[jwblilie]

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Hey all, I own the PENTAX-DA* 300mm f/4 ED-IF and I LOVE it.

But I keep eyeing the SIGMA 1.4X (and 2.0X) APO teleconverter. I have seen lots of chat that it "probably won't work with the 300 DA*" but no one has said they have actually tried the combination.

My local camera stores appear to not carry the SIGMA teleconverters for PENTAX mount. I don't really want to order one and then return it if it doesn't work. The SIGMA site chart does not give data on non-SIGMA lenses:

Lens - Teleconverter Compatability Chart

Yes, the front element on the SIGMA protrudes forward; but from my look at the rear end of the DA* 300mm, it looks to me as if it should accommodate the teleconverter.

Has anyone actually tried to mount and/or use this combination?

Any assistance would be much appreciated! Cheers!

[mel]

I haven't tried that particular combination but I did try the Sigma 2x TC and other Pentax lenses and they don't couple. The lenses just would not physically fit into the TC.

[koper]

it dose not work with the 300 DA-you can shoot only in manual focus

[jolepp]

There seems to be a US seller offering the older Sigma 1.4x APO (not DG) as "new" for $129, which doesn't seem bad to me (?):

Pentax AF APO Teleconverter 1.4x EX BY SIGMA BRAND NEW bei eBay.de: Lenses (endet 15.01.11 20:28:38 MEZ)

[Eruditass]

The Sigma 2X TC works with the Tamron 70-200mm.

[jwblilie]

Thanks for the data on the TAMRON 70-200! I have that lens as well.

Thanks for the data on the 300!
I can live with MF on the 300 (not preferred; but ...)

I may give the TC a go and see what happens. If I do, I'll write up a detailed report for the forum.

[Frogfish]

Why are you so keen on the Sigma and not on the Tamron x1.4 which has a superb reputation ? For more money the Pentax AFA x1.7 is the one to get as you retain micro-focusing when you 'get within range' (you manual focus to approximately the right focus then the AFA takes over and snaps it into place).

AFAIK the AFA x1.7 is the only TC ever made, by anyone, that can do that (at least I've never heard of any other). If I'm wrong I'm sure someone will correct me !

I have both of those and like them both - even though I don't use them very often I wouldn't sell either (BTW - I've seen some guys using both in tandem and getting some great shots).

[Lowell Goudge]

there are two things to consider with using sigma teleconverters.

First of all, unless sigma has released an SDM version of the TC, even if the TC can couple to a SDM only lens you will be stuck with manual focus. If the lens has both screw drive and SDM it should auto focus, BUT......

Second, and most important, Sigma TCs for screw drive lenses have a unique design which protrudes into the rear of the lens. The lens needs a 35mm diameter 12mm deep recess before any elements or mechanical parts, otherwise the TC will simply not fit.

Go to the sigma site for the list of current production lenses that the TC can attach to.

This TC is simply not a general purpose TC but a specific use TC intended for long and fast sigma and some pentax lenses.

I have posted copies of the lens compatibility lists that were contained in my 1.4x and 2x TCs previously, look them up

[jwblilie]

Pentaxian Lowell: Can you provide a link to those charts? Thanks!

Frogfish:

Thanks for the info.

A couple of reasons: It gets great ratings for IQ. I've had good luck with SIGMA APO products (both IQ and build). (Though their support for / interest in PENTAX AF K mounts leaves a lot to be desired.)

I'm mulling over going for the PENTAX 1.7 AF converter (and may pull the trigger soon) but it's 2X the money and used only.

On the TAMRON -- I can't seem to find any for sale at any price. I'd be happy to buy a TAMRON and would do it -- if they were readily available. I may end up opting for waiting until I can snag one. Any advice on that?

Do you mean TAMRON TC: Tamron 140F 1.4X TC?
Or this one: Tamron-F 1.4X Pz-AF MC4?

Thanks, JB

[jolepp]

I understand the Tamron 1.4x TC has not been produced for quite a while. The Pentax 1.7x is still being made, but not exported to EU or US (RoHS regulations, apparently). Another apparently decent option, cheaper than the Pentax would be the Kenko Pz-AF 1.5x; copies of this appear quite frequently on the forum marketplace whereas the Tamron seems rare even on Ebay.

[Marc Langille]

Pentaxian Lowell: Can you provide a link to those charts? Thanks!

Frogfish:

Thanks for the info.

A couple of reasons: It gets great ratings for IQ. I've had good luck with SIGMA APO products (both IQ and build). (Though their support for / interest in PENTAX AF K mounts leaves a lot to be desired.)

I'm mulling over going for the PENTAX 1.7 AF converter (and may pull the trigger soon) but it's 2X the money and used only.

On the TAMRON -- I can't seem to find any for sale at any price. I'd be happy to buy a TAMRON and would do it -- if they were readily available. I may end up opting for waiting until I can snag one. Any advice on that?

Do you mean TAMRON TC: Tamron 140F 1.4X TC?
Or this one: Tamron-F 1.4X Pz-AF MC4?

Thanks, JB

Hi JB,

It's the second Tamron (MC4) you've listed that works with SDM and screwmount lenses. I've used it with an expensive lens (FA* 300/2.8) and the image quality with the TC is excellent.

There is someone in Japan who regularly sells Pentax-F 1.7x AF TC on this forum - they are brand new. I am unsure on the pricing right now.

Regards,
Marc

[Lowell Goudge]

Check thisthread for lens compatability

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/50537-teleconverter-question.html

[Frogfish]

As Marc said you can get the AFA x1.7 brand new - it's selling for US$350. However they are no longer exported to Europe or the USA (because they contain a minute amount of radioactive material).

[WerTicus]

The Pentax one works... AKA Hoya, AKA Kenko. (Pz-AF 1.5x TELEPLUS SHQ)
There is one for sale on this forum every so often.

[jwblilie]

Thanks for all the info. I'm mulling all the options. I will probably get the PENTAX 1.7 AF, since they are still readily available. But I'll keep my eyes open for the KENKO and TAMRON ones as well.

Lowell: Thanks for the link! Very helpful!