Teleconverter for 300mm lens`

Hi all

I'm after a teleconverter for a 300mm lens, is the 1.4x DA AW the one to go for or are there other options to consider?

I've ended up with two 300mm F4, the DA* and a dated Sigma APO, I was considering a sigma TC but not sure of performance of 3rd party on Pentax lenses. I'm also keen not to 'undermatch' the DA* and get a converter that doesn't bring the best out of it.

The reason I'm asking is that the Pentax ain't cheap, and TCs don't seem to appear on the used market very frequently, so any decent priced options would be appreciated!

(I had a 2X-s but managed to lose it, I'd prefer shorter and faster and to keep the AF in any case)

Pentax 1.4x WR all day long.

IMO it was made for the DA* 300mm and amongst other things it will put the correct details in the Exif as well as tell the camera the correct focal length for SR.

The only other one is the 1.7x which is very good but doesn't give full autofocus as you have to manually get it in the right area first.

Can anyone advise why the 1.4 can autofocus properly BUT the 1.7 needs some help please?

The 1.7 was designed to provide AF for Manual Focus lenses. It focuses within its self, it does not alter the focus of the lens. The 1.4 transfers focus through to the lens it's self

Thanks Barrie

It works with AF lenses too but treats them the same way it does MF lenses - the SMC Pentax F 1.7 AF Adaptor can turn them into Pseudo AutoFocus lenses. The "help" that you refer to is simply that you have to manually focus the lens to a roughly good focus position and the Adaptor will then micro adjust the focus (by moving the elements in the adaptor itself) to provide accurate focus and correct exposure (in the case of A series or later lenses - M and before will require the use of the "green button").

IMO it is one of the highest quality converters produced by Pentax (the DA 1.4x is probably a bit higher quality, but is only APS-C) - I have always had at least one in my collection.

Thanks Lenny Bloke.

I have been slowly going through my A series lenses with the F 1.7x and it gives uniformly superb results. It does need a lens of f4 or wider (officially - although f4.5 will often work). I didn't think about putting it on a DA*300 - wow - quality 510mm ! If you want it to work with M42s you need to make the same modification to the rear of the M42's mount that you need to do with a Jessop's auto PKA extension tube set. Looking at the front of the 1.7x TC it needs to short out the 1st data pin that is at about the 7 o'clock position. The results with a Zeiss 135mm are amazing.

Ta all - I'll keep an eye out for a 1.4x DA.

Quick update the 1.4x AW arrived yesterday, I used amazon as I had a few vouchers to put towards it and it was a good price - maybe too good, as noddy inspection suggests it's an open-box despite being sold as new. The teleconverter is immaculate and looks new, just things like the paperwork was badly folded. I've had issues with amazon doing this before, I bought a smartwatch that came with fingerprints all over the screen, so it might be me being over-sensitive!

Anyway, the teleconverter works well enough, I'm just back from a trip to Tentsmuir where I wish I'd had a little more range so I'll make another trip and try it out. It's added a bit ore weight to the lens but better than adding a 400mm lens to the bag.

If it's Amazon then take pics and speak to customer service. You'll be able to get a bit of money back that way.