qn on speeding up 85/1.2 lens AF on 1D-bodies


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Jeff

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Apr 27, 2002
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I have read somewhere that disabling the lens drive function using
p-cfn function will speed up AF. just wonder how it works n how will this function impact on other lenses mounted on the same body wil that same p-cfn function.

it appears to me that this is a piece of ultra high precision glass thus the drive step is very small (correct me if incorrect)

many thks

jeff
 

Belle&Sebastain

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Jun 27, 2002
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here
www.9frames.com
+evenstar said:
actually I think it focuses slow just because there is too much glass inside..:dunno:

there are only 7 pieces of glass, rather its too many heavy glasses to move around:bsmilie:
 

+evenstar

Senior Member
Jeff said:
I have read somewhere that disabling the lens drive function using
p-cfn function will speed up AF. just wonder how it works n how will this function impact on other lenses mounted on the same body wil that same p-cfn function.

it appears to me that this is a piece of ultra high precision glass thus the drive step is very small (correct me if incorrect)

many thks

jeff
what is the C. Fn in question here? Drive speed priority mode or sth lidat??
 

Jeff

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+evenstar said:
what is the C. Fn in question here? Drive speed priority mode or sth lidat??
not custom function but personal function. apparently if you use the provided software, u r able to set personalised setting combination in the cam not available in custom function. One of these functions allows u to turn the drive in lens on or off. This is what I meant by drive function in lens. I want to know if I switch it off would it hasten the AF function of the slowish 85/1.2 here. How does this setting then affect other lenses mounted on this same body.
 

n0d3

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Feb 3, 2003
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Disables Focus Detection by the Lens Drive
P.Fn-14 determines how the camera’s auto-focus system handles subjects that it can not attain focus lock on. In the normal mode, the lens will continue to search for focus until it has exhausted all possibilities. This manifests itself in the lens hunting back and forth for focus lock. By enabling this function, if the lens has found focus once or cannot find focus lock, the lens will stop trying to find AF lock and stop. This may appear as AF lockup if you don’t realize you have P.Fn-14 set. Generally, I would not enable this function, however it might be useful for photographers who routinely use manual tweaking of the focus point after autofocus has been established. This will prevent the lens from refocusing after the photographer has changed the focus setting manually.
 

oeyvind

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Feb 25, 2002
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I actually turn that PFn on, but you need to be aware of it, and overiding with manual focus when AF failed (take longer to AF), i.e. very true is macro and some low light condition.
 

Jeff

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thnks to n0d3 n oeyvind n folks :)

this is all i need to know.
 

user111

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if u are used to lens hunting then dont disable it because turning the function will disable hunting
if u dont like hunting then enable it

if u enable it, lookout for the flickering big yellow dot when AF fails to lock on
 

xl1

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Under the Son
www.ubans.com
change your AF to back (* button) using Cfn04, and you can use FTM with the lens, after u find focus then you press the AF at the back ur cam. lots faster.
 

Jeff

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xl1 said:
change your AF to back (* button) using Cfn04, and you can use FTM with the lens, after u find focus then you press the AF at the back ur cam. lots faster.
great tips here. way faster, even from close to infinity.

many thanks.

:)
 

Jeff

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sabrewolf said:
At low light better to use manual focus with this lens. I find AF is too unreliable because of the extremely shallow DOF
quite agree here. wide open is indeed very challenging using AF handheld.

perhaps it's the fly-by-wire design, i find this lens sucking up a lot of the batts juice.
 

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