[Shakey]

I'm somewhat new at this so if this has been asked before please direct me to the specific thread.

I would like a lens with some reach for nature photography. I already own the Pentax DA 55-300 ED WR and have the Pentax 1.4 converter.

I am at least looking at the Sigma 50-500 or the 150-600 zooms...haven't decided if I can part with the $.

Can these lenses be used with a full frame (future thoughts)?

Your observations, experience or advice would be appreciated.

Thanks

[svassh]

I don't believe the Sigma 150-600 is available in the Pentax mount. I wish it was as I previously owned it for Canon and its fantastic. I know the 50-500 Sigma is available for K mount but have no experience with it. I recently picked up a Sigma 120-400 off Ebay for a great price, it is full frame. Haven't had a chance to shoot it outdoors yet with my K-1 but its well built and is sharp at F/8 indoors at least with a flash.

---------- Post added 12-28-16 at 07:54 AM ----------

Also there are Sigma lens reviews here Pentax Lenses by Sigma, Tamron, Zeiss, and more - Reviews and Specification Database - Pentax Lens Review Database

[boriscleto]

It is easy to tell if a Sigma lens will work with FF...

DG = FF

DC = APS-C

The 150-600 is not available for Pentax or Sony. Only Nikon, Canon and Sigma...The 150-500 on the other hand was made for Pentax. If you can find one it will probably be half the price of the 50-500...

The Pentax 150-450 is about the same price as the Sigma 150-600 Sport and is faster at 450...put it on the 1.4x converter and it is a 630mm lens...though it might vignette on FF...

[Scorpio71GR]

I own the Sigma 50-500 OS HSM. Yes the 50-500 is a full frame lens. As stated above the 150-600 was never made in K mount. There was also the 150-500 which was also full frame. I have used a 1.4 TC with my 50-500 on my K3 but autofocus would not work and you a lot of light. I have seen a few of these lenses on used sites for a pretty good price.

[Shakey]

Thank you for the information.