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Old Jan 22, 2006, 1:57 PM   #1
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To use older Pentax lenses you have to set your camera to "allow aperture ring" in the menu settings.

I have done so, with the result that the kit lense (DA 16-45) lense work just like always. The KA lenses work as they should when i put the aperture ring on "A", and when i put them on a manually chosen aperture they work just as the pre-"A"-lenses.

Is there any advantage in setting the menu at "dont allow aperture ring"? Why does this option exist at all? What have I missed?

Kjell
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Old Jan 23, 2006, 9:25 AM   #2
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There is a point. When you focus, your aperture will be wide open to let you have full view. If in completely manual mode, the aperture will be manually adjusted which results in dimmer light for focusing.

Daniel

bilybianca wrote:
Quote:
To use older Pentax lenses you have to set your camera to "allow aperture ring" in the menu settings.

I have done so, with the result that the kit lense (DA 16-45) lense work just like always. The KA lenses work as they should when i put the aperture ring on "A", and when i put them on a manually chosen aperture they work just as the pre-"A"-lenses.

Is there any advantage in setting the menu at "dont allow aperture ring"? Why does this option exist at all? What have I missed?

Kjell
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Old Jan 23, 2006, 11:34 AM   #3
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danielchtong wrote:
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There is a point. When you focus, your aperture will be wide open to let you have full view. If in completely manual mode, the aperture will be manually adjusted which results in dimmer light for focusing.

Daniel


No, it won't!

To be sure, I just put on a manual KAF lens (SMC-A 85 f1,4). If I set the ring to "A", and the left wheel to "M", I see the chosen time and aperture in the viewfinder, just as I should according to the manual. I also get the information wether this setting will give so or so much under/overexposure. I can change the time and the f-stop with the thumb-wheel on the right side of the body.

Then I change the aperture ring to f-stop 16. In the viewfinder I then see the chosen time but not the chosenf-stop 16, no exposureinformation and full view. If I turn the on/off button to DOF preview, i get f-stop and over/underexposure information. Just as the manual says I would with a manual lens. Of course then the camera stops down to the chosen f-stop and the view gets dimmer, but that is just what should happen, even with a DA lens.

When I change to the kit DA lens, everything works just as it should according to the manual.

All this done with the menu set to "allow aperture ring". So the mystery remains: what is the point in setting it to "don't allow"?

Kjell


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Old Jan 23, 2006, 1:13 PM   #4
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Kjell

Like you, this makes no sense to me. I guess when Pentax crippled the lens mount by leaving out one of the mechanical connections (the one which relayed the aperture position to the camera body) they had to give some method to remind users that they now needed to set the exposure manually (AE-L button). But it still makes no sense to me either.

Ira
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Old Jan 23, 2006, 4:14 PM   #5
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bilybianca wrote:
Quote:
To use older Pentax lenses you have to set your camera to "allow aperture ring" in the menu settings.

I have done so, with the result that the kit lense (DA 16-45) lense work just like always. The KA lenses work as they should when i put the aperture ring on "A", and when i put them on a manually chosen aperture they work just as the pre-"A"-lenses.

Is there any advantage in setting the menu at "dont allow aperture ring"? Why does this option exist at all? What have I missed?

Kjell

i don't think i know this subject well enough.
would any photographer prefer to use aperture instead of via the camera?
there are so many versions of pentax or pentax compatible (like tamron adaptall , sigma variants) that somewhere this feature is needed
tamron adaptall uses the AE function as it has one more stop (32) above 22 (pentax max).
maybe this function is needed if you want to set 32\\f/32?
i have not had a clue

daniel
that is just one little i know as a newbie
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Old Jan 23, 2006, 4:34 PM   #6
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danielchtong wrote:
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would any photographer prefer to use aperture instead of via the camera?
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there are so many versions of pentax or pentax compatible (like tamron adaptall , sigma variants) that somewhere this feature is needed
tamron adaptall uses the AE function as it has one more stop (32) above 22 (pentax max).
Well, if you have an older lens like my Pentax SMC-M 100mm macro f4, you really would like to use it, and it doesn't have the "A" setting and cannot be set from the body. It was made before concepts as "automatic" and "point-and-shoot" found its way into photography, but it is still one of the best optically. I got mine for nothing as i bought a Super A body with "some lenses" from a guy who had lost his interest in the hobby.

Pentax have made lots of lenses with apertures above 22. I've got one with a f45 stop, another goes to 32 and they all work fully on the DS.

Kjell

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Old Jan 24, 2006, 3:14 AM   #7
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The *ist D series camera bodies were designed to be working with any Pentax lens which should have an "A" position in its aperture or those which simply don't have an aperture ring (which is simply merely with an A position only).

When aperture is allowed to be released at non-A position of a lens, stop(ped)-down metering must be performed (in advance of pressing the shutter release) in order to get the exposure value required. For details, pls see my article below:-


http://www.geocities.com/ricehigh/K_...ure_Bases.html
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Old Jan 24, 2006, 8:47 AM   #8
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Nice work RiceHigh, good article with useful diagrams.

Ira
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Old Jan 24, 2006, 4:12 PM   #9
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Very interesting, thanks RiceHigh!

But it still doesn't answer my question, since all lenses work perfectly as intended by Pentax when you set the menu to "allow", and only the newer types when you set it to "don't allow". Im still puzzled. Why do Pentax want us to choose between good and perfect?

Kjell
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Old Jan 24, 2006, 8:35 PM   #10
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The problem is that when one mounts a Pentax lens without any "A" position, actually it does not work "perfectly". It cannot do metering by default, what the user must do stopped down metering by pressing the green button (for *ist D firmware 1.1 or later) and the AEL button (for *ist DS/DL/DS2) before releasing shutter. Otherwise, metering will not be performed (and is impossible/unable to be performed too, owing to the cripped K mount used in the *ist D series DSLR bodies) and incorrect exposure will be resulted.

To place safe, Pentax opted to lock the operation of the camera by default, if the camera cannot see the "A" on lens. The good thing is Pentax still let the users to use the non-A lenses only if they know what to do and why is that.

The last thing is that the stopped down metering is not as accurate as the wide opened metering on the *ist D bodies afterall, too.
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