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SMC Pentax-F 1.7x AF Adapter

Reviews Views Date of last review
26 118,641 Thu March 18, 2021
Recommended By Average Price Average User Rating
92% of reviewers $234.29 8.58
SMC Pentax-F 1.7x AF Adapter


This 1.7x teleconverter/AF adapter provides autofocus capability with manual focus lenses. When used with autofocus lenses, the adapter performs the focusing rather than the lens.

Features of this teleconverter:

  • Autofocus (screw drive) also with manual focus lenses
  • Supports Tv or P exposure mode (in addition to M and Av), if the camera allows
  • The converter does not transmit focal length and MTF information from lens to camera

Supported Lenses:

  • K and M-series lenses with a maximum aperture of F2.8 or faster, except SOFT 85mm F2.2
  • A-series lenses with a maximum aperture of F2.8 or faster in the focal range 16 to 400mm, except macro lenses
  • smc Pentax-A 35-105mm F3.5 (macro setting not usable)
  • Fast apertures are strongly recommended since the converter reduces available light by 1.5 stops

Autofocus lenses can also be used, though the converter will do the focusing. 

Since the converter has a limited adjustment range, in certain scenarios you may need to manually turn the focusing ring on the lens closer to the desired focus point for the converter to be able to focus within that range.  This generally applies to lenses with a long focus throw.

SMC Pentax-F 1.7X AF Adapter
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Light Loss
1.5 stops
6 elements, 4 groups
Mount Variant (Rear)
Mount Variant (Front)
AF (screwdrive)
Weather Sealing
Diam x Length
64 x 26 mm (2.5 x 1 in.)
135 g (4.8 oz.)
Production Years
1987 to 1997
Engraved name: SMC Pentax-F 1.7X AF Adapter
User reviews
The converter has a built-in AF mechanism and thus converts K, M and A-series lenses to autofocus albeit with an 1.7x extension of their focal length.
The converter is designed for lenses with a maximum aperture of F2.8 or larger, and a focal length from 16mm to 400mm. It also works with the smc Pentax-A 35-105mm lens (macro setting not usable).
When used with an AF lens, the AF mechanism of the lens will not be used. The converter will do the focusing.
The converter retains all exposure modes supported by the lens.
The converter does not relay information about focal length, MTF, or lens name to the camera.
Screwdrive AutofocusInternal FocusingAutomatic ApertureFull-Frame SupportDiscontinued
Price History:

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New Member

Registered: October, 2020
Posts: 4
Lens Review Date: March 18, 2021 I can recommend this lens: Yes | Price: $250.00 | Rating: 10 

Pros: Doubles your number of lenses, maintains or improves sharpness
Cons: PF, quite a fragile build on it, AF only works on K mount

This piece of glass is a joy to use. Snap on a lens to it and instantly have a new one with a new focal length and max aperture. I use my Vintage Auto Sears 50mm f1.7 on it and get an Auto Sears 85mm f 2.55 lens which auto focusses. Snap on a vintage 50mm 1.2 and get an auto focus 85mm f1.8 (which would be awesome). There is no noticeable loss of sharpness from the original lens.

The converter seems to produce some PF though which is very negligible and can easily be fixed in PP. My major complaint on the converter is that it will only auto focus on K mount lenses. Pentax has a lot of awesome lenses in M42 mount. The converter will not auto focus on an M42 lens with K mount adapter snapped on to it Another flaw on the converter is it has major difficulty giving AF on macro lenses (or lenses with a very long focus throw). The build quality is on the fragile side.

