Airshow Lens

Regarding my recent post about 300mm lenses, I notice that Chris @ SRS is selling the Sigma 70-200mm EX DG HSM with a 2x converter. I was contemplating the EX 100-300mm until I saw this offer, any advice from anyone as to which of these would be suitable for airshows? I used a teleconverter last year, the Kenko 2x teleplus MC4 version on the tamron 70-300 that I had at the time and the images were very overexposed.
Any advice would be welcome,
Thanks

Rob

The lens is brand new, Just came out in Pentax mount.

Chris has received the first shipment just this week, and it is unlikely that you will find many people with this lens. Or teleconverter.

The TC is a Sigma one, and goes together with the lens, so supposedly it should work.

Give Chris a call, or stop by the shop and take a look with your own eyes!

Hope this helps,

Nathan

I did read on the other Pentax forum that the Sigma teleconverters will not autofocus with the new HSM lenses as they need extra electrical contacts.
How true this is I have no idea.

I picked up one of these lenses with the 2x Sigma teleconverter yesterday from SRS, and I have to say that there appears to be some truth to the rumour that the 2x converter and the 70-200mm HSM II don't get on!

Basically, it won't AF with the 2x converter, but more worrying than that is the fact that you can't view the menu screen on the camera either. It just flashes up for a split second and then goes off, giving you no chance to select anything. It also appears to send things crazy in the view finder, with the shutter speed notification and the flash symbol going ballistic.

It does this on both my K10 and K20, and even in manual focus mode.

At the moment, I'm baffled as to why Sigma are selling this lens with the 2x converter because it clearly doesn't work...

I also tried my Kenko 1.5x converter on the lens, and it functions perfectly, AF's and I can see the menu screens. I have to adjust the exposure though, but I'd expect to have to do that anyway.

Not happy at the moment!!

Is it possible the 2x converter could be faulty. It certainly sounds like there is a fault somewhere with either the lens or the converter.
Have you given the mounts and contacts a good clean:
I would go back to Chris and try another converter if i were you.

Yes, I've sent Chris an email to let him know and see if he has any ideas.

Looking more closely at the two converters again this morning, I can see that the Kenko one has two additional contacts deeper within the converter that mate up to the two contacts on the lens, and these presumably communicate with the HSM motor.

The Sigma converter doesn't have these two addtional contacts, just the usual seven around the face that contact the camera body.

It's a funny one because the lens doesn't even work in manual mode with the sigma converter attached, and as I say sends my bodies into a bit of an electronic frenzy!

The lens itself is a lovely piece of kit though.

I've heard on another forum that Sigma are producing a newer converter that has these HSM contacts, the same as the Canon/Nikon ones, which will be compatible. How true that is I don't know!

Can I ask what made you go for the Sigma 70-200mm f2.8 over the same offering from Tamron?

I suspect the two contacts you are referring to are the power contacts which first appeared on Pentax bodies during the days of power zooms.

If they're not there, you will have no juice to drive the HSM motor.

G

Well, annoyingly, the fact that it came with the converter and had the HSM really!

I've read the reviews between the two lenses, and as usual both had strong and weak points compared to each other, but I did like the look and feel of the Sigma more and the idea that it would work with the 2x converter for the odd time when I needed 300mm+ sounded ideal for me.

If I can't find a 2x converter that is acceptable image quality wise that works with the Sigma, then I'll look at the Tamron again, and although it's not HSM, it is internal focus with screw drive which I can live with.

I suspect you're right!

I've asked Chris to try a lens with a sigma converter to see what happens, but I'm reading on other websites that the combination of 70-200 and sigma 2x converter just won't work.

My own experience and the lack of extra contacts on the Sigma converter would suggest this is true!

I can't believe they would bundle the two together if they were not 100% compatible. Seems outrageous to me.