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11-14-2010, 10:25 PM   #1
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Bug with Catch-in-Focus and AF.C

Hi fellow pentaxians,

I don't know if this has been documented or not, but this is a bug that caused me worry the last 2 days.

With an autofocus lens, if AF is set to continuous mode on the body, then you swap to a manual focus lens, then Catch-in-Focus does not work. The shutter will release regardless if the center point is focused.

Only by mounting an AF lens back on and switching to AF.S, then putting the manual focus lens on will catch-in-focus work again.

I'm wondering if anyone knows if done purposely for a reason, or a software bug that was not caught.

Cheers

11-14-2010, 10:37 PM   #2
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I don't think this is a bug.
My K-x manual clearly states that catch in focus only works in AF-A or AF-S modes
11-14-2010, 10:46 PM   #3
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Umm, this isn't a bug, this is user error.
11-14-2010, 11:40 PM   #4
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Thanks for the replies,

But I don't see why I can't access that menu with the manual focus lens on the body. I would have to mount on an autofocus body just to be able to change that setting.

11-15-2010, 07:58 AM   #5
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While I agree that it is a bug, it's not a bug with AF modes, but with the menu interface. The solution is of course to upgrade to a body with a physical AF mode switch. (K10, K20, K7, K5, possibly others.)
11-15-2010, 07:10 PM   #6
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Catch in Focus with a manual lens:

Mount lens, turn on camera.
Set focus distance and set AF mode to AF-S.

Depress shutter button.
When something comes into focus, the camera will take a picture.
Catch in Focus on the menu doesn't matter.
11-15-2010, 08:15 PM   #7
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For what it's worth -- I believe that the Catch in Focus menu choice only really pertains to AF lenses that can revert the body to true MF mode, as opposed to those whose MF switch only reconnects the focus ring to the focusing helicoid mechanism in the lens.

First generation "focus clutch" lenses would disconnect the focusing ring from the internal focusing mechanism to keep the ring from rotating when the lens was focusing via the AF system. In MF mode, the screw drive would still be engaged with the motor in the body, and you'd have to manually turn the motor when rotating the focus ring unless you also switched the body to MF. Later implementations actually switched the body to MF mode, disconnecting the lens focusing mechanism from that of the body, so pulling the focus ring back gave you actual MF mode -- including shutter priority over focus confirmation.

An example of this in Pentax lenses is the F*300/4.5, compared to the FA*300/4.5. With the F*, you had to switch both the focus ring and the body, and with the FA*, you only need to pull the focus ring back to the MF position. With DA lenses like the DA*50-135, there is an MF/AF switch on the lens which actually switch to MF mode in the body otherwise this would be redundant with Quick Shift which allows manual focusing when the AF system isn't active or is locked on. Pentax had to add the "Catch in Focus" menu choice to allow these lenses to be used with Focus Trap when in switched to MF on the lens.

Another consideration that will have to be made with the K-5 and Focus Trap -- you'll have to not only be in AF-S, but in AF-S/focus priority mode to use this feature. . . I'm sure that this will cause even more confusion in the future. . .

Scott


This is assumption on my part, and not by official word from Pentax, but I think the theory is pretty sound. . .

Scott
11-16-2010, 04:31 AM   #8
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@wheatfield Thank you for your input. I do know how to enable Trap AF, however on the K-x (I should have mentioned) does not have a dedicated AF mode switch, it is accessed through the menu. The AF mode menu becomes greyed out when an MF lens is mounted, therefore I cannot switch back to AF.S, hence the "bug".

@SnostormI suppose that's true. It will be up to the small percentage of shooters that perform MF with an AF lens to figure out the nuances to get this to work. To me, it's nice that Pentax included this feature to get more value out of older lenses, you definitely cannot see this coming years ago

11-16-2010, 08:13 AM   #9
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QuoteOriginally posted by 0rangepeel Quote
the K-x (I should have mentioned) does not have a dedicated AF mode switch, it is accessed through the menu. The AF mode menu becomes greyed out when an MF lens is mounted, therefore I cannot switch back to AF.S, hence the "bug".)
The K-x has an AF/MF switch on the body. If you're looking through the viewfinder, it's on the left side, right beside the lens mount.
11-16-2010, 11:59 AM   #10
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I'm referring to switching between autofocus modes AF.A/AF.C/AF.S not between AF/MF
11-16-2010, 12:17 PM   #11
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Are you using one of the Auto Picture Modes?

See pg 115 of your K-x manual.

11-16-2010, 03:51 PM   #12
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QuoteOriginally posted by 0rangepeel Quote
I'm referring to switching between autofocus modes AF.A/AF.C/AF.S not between AF/MF
When using a manual focus lens, there are no AF modes.
You either have manual focus (AF/MF switch set to MF, or you have trap focus (catch in focus) with the switch set to AF.

That's it.
All the fancy AF modes are there to modify the behaviour with AF lenses.
11-16-2010, 11:11 PM   #13
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Wheatfield, I think you have to try the K-x to see what I mean

Based on what I've learned this is how it works:

As you said, trap AF only works when the AF selection is set to AF.A or AF.S, not AF.C

On a body with a dedicated switch to select these modes, such as the K-5, you switch the nob to AF.S and you are good to go to use trap AF.

On the K-x, we don't get that luxury. The switch on the side only switches between AF and MF. Choosing between AF.S and AF.C is done within a menu.



Situation: Let's say I was using an auto-focus lens, and I wanted to use AF.C. I set it to AF.C and shoot, which works great. Later, I switch the lens to to a manual-focus lens, and I enable trap AF. As you've mentioned, trap AF does not work with AF.C.

Heres the caveat: As we have discussed, trap AF only works with AF.S. So, if I attach a manual focus lens, I need to change the mode from AF.C to AF.S. The "bug" I mentioned is that the menu to change from AF.C to AF.S becomes inaccessible if a manual focus lens is attached. The only way to access this menu is to swap on a auto-focus lens, which re-enables the menu, then swap back on the manual lens and shoot happily with trap AF.

This isn't a problem if I remember that I reset my mode to AF.S, but let's say one day I had AF.C on with an auto-focus lens and shoot. The next day, I only take a manual focus lens with me. I realise that I forgot to change the mode back to AF.S because the menu is greyed out. Now I have to trust my poor eyes to focus correctly, and I have no way to fix this until I head home, slap on a auto-focus lens, and access the menu.

I hope this clarifies things, because I think we're on different pages. Cheers!
11-17-2010, 06:56 AM   #14
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Understood. I still am not seeing a bug though.
With a manual focus lens attached, there may not be any way for them to have the AF stuff accessible in the menus, certainly there isn't much reason.
It would certainly be something that would be easy for the software designers to overlook.
Anyway, your workaround is to switch to AF-S prior to changing out to a manual focus lens.
And perhaps, if Pentax monitors this forum, you might get your rewrite of the software on a firmware update (but don't hold your breath).
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