The converter does not come cheap but is such a joy to use. I can just imagine snapping a Pentax A* 300mm f4 on to it so I can get a Pentax A* 510mm f6 with auto focus

Image uploaded was taken with the converter and my vintage Auto Sears 50mm f1.7 lens

Lens Review Date: March 4, 2020 I can recommend this lens: Yes | Price: $175.00 | Rating: 10 

Pros: Magician that turns MF lenses into AF
Cons: none

I bought it with my SFX in 1987, the first AF Pentax camera. I used with my 35-105, F1.4 50mm, F1.7 50mm, A* F1.4 85mm and Takumar Bayonet F2.5 135mm. It did a great job at that time. I discovered it does not work the same way with a DSLR.
With a DSLR you are obliged to set the focus ring close to what might be the distance. The AF-adapter does the rest. But I do not like the results. But that is personal. In the film era I made quite some pictures with it and they were razor sharp so to speak. With MF bodies with the split it was easy to focus, but the screen in a SF-series camera was a bit harder to focus especially when wearing glasses. So the adapter came in handy. Mind you, it is not a TC, it is an AF-adapter and nothing less and it was sold as such. You can use it with an AF-lens and by magic, it turns an AF lens into a MF one. It takes over the AF capability of any F, FA or other AF lens. I still have it in its original box with the dedicated soft case. After I'm gone it will be for sale, not before. Highly recommended but you have to learn to work with it.
Loyal Site Supporter

Registered: September, 2017
Location: Medellín
Posts: 1,286
Lens Review Date: December 23, 2019 I can recommend this lens: Yes | Price: N/A | Rating: 10 

Pros: Build quality, compatibility, unique.

This TC really sets Pentax apart, since it turns any manual lens into an AF one. Works great on my K 135/2.5 and turns it into a 230/4,2 AF assisted lens. My A 50/1.2 turns into an 85/2. A three MF lens kit turns into a five piece (2 AF).
Side note: You should only really be shooting this with normal to tele lenses, since shorter focal lenghts is not what TCs are for. Shorter focal lengths have mor DoF, thus are more forgiving in terms of nailing the perfect focus. This is why this adapter comes in handy with longer focal lengths.
New Member

Registered: November, 2018
Posts: 1
Lens Review Date: December 4, 2018 I can recommend this lens: Yes | Price: $180.00 | Rating: 8 

Pros: fast and accurate AF; optical quality
Cons: need to pre-focus

I gave this TC a score of 8 for a combination of optical quality and AF ability. Although you need to pre-focus, once you get close it will fine-focus for you to shoot. This works best close to infinity because you don't need to move the focus ring very much during manual adjustment.

I use this on my Pentax A* 300mm f4, and the image quality is on par with another Pentax TC the 1.4X-S, with moderate softness. Downsizing from 24 to 12MP plus some software sharpening improves a lot. The images do not need modification for web publishing.

I also tested this combo indoor in dim light, and the camera had no problem with AF (the camera reported largest f6.3, which is correct for this combo). This may be attributed to good AF performance of the camera (K-70) though.

These pictures were taken with the AF 1.7X + Pentax A* 300mm f4

(100% crop)

(100% crop)
Site Supporter

Registered: April, 2015
Location: Wisconsin, USA
Posts: 2,749

2 users found this helpful
Lens Review Date: June 25, 2018 I can recommend this lens: Yes | Price: $350.00 | Rating: 10 

Pros: fairly fast, dead on accuracy, works on adapted Zeiss & Leica R lenses
Cons: need to prefocus the lens manually to the approximate distance before hand - this adapter only will "fine tune" the last little bit

I only shoot manual-focus, premium, prime lenses. However, there are occasions when I find that it would be handy to be able to shoot an auto focus lens. Also, with my old eyes getting worse by the year, I'm beginning to think auto focus lenses just might enable me to take photos further into my golden years.

That said, I sure don't want to have to give up the incredible image quality I'm getting with my adapted Zeiss and Leica R lenses just because of aging eyes. What am I to do?

Well, I just discovered how I can have my cake and eat it too. In other words, use my adapted Zeiss and Leica R lenses in the AF mode.

A few months ago I purchased a Pentax SMC Pentax-F 1.7x AF adapter. Never shot it "until today".

Below is the first photo I took with it. I attached this little adapter to adapted Zeiss ZF 35mm f/1.4 lens, and attached this combination to my Pentax K-1 camera, and shot away at f/2. WOW, am I impressed! The auto-focusing was fairly fast and dead on accurate. As many of you know, the Zeiss "Classic" ZF 35mm f/1.4 lens (with heavy Leitax adapter) is a fairly large and heavy lens - but this little adapter had no trouble at all with it.

