SMC Pentax-F 1.7x AF Adapter Reviews - Pentax K-mount Teleconverters and Adapters (2024)

suitable until f 4 lenses

stop down your lens to f 5.6-8 in oder to improve sharpness and for less CAs of your personal lens

Colour fringings

for all A, K and M lenses, best results with 1.4/50 and 2.5/135. Even Tokina 3,5/35-70 with 3 achromatic elements gives you sharp results free of visible CAs. Only Pentax A 4/70-210 shows some CAs, because lens itself has already some.

Sharpness (100 ISO and f 4 = f6.8 with 1.7x)

with Pentax K-5 and 1.4/50 f.e. approx. 65 LP/mm available (center), additionally with 1.7x only approx.50 LP/mm (16MP), with PENTAX K-X 50/35 LP/mm (12MP)

with PENTAX K-S1 approx. 75/60 LP/mm (20MP)

with FUJI x-T100 - without AF - approx 90/70 LP/mm (24MP)

Affordable for macro shootings?

YES - especially with achromatic diopters - but pay attention,

Very good results with MACRO 4/100, but the 1.7x converter "hates" extension tubes

if using A-lenses, aperture is transmitted

for high magnifications pictures can be shapened by PhSh, in order to improve results

And the competitors?

the Nikon 1.6x AF converter is not so well corrected and nearly no more to find. SONY-MINOLTA hasn't neither such a lens, nor CANON. No other camera manufacturer allows anti-shake and AF with vintage MF-lenses - only PENTAX! Thank you very much. ((a friend of mine reported that the actual version V of the SONY A-adapter to E-cameras transmits only the aperture, not AF for his MINOLTA 2.8/80-200 APO - for 250 bucks! - this is absolutely foolish. he switched to the older IV version, in order still to get AF function))

highly recommended

Phil Martin
It’s quite simple really.
The AF converter contains a lens element that is driven by the autofocus linkage from the camera. This lens element focus, just like a normal autofocus lens. So the converter is actually an autofocus lens.

You attach a manual focus lens to the converter and you don’t turn the manual focus ring.

However, the focus range of the AF converter is limited. You can set the manual focus lens to infinity, this means the AF converter will focus on medium to infinity, but it can’t focus on shorter distances.

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Richard McAlpinI had one of these with my SF-1n cameras back in the early 1990s but I did not find it to be practical or enjoyable. Its operation is good but not great--certainly not on a par with autofocus Pentax lenses. Part of the problem is that multiplying the focal length by 1.7x makes wide angle and normal lenses much less useful, and even for telephoto lenses losing more than a stop of light is a poor trade-off to gain mediocre autofocus performance. I don't recommend buying this except perhaps as a historical curiosity.

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Frederik Van AsscheI have two or three, I believe. Also SMC so sharpness and rendering impact is mostly not noticeable to the untrained eye. Works great, even with DA*’s. A few quick facebook quality pics from last summer in Iceland with DA* 60-250 + F 1,7x.

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Michael JorshI have one and use it rarely. Sounds like a food mixer! However when used with a good lens, like my 300mm DA*, optics are good. I usually switch to manual focus because can be very inaccurate.

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Gerjan van OostenRising contributor

I have tried the AF Adapter on an AF Pentax with various Takumar lenses from 24 to 200 mm. The camera can focus perfectly, even with lenses that have a maximum aperture of f/4. As long as there is sufficient light and subject contrast, focusing is fast and accurate. Under a cloudy sky and with subjects that have little contrast, focusing fails!

As the focal length increases, the shortest focusing distance becomes progressively
longer. With a 24 mm lens you can still focus to the same distance as with the “bare”
lens. With a 50 mm lens, however, you get to 1 meter (instead of 45 cm), with an 85
mm lens you get to 2.5 m (instead of 80 cm), with a 120 mm lens you get to 5 m (instead of 1.2 m) and with a 200 mm lens you get to 12 m (instead of 4 m).

The best way to use the AF Adapter is to focus manually to roughly the setting you
need for a specific subject and let the camera use the AF Adapter to take over the
actual final focusing. After getting used to this method, it works very comfortably.

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Douglas StemkeTop contributor

The lens needs to be fairly fast. The slowest lens I used it with was a 300mm f4.5 F. I find it doesn't work with lenses I thought it should. I treat it more as a teleconvertor than as an autofocus convertor.

