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11-16-2011, 07:11 AM   #1
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Teleconverters for MF lenses..

Hi Guys and Gals,
Just purchased an Adaptall-2 400mm f4.0 and as always sometimes want even more reach than it offers. The seller, MightyMike, used the Pentax AFA 1.7x TC and recommends that as an option but finding one is a trick. Since the lens is MF to start with, I am not concerned with any focusing or focus assist function but am concerned with IQ and aperture data feed through. There are several current options in the 1.4 to 1.7 range and many older discontinued models. In my recent Olympus days, I had a beautiful 1.4 TC that no apparent IQ loss at all but it was expensive. Price is not a concern as long as it is in line with the products offerings. So in your opinion, what is the best TC I can get to use with my 400mm that preserves the most IQ and hopefully feeds the aperture data through but this is secondary to IQ. Also, I see references to both an AF and an AFA 1.7x. Are these two different models?

Thanks, Dave

11-16-2011, 07:28 AM   #2
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Dear Dave:

I've had a 400 f4.0 for many years (went on my LX). Used it successfully with a Pentax 2XL converter, somewhat less satisfactorily with a 1.4XL converter. If you can find my ancient posting of a squirrel you can get some idea of IQ with the 2XL on the Tamron, but re: that's a scan from a slide, and I focused on the nose whiskers rather than the eyes. By the way, the 2XL works superbly with my 200 f4.0 macro. 2XL converters show up on EBAY fairly regularly, but even used they are not cheap.

11-16-2011, 07:34 AM   #3
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If you're looking for the 1.7x converter (there is only one) I would add the the keyword "1.7x" to your watch list in the marketplace so you get an instant notification when one is posted
11-16-2011, 07:39 AM   #4
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didn't the 400/4 come with the tamron 2x teleconverter? My 200-500/5.6 did

Aside from that, there is another option other than the pentax rear converters,

I know you did not want to concern yourself with AF, but the sigma APO 1.4x and 2x EX teleconverters will probably work, because if the 400/4 is like my 200-500/5.6 the rear of the lens is completely open to allow th protruding front element to clear the lens.

THe sigma TCs go new for about $200 from memory, and will at least pass through the aperture data (although not modify it correctly for the TC effect)

the 1.7x AF TC is a good option and does modfy aperture correctly for the TC so that the aperture reported is a true aperture, this is important for P-TTL flash and also for metering if you are on a K10D or K20D especially

edit note.

Some time, I need to benchmark all my TCs, as I have a ammassed a considerable collection of them over time
. The * denotes those that I use at the moment
Sigma APO 1.4x EX *
SIgma APO 2x EX DG *
SMC-F 1.7x AF TC *
Tamron 01F 2x
Takumar A 2x
Vivitar 2x-22
Vivitar 3x-22

Last edited by Lowell Goudge; 11-16-2011 at 07:44 AM.
11-16-2011, 01:48 PM   #5
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There are two Adaptall-2 SP tele converters that might be of interest for you:

The SP 2X model 01F, and
The SP 1.4X model 140F

(actually there is a third, the SP 2X model 200F, but I have never seen that offered anywhere).

Since you obviously have the P/KA Custom Mount these would seem to be 'sensible' choices.

If you get tired (I do) of having to switch adapter whenever you switch TC in the field, you might consider Kenko. Surely, the Pentax 1.7 is better, but I recently acquired the Kenko Pz-AF 1.5 Teleplus SHQ (Phew - long name) and it works surprisingly well with all of my Adaptall-2 lenses - including my catadioptric 350mm model 06B which is otherwise a beast as far as ease of focusing is concerned. My Kenko provides focus confirmation in less than perfect lightening conditions - also for the 06B.

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