Manual Focus why doesn't AF button work

rsoph · 12-17-2011, 05:00 PM

OK, I know it sounds like a dumb question, but why not? I know I told it I want to manual focus but I don't see it any different than hitting green button in Manual mode. Buttons not doing anything else, so why not help me out when I ask it to?

Wheatfield · 12-17-2011, 06:25 PM

What would you like the AF button to do when you are switched to manual focus? You've already told the camera you don't want AF by switching AF off.

**jatrax** · 12-17-2011, 06:44 PM

You could do what you want with a quick shift lens. Set the shutter button to NOT auto-focus, focus manual as you want but hit the AF button when you want help. But you have to leave the camera in auto-focus, if you don't you are either physically or electrically removing the AF connection. Technically this works with screw drive lenses too but I don't like doing that as you are spinning the screw drive motor in the camera when you focus manually and that could potentially cause damage. I've never heard of it actually causing damage but it just does not seem like a good idea.

rsoph · 12-17-2011, 07:25 PM

I am aware of the options to take the AF off the shutter button and that is what I do but it requires menu use and equally important, remembering to put it back,

What I was wondering, more than anything else, is why not allow the AF button to work when manually focusing, similar to the green button with manual exposures. I guess the screw drive disengagement is one possible explanation assuming this is a mechanical and not an electrical connection. I would find it useful when fine tuning my focus for wildlife and suddenly the subject moves or you find a better subject. Reaim, hit the AF button and start tuning... Just wondering aloud...

**jatrax** · 12-17-2011, 10:44 PM

Originally posted by rsoph

screw drive disengagement

Yes, when MF is selected the screw drive is disconnected. I assume the electrical circuit for SDM is disengaged as well but you cannot see that, only take it on faith.

I have the shutter button always set to NOT auto-focus. I use the AF button to auto-focus, so I can press the AF button and get an AF lock then fine tune as needed with the manual focus. Takes a little practice to get used to using the AF button rather than the shutter button but it feels quite natural after you get used to it. This also allows you to focus on what you want in focus and then recompose with out worrying that the shutter button will mess up your focus point by re-focusing.

borno · 12-18-2011, 04:13 AM

Originally posted by jatrax

Yes, when MF is selected the screw drive is disconnected. I assume the electrical circuit for SDM is disengaged as well but you cannot see that, only take it on faith.

I have the shutter button always set to NOT auto-focus. I use the AF button to auto-focus, so I can press the AF button and get an AF lock then fine tune as needed with the manual focus. Takes a little practice to get used to using the AF button rather than the shutter button but it feels quite natural after you get used to it. This also allows you to focus on what you want in focus and then recompose with out worrying that the shutter button will mess up your focus point by re-focusing.

+1
I set all my cameras up this way as well, with the back button AF. You choose when to MF or when to AF and it works great. I don't have any screw drive lenses so I don't have the linkage to worry about. It only took me a day to get used to it (a year or so ago) and won't ever go back.

Fogel70 · 12-18-2011, 05:27 AM

You can also do the reverse.

Keep AF on shutter button, and disable AF by pressing AF-button for manual focus. But this only work on quick-shift lenses.

I usually have my cameras set this way.

12-17-2011, 05:00 PM	#1
rsoph Junior Member Join Date: Nov 2011 Photos: Gallery Posts: 25	Manual Focus why doesn't AF button work OK, I know it sounds like a dumb question, but why not? I know I told it I want to manual focus but I don't see it any different than hitting green button in Manual mode. Buttons not doing anything else, so why not help me out when I ask it to?

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12-17-2011, 06:25 PM	#2
Wheatfield Moderator Join Date: Apr 2008 Location: The wheatfields of Canada Posts: 15,981	What would you like the AF button to do when you are switched to manual focus? You've already told the camera you don't want AF by switching AF off.

12-17-2011, 06:44 PM	#3
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	You could do what you want with a quick shift lens. Set the shutter button to NOT auto-focus, focus manual as you want but hit the AF button when you want help. But you have to leave the camera in auto-focus, if you don't you are either physically or electrically removing the AF connection. Technically this works with screw drive lenses too but I don't like doing that as you are spinning the screw drive motor in the camera when you focus manually and that could potentially cause damage. I've never heard of it actually causing damage but it just does not seem like a good idea.

12-17-2011, 07:25 PM	#4
rsoph Junior Member Join Date: Nov 2011 Photos: Gallery Posts: 25 Original Poster	I am aware of the options to take the AF off the shutter button and that is what I do but it requires menu use and equally important, remembering to put it back, What I was wondering, more than anything else, is why not allow the AF button to work when manually focusing, similar to the green button with manual exposures. I guess the screw drive disengagement is one possible explanation assuming this is a mechanical and not an electrical connection. I would find it useful when fine tuning my focus for wildlife and suddenly the subject moves or you find a better subject. Reaim, hit the AF button and start tuning... Just wondering aloud...

12-17-2011, 10:44 PM	#5
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by rsoph screw drive disengagement Yes, when MF is selected the screw drive is disconnected. I assume the electrical circuit for SDM is disengaged as well but you cannot see that, only take it on faith. I have the shutter button always set to NOT auto-focus. I use the AF button to auto-focus, so I can press the AF button and get an AF lock then fine tune as needed with the manual focus. Takes a little practice to get used to using the AF button rather than the shutter button but it feels quite natural after you get used to it. This also allows you to focus on what you want in focus and then recompose with out worrying that the shutter button will mess up your focus point by re-focusing.

12-18-2011, 04:13 AM	#6
borno Veteran Member Join Date: Nov 2006 Location: md-usa Photos: Gallery \| Albums Posts: 2,580	Originally posted by jatrax Yes, when MF is selected the screw drive is disconnected. I assume the electrical circuit for SDM is disengaged as well but you cannot see that, only take it on faith. I have the shutter button always set to NOT auto-focus. I use the AF button to auto-focus, so I can press the AF button and get an AF lock then fine tune as needed with the manual focus. Takes a little practice to get used to using the AF button rather than the shutter button but it feels quite natural after you get used to it. This also allows you to focus on what you want in focus and then recompose with out worrying that the shutter button will mess up your focus point by re-focusing. +1 I set all my cameras up this way as well, with the back button AF. You choose when to MF or when to AF and it works great. I don't have any screw drive lenses so I don't have the linkage to worry about. It only took me a day to get used to it (a year or so ago) and won't ever go back.

12-18-2011, 05:27 AM	#7
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 3,062	You can also do the reverse. Keep AF on shutter button, and disable AF by pressing AF-button for manual focus. But this only work on quick-shift lenses. I usually have my cameras set this way.