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09-25-2009, 08:28 AM   #16
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QuoteOriginally posted by Lowell Goudge Quote
First of all, it modifies the lens information for F-Stop so that the correct F-Stop is used by the camera for exposure including the 1 1/2 stop loss of the TC.
Inexplicably the 1.7AF adaptor I had, when used with an A50 F1.4, used to give a maximum aperture of F2.8 (instead of F2.4) according to the viewfinder info in the Super-A and Z1 I used to own.

09-25-2009, 08:51 AM   #17
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QuoteOriginally posted by Spock Quote
Inexplicably the 1.7AF adaptor I had, when used with an A50 F1.4, used to give a maximum aperture of F2.8 (instead of F2.4) according to the viewfinder info in the Super-A and Z1 I used to own.
interesting, because with my vivitar 85mmF1.4 i get F2.5 which is correct.

you might have had a dirty pin.
09-25-2009, 09:37 AM   #18
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QuoteOriginally posted by Mike.P Quote
Actually it works 100% reliably on my Pentax F* 300mm f4.5 which is slower than f4

Hmm, wonder if it will work on my A* 300mm f2.8 with Pentax 1.4x-L or 2x-L converters

HI Mike,

It works 100% with my FA*300/4.5 also, and is my favorite lens combo for handheld birding.

It will work with any 300/2.8 stacked on a good 1.4x TC (and the A 1.4x-L would obviously qualify). I've used one of mine with the Tamron SP 300/2.8, Sigma EX 300/2.8 APO, and FA* 300.2.8, and this stacked combo is my favorite for tripod mounted shooting.

Here's an example with the FA8300/2.8+ Sigma 1.4x + 1.7x AFA:


With the increased AF sensitivity of the K-7, you might get it to work stacked on the A 2x-L. I don't have one, but briefly have used the AFA stacked on a Tamron F 1.4x + a Sigma EX 1.4x APO, just to see if it would work, and it was slow, but it did work on a bright day, with a bird standing pretty much in the shadows. On that same day, I also tried the FA* 300/4.5 + Sigma 1.4x + 1.7x AFA for a combined max Av of f10.7, and that combo worked with the same lighting conditions. I only tried this to see if it would work, and it did.

Here's one of the shots, heavily processed with the FA*300/2.8 + 2 1.4x +1.7x AFA using AF:


And one with the FA* 300/4.5 + Sigma 1.4x +1.7x AFA, again using AF, and again heavily processed.


Not something I would recommend or use often, but it was an interesting experiment, and these never AFed with my K20, K10, K100DS, or DS, even at noon on a clear day in June, but it did with the K-7. The K-7's increased AF sensitivity in low light also works to allow better AF functionality at the slow end of things.

Scott
09-25-2009, 10:59 AM   #19
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QuoteOriginally posted by Spock Quote
Inexplicably the 1.7AF adaptor I had, when used with an A50 F1.4, used to give a maximum aperture of F2.8 (instead of F2.4) according to the viewfinder info in the Super-A and Z1 I used to own.
I had just obtained a 1.7x AF adapter along with an A50 F1.2
I'll have to try again but IIRC, it read F2.8 on my K200d

09-25-2009, 06:24 PM   #20
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Very good IMHO

I use it a lot with my DA*200. See this picture of a GBH.

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09-25-2009, 09:19 PM   #21
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QuoteOriginally posted by Lowell Goudge Quote
interesting, because with my vivitar 85mmF1.4 i get F2.5 which is correct.

you might have had a dirty pin.
I got F2.8 on Polar 85/1.4. It is quite strange ) Anyway, It works well on DA* 60-250/4 partially, change to F6.7
09-25-2009, 10:17 PM   #22
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Well, just confirmed with newly purchased A50 1.2 - it reads f2.8 max
How many stops should it be? I thought it was 1.5 stops so from 1.2, I should be reading f2.0 right?

I also checked my other A lenses

A50 f1.2 - f2.8 (should be f2.0)
A50 f2.0 - f3.5
A70-210 f4.0 - f6.7
DA 16-45 f4.0 - f6.7
I can't speak for the IQ as I haven't had the chance to take pictures with it.
It does AF with all the above, in some cases (especially the A50 1.2), one still has to do a coarse focus - probably also depends on light conditions.
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