F & FA lens focus speeds
Posted 03/10/2013 - 15:55
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This morning two lens arrived in the post which i have just bought from fellow members, thanks guys,one is a pentax 18-55mm wr the other a pentax f 35-105mm.
Just done a quick AF speed test on both of them set at 50mm,with a K5 on a tripod and focused on the same near and far, low contrast, low light subject. The older lens focused so much faster then the newer lens. The same results were the same against my 16-45mm.
I did have the f 70-210mm until it hit the sidewalk at the weekend and that was just blistering fast, maybe to fast.
Just done a quick AF speed test on both of them set at 50mm,with a K5 on a tripod and focused on the same near and far, low contrast, low light subject. The older lens focused so much faster then the newer lens. The same results were the same against my 16-45mm.
I did have the f 70-210mm until it hit the sidewalk at the weekend and that was just blistering fast, maybe to fast.
Posted 03/10/2013 - 21:18
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Well the da 14 is a hulking piece if glass 77mm front element and 11 elements behind it, its going to be slower to focus...
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Posted 03/10/2013 - 23:23
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Mongoose wrote:
this is a guess again, but because people didn't like the manual focus feel of the F series. Their focus is so loose and the throw is so short that they are very hard to focus manually. Also, people wanted features like non-rotating front elements and quick-shift focus clutches, all of which increase the complexity of the drive train and therefore make it slower.
I'd bet that a DA 55-300 on a K5II is still faster focusing than an f70-210 on an SFX
One way to increase the resistance on the F lenses when focusing manually is to drag a finger from your right hand on the focus ring (assuming you can reach it). The SFX had a slower (less torquey) AF motor than the Z-1 designed with the FAs in mind. The FA's often had PowerZoom gubbins in them too.this is a guess again, but because people didn't like the manual focus feel of the F series. Their focus is so loose and the throw is so short that they are very hard to focus manually. Also, people wanted features like non-rotating front elements and quick-shift focus clutches, all of which increase the complexity of the drive train and therefore make it slower.
I'd bet that a DA 55-300 on a K5II is still faster focusing than an f70-210 on an SFX
The SFX does have one advantage over my K-5, the AF illuminator projects a contrast pattern onto the subject. If you're using it to focus on a surface with no contrast, the SFX nails it every time, the K-5 doesn't (unless I hook up my AF240FT flash which also projects a contrast pattern).
Posted 04/10/2013 - 09:01
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the SFX is much malligned in my opinion, sure it's ugly as sin, but it does the job nicely.
I love the old manual focus assist function on the early AF systems, where it tells you which way to turn the lens when in MF mode.
I love the old manual focus assist function on the early AF systems, where it tells you which way to turn the lens when in MF mode.
you don't have to be mad to post here
but it does help
but it does help
Posted 06/10/2013 - 06:11
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cabstar wrote:
Well the da 14 is a hulking piece if glass 77mm front element and 11 elements behind it, its going to be slower to focus...
Took the words right out of my mouth Well the da 14 is a hulking piece if glass 77mm front element and 11 elements behind it, its going to be slower to focus...
Maybe the old girl drags the clutch too
Pete
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Posted 19/10/2013 - 12:04
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Has anybody compared the F50/1.7 & FA50/1.4? I'm thinking about upgrading my F 1.7 to the FA 1.4 and wondering if there's a difference in AF speeds.
I've notice my newly acquired FA28/2.8 is much better damped for manual focusing than the F50/1.7 - almost to the point where I could potentially relinquish some of my M & A lenses.
John.
I've notice my newly acquired FA28/2.8 is much better damped for manual focusing than the F50/1.7 - almost to the point where I could potentially relinquish some of my M & A lenses.
John.
Posted 19/10/2013 - 12:18
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On the 50mm lenses as you get wider apertures the focus throw increases.
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Currently on a Pentax hiatus until an FF Pentax is released
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Currently on a Pentax hiatus until an FF Pentax is released
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238 posts
22 years
Borough of Bexley
[quote:3496ace15f="cabstar"]
Seems to make sense in theory but my DA14mm f2.8 is slower to focus than the old F35-70 f3.5-4.5.