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

Started Jul 24, 2022 | Questions thread
xmeda Senior Member • Posts: 2,133
Re: Tamron 31A (200-500 5.6) vs Pentax 150-450 4.5-5.6

gkreth wrote:

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....

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?

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.

Sig100-300/4 is all-metal FF fast focusing hi-end single tube lens and if you manage to find good EX DG sample, you will never regret. If only Ricoh created similar tool with latest glass technology... it is large and heavy, but still not like Sigma 120-300/2.8 and I do not understand why Sigma stopped that lens. Maybe due to problematic OS implementation in such design for other systems, but now they can re-use it again for ILC cameras with IBIS. With F4 it is the sweet spot between providing lens fast enough while still keeping it in usable size, weight and price. And with constant F4 it is better for video than variables.

I have Pentax F1.7xAF TC and Kenko SHQ 1.5x and 2x.
1.7x AFTC is doing AF through TC adaptor, image quality is acceptable, SR needs focal length input manually.
1.5x Kenko jut transfers everything through, but sometimes it is better to switch SR off and just use fast shutter speed 1/500s+ as otherwise camera still thinks that 300mm is mounted on, image output is comparable to DA55-300 output at 300mm if we talk about resolution.
2x Kenko again transfers everything, SR off and fast shutter is needed, Ideally around 1/1000s, some drop of image output, especially contrast is there, AF is slower and not that reliable, but you still have AF 600mm F8. Good on tripod, not that good hand-held, but usable. Original Sigma TC might do better job there.

I wonder why it is not allowed to set focal lenght manually and override what lens provides through contacts. That will simplify TC usage so much...

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