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06-10-2018, 02:56 AM   #1
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Autofocus performance? - Pentax 645 A* Green Star 300mm F4 ED (IF)

Anyone care to comment on the AF performance (and image quality) of this lens?....follows on from my other recent post.....this lens build seems to follow the same style of build as the 67 300mm M* ED(IF) , (but manual focus) I had originally???

06-10-2018, 03:31 AM   #2
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Do you mean this lens: SMC Pentax-A* 645 300mm F4 ED [IF] ?
This is a manual focus lens. If you want AF you have to go for the SMC Pentax-FA* 645 300mm F4 ED [IF]

Last edited by alpheios; 06-10-2018 at 03:38 AM.
06-10-2018, 06:15 AM   #3
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QuoteOriginally posted by alpheios Quote
Do you mean this lens: SMC Pentax-A* 645 300mm F4 ED [IF] ?
This is a manual focus lens. If you want AF you have to go for the SMC Pentax-FA* 645 300mm F4 ED [IF]
Thks - it's listed as 'Auto and Manual' focus on the listing ad on Ebay…..clearly not an accurate description!
06-10-2018, 07:05 AM   #4
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QuoteOriginally posted by BostonUKshooter Quote
Thks - it's listed as 'Auto and Manual' focus on the listing ad on Ebay…..clearly not an accurate description!
They don't mean AF, they mean it has an A mode for exposure. So, still an accurate description I think.

06-10-2018, 07:49 AM   #5
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I suspect that the original question has expired but for the record;

The 645-FA 300/4 is ponderously slow as it has a full 270 degrees focus throw from MFD to Infinity....perhaps a manual focus design adapted for AF. As a comparison, the 645-FA 300/5.6 has a focus throw of around 115 degrees from end to end so more than twice the speed assuming that the screw drive speed is constant outside the acc/decc region.

Bob
06-10-2018, 10:56 AM   #6
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Thanks all....will continue looking....after this info and the lens test comparisons earlier this week the 400mm FA looks like a better bet all round....?
06-10-2018, 11:47 AM   #7
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The 400mm has the same long focus throw as the 300/4....not quick.
06-10-2018, 03:54 PM   #8
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You will still get the confirmation beep on the Z on a MF lens.

06-10-2018, 10:13 PM   #9
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QuoteOriginally posted by Bob L Quote
The 400mm has the same long focus throw as the 300/4....not quick.
OK thks….

---------- Post added 06-11-18 at 06:14 AM ----------

QuoteOriginally posted by itshimitis Quote
You will still get the confirmation beep on the Z on a MF lens.
Yes, thks....also noticed that on the 67 165LS I sometimes use...Rgds
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