Just put your camera in the AF mode and fire away (well, it does help if you manually move your lenses' focus adjustment to somewhere close to your shooting distance before shooting). My favorite way to use it is in Live View with back button focusing. Another side benefit to using this AF adapter is that it will speed up the taking of photos a little bit (not as much as a fully auto-focus lens, but maybe half way between an AF lens and the MF lens without this adapter).

Some of you will ask, "does this adapter reduce the image quality of photos taken with it?". This AF adapter does have 6 optical elements in 4 groups inside of it. Being an expensive Pentax product, it is well made with premium optical glass inside. Having said that, if you are a pixel peeper, maybe you will be able to detect a tiny TINY drop in sharpness if you look really hard. So, if you are a photographer who demands as much sharpness out of their gear as is possible, then you may want to not use this AF adapter. However, the great majority of photographers will not be able to detect a reduction in an image's IQ by using this AF adapter.

While many of you are already familiar with this AF adapter, I guess that I thought it would not work on my "adapted" Zeiss and Leica R lenses. Well, I'm here to tell you it works just fine on adapted Zeiss and Leica lenses. So, if you love Zeiss and Leica R glass like I do, here's a little accessory that you just might want to consider trying out for yourself (especially if your eyes are not what they used to be)!


Senior Member

Registered: April, 2015
Posts: 121
Lens Review Date: November 15, 2017 I can recommend this lens: Yes | Price: $370.00 | Rating: 10 

Pros: Now my M primes focus without my help - almost
Cons: None - this is like owning a time machine

I own most M prime lenses so this is a great addition to my kit. I purchased it new in 2017 from Japan (with Richo packaging). Does not seem to work well with zoom lenses. The exception is the A 35-105. Wait till you see the results of using it with the M *300. Great Also the Sears 135 Micro produces great results. You may think i am a kid with candy - well Almost!

Note: Catch in focus does not work with the adapter - camera fires without proper focus - strange
Veteran Member

Registered: July, 2007
Location: North West UK
Posts: 382
Lens Review Date: July 11, 2017 I can recommend this lens: Yes | Price: $230.00 | Rating: 9 

Pros: AF to MF lenses, Works with the DA1.4 stacked in the right order, IQ
Cons: Not cheap, you have to work with it

I managed to find one of these second-hand as they had a great reputation.
But what do I think? yes it is worth the plaudits, the IQ is very good indeed.

If you have the 1.4x DA converter it also works with that too, with little loss in IQ. Think of it this way, a stacked 1.7x and 1.4x still gives superior IQ than my Sigma 170-500mm superzoom when mounted to my DA*300.

Well you still have to focus the lens on the end to the AF "zone" the adaptor wants, which slows you down and potentially miss the shot.
The other thing is, because they are rare, they are not cheap.

Worth it though.
New Member

Registered: February, 2012
Posts: 15

5 users found this helpful
Lens Review Date: February 5, 2015 I can recommend this lens: Yes | Price: $90.00 | Rating: 8 

Pros: Works brilliantly with Pentax-M 50mm f1.4
Cons: Less well with everything else I have tried ...

This gadget, that I bought in from an on-line photography site, launched my obsessive collecting of Adaptall lenses, so it has a lot to answer for.

In combination with the Pentax-M 50mm f1.4, I find it flawless. The combination is still fast compared with my usual consumer and bargain fare (about f2.3), it is compact, and it handles well. At events, I manually set the aperture and speed, prefocus to somewhere short of infinity, and then seldom have to adjust anything again. Autofocus is instant, I have no complaints with respect to its accuracy, and bokeh, sharpness and colours are all excellent.

Since I've been using an aggressive hood, I've come to prefer the look from the 50mm f1.4 to the 50m f1.7. I have a Pentax-A 50mm f1.7, and the combination works effectively, but to my mind the images offer nothing over the slightly slower Sigma 70-300mm f4-5.6 DG, which is at its best at shorter focal lengths.

