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Promaster Spectrum7 AF 1.7x

Reviews Views Date of last review
7 19,895 Sat August 18, 2018
Recommended By Average Price Average User Rating
100% of reviewers $106.14 8.43
Promaster Spectrum7 AF 1.7x

The PROMASTER 1.7x Autofocus Teleconverter is compact, lightweight and allows the focal length of your lens to be extended by a factor of 1.7.

The 1.7x factor has a minimal reduction to your effective aperature of only 1.5 stops. The PROMASTER 1.7x Autofocus Teleconverter communicates with most lenses for full compatibility.

* For use with maximum aperature f/4.5 or higher
* Lens Construction: 4 Elements in 4 Groups
* Lens Coating: Multicoated
* Length: 25.4mm
* Weight: 4 oz.
* Pouch

The Kenko Pz-AF 1.5x Teleplus, the Promaster Spectrum7 AF 1.7x, the Vivitar Series 1 1.4x and the Tamron-F 1.4X Pz_AF are believed to be the same or slight variants of the same TC, and Kenko has been suggested as the manufacturer. dpreview thread here.

This thread is a discussion of diffraction issues when using TC's.

1.4x Tc's discussion/comparison thread.
Price History:

Add Review of Promaster Spectrum7 AF 1.7x
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New Member

Registered: June, 2014
Location: Sydney
Posts: 12
Lens Review Date: August 18, 2018 I can recommend this lens: Yes | Price: $15.00 | Rating: 8 

Pros: Sharp, able to use with all AF lenses (see text)
Cons: None
Camera Used: Pentax K-7   

I bought this lens from a jumble sale for $AUD 20 (I think they should have priced it at $200 but they made a mistake - have seen these for up to USD$280 on e-bay !!) and on inspection, appears to have had little, if any usel. Mine is branded as a Rokunar lens and on inspection it appears to be a rebranded Promaster/Tamron item as mentioned by a previous reviewer. When attached to any Pentax or Sigmas autofocus lens (including my Sigma 70-200mm F2.8 EX DG APO Macro HSM II*) focussing is quick and accurate even in room-light. There is some hunting with the Pentax SMC Pentax-DA 35mm F2.8 Limited Macro however I put this down to a characteristic of the lens rather than the teleconverter. All in all a great buy and I am very happy with my purchase !

*Note: My Sigma 1.4x DG EX APO Teleconverter when attached to the 70-200 does not provide a stable readout of aperture when set to the 'A' setting, nor is autofocus capability enabled. The Rokunar TC works perfectly out of the box as it provides full AF and metering functionality with this lens. So grab one of these if you can find one of these at a reasonable price. highly recommended.
New Member

Registered: December, 2013
Posts: 8

2 users found this helpful
Lens Review Date: February 23, 2014 I can recommend this lens: Yes | Price: $90.00 | Rating: 9 

Pros: very sharp, low CA
Cons: poor AF-compatibility with SDM lens, some contrast loss
Camera Used: K5iis   

It has similar optical quality in comparing to Kenko Teleplus MC7 2x or Pentax af-adapter 1.7x. On equivalent aperture settings Promaster is almost twice faster then Kenko 2x and more sharper than Pentax 1.7x. TC was tested with Sigma 105/2.8 EX Macro and K5iis. Acceptable IQ loss on the border frame at F3.5. Focus is fast. Very nice results. DA 50-135 hunting all the time, AF does not working properly on K5iis. Sigma 17-50/2.8 EX HSM has the same negative result. I suppose it is because of firmware. So it is highly recommended to use TC with screw drive lenses.

I have performed many tests with different lenses and I was very impressed by the results of this TC. Optically it is one of the best TC I have ever seen. Unfortunatly I did not managed to use it with SDM/HSM lens but it works perfectly with screw drive lens, especially after upgrading camera firmware up to a last version released for pentax HD 1.4 TC.

