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08-03-2011, 01:07 AM   #1
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1.7 AF adapter + 6x7 tele lens?

I couldn't find information about using the Pentax 1.7x autofocus adapter together with a genuine Pentax 6x7 lens adapter and a 6x7 SMC Takumar 4/400.

Would I get autofocus if I do the aluminium foil short-the-contacts trick?

If so, where to apply the foil, between converter and camera or between lens and converter - or on both sides?

What do I get if I use no trick, just the devices as they are?

Focal length increase and light loss and image degrade, but also AF confirmation or focus trap?

Any help is greatly appreciated!

Vranx

08-03-2011, 01:22 AM   #2
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QuoteOriginally posted by Vranx Quote
Would I get autofocus
Takumar don't have AF anyway.

QuoteOriginally posted by Vranx Quote
if I do the aluminium foil short-the-contacts trick?
It's an old lense without any contactor of any kind, so it won't change anything basically.

QuoteOriginally posted by Vranx Quote
If so, where to apply the foil, between converter and camera or between lens and converter - or on both sides?
same as before : it's useless.

QuoteOriginally posted by Vranx Quote
What do I get if I use no trick, just the devices as they are?
same as before : no contact of any kind on the lense, so trick or no trick, it's the same just a Takumar + 1.7x

QuoteOriginally posted by Vranx Quote
Focal length increase and light loss and image degrade, but also AF confirmation or focus trap?
Yeap ! because less light will come to the light sensor du to the reduction of aperture du to the 1.7x adaptater.
08-03-2011, 01:28 AM   #3
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I know that the Takumar is a non-AF lens, but that is the purpose of the AF adpater, right?

It gives you auto focus with Pentax K, M and A manual focus lenses (at least with some of them, those with suitable focal length and apertures).

And reports tell us that the adapter gives auto focus even with M42 lenses plus m42-PK adapter, if the lens contacts (of the converter, of course, which is the only item attached that has any!) are shortened with aluminium foil.

So, let's just ask again: Does this trick work also with the medium format 6x7 lenses adapted with a genuine Pentax 6x7-to-PK adapter to the 1.7 AF adapter?
08-03-2011, 02:54 AM   #4
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QuoteOriginally posted by Vranx Quote
but that is the purpose of the AF adpater, right?
nop ! The AF adaptater won't transform a MF lense into an AF lense. It will only maintain it if the lense is AF already.


QuoteOriginally posted by Vranx Quote
And reports tell us that the adapter gives auto focus even with M42 lenses plus m42-PK adapter,
it mount only thanks to the K mount which is the same for decade. But that's all.

AF lense have some electronics / mecanichs which allow the AF. MF lense doesn't have it, so it's not physically possible to miraculously transform it into AF lense.

08-03-2011, 03:27 AM   #5
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QuoteOriginally posted by aurele Quote
nop ! The AF adaptater won't transform a MF lense into an AF lense. It will only maintain it if the lense is AF already.

it mount only thanks to the K mount which is the same for decade. But that's all.

AF lense have some electronics / mecanichs which allow the AF. MF lense doesn't have it, so it's not physically possible to miraculously transform it into AF lense.
That's pure nonsense, why don't you read the Pentax 1.7x AF adapter manual? Or the relevant section in this forums' database? And please don't answer questions if you have no idea what you are talking about.

The Pentax 1.7x AF adapter was designed by Pentax to allow auto focus with AF cameras with manual focus Pentax lenses. The manual focus lens is pre-focussed (to infinity in most cases or to circa the required distance) and the AF system of the camera meters and focusses the optics of the adapter, and miraculously, the manual focus lens was focussed automatically. The adapter, of course, does not change the lens attached physically, but it does the auto focussing job for the old lens. Again, that's what it was designed for! Pentax states in manual and lens catalogues that this is the main purpose of this adapter, the teleconverter function is a collateral issue and Pentax does not recommend it for close-up work.

Pentax introduced this adapter with the SF1/SFX camera line for exactly one purpose: achieve autofocus with the manual focus K, M and A lenses.

So, back to the question: anyone else with a little bit more of a background, please?
08-03-2011, 04:53 AM   #6
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The genuine Pentax 6x7 lens adapter (Photo) should short-circuit the contacts and effectively behave like an M lens.

Old 1.7x AF manual: Pentax Manuals

f4 also should be fast enough as the 1.7x works e.g. with the FA* 300/4.5 in good lighting conditions.

Concerning the (M*) 400/4, see:
P400ED
Luminous landscape comparison

E.g. CAs could be problematic with the Takumar versions (optics unchanged since 1969).
Pentax 67 Lens Guide

No to forget, you will need a sturdy tripod...
08-03-2011, 05:16 AM   #7
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Sorry Vranx, i missread the title and i fully missunderstand some point like it was a K mount + a 6x7 lense adapter, i was thinking it was a 67 F-AF adapter (which doesn't exist).

But, at some point i can help you and tell you it will surelly be a waste of time.

- because this TC will gives you some soft image, without great quality.
- 67 lenses produces some good images, but not as good as FF or APSC equivalent lenses.
08-03-2011, 08:32 AM - 1 Like   #8
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QuoteOriginally posted by aurele Quote
nop ! The AF adaptater won't transform a MF lense into an AF lense. It will only maintain it if the lense is AF already.




it mount only thanks to the K mount which is the same for decade. But that's all.

AF lense have some electronics / mecanichs which allow the AF. MF lense doesn't have it, so it's not physically possible to miraculously transform it into AF lense.
Uh, I think you are confused what the 1.7x afa adapter does. It has internal elements that can be moved to autofocus any lens, including manual focus lenses.

