[LeDave]

You know how when you flick the switch from MF to AF, the screw-drive pops out, while when you flick the switch from AF to MF, the screw pops in?

Wouldn't it be awesome if Pentax somehow designed the body in a way so that when you press the shutter half-way or the AF button, that the screw would pop out to AF. And when you lay your fingers off of it, the screw would pop in again? This would allow quick-shift in all lenses, especially ones from Sigma and Tamron which doesn't boast such a feature.

EDIT: Ah, epic fail. I don't know what I was thinking when I wrote this, but must be because it's 6am and I haven't slept yet. Obviously you won't be able to quick-shift after you release your fingers off it because it would have to re-AF when you press it again.

Well if there was a way to somehow program another button such as the dedicated AF button to do it. While your camera auto-focuses when your finger is half-way down on the shutter button, you can somehow press the dedicated AF button while still holding the shutter half-way down, thus allowing the screw-drive to pop-in for quick-shifting.

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Last edited by LeDave; 12-23-2009 at 05:15 AM.

[telfish]

You can just press the lens release button which retracts the screw drive, manual focus then release. You run a slight risk of a lens falling off!. Most are pretty tight on my K20.

Not sure if there are any other drawbacks to using the lens release button. Anyone?

[Diffusion]

I think the best option would be an AF system that disengages automatically when not focusing. This would have the disadvantage that you could accidentally change the focus after focusing.
The other option, more sophisticated, would measure the torque on the shaft, and either have a slipping joint or take current away from the screw drive motor.

Lots of possibilities, but they would all add to the cost.
I think the quick shift DA lenses have a torque slip joint. But put it into the camera, and all lenses would immediately be quick shift.

Hmm...

D.

[Andi Lo]

EDIT: Ah, epic fail. I don't know what I was thinking when I wrote this, but must be because it's 6am and I haven't slept yet. Obviously you won't be able to quick-shift after you release your fingers off it because it would have to re-AF when you press it again.

Why not just disengage AF from shutter and trigger AF slot drive in with the AF button? It will be the same as your suggestion, just not requiring the use of another button.

I think the reason why pentax doesnt have this (and also the reason why AF button is mechanical instead of electronic) is because it's harder to push/pull the pin with sufficient force. Nothing impossible to design around when you put your mind into it though.

Of course we can also just have improved SDM. SDM doesnt need a slot be pushed, so the lens can be just always MF unless the current flows through it.

[Canada_Rockies]

You know how when you flick the switch from MF to AF, the screw-drive pops out, while when you flick the switch from AF to MF, the screw pops in?

Wouldn't it be awesome if Pentax somehow designed the body in a way so that when you press the shutter half-way or the AF button, that the screw would pop out to AF. And when you lay your fingers off of it, the screw would pop in again? This would allow quick-shift in all lenses, especially ones from Sigma and Tamron which doesn't boast such a feature.

EDIT: Ah, epic fail. I don't know what I was thinking when I wrote this, but must be because it's 6am and I haven't slept yet. Obviously you won't be able to quick-shift after you release your fingers off it because it would have to re-AF when you press it again.

Well if there was a way to somehow program another button such as the dedicated AF button to do it. While your camera auto-focuses when your finger is half-way down on the shutter button, you can somehow press the dedicated AF button while still holding the shutter half-way down, thus allowing the screw-drive to pop-in for quick-shifting.

I can set the [AF] button on my Pentax K10D to Cancel AF - would that work for you? I have the following three options for the [AF] button:

1. Enable AF
2. Cancel AF
3. Center of AF point - If you have selected a point other than the center point, this selects the centre point.

[sajah]

I have OK button set to cancel AF too. But this alone is not enough, because even though the AF is cancelled, you still can't turn the focus ring manually, because it's still coupled with the AF screw. Unless the lens has quick-shift, where you can always turn the focus ring in any focusing mode.

I agree with Diffusion here, there's a mechanical mechanism inside DA lens to enable quick-shift, and I think there should be no problem to transfer this mechanism to inside the body instead. But I could (very likely) be wrong though

[sebberry]

Of course we can also just have improved SDM. SDM doesnt need a slot be pushed, so the lens can be just always MF unless the current flows through it.

