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06-08-2016, 11:28 PM   #1
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K-70 and 50-100 video testbed

I've got to say...the biggest thing for me here, is that Pentax is bringing a lens that doesn't have a mechanical aperture lever, and it's designed to work in conjunction with the K-70.

Along with video AF - this is a big deal for what might come in the video department at Pentax.

This is the biggest thing to come along since Pixel Shift, as something really *new* to Pentax.

On the Pentax lens mount, there isn't a new digital interface, and it would appear that *somehow* stopping the lens down electronically is going to happen with the legacy SDM/Power contacts, and the *A* contacts.

How this is going to work, is almost worth the price of admission!

Any ideas how Pentax is going to pull this off?
This is going to be radical if Pentax moves forward with this.

There are other clues too, in that we have ND filters in the Q lenses, so we might have a new direction in Pentax lenses that have electronic ND control as well as aperture.
Again, this is potentially huge in the video department.


Last edited by LaurenOE; 06-08-2016 at 11:34 PM.
06-08-2016, 11:51 PM   #2
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QuoteOriginally posted by LaurenOE Quote
On the Pentax lens mount, there isn't a new digital interface, and it would appear that *somehow* stopping the lens down electronically is going to happen with the legacy SDM/Power contacts, and the *A* contacts. How this is going to work, is almost worth the price of admission! Any ideas how Pentax is going to pull this off? This is going to be radical if Pentax moves forward with this.
Well, the camera can communicate with the lens though the digital contact, so all it has to do is send a signal corresponding to the desired aperture (rather than operating the aperture lever), and the lens will obey.

Nikon is doing this with their new "E" lenses. Works exactly the way as the Pentax KAF4 mount, with the same backwards-compatibility consequences. As a result, I don't think KAF4 will be used on all lenses going forward, but rather only on video-oriented lenses until the user base of legacy bodies diminishes significantly.

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06-09-2016, 12:03 AM   #3
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QuoteOriginally posted by Adam Quote
Well, the camera can communicate with the lens though the digital contact, so all it has to do is send a signal corresponding to the desired aperture (rather than operating the aperture lever), and the lens will obey.

Nikon is doing this with their new "E" lenses. Works exactly the way as the Pentax KAF4 mount, with the same backwards-compatibility consequences. As a result, I don't think KAF4 will be used on all lenses going forward, but rather only on video-oriented lenses until the user base of legacy bodies diminishes significantly.
I always thought, the *A* contacts were based on a resistance across the contacts, and the aperture lever was actuated from the camera body, and stopped down.

Normally the lens is open, and stops down based on what the body is doing to the aperture lever.

I thought it was basically a passive system that the camera body interpreted?

I guess I don't know exactly *which* of those contacts are the digital interface, but I never thought the interface was asynchronous?

---------- Post added 06-09-16 at 02:07 AM ----------

I found a diagram - http://www.aohc.it/_old/images/k1e.gif

Basically the digital pin is next to the mount screw on the bottom.

Last edited by LaurenOE; 06-09-2016 at 12:11 AM.
06-09-2016, 12:09 AM - 1 Like   #4
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QuoteOriginally posted by LaurenOE Quote
I always thought, the *A* contacts were based on a resistance across the contacts, and the aperture lever was actuated from the camera body, and stopped down.

Normally the lens is open, and stops down based on what the body is doing to the aperture lever.

I thought it was basically a passive system that the camera body interpreted?

I guess I don't know exactly *which* of those contacts are the digital interface, but I never thought the interface was asynchronous?

---------- Post added 06-09-16 at 02:07 AM ----------

I found a diagram - http://www.aohc.it/_old/images/k1e.gif
Yup, except now the camera will send a digital signal to the aperture actuator inside the lens at the time the shutter is released, instead of operating the mechanical lever. Think of it as the same thing that happens when the camera asks the lens to focus.

In your diagram, the contact used is almost certainly #6.

See also:

The Evolution of the Pentax K-mount - Articles and Tips | PentaxForums.com


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