Kenko 1.4 teleconverter on tammy 28-75

Hi everybody, does anyone have any experience using a 1.4 converter with a 28-75mm Tamron Thanks,
Thumbsup

If someone hasn't already done testing, I have both of the items in question, and can try to perform some tests this weekend.

TCs are not really meant for wide and/or zooms. I wouldn't expect much.

gasrocks wrote in post #6902773
TCs are not really meant for wide and/or zooms. I wouldn't expect much.

Kenko Pro 300 works perfectly with my EF 24-105.

Wilt wrote in post #6902760
If someone hasn't already done testing, I have both of the items in question, and can try to perform some tests this weekend.

That would be great let me know Thanks,
Thumbsup

Filthy McNasty wrote in post #6903610
Kenko Pro 300 works perfectly with my EF 24-105.

you mounted a 24-105L to a 3X teleconverter?

One question: Why????!?!?!?!?

f/4 + 3-stops = f/16!

Thumbsup wrote in post #6902697
Hi everybody, does anyone have any experience using a 1.4 converter with a 28-75mm Tamron Thanks,
Thumbsup

It should work, mechanically speaking. But given the focal range you're looking at, you'd really be better off just cropping. There is bound to be IQ loss. Given that the Tammy is f/2.8 the 1-stop of loss in light makes it an effective f/4. Which is still usable.

One thing I've never tested is this. Given a non-reporting TC - mount a f/2.8 lens to it and shoot the same shot with it both on and off TC. But at same effective focal length. I.E. 70mm w/o TC @ f/2.8. and 50mm (50 x 1.4 = 70mm) @ f/2.8 with the TC. So you get the same framing, both at the same maximum aperature. Remember that the 50mm @ f/2.8 is losing a stop of light so the exposure will be longer by one stop. The thing I'm curious about is the loss of light gonna affect the bokeh.

I haven't got a zoom thats faster than f/4 with which to make this test. All my fast lenses are primes.

Anyone care to run the test and put up the samples?

-Alan

The larger issue has already been declared...that a teleconvertor was designed for use with a 'telephoto' optical construction. So the Tammy would be fairly questionable, at least in theory, in the 28-50mm range, and somewhat questionable in the 50-75mm range for reasonable results. I have used a teleconvertor on a 'normal' in the past, but that was in my youth and before digital made measurebation so easy to do!

nureality wrote in post #6904424
you mounted a 24-105L to a 3X teleconverter?

One question: Why????!?!?!?!?

f/4 + 3-stops = f/16!

......... it`s 1.4 x TC

Though in Hebrew and in Nikon, that lens was tested here
http://www.kramery.com …icles/detail.as​p?iArt=407

here is the tamron 28-75 with a 1.4X tc. In the article the full exif is next to the photo, it is a non-reporting tc so the specified effective aperture is not multiplied by the tc rate.

It wouldn't matter if your TC was a reporting one or not with the Tammy 28-75, since the lens doesn't have TC contacts. For instance, my Kenko Pro 1.4x (which IS a reporting TC), reports wonderfully on my 70-200L, my 200L and my Sigma 150. It didn't report at all with my drainpipe, nor on any other lens I own, as they don't have the extra 3 pins to report to the TC.