Most SDM lenses end up being MF anyways

Ok, ok, there's other threads for that

[WerTicus]

EDIT: Ah, epic fail. I don't know what I was thinking when I wrote this, but must be because it's 6am and I haven't slept yet. Obviously you won't be able to quick-shift after you release your fingers off it because it would have to re-AF when you press it again.

Kx, K7, and K20d can disable the AF on half shutter press and move it to the AF button.

Once I tried this, I couldn't live without it, I (now) hate having the camera focus every time you half press.

Because now your camera just fires when you press the shutter instead of (potentially) dicking around And you can pre focus (for timing), and recompose without holding something down, and shoot panorama's with infinite set once... etc.

In fact the more I think about it any one outside of green mode newbies should have it disabled.

[darrenleow]

You know how when you flick the switch from MF to AF, the screw-drive pops out, while when you flick the switch from AF to MF, the screw pops in?

Wouldn't it be awesome if Pentax somehow designed the body in a way so that when you press the shutter half-way or the AF button, that the screw would pop out to AF. And when you lay your fingers off of it, the screw would pop in again? This would allow quick-shift in all lenses, especially ones from Sigma and Tamron which doesn't boast such a feature.

EDIT: Ah, epic fail. I don't know what I was thinking when I wrote this, but must be because it's 6am and I haven't slept yet. Obviously you won't be able to quick-shift after you release your fingers off it because it would have to re-AF when you press it again.

Well if there was a way to somehow program another button such as the dedicated AF button to do it. While your camera auto-focuses when your finger is half-way down on the shutter button, you can somehow press the dedicated AF button while still holding the shutter half-way down, thus allowing the screw-drive to pop-in for quick-shifting.

I tried my friend's KM 7D for a brief period when waiting for my K20D and it had this feature. The AF button toggled the screw connection with the lens.

Kx, K7, and K20d can disable the AF on half shutter press and move it to the AF button.

Once I tried this, I couldn't live without it, I (now) hate having the camera focus every time you half press.

Because now your camera just fires when you press the shutter instead of (potentially) dicking around And you can pre focus (for timing), and recompose without holding something down, and shoot panorama's with infinite set once... etc.

In fact the more I think about it any one outside of green mode newbies should have it disabled.

The one thing stopping me from using this method on my K20D is that the AF button is not duplicated on the battery grip and too far away to reach with my thumb when using the grip. Not sure how to work around this, short of buying a K-7 and grip

[LeDave]

I tried my friend's KM 7D for a brief period when waiting for my K20D and it had this feature. The AF button toggled the screw connection with the lens.

So current Sony DSLR's have this feature too then?

[darrenleow]

So current Sony DSLR's have this feature too then?

On the A700:

"Next to that is the AF/MF button, which lets you quickly switch between auto and manual focus -- handy if you need to make a quick adjustment to the focus. "

DCRP Review: Sony Alpha DSLR-A700

I guess so!

Edit: I just happened to read about a "Direct Manual Focus" mode on Sony DSLRs, which automatically disconnects the screwdrive once the AF has locked, freeing the focus ring. Pretty neat.

[LeDave]

On the A700:

"Next to that is the AF/MF button, which lets you quickly switch between auto and manual focus -- handy if you need to make a quick adjustment to the focus. "

DCRP Review: Sony Alpha DSLR-A700

I guess so!

Edit: I just happened to read about a "Direct Manual Focus" mode on Sony DSLRs, which automatically disconnects the screwdrive once the AF has locked, freeing the focus ring. Pretty neat.

Ah the A700 is such a beautiful camera, being a 7D clone and all. It's a shame current Sony APS-C's aren't built like they used to anymore. I guess it's what happens when a company's greed overtakes the better, deciding they want to save the build quality for their full frames. Just hope the K-x isn't signs that Pentax is doing the same for whatever full frame they're going to announce soon.

[Raptorman]

Memorize the selector switch positions.


Problem solved