As mentioned by others, the 1.7x AF requires the presence of a K-style aperture lever to activate the autofocus function, so it doesn't autofocus M42 lenses with adapters, or T2 lenses. With these it functions as a 1.7x Teleconverter. It's O.K., but I get better central sharpness from a Kiron 1.5x (though the Pentax is better than the other 1.5x TC I own).

If I mount a T2 or M42 lens on the 1.5x TC (which has an aperture lever), and then mount the TC on the Pentax-F 1.7x AF, it will autofocus if the lens is fast enough (f4.5), but the images that have resulted have been soft and lacking in contrast.

Although it is only specified to work with lenses f2.8 and faster, in my experience the Pentax-F 1.7x AF autofocus mostly locks on reliably, albeit slowly, when the lens wide-open aperture, after allowing for the adapter, is f11 or greater, on my Samsung GX-20 in good light.

Whether you will be able to discern more detail in the image created by the 1.7x than you would find in a 'digitally zoomed' version of an image taken without the 1.7x is another matter. Ones that pass this test for me are:
  • Pentax-M 50mm f1.4
  • Pentax-A 50mm f1.7
  • Pentax-M 75-150 f4
  • Pentax-M 80-200 f4.5
  • Tamron Adaptall SP 70-210mm f3.5 19AH
  • Tamron Adaptall-2 70-210mm f3.8-4 46A
  • Tamron Adaptall 80-250 f3.8 Z250
  • Tamron Adaptall 70-350 f4.5 CZ735
  • Tamron Adaptall SP 300mm f5.6 54B
  • Sigma 75-300mm APO f4.5-5.6
  • Tamron Adaptall-2 135mm f2.5 03B
  • Tamron Adaptall SP 90mm f2.8 72B
  • Tamron Adaptall 200mm f3.5 CT-200
  • Tamron Adaptall-2 200mm f3.5 04B
  • Tamron Adaptall 300mm f5.6 'Auto Tamron'
  • Tamron Adaptall 300mm f5.6 CT-300
  • Tamron Adaptall SP 300mm f5.6 54B
  • Tamron Adaptall SP 500mm f8 55BB
  • Vivitar (Tokina) TX 400mm f5.6 first version (77mm, 8 elements in 8 groups)
Ones that I have tried, but which don't seem to play so well are all the other Adaptall, Adaptall-2 and Adaptall SP (60-85)-(210-300) f(3.5-3.8)-f(4-5.4) zooms.

However, for all of these with a maximum focal length of 200mm or less, it begs the question, why would you? For example, the Pentax FA 80-320mm f4.5-5.6 covers almost the entire range of any such lens used with the adapter, it will be faster, lighter (even than the Pentax-M 75-150mm f4 plus 1.7x AF combination), will concede nothing in image quality, and will likely cost less than the Pentax-F 1.7x AF on its own.

Out of curiosity, I also tried my long AF Telezooms, and compared them on their own, and with the Teleplus MC4 Pz-AF DG. The MC4 only autofocuses when the attached lens is f4.5 or faster, so the 1.7x AF, which works to f5.6 and beyond, potentially offers some additional reach. My results were as follows.
  • The lenses are reported as A lenses
  • You have to set the shake reduction focal length manually
  • The aperture for the Sigma 70-300mm f4-5.6 DG could not be set successfully via the camera. The lens obviously made a complete hash of its PKA-compatible communication attempts.
  • The two Pentax 100-300mm zooms seemed to work properly as PKA lenses
  • The Pentax FA 100-300mm f4.7-5.8 wouldn't lock focus reliably past about 180mm
  • The Pentax F 100-300mm f4.5-5.6 would lock all the way out to 300mm, and it gave the best images that I achieved with the 1.7x AF, but I got better results by 'digital zooming', and still better with the MC4.
In summary, my only unqualified successes, in so far as the combination gives me something that I cannot achieve more easily and cheaply in some other way are:
  • Pentax-M 50mm f1.4
  • Tamron Adaptall SP 90mm f2.8 72B in macro mode
  • Tamron Adaptall 80-250mm f3.8 Z250
  • Tamron Adaptall 70-350mm f4.5 CZ735
  • Tamron Adaptall 500mm f8 55BB (needs a bright day and high-contrast target, but it works)
  • Vivitar (Tokina) TX 400mm f5.6
And two of these make the grade because the manual lenses were such astonishingly good value.

