I have heard that every camera with autofocus also has manual focus, so a photographer can switch back and forth at will when conditions warrent.
Are you saying manual focus is essentially worthless on the 20D because the view finder isn't good enough?
No.
I'm saying that it's not good enough for precision focusing in the context of action shots; I'm sorry that wasn't obvious.
And with "action shots", I mean those where you need to focus quickly. (Now I know some people will point out that a Leica M is good for that. See below.)
In landscape and street photography, I would more often have the leisure to check and re-check, adjust and re-adjust, and even use smaller apertures to increase DoF. And in decent lighting conditions, MF becomes easier, and I often make good use of it.
Apart from doing various landscape and street photography, I take quite a lot of pictures of pool billiards players, under extremely difficult lighting situations.
The 20D isn't good enough to do reliable manual focusing under those conditions; I'm too dependant on a wide aperture to be able to do DoF-workarounds.
But the 20D
is good enough with autofocus that it often is better at precision focusing than me, with that camera.
Sounds like you really need autofocus full time, at least on this camera. Is this a common condition with other digital cameras? Is autofocus an essential feature rather than merely a goodie?
For this kind of shooting, yes, it's essential. But I'd also regard reliable manual focus an essential feature for those times when I
know where the player's face will be in a few seconds. (I'm a pool billiards player myself, so I can anticipate these moments quite well.)
Here comes a stretch. Could it be that if autofocus were removed (and I said if), sales might really plummet because there would be a camera that couldn't be focused reliably?
Sales would plummet because the competition has autofocus, and most people who buy cameras in this class desire autofocus.
Also, AFAIK, autofocus in the 20D isn't considered particularly inferior to its competition.
But the 1-series cameras have superior autofocus, and for center focus, the 5D is also pretty good.
Don's points are also interesting; I didn't realise that changing the focus screen would mess up metering.
Too bad there are so few fast Leica telezooms (or even tri-elmarits, or quads, or whatever!) around 70-300 mm with IS. Even worse, too bad that I wouldn't be able to afford that.