Who's better, You or your AF?

[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.

[Daniel Browning]

Generally speaking should AF be able to resolve as much detail as MF?

With the standard APS-C viewfinder screen and a calibrated system, I think that the f/5.6 autofocus sensors are a little more accurate than I can do with manual focus through the viewfinder. But the center f/2.8 AF sensors are definitely better than anyone can do with the standard screen.


If you use a high precision screen, MF can get close to the accuracy of a calibrated f/2.8 AF system at f/2.8, but personally I think the latter is still a little better. If you have an f/2 or faster lens, then I find MF becomes better than even the f/2.8 AF sensor, doubly so if coupled with a true ground glass or split prism viewfinder (e.g. Katzeye).


Liveview beats them all, of course, for subjects that are slow enough to use it.

I'm getting more resolution by focusing manually.

Your body and/or lens may be slightly out of tolerance at the zoom and focus distance you are using. If you had microadjustment (e.g. 50D upgrade), you might get sharper results. My 70-200 and 50mm f/1.4 lenses both required micro-adjustment.

[canoli]

Hooray! Someone actually mentioned the "Katzeye" system! I posted last year asking for KatzEye impressions but no one replied. []


I'm sure there are reviews on other sites but this is the only photo forum I ever read and I trust you guys.


Have you used a Katz screen Daniel? Anyone else - even if it starts out "I know this guy who's girlfriend's mom's best friend had one..." Seriously, anything you know about them would be helpful to me. I've read their site many times; the metering adj doesn't bother me. I'm just curious if it's anything like the Leica split prisms. (must be the 1.6x FOV complicating things for me, as I do see a big difference with the 1-series, but I still can't get over how dinky [and dark] these DSLR VFs are).

If you have an f/2 or faster lens, then I find MF becomes better than even the f/2.8 AF sensor

That's the larger aperture at work, right, allowing a brighter image in the VF?


I get the impression most folks here don't do much manual focusing, but whatever thoughts you'd care to share, I would appreciate reading them. Thanks All!


{btw, if you haven't tried it in awhile I recommend taking a day off from AF. What I've lost in blurry photos I've gained in slowing down the whole process and thinking more about each shot.}

[Daniel Browning]

Hooray! Someone actually mentioned the "Katzeye" system! I posted last year asking for KatzEye impressions but no one replied. [img]/emoticons/emotion-6.gif[/img]

Yeah, I saw your thread. As I recall, you specifically asked for people who had used it themselves, so I didn't respond.

Have you used a Katz screen Daniel?

No, but I would assume it's like using a film camera with a split prism.

That's the larger aperture at work, right, allowing a brighter image in the VF?

That's a part of it, but I was mainly thinking because the visible DOF is slightly thinner. It's not as big as the difference from f/4 to f/2.8 with the high precision screen, but it's there. With a true ground glass or split prism, the difference would be even larger.

[Fast Glass]

I have used a split prism focusing screan before on myMinoltaX-700 film camera, it works great. It gives you some feedback when you have achieved accurate focus.


Hey Daniel, how does AF confirmation compare to MF or Live View? Would it be faster than MF or Live View?


John.

[Daniel Browning]

Personally, I find that AF confirmation is a good technique to use to supplement MF, but I don't find it any faster than MF alone. Live view is the best I think, but for mobile subjects it can be slower as you lose and re-acquire the subject at 5X.

[canoli]

How do you get confirmation when you're in MF mode? Do you mean your lens is in AF mode but you focus manually, and then when you think you've got it you press your shutter halfway (or press the AF button if your cam is setup that way)?