When I am going out with just fast primes, I do pack the 1.7x AF for the potential additional reach, and to fill the gaps, but I seldom deploy it.

So, whilst I recommend the Pentax F 1.7x at the price I paid for it, I would never be able to justify paying $200 plus.
Senior Member

Registered: March, 2010
Location: Svealand
Posts: 172
Lens Review Date: August 10, 2014 I can recommend this lens: Yes | Price: $185.00 | Rating: 10 


Well what could I add after reading cyberjunkie's and so many other great rewiews of this adapter. I can only say that it's really strange to see that my manuall lenses now have AF. I will try this adapter with my manuall lenses and tell you how it worked with the different lenses.
Veteran Member

Registered: March, 2010
Location: Bologna, Amsterdam, Chiang Mai
Posts: 1,094

10 users found this helpful
Lens Review Date: February 15, 2013 I can recommend this lens: Yes | Price: N/A | Rating: 9 

Pros: everything, if used correctly
Cons: everything, if used the wrong way

After reading a few of the previous user reviews, i think it's better to try to understand what this piece of equipment was meant for. when it was manufactured.
Before buying any tool, the first thing to do is to realize what IT IS, and what IT IS NOT.

What it is NOT:
1) a conventional converter, there are cheaper and better choices, either 2x or 1.4x
2) good for zooms; even a conventional converter does not mate well with zooms!
3) a replacement for a full-fledged AF system: the focusing of the lens must be roughly adjusted beforehand
4) a converter for AF lenses (there is not such a thing - EDIT: sorry, i didn't check! I have seen them on sale... too expensive, IMHO)
5) compatible with slow MF lenses (it should not lock the focus with lenses slower than f/4.5, better if little faster, if there is scarce illumination... but i had success a few times with a f/5.6 lens, so i guess it's dependent on the amount of available light)

What it IS:
1) the only way to turn a compatible MF lens in an AF one
2) a decent 1.7x converter, if used with the "right" lenses
3) perfectly compatible with the electric contacts of KA lenses, allowing to use any exposure mode with modern DSLR cameras

Super-fast lenses apparently don't mate well with this converter, but i have little personal experience about it.
I didn't notice any particular problem with my 1.4/50mm M, but i didn't use it wide open with the AF converter.
I am sure that it performs admirably with a Tamron 2.5/90mm Macro, with P-KA Adaptall-2 adapter.
While high magnification macro photography is done strictly in MF mode, macro "hunting" at much lower magnifications can benefit from AF focusing (which allows to shoot quickly).
I have been very satisfied by the Tamron/1.7x AF combo: if we add the conversion factor to the crop factor of the APS-C sensor, we can get a powerful macro tele which allows to shoot small critter from a distance, filling the frame with the subject.
In such condition, a monopod and an off-camera fill-in flash would be extremely helpful.
I used the AF converter with a 2.5//135mm K, with decent results, but the best match are A lenses.
The way i use the camera, K and M lenses aren't exactly super fast to operate... so there would be little meaning in turning them into autofocus ones, to save one or two seconds!
The other lenses i own are not perfect candidates for the AF adapter, as wide angles (albeit sometimes usable as "normal" on DSLR) don't match well with optical converters. Retrofocus design isn't made for duplicators!
Most of the others, for a reason or another, are not good for this converter.
I must admit that i have a couple of A* lenses (1.4/85mm and 2.8/200mm) which could be a good match, but i never had the heart to bring them with me when i use the 1.7x AF. That is, when i leave for a naturalist/macro outing in the deep of the bush.
For other types of pictures, i prefer to use manual focusing, so the AF adapter isn't needed.
Someday i will test those lenses in AF/converted form, just for curiosity

