Wednesday, April 20, 2016

Which PASM Mode Is Best: Program, Aperture, Shutter or Manual?

I get asked frequently which shooting mode one should use. Almost every camera nowadays has a dial with "PASM" on it, which stands for Program, Aperture Priority, Shutter Priority, and Manual. Besides that, you can expect to find at least one option for fully automatic. Which one is best? Which should you use?

Let me give you a brief history of myself. My first SLR, a Canon AE-1, was a fully manual camera. Yes, it had a shutter priority mode, but I never used it (not even once). From my first photography class in college through the next decade I only used fully manual cameras.

What does "fully manual" mean? It means that I set the aperture, the shutter, the ISO (depending on what film I loaded) and the focus. I didn't let the camera (if it was even capable, which, most often, it wasn't) choose anything itself. I was in complete control.

Most cameras now have a number of fully auto and semi-auto features. In fact, a few don't even allow for fully manual operations. For someone starting out it can be tough to know which mode to use, and so I think the default that these people often choose is fully auto. But is that best idea?
Rangefinder & Film
I believe that every photographer should be comfortable using their cameras manually. Why? Because if you understand photography and how a camera works, it's not all that hard to go fully manual. And if you are a photographer you should understand these things (and if you want to be a photographer you should want to understand).

It goes well beyond just knowing for the sake of knowing. You will find yourself one day needing to operate your camera in full manual mode in order to get the shot. If you don't know how you will not get the exposure--you'll completely miss the opportunity! There are indeed practical uses for the "M" on your camera's dial, so you need to know how to use it.

The best way to learn how to manually use your camera is to simply use it in manual mode. Set the dial to "M" and play around with it. Change the aperture. Change the shutter. Change the ISO. Turn the focus wheel. See what happens. Change it some more. See what happens. Change it again. And again. And again. Take note of what worked and what didn't and try to understand why it did or didn't work. This is not a quick process. You'll get a bunch of crummy results at first. Give yourself a month or two of only using the camera manually and see what you learn.

Once you've got a handle on using manual mode I would then suggest trying the semi-auto modes. This would be the "P" (Program), "A" (Aperture Priority) and "S" (Shutter Priority). Let's take a look at each.
Peaks - Lehi, Utah
I chose a small aperture for a large depth-of-field.
Let's start with Aperture Priority mode. This let's you choose the aperture while the camera chooses the shutter speed and ISO (if you are using auto-ISO). This is what I normally use in bright-light situations. It allows me to get the depth-of-field that I want (either shallow or large, depending on the situation and which aperture I chose), and I don't have to think about the shutter speed and ISO because the camera will set that for me (and, because it's a bright-light situation, I know that the camera will choose a quick shutter and a low ISO).
BNSF Intermodal - Tehachapi, California
I chose a fast shutter speed to freeze the quickly moving train.
Next up is Shutter Priority mode. This let's you choose the shutter speed while the camera chooses the aperture and the ISO (if you are using auto-ISO). This is a good option if you need either a quick shutter (to freeze motion) or a slow shutter (to show motion), but don't really care about the depth-of-field (whether shallow or large). I use this occasionally, but, more often than not, if I want a slow shutter speed, I have the camera on a tripod and am using manual mode.
Ethical Drugs - Hollywood, California
I chose a high-ISO because this was captured handheld after the sun had set.
Then there is Program mode. This let's you choose the ISO (if you are not using auto-ISO) while the camera chooses the aperture and shutter speed. You also have the ability to adjust the aperture (like Aperture Priority mode) if you want, and the camera will adjust the shutter speed accordingly. In a way this mode isn't any different than Aperture Priority mode (if you adjust the aperture from whatever the camera chose), and in a way it's a fully auto mode (if you use auto-ISO and don't adjust the aperture). Some people like Program mode because it gives you control (of the aperture and ISO) when you want it and when you don't want control the camera decides everything for you.
Jonathan's Shadow - Tehachapi, California
I chose to let the camera decide the settings because it didn't matter.
Finally, your camera likely has at least one fully auto mode, and maybe even two or three different options. I'll often use these for snapshots, but otherwise I avoid them. I will say that cameras have gotten much better at figuring out what settings are most appropriate in auto mode, and what the camera chooses might be pretty close to what you would choose yourself. However, I know already what settings I want, so I don't want to leave it to chance that the camera will get it right.

So which one should you use? Which one is best? Which should you not use?

It all depends on what's important to you. Do you care about depth-of-field but not the shutter speed? Do you care about the shutter speed but not the depth-of-field? It's all about what you want to control and what you don't really want to control. If you want to control everything, use manual mode. If you want to allow the camera to choose some things for you, pick which semi-auto mode works best for whatever it is that you want to control. If you feel comfortable letting the camera choose everything, there is nothing wrong with that (just so long as you know how to get what you want when you want it).

It's more about understanding photography and how a camera works than choosing the "right" mode. If you know how it all works, then you know how to control the outcome of your photographs. If you're leaving it all up to chance because you don't understand how it works, that'll only get you so far, and you should consider learning what controls what on your camera and what it all means.

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