Originally posted by oeriies Yes, I've used the Tamron TC with the DA*300. It works in good light with contrasty subjects but the autofocus hunts in conditions that wouldn't be a challenge without the TC, e.g. a bird among branches in a tree. As I indicated in a previous post in this thread, I prefer to use the DA*300 without a TC. It produces very sharp images that can be cropped 50% and still look great whereas a get fewer keepers with the TC attached.
Maybe this has been discussed somewhere on this forum already, but I've wondered whether the in-camera shake reduction is introducing blur when using the Tamron TC. With the DA*300, for instance, the camera thinks it is adjusting for shake for a 300mm lens when in fact with the TC attached it is a 420mm lens. I would think this would lead to an underadjustment. Anybody know the answer?
when using a TC that does not alter focal length, the camera is under compensating the vibration, so it is not so much introducing blurr, but undercompensating for it. I have this issue with my sigma 70-200F2.8 and the 1.4x and 2x TCs I think if you search the forum for TCs to use with the DA300, most members recomend the SMC-F 1.7x AF adaptor. The AF is very fast and quiet because it is moving only the small elements in the TC, and because on a long lens, the TC only works for a small focal length range, you get "selective focus" you can shoot through branches to your subject because they are outside the focus range.
I use this TC on my K300/4 and it works very well.
The other advantage of the pentax 1.7x adaptor is that it compensates for aperture, so when using P-TTL flash, for example, the exposure is correct, because the camera knows the true aperture.
the only down side I can see, is the price. I bought mine brand new in 1991 with my PZ-1 so I have not had to worry about getting one lately, but have seen posts suggesting the price is now about 500US