Pentax diaghram coupler question

Nass · 09-02-2011, 04:09 AM

Quick (probably stupid) question of the day, do all Pentax lens ranges use the lever thing on the back of a lens to control the aperture of the photograph that's finally taken, or do any Pentax ranges close the diaphram drawing power from the contacts without needing the mechanical lever thing?

The way I think about that lever is like this - you set your f stop in camera, and when you take your shot, the information is sent to the lens about the stop you chose and a lever in the camera then pushes the lever on the lens which closes the diaphram and uses the f stop based on the info transmitted through the various electrical points. Is that more or less about right?

Bottom line, building one of these EOS retro reverse adapters for a Pentax is pretty trivial, but that's only true if there's no mechanical lever part to the equation. Just 2 parts of an extension tube with holes and a CAT5 cable connecting the points. But if that mechanical lever is required then I'm stuffed and it aint gonna happen

Cheers

Adam · 09-02-2011, 04:47 AM

Yes you need the lever to get the aperture to move, as there's no in-lens motor.

Nass · 09-02-2011, 04:55 AM

Thought so. Bugger.

Dr. Evil · 02-10-2013, 01:53 PM

Oc, another one question about aperture ~~coupler~~ actuator:
Could somebody explain me, or (better option) show in the diagram/picture or so,... how the lever works in long lenses?
Thanks for help.

edited

Last edited by Dr. Evil; 02-10-2013 at 02:59 PM.

**Kerrowdown** · 02-10-2013, 02:42 PM

I'm guessing the that the aperture mechanism that the lever controls is always to the back of the lens, i.e. near to the camera body, so the lens physical size is never an issue.

**baro-nite** · 02-10-2013, 02:50 PM

Small pedantic note: I'm pretty sure the correct term for what we're talking about is actuator. The coupler is the missing feature in the crippled mount.

Not a Number · 02-10-2013, 02:52 PM

Even if the iris wasn't near the end it might not matter. Look at the Auto Extension Tube K 100mm for instance

09-02-2011, 04:09 AM	#1
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402	Pentax diaghram coupler question Quick (probably stupid) question of the day, do all Pentax lens ranges use the lever thing on the back of a lens to control the aperture of the photograph that's finally taken, or do any Pentax ranges close the diaphram drawing power from the contacts without needing the mechanical lever thing? The way I think about that lever is like this - you set your f stop in camera, and when you take your shot, the information is sent to the lens about the stop you chose and a lever in the camera then pushes the lever on the lens which closes the diaphram and uses the f stop based on the info transmitted through the various electrical points. Is that more or less about right? Bottom line, building one of these EOS retro reverse adapters for a Pentax is pretty trivial, but that's only true if there's no mechanical lever part to the equation. Just 2 parts of an extension tube with holes and a CAT5 cable connecting the points. But if that mechanical lever is required then I'm stuffed and it aint gonna happen Cheers

09-02-2011, 04:47 AM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Yes you need the lever to get the aperture to move, as there's no in-lens motor. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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09-02-2011, 04:55 AM	#3
Nass Veteran Member Join Date: Aug 2009 Location: The British Isles Photos: Gallery Posts: 2,402 Original Poster	Thought so. Bugger.

02-10-2013, 01:53 PM	#4
Dr. Evil New Member Join Date: May 2012 Posts: 15	Oc, another one question about aperture ~~coupler~~ actuator: Could somebody explain me, or (better option) show in the diagram/picture or so,... how the lever works in long lenses? Thanks for help. edited Last edited by Dr. Evil; 02-10-2013 at 02:59 PM.

02-10-2013, 02:42 PM	#5
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,818	I'm guessing the that the aperture mechanism that the lever controls is always to the back of the lens, i.e. near to the camera body, so the lens physical size is never an issue.

02-10-2013, 02:50 PM	#6
baro-nite Loyal Site Supporter Join Date: Aug 2011 Location: North Carolina, USA Photos: Gallery \| Albums Posts: 5,294	Small pedantic note: I'm pretty sure the correct term for what we're talking about is actuator. The coupler is the missing feature in the crippled mount.

02-10-2013, 02:52 PM	#7
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Even if the iris wasn't near the end it might not matter. Look at the Auto Extension Tube K 100mm for instance