Pentax-F 1.7 AF Adapter

This may be a silly question but could anyone advise on what lenses i can use this adapter on and what functions i would lose (I have m series, an 80-320 auto and the new 18-55 that came with my Ds) Thanks.

The 1.7xAF adaptor will not work correctly with non auto focus bodies.

You can connect practically any lens to the front of the adaptor - including manual focus lenses. The adaptor itself will do the autofocus operation.

So, when using an AF lens on an AF body with this, it becomes a little tricky. You have to partially manually focus to get the lens in the right "ball park", then let the camera autofocus the 1.7xAF. Elements move inside the 1.7xAF so that you can achieve a focus lock. Of course, if the lens is focussed incorrectly, then the 1.7xAF will not be able to lock on.

If you try and use it in manual mode you can find the adaptor at either end of its focus range and you'll will not get the full focus range when trying to focus the lens.

Hope that makes some sense!

There are other third-party adaptors that may be more suitable for the M-series cameras.

Matt

You can experiment by using a small (watchmaker's type) screwdriver to adjust the AF coupler in the adapter before mounting it onto the camera.

The suitable lenses are those with a maximum aperture of F2.8 or larger (if using an AF body) although you can get away with smaller apertures providing the subject is bright enough.

I assume you intend to use the adapter on your DS, if so then I can't really advise you because I've never used one but I suspect that your lenses may not be usable and you should be wary of any lens whose rear element projects significantly - could come into contact with the element in the converter.
As with all converters, the best lenses are fast prime's and moderate zooms.

As for functions, the adapter has lens information contacts thus allowing full auto operation with A series and later lenses but you'll have to set the aperture manually with M lenses.

Hope that helps, don't be afraid to experiment - you never know!

Whoops, I didn't read the original reply carefully enough.

You won't need to use a jewellers screwdriver with the *ist-DS

Here's how it works on the *ist-D (and almost certainly on the *ist-D):
* AF from the camera controls the elements within the 1.7x only
* You manually focus to ball-park
* Half press the shutter and the 1.7x does the rest

Aperture etc works as before.

I regularly use the 1.7x with an old (but very sharp) SMC-F 70-210, even in relatively dark conditions. The *ist-D autofocus is very capable indeed. (e.g. http://www.ephotozine.com/gallery/showlargepic.cfm?photoid=245613 )

Sorry for the confusion!
Matt

Thanks for the comments, I have been offered one for £20 in near mint condition and from your comments I think it would be a handy bit of kit. Thanks again.

£20 is a fraction of the going rate for this. If you have an autofocus body, snap it up.

G

I was going to say the same, George!

I bought mine brand new (something like fifteen years ago) for £80 and I imagine the price was considerably higher than that a few years later.
I don't know if it's still in production but £20 sounds like a real bargain and as with most Pentax glass, it is very good indeed.

The list price is something like £130.
I bought one boxed and mint via ebay for around £60, so £20 is a real bargain. I'd get it even if you didn't have an AF body!
Matt

Thanks for the comments guys. I feel a little bit guilty (I dont think) reff your comments on the price but we all have to get lucky sometime, anyway on your advice I have bought the adapter and played with it at the weekend and am very pleased. It works a treat on my M 50mm 1.7 and 200mm f4. Thanks again (any one know of a 300 prime for £25)

I have two 300mm lenses. One cost £9.50, the other £410. Both second-hand.
The £410 was the better buy.
I'm afraid that if you are waiting for a bargain 300mm, you're going to be waiting awhile.

G

Hi,
Just to amplify on something Matt said, I have used the convertor with a large number of lenses and bodies. The best thing to do is set the lens to infinity. The convertor will then cope with everything up to it's closest point. You only need to "focus" the lens if you need closer than this and then it's becomes like a macro convertor. You can also use it with AF lenses and a "straight" 1.7 convertor. However, I have found with the D that you cannot use it in the green mode but must use either the program mode or one of the others.

Regards
Kim

hi,
just to add my two-penneth: I've used the 1.7x converter on 50mm and 85mm manual lenses, the 135mm FA and a 300 A* and it gives excellent (or, in the case of the 85 f/2 M-series, servicable) results on all. As mentioned, set the lens at ? and re-adjust for closer stuff (portraits, etc.). The 50mm and 1.7x is pretty useful lightweight stop-gap for portraits, if you like them soft and 'flattering' (to please the over-25s
gus

Should the AF portion of the AF adapter work with my istD, K to M42 adapter, and an M42 microscope adapter?

The AF will function - the coupling is only from the body to the AF1.7x adaptor. The focus function affects elements inside the 1.7x only. So, as long as it can be focussed, it should

Incidentally, it makes it much quicker to focus when you use 1.7x+telephoto because the body hasn't got to rotate the lens, only the elements inside the 1.7

Matt

Well, no go on focusing, until I shorted out the contacts. The microscope adapter does not cover the contacts on the lens flange of the 1.7x AF adapter as a K lens would, so it will not auto focus at all. I think I need a giant washer with a 42mm hole. I recall having this same problem with some M42 lenses that are still black on the back surface (and hence don't short the contacts).

Thanks,
Gerry