For example I have tryed Promaster TC with DA 55-300 at F8 up to 200mm and at F11 up to 300mm. It is highly recommended to use such combination in a bright daylight otherwise AF speed will be lowered or AF will hunting after 200mm. Also I would recommend to use post processing to increase picture contrast or set camera profile to do so. If all is done right you may have 93-510mm tele-lens with extremally light weight. It is very handy during traveling. And you may always remove TC for a shooting in a lower light conditions.
New Member

Registered: January, 2010
Posts: 23

2 users found this helpful
Lens Review Date: October 4, 2013 I can recommend this lens: Yes | Price: $149.00 | Rating: 9 

Pros: Sharpness, 1.7x
Cons: Need a good high ISO performer camera; hunt a bit

1.7x demands good lighting. When shooting at 300mm, it gives 765mm in 35mm equivalency. The Kx in-camera stabilization does not help much. I need to bump up the ISO to 800 or more to possibly get a fast shutter speed and keep the aperture under f9-f10 in order to maintain workable DOF for the creature like dragonfly. To my disappointment, Kx's high ISO setting gives significant noise even under good light and with the "Natural" shooting mode. I recall Kx is rated the best high-ISO APSC DSLR when it first came out, but its actual performance really disappoints me. The resolution can be compromised when I try to suppress the noise in post processing.

Back to the teleconverter, I think Promaster 1.7x performs really well. Once in focus, you could hardly see the degradation in IQ. AF hunts a bit though but it could be the camera too.

765mm (35mm equivalent), taken with K-x and DA 55-300mm, ISO = 1000, 1/640, f/13. The uploaded image loses some resolution!

765mm (35mm equivalent), taken with K-x and DA 55-300mm. ISO = 800, 1/400, f/8. The uploaded image loses some resolution!

taken with K-x and DA 55-300mm

taken with K-x and DA 55-300mm
Site Supporter

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

2 users found this helpful
Lens Review Date: January 18, 2011 I can recommend this lens: Yes | Price: $129.00 | Rating: 9 

Pros: Neat, easy to use, works fine with Kx and FA lenses- the best in the market
Cons: Noisy - but does the job

I bought this by mistake. I meant to buy the Pentax 1.7x adapter for my M lenses. However, I kept it to use it with my FA lenses and it does work for fast lenses mostly. I use my FA 50mm f1.4 to obtain a focal distance of about 80mm and the fstop goes to f2.5, still fast. I used it with my FA 100-300mm f4.7, and it moves it nicely, but it slows down a lot at 300 (x1.7) or about 500mm. So, I do get a to use it with this lens at at 350-400mm well in decent light conditions. The lens FA100-300 is very sharp, probably the best sharpness in that range of variable f. I have a 2x Sears for my M-50mmf4 lens and obtain formidable macros. Better than the extension tubes. Although someone said bad things of the lenses in the converter. This is a good thing to have, but do not expect much. I tried it with my kit lenses DA 50-200mm and the results were bad. Althougth it moves and focus, the image enlargement was not there, and the DA 50-200 is a good lens. I guess no TC works well with the DA lenses. I see now an explosion of those converters on eBay and I am afraid, because the cost is almost ridiculous, that says a lot about the lens they use.
Veteran Member

Registered: November, 2008
Location: The Untied States
Posts: 1,881

2 users found this helpful
Lens Review Date: December 25, 2009 I can recommend this lens: Yes | Price: $125.00 | Rating: 9 

Pros: Incredible IQ, virtually no sharpness lost; Smaller than 2x and more reach than 1.4x/1.5x
Cons: Some loss of contrast; Slows AF speed considerably; Increases AF noise

This is a fantastic TC, plain and simple. I believe it's a Tamron rebranding, and it shows. Superb image quality with virtually no added defects to the IQ -- that is, just like any other teleconverter, this with "multiply" the defects already present in your lens, such as increasing the level of CA, and decreasing the sharpness. However, many cheaper teleconverters not only have this unavoidable mathematical property, but also add a lot of extra CA, resolution loss, coma, contrast loss, etc to the final image due to poor construction and material quality.

