Tamron 31A (200-500 5.6) vs Pentax 150-450 4.5-5.6

Started 4 months ago | Questions thread
OP gkreth Veteran Member • Posts: 3,128
Re: Tamron 31A (200-500 5.6) vs Pentax 150-450 4.5-5.6

xmeda wrote:

gkreth wrote:

xmeda wrote:

gkreth wrote:

xmeda wrote:

Get Sigma 100-300/4 and be happy With K3 you have same reach as 150-450 on FF

Well, yes, a 300mm on a K3 has the reach of a 450mm on FF, but 450mm on a K3 has the reach of a 675mm!
Just looking for more reach, without dropping $1500....
Greg

You can always slap 1.5x TC or 2xTC on it and get 150-450/6.3 or 200-600/8

Wait, is that correct?

  • A 1.5X TC decreases the aperture by one full stop; so a f/5.6 would be f/8, not f/6.3.
  • A 2X TC decreases the aperture by two stops; ; so a f/5.6 would be f11, not f/8.

Am I missing something?
Greg

missing Sigma 100-300/4

Ah, I see, now. Well, that brings up an interesting point.... 
I already have the 60-240 f/4, as well as the Tamron 1.4x TC and Tamron 2x TC.
I suppose I could try playing with those combinations, to see what I get. Of course, with the 1.4x, I'm only getting to 336mm, so I'd really have to use the 2x.
For quite some time, I searched eBay for a Sigma 100-300 f/4; I think I stopped looking when I got the 60-240.

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