I've used it on my 1000mm reflex and my 2000mm reflex without issue. Those lenses have no contacts of any kind. I expect your 6x7 will work the same. You prefocus close and then use the afa to snap the focus into place.

08-03-2011, 02:37 PM   #9
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Talk about ships passing in the night!!! This thread was getting out of control.

It would be nice if there was someone that has the 1.7X AFA and some 6X7 or 67 lenses and K mount adapter to try this out. I have been tempted to buy some 67 lenses hoping this will work but I don't want to be left holding the bag if it doesnt. I have also heard it doesnt work with the M42 adapter and screw mount lens???
08-03-2011, 03:29 PM - 2 Likes   #10
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QuoteOriginally posted by littledrawe Quote
Talk about ships passing in the night!!! This thread was getting out of control.

It would be nice if there was someone that has the 1.7X AFA and some 6X7 or 67 lenses and K mount adapter to try this out. I have been tempted to buy some 67 lenses hoping this will work but I don't want to be left holding the bag if it doesnt. I have also heard it doesnt work with the M42 adapter and screw mount lens???
Littledrawe, you are in luck. I mounted a generic P67 to PK adapter to P67 SMC Takumar 300/4.0 and the AFA 1.7x to my K20D (I have no doubt the genuine Pentax P67 to P645 + p645 to PK adapter would work just as well, but they are buried deep in my Medium format bag). Set the camera to AF.s, manually focus the camera and half press the shutter and AF works quite well. Any subject within the same vicinity (+,- 50 feet) the AF works. Mind you it's very bright outside, in less than ideal conditions AFA 1.7x and an f4.0 lens do not work so well. I haven't checked the IQ but I've had good results with AFA 1.7x and other 300mm lenses.

I can also confirm that an m42 lens with an infinity type adapter will not AF with the AFA 1.7x, however with a non-infinity type adapter (chrome plated) the AF functions as well as the P67 lens. I haven't tried it with the black anodized non-infinity adapter - will try to do so later on.

Hope this helps,
08-04-2011, 05:03 AM - 1 Like   #11
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I have used the 1.7X Autofocus Adapter with all sort of lenses and I can confirm it will convert any lens (even an office magnifier) into an autofocus lens. I have used old barrel lenses dating back from the 19th Century and they magically turn into autofocus lenses.

As you stated, you will need to shotcut the contacts in order for the Autofocus Adapter to work with older lenses which are not equipped with the proper contacts. You can indeed use a piece of aluminium foil for this purpose, either between body and adapter, or between adapter and lens. I find it more convenient tu put it between adapter and lens, because I can leave the piece of aluminium in place when unmounting the adapter + lens assembly. You could even imagine having two telephoto lenses in you bag, each one having its own AFA semi-permanently mounted with a piece of aluminium foil, allowing you to switch between lenses more rapidly while shooting.

When using a mount adapter on top of the Autofocus Adapter, just make sure the whole contraption is rigid enough, especially with long and heavy lenses. The P67 adapter shouldn't be a problem, but I have had some trouble with flimsy M42 adapters.

The Autofocus Adapter is really a great contraption: it turns any old telephoto into a powerful AF supertele lens, with a built-in focus limiter insuring lightning fast AF operation. This is certainly the cheapest way to get a 500mm+ AF lens for birding!

The only caveat is the max aperture of the lens. If you want to get a fast and reliable AF lock, you'll preferably need a lens faster than F/5.6. AF performance depends somewhat on the lens formula: it might be nearly impossible to get a focus lock with some F/5.6 lenses, while it can be feasible with others. You shouldn't have any problem with an F/4.0 or F/4.5 lens.

Cheers!

Abbazz
08-04-2011, 06:35 AM   #12
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QuoteOriginally posted by Abbazz Quote
As you stated, you will need to shotcut the contacts in order for the Autofocus Adapter to work with older lenses which are not equipped with the proper contacts.
I haven't experienced this. I've used this adapter with MF lenses that have some contacts, and others that have none without any issue. Am I missing something here?
08-04-2011, 06:53 AM   #13
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I used this TC with adapter for 645 and an 300mm 645 lens. It does AF, but not to speedy. I think that I can beet it in manual focus. It does work.
08-04-2011, 07:30 AM   #14
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QuoteOriginally posted by Clinton Quote
I haven't experienced this. I've used this adapter with MF lenses that have some contacts, and others that have none without any issue. Am I missing something here?
If your lens, or the adapter you are using, has a rear flange made from bare metal, then it will effectively shortcut the contacts, thus allowing the AFA to autofocus. On the other hand, many lenses and adapters have a black finish from anodized aluminium or enamel, which acts as an insulator, thus preventing the AFA from autofocusing, unless you insert a small piece of aluminium foil to shortcut the contacts.

The genuine Pentax 67 to K-mount adapter has a rear flange made of bare metal, but some Chinese clones come in black anodized finish.

Cheers!

Abbazz
08-04-2011, 07:55 AM   #15
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"Shortcutting" shows the body (with adapter) that a (non-AF + non-A) lens is mounted and action can begin...
QuoteQuote:
aluminium foil for this purpose, either between body and adapter
Have you really tried this? Communication between adapter and body is required for AF functionality (digital-info contact). Furthermore, one has to take care not to intervene with the auto-focus transmission shaft. So the other solution is not only more convenient but also less error-prone.

Objectifs Manuels sur K-m
Features and Operation of the Ka Mount (on lens side of adapter: https://www.pentaxforums.com/forums/sw/attachments/sold-items/20812d122461356...r-1-7front-jpg)
Features and Operation of the Kaf Mount (on body side of adapter: https://www.pentaxforums.com/forums/sw/attachments/sold-items/20814d122461360...er-1-7rear-jpg)
Features and Operation of the Kaf2 Mount
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