Originally posted by Malsi Hi,
Thank you for your fast answer
! Do you know if it is “neutral” regarding the lens and camera characteristics (AF still working...).
No not all teleconverters offer contacts for aperture, or AF couplings or the power couplings for HSM lenses, you need to know what you are looking for in very specific terms. Additionally, depending upon your prime lens, and aperture, AF will not work even if the TeleConverter (TC) is electrically and mechanically compatible. From my experience if the combined aperture of the lens + TC is slower than F6.7 then AF simply won't work due to the low light.
Also, SIGMA TCs are unique in that they protrude into the rear of the lens, and the lens needs an open cavity 35mm in diameter and 10 mm deep to insure the rear of the lens does not hit the front element of the TC. There are also some pentax TCs with a similar problem
Quote: Do you think that they are all equivalent in terms of quality?
no there are cheap ones and good ones. I am quite pleased with the SIGMA TCs and use them with my 70-200F2.8 lens, and am also pleased with Pentax's SMC-F 1.7x AF TC which provides a limitred range of AF capability to MF lenses. typically stay away from TCs with 4 elements,
Quote: There are a lot of choices and I’m lost.
Regards.
Malsi
check the forum there are lots of threads on TC's and postings of photos using them.