High-end cameras like SLRs have modes — Program, Aperture, Shutter Speed and Manual. These let you specify the parameters you want, while leaving the others to the camera. In theory. In practice, this is a bad interface, for many reasons.
To take a step back, the problem this tries to solve is that there are three variables — aperture, shutter speed, and ISO — that need to be set. The user can choose to specify any combination of these, leaving the rest to the camera. Modes are one way to solve this problem, but a bad way:
- Why are aperture and shutter speed modes, while ISO is not? The answer is that ISO is merely a setting that you can specify in other modes, either as a specific value, or as Auto. That explanation is fine as far as it goes, but it’s still an inconsistent user interface when one of the three variables (ISO) is handled differently from the others (aperture and shutter speed).
- Why can’t I specify ISO in Auto mode? The camera sternly tells me to use Program mode. Well, then, switch to Program mode on the fly and let me set the ISO, and let me know that the mode changed. A good user interface lets the user do what they want to do, aiding the user in achieving their goals rather than obstructing them with needless error messages.
- ISO can’t be set to Auto in Manual mode, on my camera, and many others. Why not? This is an arbitrary restriction, and does nothing but annoy the user with needless roadblocks .
- The mode system lets you set a value for a variable, or leave it at Auto. But I often want to set a maximum value, such as: use ISO 800 or less, to keep noise at an acceptable level. Or a minimum value, such as a shutter speed of 1 second or longer (when I’m shooting a moving train, and want some blur, but I’m not particular as to the exact amount of blur). Or both a minimum and a maximum value, such as using an aperture between F8 and F11, since my lens is sharpest here.
The solution is to get rid of modes completely. Nokia developed a brilliant UI where you have three variables, each of which can independently set to Auto, or to a specific value:
Just add the ability to set a minimum and/or maximum value, and the problem is solved.
Cameras should detect if they are on a tripod and automatically choose a longer shutter speed (and correspondingly lower ISO and sharper aperture) to result in a better photo. Cameras normally choose a short enough shutter speed to prevent shake, assuming that the camera is handled. But that’s not the only situation in which cameras are used. Try to detect tripods and do a better job. The algorithm to detect a tripod needn’t be perfect as long as it doesn’t have false positives — thinking it’s on a tripod when it’s not, and producing a blurry photo. As long as the majority of tripod-mounted photos come out clearer, that’s an improvement. The point really is to do a better job when possible.
Cameras should also do a better job of warning users if their settings are going to result in bad photos. For example, I took photos of a sporting event, but I didn’t realise that I had the camera in manual focus mode from night photography the previous night. Almost all the photos came out mis-focused and blurred, which was not visible on the tiny screen. The camera should have detected the mis-focus (after all, autofocus works reliably in daylight, that too with a phase-detection lens) and warned me about it.
I’d also like to be able to specify that a priority between ISO, aperture and shutter speed. I want to tell the camera to use ISO 100, but if the scene is so dark that that results in inadequate exposure even at 30 seconds , increase the ISO to 200 to take a good photo. In other words, I sometimes want to tell the camera to try to use ISO 100, not that it must use ISO 100.
This matters a lot when you’re doing night photography, and often bumping up against the limitations of the technology. Rather than having to keep changing the settings all the time, I’d like to tell the camera the priority — increase the shutter speed before increasing the ISO — and let it figure out the exact values to use. This is a more automatic and less tedious solution to the problem. It does add a bit of complexity in learning the feature, but actually eliminates a far greater amount of complexity in day-to-day use. And if you don’t care for this feature, you can ignore it, and the added complexity is just one unused settings menu item, which is not much given the value of this feature. Remember that we’re not talking about the iPhone Camera app, but a $1000 camera-and-lens combo. Of course it should have features that make advanced photography easier.
So, to summarise, get rid of modes. Let the user independently specify aperture, shutter speed and ISO, or any combination of them, while leaving the rest to the camera. And let the user specify not just a specific value but also a minimum and/or a maximum. And have a notion of priority, which tells the camera which variable to change before or after changing others.
This will make cameras much simpler and easier and less intimidating to learn and use, get rid of useless error messages and roadblocks, reduce the need to often fiddle with the settings, and result in better photos.
 Supporting Auto ISO in manual mode is trivial — the user has already specified the aperture and shutter speed, so it’s trivial for the metering algorithm to decide what ISO to use to correctly expose the scene. This is easier compared to aperture or shutter speed mode, where the algorithm has to determine two variables (shutter speed and ISO in aperture mode, and aperture and ISO in shutter speed mode), to say nothing of Auto mode, where the camera has to decide all three factors. Deciding only the ISO when the aperture and shutter speed are specified is a constrained, trivial problem in comparison.
 While we’re at it, increase the shutter speed limit to 5 minutes or so. If the light level is so low that the autofocus or metering algorithms can’t work, ask me to manually set the focus and / or exposure. But don’t disallow longer exposures.
 I would also like more flexible bracketing, such as taking a bracketed set of photos with different aperture and the same exposure.