Birding on a budget

[Dazz1]

It will be while before I am after a teleconverter (hopefully )

[arthurking83]

....

Definitely try one out in a shop first

I wouldn't even bother with that.
I'd be inclined to use that time to play with some other more interesting stuff on whatever other shelf they have going.

You can bet your last dollar that the 2x TC will not yield much in the way of IQ at all, especially when the aperture is going to be diffraction limited from the get go!

Even taking into account the ETTR process, you could somehow manage to get a good exposure at some point in the future tho.
(maybe not just yet, even tho many cameras do have very nice IQ at ISO25K ... eg. Nikon Df, D4/D4s .. etc)

I reckon that teleconverters still have a way to go before they have exceptional quality abilities, and hopefully one day that will come too.
I don't know much about most of them .. never really been all that interested, but of the two I've (accidentally)read about Nikon's latest 1.4(the TC14IIIe) and Canon's integrated TC in the 200-400/4 lens appear to be almost perfect in many ways.

I'm sure that one day, manufacturer's will start to push each other on the teleconverter quality front too.
They seem to have spent many years doing this with lenses, and us consumers have ended up with many fantastic lenses at the moment! ..

Only a few years ago(say 3 or 4) .. who'd have thunk that a Sigma super tele zoom lens would even be as close as excellent as they are now .. same with Tammy too!

I think it's only a matter of time now, that both Tamron and Sigma will really start to push the TC effort(probably starting with Tamron first, as they probably have a bit more to prove to the world)

[J.davis]

I have the dock for the 150-600 and was pleasantly surprised that the focus adjustments are available for my '24-105 A' lens. Another + for Sigma in my books.

[ameerat42]

Well, just ge-e-e-tting back to teleconverters, Wets, I found an interesting POINT TO NOTE
- and one I don't like much, either. Your lens will retain both AF and OS with a Σ1.4X teleconverter,
but it will retain ONLY OS and you will have NO AF with a Σ2X. See the table in the link below...

The link below.

That's the case with my 50-500, no AF with the 2X

So that limits you to 840mm FL if you go that way.

- - - Updated - - -

PS: Don't tell anybody I mentioned teleconverters again

[Dazz1]

Yes, teles seem to cause problems with AF. Some say you might get it to work up to f/8. Not a good thing generally.