Why use manual exposure when you could use automatic?

Answer 1

Usually because you are smarter than the camera. Left to its own choices the meter in your camera "sees" everything as 18% gray - the mid-tone in an average scene. If part of your scene is brightly lit and part is in deep shade the meter still calculates exposure to render it as 18% gray. Since you are smarter than the meter you know that the brightly lit areas will be over-exposed. So you MANUALLY meter and then stop-down 1 or 2 stops to give proper exposure to the brightly lit area. Or, you MANUALLY meter the highlight area and the shadow area and AVERAGE them. (Suppose the highlight area requires f11 @ 1/125 sec. and the shadow area requires f2.8 @ 1/125 sec. You can count down from f11 and up from 2.8 and arrive at f5.6 or you can exercise your math skills and calculate it using the geometric average. 2.8 x 11 = 30.8; the square root of 30.8 = 5.549 or 5.6).

Some wise person once quipped: "Automatic is fine 95% of the time. The other 5% are in magazines".

Answer 2

Good question. And to be honest here, it's like driving a car. If you have driven an automatic and a manual, you will know how you have more control with a manual. And it's also a lot easier to drive an automatic. Either way, it still does the job.

When shooting weddings, I use auto because my Nikon D200 combined with the SB-800 speedlight does a more than excellent job at getting the exposure perfect in nearly every situation. Although there are times I need to use manual settings to get certain shots if the scene is such that the meter is fooled. Everything else, I use manual entirely because I have the control I prefer.

Once upon a time, if you didn't use manual settings all the time, you were frowned upon by other photographers because you were 'lazy' for shooting auto. But the truth is, camera metering systems are so advanced and accurate these days, why would you want bother with manually adjusting your camera for every image during a wedding shoot for example when you can easily use auto and get excellent results.

Answer 3

Like the other answer said, you are often smarter than the CPU of a camera. Sure, you can spend $1200 on a DSLR and use it in auto exposure mode. But why, when you can buy a $150 camera that will do the same thing? The simplest example I can give is photographs at night of an interstate, where there are light trails. A shot like that is obviously meant to show something, especially considering it could be exposed properly another way. The camera will set a wide aperture and fast shutter speed to expose for an average of light found within the capture, this will typically freeze motion when shot on a tripod. Yay, cars. You'll see them and their lights frozen in time, a "snapshot". When you decide to bypass the camera's best calculation of how the capture should be exposed and use some artistic composition, you may want to show something other than cars with their lights on. It's known as interpretive composition, you want whomever is looking at it to interpret your vision. The light trails are meant to show motion, life. In order to expose for motion you must use manual exposure mode because as I said, the camera will expose for a differential value of an averaged metered exposure. In auto mode, you will not to achieve a shot meant to show motion. YOU, will set a small aperture and a SLOW shutter speed. This increases the time that the shutter remains open, usually 4-8 seconds, the film or image sensor records everything in motion as blur, or in this case light trails. A properly exposed shot, done a different way, using the same ratios of exposure values at different stops. If f/2.8 @ 1/30 is the proper exposure, choosing f/22 @ 8" (example) would be the same value of light, but a different "kind" of exposure. The exposure value of the cars are lower than the light so you don't see them in the final composition, but by looking at it you know they were there. The ability to show time in a two dimensional image is a very important aspect of artistic composition and makes your work more that just a snapshot.

That is why we use manual exposure mode instead of auto.

Answer 4

Doing all of your Photography A level homework here?

Manual exposure allows you to control the exposure for an effect or for a particular subject. Automatic exposure is OK in most cases but if there is unusual lighting or a very bright or dark subject then the automatic exposure will probably set the exposure for the wrong part of the image.