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03-28-2011, 05:23 AM   #1
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K-r with Pentax-M lens and light measuring.

I have bought a Pentax M 50mm 1.7 lens for my K-r.
It is a manual lens and I shoot in M mode (Av doesn't allow changing aperture)

My question is, is it possible to make the camera adjust shutter speed with green button WITHOUT the shutter going down. Just like with the KIT lens?

03-28-2011, 07:14 AM   #2
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The shutter doesn´t move when you meter, the aperture does (it closes down to whatever is set on the ring). I´ll assume you´re talking about that? In that case...

Not really.

Technically, you could set it to "A", check what shutter speed it gets wide open, then change to "M" and calculate the shutter speed depending on how much you´re going to stop down. That assumes your metering is correct, which it likely wouldn´t be on my K200D, but the K-r is probably better in that regard. It´s more complex & time consuming than using the green button though.

Why don´t you want the aperture to close?
03-28-2011, 07:34 AM   #3
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QuoteQuote:
The shutter doesn't move when you meter, the aperture does (it closes down to whatever is set on the ring).
This really answers my question. I was worried that it is the shutter that moves (it gives different sound than the one when you actually take a picture but I wanted to be sure).

I was concerned that every time I click the Av button to measure the light the shutter goes down and up and in consequence the shutter life span shortens.

Thanks for the answer, it calmed me down.
03-29-2011, 01:04 PM   #4
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After reading this topic I am no longer sure if the mirror stays down when I am measuring the light. Can someone confirm this?

https://www.pentaxforums.com/forums/pentax-dslr-discussion/87660-green-button...fferently.html

03-29-2011, 01:21 PM   #5
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Yes the mirror moves when you're using the green button with an M- or K- lens. It's easy to see: Just just set the aperture to wide open and press the green button. The viewfinder blacks out momentarily even though the aperture doesn't close.

Interestingly when using an M42 lens there is no sound/mirror flip when pressing the green button. The body somehow knows there isn't an aperture lever present.
With my old K200D the aperture closing sound was the same regardless of what type of manual lens you were using.
03-29-2011, 09:19 PM - 2 Likes   #6
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Ovim, someone helped me with my 'problem' and now I can use the Pentax-M lens in Av mode with no problem, it works the same as with the KIT lens, it's great!

All you have to do is press the lens lock button and rotate your lens CCW about 10 degrees. Then you can use it in Av mode. Just be careful not to twist the lens focus adjustment so far as to make the lens drop off. I also heard you can drill extra lens lock but I didn't try that yet
04-04-2011, 08:06 PM   #7
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thanks for the info!

it seems like on my older metal mount lenses, even after having it loosened 10 degrees, they're on there pretty snug.
now i just keep the mode dial in Av, set my aperture where i want it, and never have to use that green button.

Last edited by BobDoLe; 04-04-2011 at 08:35 PM.
04-05-2011, 12:56 AM   #8
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Can anybody explain how the solution related to turning the lens 10 degrees works?

04-05-2011, 07:54 AM   #9
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QuoteOriginally posted by TORPO Quote
Can anybody explain how the solution related to turning the lens 10 degrees works?
It prevents the camera from locking the aperture open even when you stop the ring down. In normal use, the aperture only closes when the pic is taken or when you meter with the green button.

But it risks the lens falling off as it´s not locked in place.
04-05-2011, 07:57 AM   #10
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QuoteOriginally posted by TORPO Quote
Can anybody explain how the solution related to turning the lens 10 degrees works?
With your K or M lens off the body, you'll notice the aperture blades actually move as you rotate the aperture ring. Basically, you're just making it loose enough for that to happen while the lens is "mounted" on the body. Just stop the lens down, mount it on the camera, and then rotate it like you're removing it as you look down the barrel. Once the blades close to maximum you can use it in Av. Just be careful it doesn't fall off.
04-05-2011, 08:53 AM   #11
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Thank you for explaining it to me.

I can see that it is the litle blade/pin on the lens which opens the blade when the lens is mounted on the camera.

Has anybody tryid to remove this blade/pin to have the possibility to us Av priority with the lens fully fastned?
04-05-2011, 09:15 AM   #12
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QuoteOriginally posted by TORPO Quote
Thank you for explaining it to me.

I can see that it is the litle blade/pin on the lens which opens the blade when the lens is mounted on the camera.

Has anybody tryid to remove this blade/pin to have the possibility to us Av priority with the lens fully fastned?
Yes some people have done it. With a little patience and a couple of small screwdrivers it's usually possible to remove it so that it will also be possible to put it back in if necessary. Using pliers/dremel/hacksaw usually lowers the lens' resale value considerably (and makes Pentaxians angry )
04-05-2011, 09:37 AM   #13
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Hmm - My first thougth was something close to sawing the pin off, but I will of cause not make any Pentaxians angry.

If I dismantle the lens I would be afraid of small springs and aperature blades suddenly flying around and dust getting into the lens, bút perhaps it is not a problem.

The disadvange must be a dark viewfinder when the lens is stopped down, but it is also a disadvange to be forced to use the green buttum.
04-05-2011, 05:28 PM   #14
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QuoteOriginally posted by ovim Quote
Yes some people have done it. With a little patience and a couple of small screwdrivers it's usually possible to remove it so that it will also be possible to put it back in if necessary. Using pliers/dremel/hacksaw usually lowers the lens' resale value considerably (and makes Pentaxians angry )
i hear that. i was thinking about removing it, but then i also figured long after i die, some future pentaxian will pick up my 50mm f1.4 on ebay for $500+ and wouldn't appreciate it.
04-06-2011, 07:10 AM   #15
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I heard it works great when you decide to remove the hmm "Aperture lever" (?).
I almost decided to do it myself but I made a good deal selling the M lens and I bought myself the A50mm/1.7

You can also drill a hole in the lens and make extra lock hole so it won't fall off. That's actually the more popular solution. The silver ring on the lens is very easy to remove, only 5 screws and it goes off with no effort. You can drill the extra hole through the ring, it doesn't have to look like the original one
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