I bought this item brand new from ebay store Wolfes-Camera and the price I paid was fairly decent for $69.99. I doubt initially if the AF would work at all when I purchased this item. And I tried it on both of my Tamron 28-75 f/2.8 and Tamron 70-300 Di LD Macro and auto focus works though there is more obvious focus hunting for the long Tamron zoom in the long end
The TC has all the 7 electrical contacts on the rim outside along with two golden SDM contacts inside. It has 4 groups with 4 elements and it has MC coating as noted in the specification.
Auto focus is slower than the Tamron 1.4x Pz-AF MC4 TC. Perhaps the field of view is narrow at 510mm, a busy surrounding and low light will have it hunt for focus. Once target is in focus, it is not as bad. And I am more than thrilled to have a 510mm for bird photos from a good distance. Some test shots with Tamron 70-300 Di LD Macro in ISO 400 and mostly f/8.0.
Impressions & Notes:
- AF obviously works and I have tried it successfully on Tamron 70-300 Di LD and Tamron 28-75 f/2.8
- AF is slower in Promaster 1.7x as compared to Tamron 1.4x TC
- I am extremely surprised that PF/CA are not seen yet with the TC. I shot the similar locations when the bird is resting with backlighting branches, Tamron 1.4x TC all end up in purple tree but not so with the Promaster 1.7x. I am hopeful that this TC works better with PF/CA control.
- Color and contrast are a bit flat but reasonable in the shot
- 510mm is very achievable with the TC and IQ are yet to be confirmed with more use
- I am happy as a clam to get a 510mm rig with this TC
- The Promaster weighs 4 oz and it is not that much bigger than the Tamron 1.4x TC and hand-holding with Tamron long zoom is very feasible. Though SR stays at 300mm for the long end and my short trial seem to have reasonable sharpness.
- Most of my initial test shots range from 10 to 15 feet away from the birds, a longer distance testing will help to judge the TC.
- IQ with shots in close range shorter than 30 feet seems very good, SR at 300mm in long end still helps in shorter distance shooting.
- IQ at full extension to 510mm with subjects at far distance seem to have more problems with blur images.
- In all testing, AF works effectively in good lighting condition.