This TC is different. I see virtually no resolution loss in a lens that already outresolves the sensor of my camera, such as a professional lens like the Tamron 70-200mm f/2.8. It will only multiply the amount of CA present in the lens by roughly 1.7x, instead of adding much more like other TCs. So basically, good input, great output with this TC, all with the added benefit of considerably longer reach.

There are small problems with it though. AF is slower, noisier, and hunts more -- I almost exclusively use MF on the Tamron 70-200/2.8 that I couple with this TC. But it doesn't really impede my shooting style, and AF does indeed still work if you need it. There is also some considerable contrast loss, but this can be fixed almost completely in photoshop or similar, or even an in-camera image mode.

I prize IQ more than most other features that usually combat with IQ in lenses, such as AF speed and accuracy. For that purpose, this TC excels all others I've used to date. You can see some pictures taken with this TC and the aforementioned Tamron 70-200/2.8 here:
Senior Member

Registered: July, 2008
Location: Bhubaneswar, India
Posts: 104

2 users found this helpful
Lens Review Date: May 28, 2009 I can recommend this lens: Yes | Price: $135.00 | Rating: 7 

Pros: Price, image quality, fully supports non-SDM AF
Cons: Doesn't lock focus on SDM AF lenses, noisy AF screw, increases CA slightly, doesn't record true EXIF data hence affecting Shake Reduction performance

I have been using this TC since December '08, primarily with my Pentax DA* 300mmF4. I bought this TC on a gamble, crossing my fingers that its twin Power Zoom contacts will allow AF on my SDM lens. Well, they do, partially. The lens begins hunting with AF on but doesn't lock focus. However, in time, I learnt to 'coax' it to lock by very gradually pressing the AF button until it locked- that allows me to keep track of not-so-fast moving birds now. Funny, but works, in most cases at least Taping the SDM contacts to try to 'fool' the DA* lens and my K 10D into thinking that a K 100D might be mounted and hence activate the screw drive AF failed to work.

That apart its very good value for money and auto focuses fine with screw-drive AF lenses like my Tamron Di 90mm f/2.8 macro. But the screw drive shaft is very noisy. Image quality is good and I don't think one can expect much more from a teleconverter of this price and age. It doesn't alter EXIF data correctly and the images still say '300mm, f/4' where they should be saying '510mm, f/6.8' causing the SR in the body to become less effective as the body still thinks that the focal length is only 300mm.

I like the 1.7X multiplication factor as it is a good compromise between reach and speed, i.e., 2X and 1.4X, but I think I'd definitely pick up a nice new SDM WR 1.4X TC if Pentax comes up with one. Also, I think I'd be tempted to pick up a Kenko 1.5X version that supports SDM AF. But at the same time, perhaps I would still keep this. If Pentax never comes up with a DA* 500mmF4 SDM I'll be forced to buy a Sigma 500mm/4.5 non-HSM sooner or later and then this TC will be useful.

Some sample images made with this TC and the DA* 300mF4 can be seen here:


Registered: March, 2007
Location: chicago burbs
Posts: 3,381

1 user found this helpful
Lens Review Date: April 2, 2009 I can recommend this lens: Yes | Price: $99.99 | Rating: 8 

Pros: Inexpensive, compact, AF works with Tamron 70-200mm and Pentax f*300mm
Cons: loss of 1.5 stops, some image degradation (both to be expected)

I've used this with good results on theK20D with the Tamron 70-200mm f2.8 and Pentax f*300mm f4.5. The converter allows full metering and auto-focus with both lenses. The AF is a bit slower on the 300mm lens and there is some focus hunting, both expected from using a teleconverter. Images are reasonably sharp and I find the ability to 'get the long shot' vs IQ loss to be a worthwhile trade-off.

Update: Same results using the above combo with the K7 body

For an in depth review, visit:
Add Review of Promaster Spectrum7 AF 1.7x

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