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Canon USM and AF-MF


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#1 jgrjr777

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Posted 03 September 2003 - 07:08 AM

I have seen there are now quite a few Canon users on the forum. I am in the process of moving to the Canon system.

With Canon USM each lens has an AF-MF switch. This switch can be left in th AF position and manual overide is done with the focus ring. This is different than the Nikon 105 for example. Which has a ring switch that must be thrown from AF-MF.

This would seem to be an advantage for Canon. Can Ring USM len's be left in AF mode with a focus gear engaged? Does the switch have to be used? I have not seen how AF-MF will be switched in Canon housings. In Nikon housings a number of elaborate AF-MF switching arrangements have been implemented by various housing manufacturers.

Not all Canon len's are ring USM though. Some like the Canon 50 Macro 2.5 will not allow adjustment on the fly but require throwing a switch on the lens. I know that AF would not be important on a 50 macro. It is nice to be able to move from MF-AF for fish portraits on the same dive though. What do you Canon users do?

#2 james

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Posted 03 September 2003 - 07:22 AM

Just for the record (and this is not Canon related) the Nikon AF-S lenses operate the same way as the Canon USM lenses. The Nikon AF-D lenses have that annoying AF/MF button/ring that has be be turned an 1/8th turn to switch to MF...

With and AF-S lens, I think you can just flip the MSC controller to M and then rotate the focus ring, but I haven't tried it.

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#3 bobjarman

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Posted 03 September 2003 - 10:29 AM

Any canon lens that has full time manual focus with the ring USM (generally the higher$$$ ones), do not require you to flip the switch to fine tune the focus.

Just remember, unless you have reset your focus button to the back, (CF4 usually will switch the focus to the ae lock button) your camera will refocus as soon as you touch the shutter button. You could partially depress the shutter, than try manually focusing to adjust it. I do this often on land, but I think that would be very difficult underwater.

I either set my switch for manual or auto when diving. I think the logistics of using manual override to tweak your focus underwater negate any advantage of the full time manual focus. that said, it is a dream on the surface where I can use both hands.

#4 jgrjr777

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Posted 04 September 2003 - 06:54 AM

When using the Nikon 105 Macro it is nice to be able to switch between AF and MF for fish portraits if the oportunity arises. I am trying to figure out if this will be possible with say the Canon 100 without some type of control flipping that small lens switch.

Right now I do use CF 04 to move the AF function to the AEL button. This does seem to be impractical with a housing.

Canon requires no MSC switch, all the AF-MF swiching is done on the lens. Could a manual focus gear be left on say the 100 macro with ring USM? Yes but then you run into the problem of refocusing when you hit the shutter unless we use CF 04 and move the focus fuction to AEL. We could leave the Camera in One Shot AF mode then bump the focus with manual. That is how the Canon system is designed. Probably not practical UW. Plus you really need Dynamic AF to get the fish portraits with the Canon 100 or Nikon 105.

What I am trying to say here is we seem to be screwed with Canon right now. There is no easy way to change between AF-MF without a control that flips that small switch on the lens. That is unless we reprogram the AEL switch on the housing. As stated above that seems impractical and would not work with non ring USM len's anyway like the Canon 50 Macro.

If everyone remembers this situation first came about with the Nikon 60 and 105 macros and thier infernal on the lens locking ring switch . Most housing manu. have solved this one way or another.

I have enjoyed using the Nikon 105 and being able to change mid dive. There does not seem to be similar solutions for Canon. No housing manufactur seems to have dealt with this. Could any of the Canon users take a shot at this? What do you do?

Even for Wide Angle it is nice to be able to change from AF-MF. What do you Canon users do now? Right now it seems the only choice is choose AF or MF at the surface. Quite a step backwards I think.