Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
07-31-2012, 09:41 AM   #1
Veteran Member

Join Date: Jan 2010
Location: Durham, nc
Photos: Albums
Posts: 895
K-mount adapter question

I have a question... Does auto-aperture and metering work on the adapter? Or if I set the K lens to F16, will the Q's screen go completely dark? I know there's no autofocus, but does it communicate lens information with the Q at all?


07-31-2012, 10:06 AM   #2
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 42,838
I'm not 100% sure, but I think it has a manual diaphragm, and that the live view image will indeed grow darker when stopped down.

Adam Webmaster (Site Usage Guide | Site Help | My Photography)'s high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

07-31-2012, 11:23 AM   #3
Veteran Member
ve2vfd's Avatar

Join Date: Aug 2007
Location: Montreal, Canada
Photos: Gallery
Posts: 2,433
I use a third party adapter with manual lenses and it has a switch to turn the diaphragm on and off so I can set the aperture to f16 (which darkens the screen) and turn it off to focus with a brighter screen. There isn't any auto anything.

I will be curious to see what the Pentax brand adapter will offer.

07-31-2012, 12:07 PM   #4
Veteran Member

Join Date: Jan 2010
Location: Durham, nc
Photos: Albums
Posts: 895
Original Poster
When will that be on the market?

With the new Canon mirrorless system working as it does, I wonder if Pentax will go back to the drawing board and give us autofocus... or at least auto metering. It shouldn't be hard to slap a screw drive motor in there, there's plenty of room.


07-31-2012, 12:09 PM   #5

Join Date: Oct 2006
Location: Chicago suburb, IL, USA
Posts: 1,535
QuoteOriginally posted by ChopperCharles Quote
I have a question... Does auto-aperture and metering work on the adapter? Or if I set the K lens to F16, will the Q's screen go completely dark? I know there's no autofocus, but does it communicate lens information with the Q at all?
Hi Charles,

With the third party K mount adapters, the aperture is fully manual, and there is no communication between the lens and the camera body. The screen does not go completely dark at small apertures though -- it's not an optical VF, after all, and the LCD gains up to show a preview of what the actual exposure would look like. If you're able to set up with acceptable ISO and shutter speed to get a reasonable exposure, then that's what you'd see on the LCD. The lens doesn't have to communicate with the camera to do this.

It might be nice to have an "automatic" button on the adapter to allow focus at max aperture, then stop down to a preset aperture for the exposure, but with electronic VF, this is not as big an advantage as it is with an optical VF, and would involve a considerably more intricate mechanism, which would make the adapter that much more expensive for only some slight functional advantage in certain cases. With the small sensor, very small apertures are not that practical, as diffraction starts to take a real toll at f5.6 to f8 (it's a YMMV thing, so let's not get into that discussion). Since most will not be stopping down much past these apertures, there is really little practical need for this kind of sophistication in the adapter, IMO.

On the other hand, the Pentax OEM adapter is supposed to have an integral shutter mechanism, and this can be a very useful feature, not available in third party adapters. The Q can only sync with a flash at 1/13 sec with adapted lenses as it's forced to use the digital shutter since there is no mechanical shutter in the body. With a shutter in the adapter, this limitation would be lifted, and with adapted lenses it should be able to sync at 1/250 with external flashes and up to max shutter speed with the popup flash. This would be a boon to macro shooters shooting with adapted dedicated macro lenses and flash, and should be worth the significant extra cost that it will surely entail.

07-31-2012, 05:05 PM   #6

Join Date: Oct 2009
Location: North
Photos: Gallery
Posts: 3,908
As mentioned by the others, the aperture closes down with the adapter.
The camera raises the gain to display the scene on the LCD. In adequately lit conditions, even f16 is not an issue.
The gain up screen can be noisy if its really dark.

Auto aperture may not be the best thing for MILCs.
It adds an additional mechanism to the camera and perhaps complicates its a bit more.
The benefit is viewing/focusing wide open, but then the user deals with the hassle of exposure (eg. green button exposure metering like Pentax DSLRs) and lack of WYSIWYG DOF.

The OEM adapter is supposed to have a built in shutter, and the expectation is a max flash sync speed of 1/250.
With 3rd party adapters w/o a shutter, its 1/15 right now.
Its not that big a deal actually as in macro, the lens is stopped down f8-f11using ISO125 and in the shade, the ambient is cut-off at such settings.
The only light contribution will come from the flash and even at 1/15, it will be instantaneous and motion stopping.

I've taken quite a few macros this way :

  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
adapter, camera, k-mount adapter, lens, mirrorless, pentax q, pentax q10, pentax q7, q10, q7
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Jupiter-9 K-mount adapter question Rainy Day Pentax Camera and Field Accessories 8 05-15-2011 04:50 AM
And again a P-to-K mount adapter question..... Rense Pentax SLR Lens Discussion 3 01-27-2009 09:36 AM
M42 lens adapter question & KA mount greenboy Pentax SLR Lens Discussion 15 01-25-2009 09:43 PM
K mount adapter question Andi Lo Pentax Camera and Field Accessories 4 09-20-2008 08:25 AM
Pentax m42 to k mount adapter question. Deni Pentax SLR Lens Discussion 6 07-07-2007 08:54 PM

All times are GMT -7. The time now is 05:51 PM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]