Focus accuracy

[j. rivera]

Happy Holidays to all!

 

<p>

 

Shooting some snaps of my son this morning in low light with the Reb 2000 I was having trouble with the AF. Switching to MF I noticed a very large range in lens travel were the indicator said I was in focus. That got me to thinking about an article I read on Robert Monaghan' site about AF focus accuracy. Basically, it said it sucked and you could get better sharpness with manual focus. Of course this is problematic without a focusing aid in an AF camera. My Eos 5 has interchangeable screens but none with a microprism, let alone any choice for the 2000.

 

<p>

 

So the question is, what do you think? Do aftermarket screens for the 5 make manual focus easier (Maxwell, in particular)? Should I not worry?

 

<p>

 

Thanks as always, (by the way, my family is now asleep, I didn't ditch them to post this :-))

[Ken Katz]

I shot MF SLRs for almost 25 years before buying an Elan II, and

unless we are talking Leica M6 or medium format, I would never go

back to MF. Microprisms and split image range finders were no thrill

for low light, low contrast subjects, especially with slow (f4!)

lenses.

 

<p>

 

AF is very accurate, but not infallible, with operator error

providing most of the problems. I almost never trust the auto sensor

select features, and prefere to specify the focus sensor and, for

people and critters, lock focus on the eye. For situations with

limited DOF (close up, long lens, wide apeture, ect) this should

provide a high percentage of sharp photos.

[puppy_face2]

AF accuracy varies from model to model. The EOS 1N, 1V and 3 all have a high

precision AF cross sensor. I haven't noticed any difference in accuracy between

my EOS 3 and A2 using my EF 50 1.4 USM. However, if you use a 600 mm

telephoto wide open the range of acceptable focus is mere millimeters and

accuracy will matter.

 

<p>

 

I read an article in Pop Photo a few years ago where they proved that manual

focusing was slightly better than AF. However, they had to use static test

targets, a tripod and a magnifying eyepiece to beat AF.

 

<p>

 

I can say without doubt AF is much better at nailing focus than I ever was with

my manual Nikon FM. I remember stopping down to F11-16 and setting the

hyperfocal distance on my 28 mm lens to get a simple grab shot. Otherwise, I'd

be trying to focus long after the action passed.

[bobatkins]

All the Popular Photography piece showed was that the particular

camera they used wasn't always as accurate with AF as it was with MF.

You could either conclude MF is better than AF, or equally well you

could conclude their camera should have been sent in for service!

 

<p>

 

I've done a LOT (too much!) testing on EOS cameras from the 630

through the 10s, Elan, Elan II and EOS1n to the EOS-3 and my tests all

point to the conclusion that a properly set up EOS body focuses as

accurately as, or more accurately than, manual focus 99% of the time.

[isaac sibson]

Not to mention faster...

 

<p>

 

Ok, so I've grown up with AF, and never owned (and only once or

twice used) an MF SLR. But even so, I don't believe that anyone is

telling the truth if they say they could manually focus quicker than

an EOS 3 + ring USM can autofocus. I certainly can't.