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Old Feb 11, 2010, 5:20 PM   #11
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Originally Posted by John.Pattullo View Post

as an update i have begun saving for the da* 300 f4 - i've descided not to bankrupt myself right now though and will just put some money away over next few months as i dont think there is any urgent need for it i just want it =)

Hi John,

I'd also keep my eye out for used F* and FA* 300/4.5s. IMO, not quite as good optically as the DA* (but the difference is hardly noticeable), and 1/3 stop slower wide open, but both are considerably more TC friendly, with past and currently made models.

A significant advantage of faster premium tele lenses for me is the ability to stretch their reach without any significant loss of IQ or AF functionality (within reason, considering the inherent light loss) with a TC. Unfortunately, SDM compatibility with TCs is still questionable at this point (IMO), as none of the current PZ compatible TCs were designed with SDM focusing feedback functionality in mind. Some of them work "acceptably" from reports -- the Tamron F 1.4x AF PZ MC4 and Promaster 1.7 PZ AF being the most often cited as working "acceptably" with SDM lenses. I've had numerous "discussions" with various users of these combos, and it seems like "acceptable" performance to them is that the AF is a bit touchy, and sometimes needs manual prefocus to lock reliably, even in bright sunlight.

It may surprise some that I find this to be unacceptable for my use since I'm a vocal fan of the Pentax F 1.7x AFA which requires manual prefocus of the lens to allow the AFA to focus the combo, but the difference is that this is a design limitation of the AFA with tele FL lenses, and shouldn't be a limitation with a TC that relies on the AF capability of the lens.

Just a thought. . .

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