Who's better, You or your AF?

[canoli]

I need a little input here; hopefully you can tell me if what I've discovered about my camera's AF is unusual or if it's normal.


Obviously AF is quicker than focusing manually. But is that its only advantage? Generally speaking should AF be able to resolve as much detail as MF?


In low light I'm better than my camera nearly every time. But even at 1/800 5.6 I'm getting more resolution by focusing manually.


Should I be disturbed by this?


The body is a 40D and the lenses I've used are the 70-200 2.8 IS and the 50 1.4.


Thanks for any thoughts you'd care to share.

[Jon Ruyle]

Do you mean with the viewfinder or with live view?


In almost all cases I can focus more accurately with live view than af. But the subject had better not move

[wickerprints]

The standard focusing screens make precise manual focus very difficult if not impossible. You simply can't *see* well enough. A properly calibrated AF system will win against standard screen MF.


With practice, a split prism screen or super-precision matte can achieve more precise MF but I don't feel like it would be faster than AF in many situations.


As for MF in Live View, provided you can hold the camera still and the subject isn't moving, you can almost always nail focus. I like using this method for stationary subjects while on tripod. Handheld is more difficult because you're introducing a lot more camera shake by holding the body away from your face.

[canoli]

Ah I meant to specify - No, through the VF - not Live View. Live View, with the 10x magnification isn't a fair comparison anyway.


I do use Canon's AF-S screen - whatever it's called, the one that's supposedly meant for MF. Honestly I don't notice much difference. The screen the body shipped with and the one I bought seem the same to me.


But there's no competition between my eyes and AF - I win every time.


Naturally I can't focus as quickly but the resolution is much better when I'm in MF.

[Fast Glass]

AF "should" be just as acurate as MF, if you are getting soft images you should have your camera focus calibrated.I use lots of manual lenses, I have 13 lenses 1 of them being AF! The EF 28-80mm f/3.5-5.6.


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This was taken with my Minolta 600mm f/6.3 manual lens andmy XTi. Can't tell it was manual focus can you? I didn't think so.[]


John.

[Jon Ruyle]

I find that I can judge focus for closeups better because usually I stop the lens way down (so what I see through the viewfinder has a far smaller FOV than the actual picture).

This was taken with my Minolta 600mm f/6.3 manual lens

Nice.


Amazing that a 600mm lens can focus so close. That takes a *lot* of travel. And I see no CA. Must be a monster of a lens. Any idea how much the thing weighs?

[Bill W]

Canoli....I have the 40D also and sometimes the AF frustrates me, especially inlow light, subjects moving, outdoors.Generally speaking I go w/the AF and temper my frustration....though I know some of the errors are my fault.


If I'm shooting a perched (I like to shoot birds) scene, I'll use live view everytime (tripod).


I'm really on the fence whetherto buy a big prime (currently shooting w/100-400)or a better focusing system body,e.g. the refurbished 1D Mark lll on Adorama is very tempting. [^o)]

[Cris]

I find my brother's 40D auto-focus to be somewhat inaccurate, when compared to my 50D. The 40d just does not focus as spot on like the 50D the 40d sometimes makes front or back focus, where the 50d don't. My 50d was focusing well when i got it, but then i spend some time testing and using the microfocus adjustment and now every single photo is spot on sharp.


I use a Kps 1,35x viewfinder magnifier on the 50d all the time and it makes the viewfinder like the size of the 5dmk2 (but not as easy to see), wich is great for manual focusing which i don't do a lot.


I manual focus only in live view using the magnification when on a sturdy tripod.


I rely in autofocus every time and it work perfectly.

[canoli]

you should have your camera focus calibrated.

From
what I understand calibration is pointless unless you're calibrating to
the lens. And unless the body has the micro-adjust feature, where you
can set up all your lenses, you're stuck calibrating only one lens I
guess - which may or may not be such a good idea, depending upon what it does to your other lenses.


Is it realistic to send Canon my 40D and 3 or 4 different
lenses, ask them to test all of them and then what? There's bound to be
competing interests amongst the 4 lenses - the 50 1.4 needs a +0.3, the
17-40 wants a -0.2...


Lucky for me that I enjoy MF. AF takes half the fun out of shooting so I really don't mind, but it is a little disappointing...


****************************


One more (dramatic) question, if you guys don't mind playing along...


Here's the stakes - if someone can focus better manually and get a crisper shot, you are instantly beheaded.


If you had to nail focus - it was a matter of life or death -
and you were shooting hand held, no Live View, plenty of light - would you feel totally
confident using your cam's AF?


Would you AF in low light as well? (same stakes apply!)


Thanks for your input everyone - I really appreciate it.

[lcnewkirk]

I use lots of manual lenses, I have 13 lenses 1 of them being AF!

I've got a couple of questions for you, Fast Glass: do you use a MF focusing screen, and do you have to have sometype of converter to use manual lenses? It was my understanding that FD lenses just plain wouldn't fit on aCanon DSLR. I guess I'm assuming that some of your 12 MF lenses are FD...


Lewis