[hestipod]

Unless I am misunderstanding your wants you can already do that. Leave the camera's main control dial on Auto for the instant shot or P(rogram)...with appropriate auto ISO settings if so desired...to meet the requirements of your second sentence. When you power on you will be in the chosen mode. Some cameras/lenses do allow AF override but its a simple flick of a switch to turn MF on if not. This stuff is where buttons, switches, and dials outshine menus any day.

[souprock]

I don't want to have a main control dial or equivalent menu. It could be in the wrong position at power-on when I am in a hurry. I want the camera to always be fully auto at power-on, and I don't want to have to touch a main control dial to go into manual mode. Moving the settings should be enough.

Aside from focus, there are 4 user settings (ISO,shutter,exposure,aperture) to control 3 physical settings (ISO,shutter,aperture). It is thus overspecified. On power-on, the camera should control all of that. As soon as I have changed 3 user settings, the 4th is also determined and there is nothing left for automatic control.

If I change less than 3 user settings, the camera should automatically adjust the remaining settings. If I change 3 user settings, then the camera is in manual mode and the 4th user setting is determined by the other 3. If I then change a 4th user setting, there is a conflict which might be resolved by using the most recently adjusted 3 user settings.

Going back to auto mode is rare enough that it can be done by flipping the power switch twice, off then on. A menu item is also fine for this, but not needed.

[throwaway9d0291]

It sounds like Fuji does part of what you want.

Fuji (at least the X-T3 I own) doesn't have an explicit "Aperture priority, shutter priority, auto, manual" mode dial like most cameras. Instead it has physical dials for aperture, shutter speed and ISO. The dials have "auto" positions and the shutter and ISO dials can be locked in place.

So instead of aperture priority, you leave the ISO and SS dials in "auto" and change the aperture on the lens. If you care about the ISO, you can change that and it'll automate the shutter speed.

The main thing it doesn't do is default to full auto at power on. I frankly think that's insane and would never buy a camera that allows it. I don't trust auto to do what I need.

[souprock]

You might not trust auto, but don't you trust the previous manual setting even less? It could have been under completely different lighting conditions.

Suppose you are up in a high desert. At night, you take pictures of blossoms by starlight. The next day at noon, you spot an interesting and rare bird of prey quickly flying by while holding an interesting prey item. Quickly you flip the camera on and take a photo. Oh bummer, the camera was still configured for starlight, and you'll probably never have another opportunity for a similar photo. All pixels are white.

Anyway, thanks for the mention of Fuji. That sounds better than normal. Why can't you lock the aperture in place? Why do you need to lock something in place if there is a separate dial position for auto? (if not auto, isn't it locked?)

[throwaway9d0291]

> You might not trust auto, but don't you trust the previous manual setting even less? It could have been under completely different lighting conditions.

Usually it'll be in similar lighting conditions because I shoot with my camera pretty continuously.

> Suppose you are up in a high desert. At night, you take pictures of blossoms by starlight. The next day at noon, you spot an interesting and rare bird of prey quickly flying by while holding an interesting prey item. Quickly you flip the camera on and take a photo. Oh bummer, the camera was still configured for starlight, and you'll probably never have another opportunity for a similar photo. All pixels are white.

This is unlikely to happen because I tend to shoot with my camera continuously. I'd have taken a photo of an interesting cactus long before I saw the bird.

That said, assuming I already had a super telephoto lens attached to the camera (which is the bigger problem, if I was shooting blossoms I probably wouldn't have the right lens attached), it'd take me less than a second to move the relevant dials on the Fuji to something acceptable. On the Sony that's not possible but that's just a sacrifice I make by shooting Sony.

And in this situation, I'd expect the auto settings to do something stupid like expose for the sky instead of the bird. For example the camera might choose low ISO, wide aperture, relatively slow shutter speed while I'd want max shutter speed, moderate ISO and whatever aperture works with the other two.

> Why can't you lock the aperture in place?

The lenses just don't come with a locking mechanism for the aperture wheel. It has some little clicks but that's it.

> Why do you need to lock something in place if there is a separate dial position for auto? (if not auto, isn't it locked?)

The lock is a physical mechanism to stop the dial from turning accidentally while in your bag or something like that. Otherwise even if you put it in auto when you put it away, a bit of jostling in its bag can turn the dial to a different setting, which can be an issue when auto is usually between the extremes.