Depending on the lenses you own, and how you use them, this adapter could be either extremely useful, or worthless.
There are no other tools that can be used in its place.
For what it does, it does it extremely well, provided that you use it with the right lenses.
One advice: if you want to know in advance how this adapter would mate with your lens, and you can't find the right informations on the web, it is very likely that a lens that works well with a 7-elements duplicator, would also give a satisfying IQ with this AF teleconverter.
Senior Member

Registered: August, 2007
Location: Los Angeles
Posts: 233

4 users found this helpful
Lens Review Date: January 15, 2013 I can recommend this lens: Yes | Price: N/A | Rating: 8 

Pros: Grants limited AF to MF lenses. Not a 2X teleconverter
Cons: Can't use as teleconverter for AF lenses. Doesn't work for screw mount lenses either.

This is a really strange animal.

For years, I held off on getting one because the prices are so high and I generally don't like teleconverters that much (due to the lost of quality and my being a wide angle guy).

That being said, I really love manual lenses and having even limited AF on them sounds really appealing. Finally, I found a good price on one and decided to give it a try.

This thing gave me one pleasant surprise and two bad ones.

Good news first: The lost of quality is pretty minimal, better than most teleconverters and better than a 2x tele for sure. Also, despite its limited AF capability, it is pretty easy to focus into "close enough" range for this thing to take over. For "A" class lenses, it also correctly translates the f-stop to compensate for the loss of light.

Bad news 1: This thing can't be used as a teleconverter for natively AF lenses unless you want to lose your full AF and live with a "limited" AF! I was shocked that no one ever mentioned this! When mounted, the camera's AF only moves the AF of the teleconverter, the screw doesn't reach the actual lens at all, so now your normally fully AF lens is a limited AF lens! (I guess I should have downloaded the manual before buying, but it just never occured to me.)

Bad news 2: This doesn't work with M42 screw mount lenses even though you have an original Pentax M42 adapter. Apparently, the aperature lever clicks something on this thing and it allows the AF function to engage, since M42 lenses don't use the K mount aperature lever (it uses a pin), it just functions as a Non-AF teleconverter if you mount screw mount lenses to it. This sucks.

If you use this thing with "A" class lenses, it works just as advertised. Allows you to focus almost as quickly as an autofocus lens for the price of 1.5 stops of light and a 1.7x magnification.

If you use it with "M" and "K" class lenses, it still works OK, of course you have to use your camera in M mode with the green button unless you just shoot wide open.

If you use it with any autofocus lenses, you've just downgraded your lens to a semi-autofocus lens.

If you use it with any M42 screw mount lens, then it's just a plain old dumb tele-converter.

So the guy who wrote the review saying that this isn't a teleconverter was correct. This is a device meant primarily to convert "A" class lenses to partial AF lenses. It just happens to provide 1.7x maginification. In that regard, this thing works just perfectly.
New Member

Registered: January, 2012
Posts: 4

4 users found this helpful
Lens Review Date: January 27, 2012 I can recommend this lens: Yes | Price: $400.00 | Rating: 9 

Pros: gives me a good portrait lens with 50mm f1.7
Cons: none

I got this gadget on a hunch -- one of those impulse purchases on e-bay. When I combine it with with my manual 50mm f1.7, it becomes an f2.8, 85mm lens -- very useful for portraits on my K5.

But here's the absolute plus: the portraits that the combo creates are much more interesting attractive, and warm than those same subjects taken with my 77mm ltd. I love the character of these new pics. The colors are more accurate, the subjects more calm and alive than in pics with the more clinical 77mm -- a lens I also like.

The combo has become a very special lens for me.
Site Supporter

Registered: October, 2010
Location: Paris, TX
Posts: 12

9 users found this helpful
Lens Review Date: January 20, 2012 I can recommend this lens: Yes | Price: $125.00 | Rating: 8 

Pros: good build quality; performs as designed
Cons: overpriced if $400; must carefully select lens used with it (i.e. 200/2.5, MF 300/2.8)

Back in the day Pentax had a mighty lineup of manual focus lenses for film bodies. Then oops Minolta started the AF revolution, Canon and Nikon jumped on board, and Pentax... well they created the little 1.7x AF Adapter.

