[zzeitg]

Anybody here who tested this combo?


Is it safe anyway to combine Pentax 1.4x TC (the current one, i.e. HD Pentax-DA AF Rear Converter 1.4x AW) with Sigma 150-500?

[JimmyDranox]

I think that you can use it only in manual focus. Not because of the TC, but because of Sigma lens. There is a compatibility chart on their site, and you can see that this lens, and others, are not compatible with their own TC for Pentax mount, or can be used only with manual focus. From my experience with a Sigma 70-200/2.8 HSM II, even if they represent the lens of being incompatible with TC on Pentax, I've used it with manual focus very well, with a two types of TC, a Soligor 1.7x AF TC, and a Vivitar 2x TC.

[boriscleto]

It's not compatible with the Sigma TC because the Sigma TC for Pentax doesn't have HSM.

[JimmyDranox]

Maybe, but my Soligor 1.7x AF TC has HSM-SDM contacts, and is working with other Sigma HSM lenses in AF mode. I've just used it today.

[zzeitg]

I think even if AF would be supported it would be struggling... So MF mode only, I guess. But is it safe to give it a try? (I mean in case of DA15, 21, 40...it's declared that "damage to lens or converter will occur" - so what about 150-500 ?)

[jeallen01]

I tried the Kenko 1.5x (Pz version) with the 150-500 HSM in my bedroom at night with poor lighting on K-30 K-5 & K-3, and it DID autofocus, after a fashion - but I'm not sure how well it would work in the "real world"!

Edited 16 Aug 2015:
Yesterday I went to an airshow, and now I think I can say that the combo does NOT appear to work in the "real world!" - or at least not on my K-3, because two things became apparent:
- With the lens in Autofocus mode "1", it completely exacerbated the tendency to defocus every shot by focusing to a shorter distance when I pressed the shutter release.
- With the lens in Manual focus mode it would not allow me use Catch in Focus shutter release.

Got virtually nothing but blurred shots for a long time, and then I finally removed the T/C and began to get some moderately sharp shots - the planes were a long way away, so I was not expecting much anyway.

Would have much preferred my 100-300 Sigma & Sigma 1.4 T/C - but that lens is away having (I hope) a new board fitted to correct the excessive backfocus it has - may get it back at the end of this week with a bit of luck.

Edited 20 Aug 2015

Just dawned on me that the OP specifically mentioned the 1.4X PENTAX HD TC but most of our comments then discussed OTHER TCs.
BTW: the Sigma 1.4x TC won't even fit on the back of the 150-500 because of the protruding front element of the former (and the 2.0X even more so) - nothing to do with not having HSM contacts!.

So, returning the OP's post - has anyone specifically tried the Pentax TC with the 150-500HSM because AFAIK that has the necessary contacts and supports the command set for the SDM lenses and those are the same contacts used for HSM operations (I think!)?