Thanks for the thoughtful replies. I appreciate it. More inline.
But this thread has helped me zero in on exactly what's giving me trouble. Program will attempt to maintain exposure by slowing shutter speed and widening the aperture until you reach maximum aperture of your lens. Once there, Auto ISO only gives you enough ISO to make 1/selectedmin @ Max aperture, regardless if that selected Auto ISO is lower than the set maximum.
Why would the camera needlessly alter ISO? Camera exposure modes offer different ways to choose
exposure settings. Shutter speed and f-stop control exposure. ISO isn't an exposure setting.
It's not needless, it's in response to the users' request to shift the selected program further.
The issue isn't that programmed auto doesn't perform as it should. The issue is you've chosen an exposure mode that isn't a match for your needs. You want control over both exposure settings. Why not take it?
I want to be able to ask for more shutter speed and for Auto ISO to raise the ISO higher, still respecting my set limits.
You should try shutter priority. Doing so will give you the control you want over shutter speed. Manually dial in an ISO to get the corresponding exposure you'd like to target. Then, set ISO to auto and use EC to get the image lightness you desire in the EVF.
As you increase shutter speed, the camera will adjust f-stop (to maintain your chosen target exposure) until the lens is wide open. At that point, the camera will increase ISO in response to a faster shutter speed to maintain image lightness while exposure continues to decrease.
Yes, that's understood, but isn't always what I want. Ultimately I am thinking about both my required shutter and field depth,
If you want control of both, you need to be in manual exposure mode. In manual, you choose the depth of field and how movement is rendered.
so with Shutter priority and Auto ISO you inevitably end up at maximum aperture only with the minimum ISO required to make an exposure meet your requested EC.
Hmm, not so much.
Suppose you set ISO 800 as the target in auto ISO mode on your Z6III so, the camera is working in its invariant range. You've set a shutter speed of 1/2000 to freeze wing movement on a bird in flight.
The camera will pretty quickly choose the widest aperture the lens offers. It's done this at your request: maximize exposure at the target ISO. If clouds roll in or the Sun gets low and the scene darkens, the camera will increase ISO to maintain image lightness. It can't open the lens aperture any wider to maintain exposure at the shutter speed you've selected. It can only maintain image lightness through an increased ISO.
Suppose a deer walks into view and begins casually grazing. You don't need a 1/2000-second shutter speed to freeze that movement so, you dial-in 1/500. The camera responds to the 2-stop increase in exposure by reducing ISO to your target of 800 and, if needed, closing the lens.
If you want the lens to be wide open for a shallow depth of field, press the ISO button and lower the target ISO until the lens is back to wide open. Moving forward, the camera is now targeting a greater exposure. It will still increase ISO if the scene lighting darkens enough.
Replace the bird & deer with pedestrians on a street or any other subject. This is how Nikon cameras work. When you set a target ISO, you tell the camera, "Target the exposure that pairs with this ISO." The camera will do that. It will deliver the exposure you've targeted until it's no longer able to do so. At that point, it'll deliver the target image lightness you've selected.
In any auto exposure mode, the camera will choose settings that deliver the user-targeted exposure. If auto ISO is also engaged, the camera will increase ISO in response to a user-targeted exposure that results in an image lightness below an on-meter reading of 0.
If these results aren't meeting your needs, take more control. Take as much control as is needed to get what you want.
It just seems strange to me to have this artificial constraint. Program is a very useful mode and could be much more widely adopted if this behavior was fixed.
Nothing needs to be fixed. You're struggling a bit with reconciling the fact that exposure modes don't control ISO and that no automated exposure mode in any model camera always make the choices you'd make. If the camera isn't making settings choices you like, you've got three options: change EC, change metering, or take control of the setting.
My bone is that Auto ISO appears to interact with Program in one direction only, not bi-directionally.
Its performance is driven by your selected target exposure. That's not going to change.
It isn't smart or flexible enough to interact with Program to support greater latitude in the shifts available, once light falls below the given threshold A-ISO will cause Program to allow the greatest light-gathering pair only. So from that perspective I understand why it works the way it does.
Any auto exposure mode will respect the exposure you target.
