Is A mode a good idea when trying to take low-light photos of people?

Question

I 'm wondering if my reasoning about a specific shooting scenario is correct.

Suppose you are in a setting where:

• there is plenty of light from a human perspective but clearly less light than required for taking an easy shot (e.g. living room at night with the lights on)
• there are people in the room going about their business so there is motion, but it's neither sudden nor constant for the most part (e.g. two people talking might well happen to stand practically motionless for half a second or so)
• you cannot or do not want to get the people to pose
• using flash is not an option
• it's OK if a non-blurry shot turns out to be impossible (but obviously you 'd want to maximize the chances of taking one!)

In this setting, consider this strategy:

• put the camera in A mode and select the widest aperture possible
• adjust ISO to a reasonably high value for the given camera (readjust upwards if reasonable and the camera tells you exposure needs to be 1s or something equally ridiculous)
• measure the light and if there is a reasonable chance of the shot being possible try to take it ("reasonable chance" in my mind is something like 1/10s shutter)

The reasoning is pretty simple: set A and ISO to help as much as possible then see what you can make of the situation.

But is it correct? Am I overlooking something obvious to an experienced photographer? Is this one of those ideas that looks good on paper to someone inexperienced but veterans can instantly tell it won't work? Can it be improved? If not, what would you do instead?

Answer 1

Your strategy with aperture priority mode is a good way to go. If the light in the room is quite even and doesn't change, manual mode will give you more consistent results once you have found your settings.

Choosing the right settings for the exposure triangle (aperture, shutter speed, ISO) is always a trade-off in low-light situations. Keep in mind that for group shots, you don't want your aperture to be too wide open as you might not get all the faces sharp. Also, don't be afraid of high ISO, as you typically get even more noise if you have to correct an underexposed image in post than if you chose higher ISO to get a correctly exposed image in the first place.

Answer 2

Another alternative is to set it up yourself.

1. Put the camera in manual mode
2. Select your widest aperture
3. Select the longest shutter speed you feel comfortable using (~1/focal length without stabilization is a good start)
4. Dial up the ISO until your camera is metering about right (do not underexpose, a properly exposed shot with a higher ISO, is much better than an underexposed shot with a lower ISO)
5. Take a test shot and look at the histogram. If you are clipping on the low end bring up the ISO, in the unlikely case you are clipping on the high end bring down the ISO/increase the shutter speed/use a smaller aperture.
6. Practice, after a few times, this process can become second nature and as long as the lighting is not changing rapidly, you will get excellent, consistent results.

Answer 3

Manual mode is especially good in low-light situations where the background is constantly changing brightness. The camera's light meter is measuring reflected light, while what's important is the amount of light shining on the subject. Many times, especially in low-light situations, the amount of light shining on the subject--also known as incident light--is consistent, while the reflected light is constantly changing.

For example, high school football. High school football games are usually played at night outside on a field under lights. The lights will light up the field in a consistent manner, however the reflected light is constantly changing. The player's uniforms, brightly colored buildings, bleachers, etc., will cause the camera's light meter to change--sometimes radically, however the the actual exposure is consistent. Experienced high school football photographers will know the proper exposure for a given field, and will largely ignore the camera's light meter.

If what you're photographing is an event, and you have access to the venue ahead of the event, it really pays to check the lighting with a incident light meter, and to find any "hot spots", bright areas, are before the event and set the camera appropriately.

Answer 4

Personally, I'd go with Tv (shutter priority) mode in this kind of situation. That way, you can set the minimum acceptable shutter speed and let the camera take care of the aperture. As for ISO, go as high as you have to without straying into the expanded modes. I don't have a lot of experience with modern auto-ISO systems, so I can't help you there.

Answer 5

In low light situations like this, you'll need to make trade offs between shutter speed, aperture, and ISO. Choosing between aperture priority and shutter priority will depend on whether you need to prioritize control of the depth of field or freezing motion.

In the described circumstances, camera motion is likely to be a bigger problem than subject motion. A camera or lens that has image stabilization will allow you to get photos without visible camera shake artifacts with shutter speeds about one to four stops slower than without image stabilization. Alternatively, some kind of solid support such as a tripod, monopod, or even just bracing the camera against a wall or furniture can reduce camera shake. Then your shutter speed will be limited only by the subject movement.