What it is
Program exposure mode is the thinking person's auto: the camera chooses the most important settings for you -- shutter speed and aperture -- but gives you the choice of overriding any of the other defaults. It's called "program" because it algorithmically picks from a list of predetermined settings based on the amount of light (exposure value, or EV) that the camera measures when it meters. It's the best way to take baby steps for breaking out of the limitations of auto mode.
For more information about other cameras modes, check out What are all those camera modes for, anyway?
Who can use it
Anybody with a mode dial on their camera, either physical or virtual -- dSLR, interchangeable-lens mirrorless, advanced compact, or even a phone with manual controls.
When to use it
Frankly, if you're using full auto now, you probably should use Program all the time instead. But if you're happWy with auto mode and don't feel terribly adventurous, then you may just need to switch to Program in those cases where auto tends to fail:
- When autofocus is choosing the wrong subject
- When the camera is producing too-noisy photos because it's jacking up the ISO sensitivity more than necessary
- When you want to shoot raw or raw+JPEG, which some cameras ban from auto
- When you find the subject of the photo is too dark or too light
- When you want to override the automatic flash behavior
and myriad other situations where you think the photos aren't coming out right.
How it works
In older "dumb" implementations, the camera would pick a particular shutter speed and aperture to match a desired EV and that was it. Most modern cameras now support Program Shift, which allows you to change the shutter speed and aperture in tandem; for instance, if the camera chooses 1/200 second and f5.6, it might let you shift it to 1/125 second and f6.3 or 1/250 and f4.5. (Note to purists: these are not same EVs mathematically, and in fact differ by a third of a stop. However, they do reflect an actual program shift that delivers similar exposures. No camera is mathematically perfect.)
How to use it
At the most basic level, using Program mode is as easy as rotating the mode dial to the big 'P.' Some cameras have a locking mode dial that requires pressing a button; if there's no physical dial, usually more common with ILCs and advanced compacts than dSLRs, then you usually pull up the mode settings via a quick-menu or function button. If you're not sure, then you'll have to consult the manual.
Once you've set the camera to Program, you can still use it the same way you used Auto, though that would defeat the purpose. Take advantage of your newfound freedom by changing some of the settings that can improve your photos. You don't necessarily need to change them from the defaults, but you might want to if you're still unhappy with the results.
Most important settings to consider
- Shutter speed and aperture
As mentioned earlier, one of the advantages of shooting in Program mode is the ability to change these. The automatic choices the camera makes are usually pretty good, except in the extreme cases. Since they move in tandem, adjusting them does not change the exposure of the photo; to do that, you need to either change the metering mode or use exposure compensation. No camera will let you choose an aperture wider than the lens supports -- that f3.5-f5.6 designation on the front of your kit lens, for example. If you're constantly frustrated by that aperture limit, you may need a better lens. When changing these settings, just remember:
Increasing the shutter speed stops action and decreases the amount of light hitting the sensor.
Decreasing the aperture value (which actually opens the aperture wider) blurs the background more and increases the amount of light on the sensor.
Some cameras will let you change the range of shutter speed and/or apertures available for Program in the menus.
- ISO sensitivity
This is actually one of the more important settings to pay attention to. Most cameras default to auto, which means that when lights get low, they automatically boost the ISO sensitivity to capture more light, which in turn introduces color noise and all sorts of other things that make images look bad. Most of the time a camera will err on the side of a low sensitivity to minimize artifacts. But in low light, when cameras choose the appropriate setting, they do it based on assumptions about the capabilities of the photographer: when possible, they tend to set the ISO sensitivity high enough so that the shutter speed doesn't have to drop too low. But the camera doesn't know if you're capable of shooting handheld at 1/10 second, or if your camera's on a tripod, or any other extenuating circumstances. So you might be better off manually dropping the ISO sensitivity and lowering the shutter speed.
Also, some cameras won't budge the ISO sensitivity setting once they've picked it, and may limit the shutter speed or aperture they'll accept in the program shift.
- Metering and exposure compensation
Because Program mode is designed to determine the settings for what the camera perceives as a correct exposure, if you want something darker or lighter you'll have to tell the camera. You can do this either by changing the metering mode -- changing the way the camera decides what "correct" means -- or using exposure compensation, which simply increases or decreases the brightness by a specified amount after the camera has made its choice. These settings become important in cases where "correct" is too dark, such as happens with snow scenes or backlit subjects, or too light, when important details of the image may be blown out.
No autofocus system I've used has been able to pick the correct subject to focus on 100 percent of the time; only you know what's important in the frame. Many of the advances in autofocus over the past few years -- most notably face detection -- have been designed to compensate for that fact. So try to use autofocus options that limit the area, like expanded center point autofocus if it's available, or center-point autofocus.
What are the drawbacks of Program mode?
- The camera may not change the ISO sensitivity setting (in Auto) once it's taken the initial meter reading for a scene, which effectively limits the range of shutter speed and aperture values you can choose from to preserve the exposure. Pentax cameras offer a nifty Sensitivity Priority Mode, which fixes the shutter speed and aperture and allows the ISO sensitivity setting to fluctuate.
- If you want to have consistent settings across exposures, Program won't work; every time you half-press the shutter the camera redetermines the settings anew, and even if the camera hasn't moved and the metering settings haven't changed, the camera won't necessarily choose the same shutter speed.
- Many cameras have a fixed range of ISO sensitivity, aperture, and shutter speed settings they're allowed to choose from -- i.e., the program -- and you may need to pick settings outside those limits.