Exposure Modes - PASM
Which Exposure Mode should you use? It depends. By the time you get to the end of this long article you'll have a good idea what to use when.
Program Mode
Would you like to just point and click and take decent pictures? Then use the green (or red) Auto mode. If you'd like to control your flash or have more control over your cameras menu options, Program mode is one choice for you.
The big letter 'P' on the dial, right next to Auto mode, is Program. The camera still picks the Aperture and Shutter Speed for you. It goes for an average combination and is suitable for general photography. The best thing about Program mode is all the menu options that will be opened up for you.
Besides being able to force your flash on or off there's also a number of other settings you'll have access to. (These will vary so check your camera manual to see what you have available.) Some of these settings are:
- Changing the ISO
- Shooting in Single or Continuous mode
- Changing the White Balance
- Exposure Compensation (forcing the camera to under or over expose the picture)
- Program Shift (changing the aperture/shutter speed combination used)
Having more control over your camera means having more control over how your pictures turn out. Isn't that what you want? As I discuss the other Exposure modes you'll discover when to use them and why.
Shutter Priority
Look at your exposure dial for the big letter 'S' and you've found Shutter Priority mode. If you're a Canon user you'll be hunting for 'Tv' on the dial. Canon calls it Time Value just to be different.
Shutter Priority allows you to preset the shutter speed and the camera will pick the correct aperture for proper exposure. Sports and action photographers are most likely to use this mode. They need to make sure the shutter speed is high enough to stop the action they are shooting. You could also use Shutter Priority to preset an appropriate sync speed when using your flash. Great for those times when using fill flash outdoors.
Depending on your lighting conditions, it is possible to try to set an unusable shutter speed. Your camera will give you some sort of Error message in the viewfinder. My Nikon D70 displays a 'Hi' or 'Lo' to tell me I'm outside the usable range. The solution is to change the shutter speed until the error goes away. Sometimes, like in low light conditions, you may have to bump up the ISO in order to get an appropriate shutter speed.
Whereas Sports mode tries to push the shutter speed as high as possible, Shutter Priority lets you use the full range. You get to decide whether to use a slow or fast shutter speed. Try Shutter Priority the next few times you're out shooting and see if it's a useful tool for your style of shooting.
Aperture Priority
Similar to Shutter Priority, Aperture Priority is the other semi-automatic exposure mode. Here you'll be able to preset the Aperture and let the camera pick a shutter speed to go along with it. The big letter 'A' on your exposure dial is Aperture Priority. Again, you Canon users will be looking for something different. Canon uses 'Av' for Aperture Value.
By controlling the aperture you'll be controlling the Depth Of Field (DOF) in your pictures. Remember that Depth Of Field is the amount in front of and behind your focus point that is also in focus. Smaller apertures give more DOF, larger apertures give less DOF.
The Portrait and Landscape scene modes do this for you "auto-magically". Aperture Priority gives you more control and lets you use your brain instead of the cameras. By using Aperture Priority and precisely selecting your focus point you can maximize or minimize DOF. This is important in portrait photography, where you want the background to be blurred and not distract from your subject. It's also useful in macro photography when you need to maximize your DOF.
As always, I encourage you to experiment the next time you're out shooting. Try Aperture Priority. Use a couple different apertures on the same subject. Look at the images on your computer screen when you get home. Personally, I use Aperture Priority about 60-70% of the time. The rest of the time I shoot in Manual.
Manual Mode
I've encountered many people over the years who seem afraid of Manual mode. They worry that their pictures will be all screwed up. Don't be scared! Every picture you take comes down to a single aperture/shutter speed combination.
It doesn't matter if you arrive there in Program or Auto mode or Manual. A shot at 1/125th and F11 in Program mode is the same as a shot at 1/125th and F11 in Manual mode. Manual mode just requires a little more work on your part.
In Manual mode your camera will have some sort of indicator to show if your exposure is good or bad. There will be a Zero in the middle and Plus and Minus on either side. Your camera may use a needle or LEDs or display a scale with blocks. (Consult your camera manual to see what you've got.) Your goal is the change the aperture OR shutter speed to move the indicator to Zero. Simple!
I use Manual mode for some of the following reasons.
- Consistent exposures - the settings are locked in
- I can intentionally under or over expose
- Excessively bright or dark subjects fool the meter
- My OCD kicks in occasionally :}
When you use Manual mode you need to check your settings when the lighting conditions change. I suppose that's why many people use some sort of Auto mode. Manual mode requires that you engage your brain a lot more.
Here we've been discussing Manual Exposure mode. It is independent of your Focus mode. You can still use Autofocus when shooting in Manual mode, or any other exposure mode. If you really want to be old school, you can go manual focus and Manual exposure. If you do, I'll be so proud.
Your challenge now is to go out and try some of these different Exposure Modes. If you've read any number of the articles here you've realized that I think AUTO mode is EVIL! It's true. Just spin the dial to any of the above and you'll discover that your pictures aren't all screwed up. Experiment and find what works for you.
Now go shoot something!