Skip forward many years, and I wrote a review on this adapter. Today I am completely revising that review upwards. I have changed my mind about the 1.7x Adapter, rating it 8 instead of 7, and going with a 'yes' recommendation.. It could be because I'm thinking of selling my spare one soon.

Other reviewers tell about the pros and cons of this lens. They mention the occasional sky ooohigh price. If I were offered $400 I would try to tell the buyer he could spend less for something more useful. But the average of recent ebay 'sold' listings is a bit over $200, which could be a fair deal, counting for inflation since it first came out.

If you have a certain lenses it can be useful, though sometimes slow to get the shot. My favorites, with FF or digital crop factor, in no particular order:

A* 200/4 Macro [yummie]

M 200/2,5 [510mm / f5.1 in a small package, though heavy and slow to focus.

A 50/2 or A 50/1.4 - especially good full frame combos.


most any 90 - 100 lens: normal or Macro, MF or AF, f2.8 or 4.

M 300/f4

old Cult Classic Vivitar 90-180/f4.5 zoom, with tripod foot - see M200/2.5.

I never had the A 200/4 or the 400/5.6 so can't comment.

I tried it on my FA* 600/f4 several times but could not get the Adapter to quit hunting, not even with the 600 set to Manual Focus.

Look for my spare to be for sale somewhere, sometime. I just don't shoot much beside family snaps anymore.
Site Supporter

Registered: January, 2011
Location: United States
Posts: 63

3 users found this helpful
Lens Review Date: July 13, 2011 I can recommend this lens: Yes | Price: $50.00 | Rating: 10 

Pros: Amazingly little quality loss, adds AF to manual lenses, reasonably fast AF
Cons: Nothing really

I have found a NEW unused copy of this beauty online. It was marked down CLEARANCE for $30 and I paid $20 for overnight shipping. For the price I paid, I must say, this is a spectacular piece of glass.

I have a nice collection of Pentax A lenses (50mm 1.7, 28mm 2.8, 135mm 2.8) and this converter adds autofocus to all of them at only one and half stop light loss. Having this adapter is like having three more primes that has AF. I have always liked manual focus lenses better than AF lenses, so having to approximate focus first does not really bother me. I have also tried this with my DA 18-55 and 55-300 and Tamron 70-300. Works alright with them as well. Since these are not very fast lenses, the performance is not nearly as good as my fast primes. I don't use my zoom lenses very often anyway.

Overall, I think this is a great addition to anyone's collection. And, if they have Pentax manual lenses, then this is a MUST as it will produce incredible versatility.
Site Supporter

Registered: November, 2010
Location: California
Posts: 2,223

5 users found this helpful
Lens Review Date: April 20, 2011 I can recommend this lens: Yes | Price: N/A | Rating: 10 

Pros: It convert manual lenses into Autofocus and also multiplies the focal lenght
Cons: Takes almost 2 f-stops of light

The reason I chose Pentax over Canon is because I could make some manual lenses AF with this converter. So, this is a must have adapter. This lens is like a wife, it it good but this or that, but you have to have one. Really, this lens works fine with my Pentax M50mm, f1.4, f1.7, f2, M28mm f2.8, M135mm f2.8, M200 f4, but did not work well with my Pentax M400 f5.6 although it tried. It works fabulous with my Manual Tamron Adaptall SD 300mm f2.8. Sometimes I wish it were 1.4x instead of 1.7x. I hesitated to buy it, but after a while, and after having the 300mm f2.8, I had to have it. So, go and get yours quickly. It also works well with all my FA and A lenses. It is a must with my PKA and my Adaptall lenses. I have two and looking to get one more.
The photo below was taken with my Tamron 300mm f2.8+ the 1.7xAFA

Here is a photo with the Vivitar 105/2.4:

Vivitar105mmf2.5&PX1.7xAFA-BigFly-1 by Palenquero, on Flickr

Vivitar105mmf2.5&PX1.7xAFA-Moth1-1 by Palenquero, on Flickr
Add Review of SMC Pentax-F 1.7x AF Adapter

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