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Geff GascayTop contributor

I have one of these, as well as the HD DA 1.4x and a couple of the Tamron PZ-AF 1.4x TC’s that I use. All of these specific TC’s have pass through data pin contacts to allow communication from the lens to select the MTF curve and set aperture from the body if the taking lens has that ability.
As others have said, it is essentially a good quality (depending on individual condition) 1.7x teleconverter. It also has a moving set of elements that allow focus adjustments to be made by most camera bodies on most lenses.
Is it perfect - no, but it does work, often with great results for fast telephoto prime lenses. The light loss is -1.5 stops so the camera used and the AF central spot point makes a big difference in the AF accuracy. You don’t want to try to use anything other than center spot AF and AF-s, but with those settings, it generally works very well.
The most common lenses it was paired with originally, were the older manual 100mm f2.8 providing 170mm f4.8 or the ubiquitous 135mm f2.8 giving 230mm f4.8, providing good AF telephoto upgrades to those lenses.
Some other good and often used examples are the 300mm f4/4.5lenses become 510mm f6.3/7.1 and in the other direction, an 85mm f1.4 becomes a 120mm f2.4 or the 50mm f1.2 becomes an 85mm f1.7 to round out some of the common focal length options.

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Galen McAllisterGerjan van Oosten and Geff Gascay have outlined the strengths and weaknesses fairly well. I use mine on my K-1ii and K-20d with my "antique glass collection"... mostly telephoto (300mm f4, 400mm f5.6, 1000mm f11 SMCs). "Pre-focusing" to nearly correct and then letting it do the rest works reasonably well. It takes a bit of practice to learn what it will and will not do for you. I get good enough shots for most people to enjoy a print at around 12x16", but dedicated pixel peepers will not be happy... for that matter, dedicated pixel peepers aren't happy with the sharpness of the old SMC lenses when shooting without it!

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Roger ListerRising contributor

I snagged one last year, as I found it confused me. Until... I used it with my older Tamron SP 300mm f2.8. Maybe I got a really good one. But it does impress me. Don't expect it to do the whole range, or be in a hurry. You need to keep your focus ring in a range. And keep moving it if your subject keeps moving closer or further...

I found it works well with my Tamron SP 200-500MM f5.6.

It focuses best with my K3ii, but does well on my K5 and K30. For giggles, I tried it on my *ist DL, and it is super slow.

I have yet to try it with other lenses.

Pentax was conservative in their compatibility criteria - this unit works adequately with a lot of lenses that are far slower than the recommended f2.8 aperture. I paired it with my K-5II and SMC-A 400mm f5.6 and it worked perfectly in bright conditions. Optically, I'm not sure I'll use this combination much, as the results don't appear to be as good as the 400mm cropped to the same size as produced by the 680mm combination. I doubt it's any sharper than my Sigma 50-500 f4-6.3 with its matched 1.4x converter, either. That's fine, I got it primarily to mate with the 135mm Rokinon for a sharp, autofocus mid-range telephoto prime. Pentax User (https://www.pentaxuser.com/review/smc-pentax-f-1-7x-af-adapter-review-2233) tested the 1.7x AF with the SMC-A 50mm f1.7 and highly recommends this extender. Owning that particular 50mm myself, I'd never use that combination as it does nothing my Tamron 90mm f2.8 AF Macro can't do with less complexity and better resolution. I have no intention of using it with any of my SMC-A zooms, either.

Recommended if you can find an example in acceptable condition and have enough vintage and/or manual focus primes to justify its price.

I mean, I have paired mine with a Pentax M 135mm f3.5 and worked perfect, but specifications say that it goes only with lenses up to F2.8 or lower.

It brings a 1.7 times magnification of your image and overall it works very really well. Of course, pair it with F Series lenses and probably will be the best combination.

As this TC is quite compact (for it's age) you can easily carry an F 28mm of an F series 50mm f1.7 and have two lenses in one the 50mm and the 50x1.7 = 85mm lens in you.

I find it not very accurate with my zoom lens at 300mm but probably it is because zooms at the end (its a 100-300mm lens) tend to prone to loose sharpness. Not in this case but probably attaching the TC to it then it produces this effect.

Other than that this is a gem no other brand has ever been able to create that I know.

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

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)

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)!

.

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

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.

Downsides?
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.

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)

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.

• 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

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.

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.

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.