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04-02-2019, 06:35 PM   #1
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opinions on the Pentax mount

Hi everybody, not sure if this has been discussed before but here is my question. Every camera but Pentax have the electric contacts inside the camera body, including the Pentax 645. This may have ben a technical decision to make the older lenses compatible, but is this a weak point in the built of the camera? will be a limitation in the future?
Just a curiosity since I own a K1000, an MX and a K1II DSRL.
Thanks for your opinions.

04-02-2019, 06:58 PM   #2
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I've never known this to be an issue. Never really thought about it, actually.
04-02-2019, 07:05 PM   #3
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What would the issue be?
04-02-2019, 07:07 PM   #4
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It does not seem like an obvious weakness. An in-camera system is probably cheaper to make using molded plastic contact frames versus precision-machined holes. But the in-camera design might leave the lens contacts a bit more prone to damage.

In theory, it might seem that the Pentax mount-contact system would be more prone to moisture problems but, in practice, Pentax seems to have a better track record for weather-resistant lenses and bodies than do other makers.

It's certainly not a limitation in the future in that Pentax could easily: 1) add more in-body contacts, 2) add more on-mount contacts, or 3) reuse the existing mount contacts with a smart interface that recognizes old and new lenses.

04-02-2019, 07:18 PM   #5
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I am not sure what constitutes a "weak point" in the build of the camera. Perhaps it enough to say that at present, the K-mount is not a limiting factor in that recent bodies are able to support any feature found in brands who placed all of their contacts at the entry to the mirror box. It is also fair to say that the K-mount is no more fragile than the mounts on other cameras in normal operation with normal levels of mechanical load. Examples I have seen of damage due to being dropped almost always involve screw separation, sometimes with subsequent twist breakage of the mount flange itself.


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04-02-2019, 07:21 PM   #6
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To add a small bit of clarification...No camera mount is designed to support the weight of any lens whose design includes a tripod collar, though all are designed to support the weight of the camera suspended from a lens.


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04-02-2019, 07:57 PM   #7
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There has been some discussion before that the mechanical aperture mechanism was more of a pain for third-party manufacturers to deal with, so they were less likely to make Pentax-compatible lenses in that case. Though now Pentax has an electronic aperture capability in KAF4 lenses.

(Which is also referenced in this thread: Another recent tour of Sigma factory at Aizu)
04-02-2019, 08:05 PM   #8
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Actually, it just occurred to me that I used to shoot frequently with m42 lenses and the contacts were exposed. Never had any reliability issues with them, though. So probably nothing to worry about.

04-02-2019, 08:54 PM   #9
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Technically only one pin of those lens mount contacts is actively transmitting data to/from the lens, the others are passive coding of lens aperture info. The sdm pins are inside the mount, and as far as I know only supply power not more communications channels. If anything, the design may reduce the speed at which data can be sent to and from the lens which might limit some features that rely on larger and faster data movement. But I'm not aware of any such requirement in existing competing systems.

As someone else mentions, the existing passive contacts might be possible to repurpose in a way that was backward compatible, passively reading old lenses and adding needed contacts for wider data pathways which could be active only if the lens requested this.
04-02-2019, 09:07 PM   #10
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QuoteOriginally posted by Sevilla Quote
will be a limitation in the future?
The same question might be asked of any brand's mount. Nothing is future-proof and sometimes the mount disappears with the company or with a class of cameras.


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04-02-2019, 09:15 PM - 1 Like   #11
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QuoteOriginally posted by UncleVanya Quote
Technically only one pin of those lens mount contacts is actively transmitting data to/from the lens, the others are passive coding of lens aperture info. The sdm pins are inside the mount, and as far as I know only supply power not more communications channels.
There is some evidence that the power contacts in the mirror box may be used for both handshake and power for both AF motor-in-lens and KAF4 aperture actuation. The data contact communication has traditionally been viewed as one-way polling of lens status only.


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04-02-2019, 09:26 PM   #12
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QuoteOriginally posted by stevebrot Quote
There is some evidence that the power contacts in the mirror box may be used for both handshake and power for both AF motor-in-lens and KAF4 aperture actuation. The data contact communication has traditionally been viewed as one-way polling of lens status only.


Steve
Steve I thought I had read it was a serial communications protocol. Can't find it right now. Interesting either way.
04-02-2019, 10:34 PM - 2 Likes   #13
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QuoteOriginally posted by Sevilla Quote
but is this a weak point in the built of the camera? will be a limitation in the future?
Advantages and drawbacks, like for everything. The pentax K outer contacts are made shallower to avoid risk of external damage which leave less room for mechanical play on the mount. But the advantage is that the contacts are very easy to clean without needed to risk introducing dust inside the cavity. Works very well for me.
04-02-2019, 10:42 PM   #14
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QuoteOriginally posted by biz-engineer Quote
Advantages and drawbacks, like for everything. The pentax K outer contacts are made shallower to avoid risk of external damage which leave less room for mechanical play on the mount. But the advantage is that the contacts are very easy to clean without needed to risk introducing dust inside the cavity. Works very well for me.
X 2. I've never had any problems with either the old Pentax M42 screw mount or the K bayonet in 50 + years. Touch wood. They've always worked for me.

Strong like bull...as we used to say on the farm.
04-03-2019, 08:22 AM   #15
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QuoteOriginally posted by UncleVanya Quote
Steve I thought I had read it was a serial communications protocol.
It is serial through the data pin, but is dumb polling.


Steve
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