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10-02-2010, 12:59 PM   #1
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trap focus with K-5 (and others?)

so ... am I correct in thinking that on the Pentax dSLRs if you mount a manual focus lens there is a custom function or setting where you can request that the camera only follows through with taking a picture if it is in focus? is it called focus trap or trap focus or something?

I'm keen to get a new camera, a Pentax, most likely the K-5. And this is a feature that would win this system over to me comparing with the Nikon D7000 or Canon 7000D.

I have plans to get a Voigtländer Ultron 40mm f2 ... and this is available in three fittings: Canon (not thanks, QC lost is in 2005), Nikon (been there, got my yellow stripes), Pentax (this is where you come in)

Is its really as simple as it sounds. press and hold the shutter button, manually focus the lens .... as soon as focus is achieved: click - frame taken?

thanks

10-02-2010, 01:08 PM   #2
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My K-7 has a feature called 'catch in focus', which is what I believe you are looking for.
10-02-2010, 01:19 PM   #3
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QuoteQuote:
Is its really as simple as it sounds. press and hold the shutter button, manually focus the lens .... as soon as focus is achieved: click - frame taken?
If you don't change the custom settings for shutter half-press, then yes. You need to be in AF-S (AF single) mode and the sensor point used will always be central.
10-02-2010, 01:22 PM   #4
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thank you

mmm, so centre point only ... that is a little bit of a shame.
Is there a focus confirmation light if you use the other points?
(such a shame that none of the camera stores in town stock Pentax!)

and 'catch in focus' it is then.

10-02-2010, 01:28 PM   #5
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QuoteOriginally posted by dCap Quote
Is there a focus confirmation light if you use the other points?
Things might be different in K-5, but in K-7 and previous Pentax cameras, only center point can be used for confirmation when you install a manual focus lens...
Don't know why it's done that way - if you have an auto-focus lens in mf mode, it shows all the dots.
10-02-2010, 05:14 PM   #6
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Hi dCap,

All Pentax DSLRs (and AF film bodies AFAIK) feature Focus Trap (I like this name better) with manual focus lenses. AF S (single frame AF) is focus confirmation priority, which means that a focus confirmation must be sensed before the shutter will fire.

I could be wrong, but I believe that the Catch in Focus menu choice only pertains to Pentax branded AF lenses (FA and DA series) which have AF/MF switches on the lens that are capable of turning the body into the functional equivalent of having a true MF lens mounted on an MF body by switching the lens alone and leaving the body switched to AF.

F series lenses with AF/MF switches (AFAIK) also need the body to be switched to MF to disengage the screw drive motor and switch the body to shutter priority from focus confirm priority. The FA* 300's focus ring functionality was a refinement of the focus clutch idea.

This sounds convoluted, but it's really not. I can possibly illustrate this with lenses that I know, and can't really say if the same is true of all lenses in either series.

The F* 300 f4 and FA* 300 f4 both have focus rings that connect/disconnect from the focusing mechanism with a push/pull of the focus ring. To disconnect the screw drive from the lens, and switch to shutter priority in the body, the AF/MF switch on the body must also be switched to MF with the F*300, but all that is needed on the FA* is to pull the focus ring on the lens back. The same is true IIRC with the DA* 50-135. The AF/MF switch on the lens totally disconnects the drive and switches the body to shutter priority. This last part defeats Focus Trap, so the Catch in Focus menu choice is necessary to reactivate the feature with these lenses.

Regardless, with a true MF lens like the Voigtländer you mentioned, any Pentax DSLR will Focus Trap or Catch in Focus just as you described when the body switch is in the AF position, and the Catch in Focus menu choice does not have to be turned on for the shutter to fire on focus confirmation.

Probably more confusing that explanatory, but I think that there's generally some confusion about the menu setting. You only have to set this menu choice to "on" if you have an FA or DA lens with an AF/MF switch and want to use Focus Trap.

BTW, you can't use Focus Trap with any other AF lenses unless you short the Data Pin with some foil or metal tape, AFAIK.

Edit: To make things more confusing, the K5 has two AF S modes, Focus Priority and Shutter Priority, so with this model, you need to have the camera set to AF S Focus Priority mode to use Focus Trap. . .

Scott

Last edited by snostorm; 10-02-2010 at 05:31 PM.
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