How to lock the focus?

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Pirate Neilsouth

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cokebottles said:
I've never used one, but understand how they work. I kinda want one myself. One thing you may need to consider is the fact that your EFS 18-55 rotates to focus, so you'd probably need to autofocus, then lock the focus, adjust the circular polarizer, then shoot the image. If you don't do this your polarisation will change as the camera rotates the filter to focus.
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How do i (lock the focus) on this lens/camera?

( canon digital rebel xti 400D )
 
You could autofocus then turn the focusing onto manual focus on the lens. :)
 
Various options
1) switch to manual focus
2) In One Shot autofocus keep the shutter button half pressed - this will lock the focus.
3) set custom function 4 to 1 - this will swap autofocus and autoexposure... so the * button (AE lock) becomes your autofocus, and AE locks when you press the shutter button.

If you're just bothered about its use with a polarizer then focus first on the subject, then rotate the filter. When you next press the shutter button the lens shouldn;t rotate noticably unless you have moved or changed the subject.

HTH
 
IIRC, there's an AF-lock button on the 400D?

If not, then just half press the shutter while the lens is in AF mode..

Ooops, just noticed onefivenine has beaten me to it..
 
Remember focus lock only works in One Shot mode.

It doesn't work in AI Focus or AI Servo mode. (Edit: But Custom function C.fn 4-1 gives you a way round that) ;)
 
If you turn the AF of the lens rotates rather freely. Not a good idea if you are twiddling a polariser.

Just tried it on my aging 300D, Try this

Leave the focus on AF, This to some extent locks the focus mechanism ( well it doesn't but you need a lot more effort to turn it). You can now focus as normal and then adjust the polariser. now as you press the shutter button it will focus again but the lens will only move a small amount if at all
 
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