My mother is taking a course on photography and she was commenting on how her teacher was touting the advantages of shooting in manual. While I am no stranger to manual I really think this argument is directed to people who set the camera to program and then don't notice what settings the camera picks. This is a crucial point - there is not an iota of difference between the camera picking 1/125s - f/4 and you setting the same in manual. The only difference is that you saved yourself the time and trouble, and maybe got a shot you wouldn't have had time to get.
"Sure," you say, " but what about when the meter is wrong?". Good question! You simply change the exposure compenstation dial to correct a stop or two. With digital you have a histogram on the back plus the image itself so instant feedback helps you quickly get to the right exposure whether in manual or auto exposure. I have the following comments on the several Canon Auto Modes:
1. Program. While I have nothing against program mode, it will pick both shutter and aperture for you. While the shutter speed doesn't really matter as long as it will stop motion (if that is what you want) the aperture does play a big part in the final picture. Since you don't really have control over either I never use program mode (see below). I do realize that you can quickly adjust with the command dials to get the shutter/aperture you are after but I hate having to wheel in a good aperture every time I take a shot.
2. TV. Time value. This is the shutter priority mode. You set the speed, the camera picks the aperture. I always use this mode for long exposures (blurred water, motion blur, etc.) since time is the key variable you want to control. Otherwise I stick to AV.
3. AV. Aperture value. This is my preferred mode. I set an aperture I want for depth of field, or perhaps for optimum sharpness or also just to get the fastest shutter speed (wide open). In all three cases I have lots of options to meter. I can use the spot meter and lock the exposure with the '*' button. I can dial in exposure compensation 'knowing' I will need it, etc. Finally, I am just a click away from the manual mode if I really need to lock down the exposure. What I like about using this mode, is that when light conditions are changing the camera still takes that into account. With manual there is the danger that you don't notice when the light drops half a stop or more.
4. Manual. Unless light on my subject is constant or I need more than 2 stops exposure correction I usually stay out of manual mode outdoors. There are some very handy times to use it though - like when doing a panoramic with multiple shots. In that case you'll want to lock the exposure in so that it is consistent from shot to shot. Another is when using flash. I hate the way Canon locks the shutter to 1/250s for flash shots in AV mode (or lets the ambient dictate both shutter and aperture). I prefer to switch to manual so I have independent control of the ambient (via the manual exposure / shutter speed) and the flash exposure (via the aperture). I can also keep my ambient sharp by keeping the shutter at a speed I can hold. I may not get full exposure on the background, but I hate what program mode lets my shutter drop really low and I pick up blur from parts of the photo when I don't expect it. Oh - and for another case where manual is good: when you have constant light but your subject's brightness changes a lot. Think bride and groom standing in the shade. Black. White. Black. White. Both. No meter can figure that out!
I've tried operating in manual outdoors and here is what I found:
1. I lose a shot or two. I almost always forget to set the camera first and miss my first shot. I'm sure I would get over this after a while.
2. Some people seem to think that you aren't really taking pictures until you spend a few minutes working out the 'sunny f/16' rule, etc. on each shoot. I prefer to get an 'auto' exposure shot as my first picture and then work from there. If it turns out well I'm done!
3. Light changes. The camera is a lot more sensitive to light than we are and keeps adjusting to suit. Either you shoot on manual and are constantly checking the display or you run the risk of lighting changing.
4. My kids don't stand still! If you have every tried to follow your kids in and out of the shade and sun on a hot summer day I can't believe you still prefer manual.
5. Why guess? My camera has a meter that works very nicely. Why would I spend a lot of time trying to get myself so in tune with the light that I can manually set what the meter would pick? I doubt I'll ever get to 1/2 stop accuracy...
6. I bored of this a long time ago with my old AE-1 and non-auto lenses. I paid my dues - let me use my digital camera's sophisticated meter!!!
Please be aware that some of these comments are tongue in cheek. I don't wish to tell anyone else how to use their camera. If you shoot in manual all the time and get great shots - wonderful! I don't find that it works well for me. If you have some advice that will change my outlook on manual forever then please comment away. Note that the Pentax K10D (and 20D I assume) has a cool feature where in manual mode you can simply hit the green button and it grabs the metered exposure and resets the aperture and shutter to match. You are ready to run with that or adjust away. If Canon had something like that, I think I could finally make the move to manual.
Anyways, if this helps someone who feels they must use manual to get the 'real' photo taking experience feel like they aren't cheating shooting in aperture priority then my mission is accomplished! Progam isn't just for amateurs - it is for people who want to use the built in meter. Just don't get me started on the really automatic Green mode ;)