments there. I'm constantly amazed by the things that Canon leave out of firmware / badly implement in firmware, where there's no additional R&D cost, implementation cost or anything, just some common sense needed. I mean really, someone at cannon either said "no-one ever wants a minimum shutter speed of more than 1/250" (lost for words) or "lets deliberaly make this less useful than i could be so we can upgrade it later" (again, lost for words).

Another thing I find slightly annoying is that while there is 1/125, and 1/250, there is no 1/200. Why does that matter? Because the x-sync speed of the 5D3 is 1/200!!! Come on Canon, you have a lot of grey matter at your disposal...

The 5D3 is a fabulious camera - the best camera I have ever owned or even used, from any brand, and one I really think I'll be using for a very very long time (been quite while since I felt that about a camera body) but some things still just make so sense.

RMH wrote in post #16534411
Sounds to me like you really want a 1/1000 second (or whatever) min shutter speed in Av mode. Then if we get down to ISO 100, the shutter speed can go up to 1/2000 or 1/4000 or whaever if the ligth increases, and stay at 1/1000, but with higher ISO if light decreases....?

Most of the time, even when the light is 'highly' variable, we are looking at perhaps 3-4 stops total between brightest and darkest.

But here is the key (for me). A lot of the times that I will hit variable light, I will also be in low light.....the kind of situation where I am working against a maximum aperture and a minimum usable shutter speed while wanting the lowest ISO. And in this situation M mode + auto ISO will deliver the lowest possible ISO level for each shot.

Compare this situation in Av (standard) against Av (with auto ISO) and M (with auto ISO) assuming light is swinging three stops.

Assume that I can get the shot at f/2.8, 1/1000 and ISO 1600 when it is brightest and f/2.8, 1/1000 and ISO 12800 when it is darkest.

Av mode (standard) = I pick f/2.8 and ISO 12800. The camera will use shutter speeds between 1/1000 and 1/8000 depeding on the light. But this is stupid because I'm burning high ISO (12800 constant) in the better light to gain shutter speed (1/4000 - 1/8000) that I don't need. If I set ISO to <12800, I will get shutter speeds below 1/1000 when the light is worse than the best case.

M mode (auto ISO). Set f/2.8 and 1/1000. The camera will select ISO 1600 to ISO 12800 as needed, but will only use the higher ISO levels when it is darkest, and it will never select a shutter speed faster than 1/1000 or underexpose the shot.

Av mode (auto ISO) = I pick f/2.8 and set the shutter speed floor to 1/1000. I suppose I also set the ISO maximum to 12800, but the result in this case will mostly be the same as we get in M mode. The difference is that when the light is better than the worst case, the camera is likely to select shutter speeds faster than 1/1000 while using ISO levels higher than 1600.....same problem as regular Av mode.

While we are at it, Tv does kind of the same thing where it will stop the lens down from maximum while sticking with a less than optimum ISO level.

Basically....while trying to deal with low light, you want a mode that sticks with your absolute limits for aperture and shutter speed while giving the lowest ISO you can get. This mode in M mode in steady light, and M mode with auto ISO in variable light.

RMH wrote in post #16533996
I think what he'as saying is it's better to have the right ISO than set a limit and then need to push it 3 stops in post

I must admit, I don't really understand the need to shoot in M in this way - I've never really encountered a sitution where I wanted a speciffic shutter speed and still needed to adjust quickly, just a minimum shutter speed, so Av makes more sense to me, but that doesn't mean it doesn't exist - I only shoot photos of more or less stationary people, so my needs are not your needs

One thing I do find odd, and not quite right even on the 5D3 (though it doesn't actually affect me) is the choice of min shutter speeds -- it goes from 1/1250 down to 1 second. Really canon? You don't think anyone shooting sports would like to be able to set a minimum of 1/500 or 1/1000? And is 1 second really useful as a min shutter sppeed? If you're shooting that slow, you're probably on a tripod and taking a very considdered approach to your shooting, and probably in manual everything :S

For Stationary subject you no need control the shutter speed, so AV mode is ok. But for moving subject and panning the shutter speed is the important variable.