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03-04-2012, 06:35 AM   #16
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QuoteOriginally posted by Docrwm Quote
Optical quality is the biggest selling point for primes, but SDM is a deal breaker.
SDM certainly deserves its bad rep but haven't the biggest problems been with the zooms. I thought the SDM primes had significantly fewer problems.

03-04-2012, 06:39 AM   #17
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Back on subject here, my view is most AF lenses have insufficient focus throw to be accurate on MF. My sigma 70-200/2.8 has a 90 degree throw, against 180 degrees for my Vivitar series 1 70-210/3.5 or the 270 degrees of my K300/4

While you can manually focus an AF lens it is just not as accurate
03-04-2012, 07:16 AM   #18
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QuoteOriginally posted by Lowell Goudge Quote
Back on subject here, my view is most AF lenses have insufficient focus throw to be accurate on MF. My sigma 70-200/2.8 has a 90 degree throw, against 180 degrees for my Vivitar series 1 70-210/3.5 or the 270 degrees of my K300/4

While you can manually focus an AF lens it is just not as accurate
True, and most don't have any meaningful dampening either - which contributes to the difficulty of manually focusing.
03-04-2012, 11:09 AM   #19
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QuoteOriginally posted by Lowell Goudge Quote
Back on subject here, my view is most AF lenses have insufficient focus throw to be accurate on MF. My sigma 70-200/2.8 has a 90 degree throw, against 180 degrees for my Vivitar series 1 70-210/3.5 or the 270 degrees of my K300/4
But isn't the Sigma lens also much wider, being a faster zoom? Short angular throw is not an issue if the focus ring has a long circumference - it's the distance that a fixed point on the focusing ring travels that matters for precision, not the angle. I have a VS1 35-80/2.8 and it only has 90 degrees of throw, but the focusing ring is really precise and nice to use. On the other hand, the VS1 28-105 that had the same angular throw was much harder to use.

03-04-2012, 11:36 AM   #20
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QuoteOriginally posted by Laurentiu Cristofor Quote
But isn't the Sigma lens also much wider, being a faster zoom? Short angular throw is not an issue if the focus ring has a long circumference - it's the distance that a fixed point on the focusing ring travels that matters for precision, not the angle. I have a VS1 35-80/2.8 and it only has 90 degrees of throw, but the focusing ring is really precise and nice to use. On the other hand, the VS1 28-105 that had the same angular throw was much harder to use.
Circumference is a better way I suppose of measuring throw. It's just listed as degrees so often but I know what you mean, the difference in circumference between my 35/2.4 and my 10-24 is huge and so the total travel distance is different even if the degree of movement is nearly the same.
03-18-2012, 11:01 AM   #21
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I have owned a 300mm f4 A lens for over 20 years. Superb lens. Only real down side to me is the close focus distance of 13 feet or so. Compact, sharp and great color. The favorite among my Pentax lenses.
03-18-2012, 01:33 PM   #22
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I have owned DA 55-300 two years now. 6 months ago I got A*300f4 for tele use (birding) and have not used DA 55-300 much after that. When comparing manual focus, there is no comparison: A*300f4 focusing is silky smooth with great feel, when DA 55-300 is more like rattling and not-so-good feeling. Still the DA 55-300 is quite good to manually focus, thanks to quick shift.

Talking about image quality, it's a bit of mixed bag for me. When I used DA 55-300 I always knew what to get and it never disappointed. When I got the A*300f4 I expected to get much better results. Because of manual focus it was not that easy after all. I felt I missed too many shots and also I felt that A*300f4 was too soft wide open as well as images had too much CA. I got Ee-S focusing screen and things got a bit better. When focus hits, the resolution is quite good wide open. But what concerns me most is the CA wide open, which is considerably more than in DA 55-300. More I have used the A*300f4, more I have begun the respect the achievement that Pentax made with 55-300.

But A*300f4 has it's place in my bag. I really like the bokeh and color rendering as well as "feel" of the lens. I know the lens is capable of producing much better results that I have managed to get from it and that is what keeps me using it. The lens gets some time to get used to, but I'm sure it will show why it has gained it's reputation. And more I have used the A*300f4, more I desire the DA*300f4
03-18-2012, 02:03 PM   #23
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QuoteOriginally posted by Lowell Goudge Quote
Back on subject here, my view is most AF lenses have insufficient focus throw to be accurate on MF. My sigma 70-200/2.8 has a 90 degree throw, against 180 degrees for my Vivitar series 1 70-210/3.5 or the 270 degrees of my K300/4

While you can manually focus an AF lens it is just not as accurate
Well that depends on the lens Lowell - the DA*300 is a delight to MF !

03-18-2012, 02:21 PM   #24
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QuoteOriginally posted by Frogfish Quote
Well that depends on the lens Lowell - the DA*300 is a delight to MF !
I remember that to be the case too from my very short experience with this lens. Was it because the ring is decoupled during AF so it doesn't need to have a short throw?

I think Lowell was thinking of lenses like the DA 55-300, which are indeed a pain to MF.
03-18-2012, 02:29 PM   #25
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Someone was selling an XR Rikenon 300mm f/4.5 in the marketplace a while back, might still be there. That lens is smooth to focus, well damped, and focuses quite a bit closer than the K 300. I may even consider selling mine, now that my 1.7X AFA bit the dust.
03-18-2012, 02:34 PM   #26
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Well as an update I just purchased the A*300 F4 that was listed here in the marketplace. I'll let you know when I have taken it out for some test shots.

Chances are I'll still get a DA55-300 for a general walk around lens at some time.
03-19-2012, 01:39 AM   #27
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QuoteOriginally posted by Laurentiu Cristofor Quote
I remember that to be the case too from my very short experience with this lens. Was it because the ring is decoupled during AF so it doesn't need to have a short throw?

I think Lowell was thinking of lenses like the DA 55-300, which are indeed a pain to MF.
The quick shift helps of course but I use the lens like this : AF to proximity of the bird, depress AF button (custom set to disengage AF), MF to focus (the ring has a long throw and is very precise). Works very well for me.
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