Tamron AF 1.4x Teleconverter for Canon Mount Lenses: Customer Reviews & Product Details

I bought the Tamron 1.4x Teleconverter because I'd rather loose one f-stop, than two (which is what would have happened had I bought the 2x one). I use it mainly with a Canon 70-300 IS USM lens and on a sunny day it works great and auto-focuses with no problem at all.

However, I've found that on a heavy overcast day, or a rainy day, or in the early morning, or late evening, (anytime you have "low light" conditions) the Canon lens finds it harder to auto-focus with the 1.4x attached. But, by using the manual focus ring on the Canon lens, I can get a fairly sharp image. Usually, I'll just snap several pics as I slowly turn the manual focus ring on the lens. One of them will usually be in good focus.

In short, I'm enjoying the Tamron 1.4x Teleconverter, but more so on a sunny day.

The Tamron teleconverters will not work with Canon's EF-S lens line for cameras with APS-C sensors. The Canon lens will not mount on the teleconverter due to the changed mounting configuration (white dot) on these lenses. The Tamron teleconverter works as advertised with full frame (EF) lenses.

I have been using the 1.4 teleconverter with a Tamron 75-300 lens that's pretty slow (f5.6 at 300), so I can only use manual focus. I have read that teleconverters will give images that are no better than what you would get by cropping and then enlarging with a regular telephoto. I am glad to say that I have found the images with this teleconverter to be much better than that. When I was cropping and enlarging images taken at 300 mm, I was able to see identifying marks on birds but the images themselves were really bad. The images with this teleconverter are much better, though it's true that I've only used it in daylight and with a fairly high ISO to get a decent shurtter speed. I find some of the images to be a bit soft around the edges, but am overall quite pleased with this relatively inexpensive solution to needing more reach to take pictures of birds and wildlife. Someday I hope to be able to afford a really good, really long telephoto. Until then, this teleconverter and the Tamron 75-300 together cost about one fourth the cost of the cheapest good long telephoto I've seen.

I opened the box and saw those descriptions were missing from the Amazon product descriptions:

From Tamron manual in the box -

"For best results, use the Tamron tele-converter with telephoto lenses ranging from 50mm to 135mm."

"When used on Digital SLR cameras: This teleconverter is not designed for digital use. We do not guarantee its performance when used on Digital SLR cameras."

Am using this teleconverter on my Canon 40D with a 200L lens mostly for shots of wildlife. The auto focus works great, and I can tweak it manually if desired. With wildlife standing in their native habitat of brush and trees any drop off in sharpness has not been noticeable.
Have also tried a few long range shots of mountains with unusual lighting and cloud formations. The results have been great so far.