Any program mode generally will suggest a shutter/aperture reciprocal pair that will provide metered exposure (±EC) at a given sensitivity, and usually allow you to shift along all the reciprocal pairs available that provide that exposure. If I want to change the brightness I will adjust the EC. I want to select from more options that provide a given brightness, and I want A-ISO to enable that. i.e. making a conscious decision that although available light is lower, I want or need greater depth of field. So keep the shutter at the set minimum, close the aperture one increment, and increase the iso one increment, and so on. In this line of thought it's still a reciprocal pair, just shutter/ISO instead of shutter/aperture.
You may be able to make P mode be the square peg that fits in the round hole. You may be less frustrated by taking more direct control of the exposure settings.
Edit: Amended version of my initial take describing the issue:
Let's say the camera says 1/60 F5.6, ISO 400. Turn the main dial and you can shift to 1/120 F4 ISO 400, then 1/240 F4 ISO 800, all the way until you hit your auto ISO limit. The Nikons will not raise the ISO in response to your Program shift, so you'll be stuck at 1/120 F4 ISO 400, with no faster shutter available.
ISO isn't an exposure setting. The P, S, A and M modes don't control ISO in any camera. Full auto does because, well, it automates
everything.
Try shutter priority. It gives you the control you want over shutter speed and the flexibility to use EC and auto ISO to maintain a desired image lightness while delegating 2 of the 3 main image making settings.
I understand that exposure modes don't control ISO and that ISO isn't exposure per se, but it affects the amount of light you are required to capture to meet an exposure. Given ISO is totally flexible now compared to film, I think it's reasonable to consider these 3 factors. I also suspect people who came of age shooting film think about this totally differently than people who cut their teeth on digital. Now even with ISO invariance one could argue that my way of thinking makes more sense.
What I'm seeing is a photographer who wants an auto mode to behave contrary to it's rational programming. I recommend you stop fighting the camera and acknowledge that you want more control. Take more control.
My reason for saying that it's slower to do this via M+A-ISO, is that well, it just is. I become responsible for shifting 2 dials, and the 2nd dial (sub) on the Z6iii is not prominent and a little tricky to turn quickly.
That's not the issue. The question is, do you have enough time to control both exposure settings? The answer is, yes.
Think, I'm walking around an indoor event in the evening. I'm taking some close-up portraits, for which the subject is somewhat but not entirely still. So in A mode we're already at minimum shutter speed and A-ISO is only going to give you enough sensitivity for that minimum. Fine.
The camera will increase ISO in response to too little light. It'll increase shutter speed in response to too much light. Where'sc the problem?
So, S mode then, and we pick a shutter that's a little bit faster so we get a nice sharp picture, and A-ISO moves up to support that. But, we're locked now at maximum aperture. Now we want to take a group photo.
If aperture becomes the priority over shutter speed, switch to aperture priority. Or, you can simplify things and shoot in manual. Whether movement or depth of field is the priority, you're in a mode that allows the control you want.
The way I remember on Canon, in P, I can then just zip the main dial and ask for a smaller aperture, riding the minimum shutter speed I have set, and increasing the ISO to support that exposure.
If you're in P mode instead of S or A, rotate the command dial until you get to the aperture you want. If the shutter speed is too slow, press the ISO button and increase the target ISO...reduce the target exposure.
The camera isn't going to reduce exposure - lower image quality - unless you tell it to do so.
Or simplify things and shoot in manual.
It is slower to now be forced to change the main mode selector constantly between modes. But the more I talk about this, I realize I am pretty much describing Canon's flexible priority mode. I don't think this existed as a standalone mode on 5DIV, but P+A-ISO I think pretty much functioned the same way. As far as I can tell an equivalent does not exist on Nikon.
You're no longer shooting Canon. You've upgraded to Nikon. Trying to force the Nikon peg into the Canon hole only leads to frustration. Embrace the system you have. Take advantage of all it offers.
I am trying to get more comfortable with the camera, it always takes time, and I will continue to think if this is a dealbreaker for me or not. Thank you everyone for your time and input.
--
Bill Ferris Photography
Flagstaff, AZ
