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12-19-2012, 04:35 PM   #16
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I find AF confirm accuracy in my K-x to be decently accurate from about f/2.8 onwards, preferably f/4. At f/2.8 and faster I tend to be using live view + magnification.

12-20-2012, 10:49 PM   #17
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QuoteOriginally posted by vrrattko Quote
That is not true IF you are using either focus confirmation or catch-in-focus with your manual lenses.
But it is true. Using focus confirm or catch-in focus is only as good as the AF system in the camera and as we all know the AF systems are less precise (and usually less accurate) than a proper focus screen. As per the comments above, the stock focus screen in Pentax dSLR cameras is not a whole lot better than the AF system! DOF is equivalent to about f/4 regardless of how fast your lens is. As a result, critical focus is virtually impossible with the stock screen.

The solution is an aftermarket screen. I have the Katz Eye but others are probably quite serviceable as well. That screen made all the difference in the world.

In the mean time, Live View is your friend. Get a 4x loupe and you are set for VERY accurate focus.


Steve
12-21-2012, 01:07 AM   #18
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If your fast lens has focus shift, and you're not shooting it fully open,
then neither live view nor a fancy focus screen will offer any direct help.
Unless you really know your lens very well, and know how to compensate,
focus bracketing is probably your best option.
12-21-2012, 03:02 AM   #19
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Stevebrot - Ok, I'm a little confused through my lack of knowledge. If I get a new focus screen is this just to provide better manual focus, or does it also improve AF as well? I'm certainly learning a lot from this thread so glad I started it... I had previously thought that what you see through the VF is exactly what gets captured but I guess I need to know lots more about the inner workings of the camera to understand why this is not the case.

Lytrytyr - my lens is an A so completely manual focussing. In he short term if wide open and not a planned shot (where I can use LV) then I will compensate with multiple shots and slight tweaks of focus. Hopefully that will get me he right shot.

12-21-2012, 05:34 AM   #20
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QuoteOriginally posted by thechumpen Quote
Lytrytyr - my lens is an A so completely manual focussing.
Just to clarify, by "focus shift," I mean the tendency of many lenses,
whether manual focus or auto focus,
to have their point of sharpest focus change
as the aperture is stopped down from fully open.

QuoteOriginally posted by thechumpen Quote
I will compensate with multiple shots and slight tweaks of focus.
That's exactly what I mean by "focus bracketing."
Hand held, you can just move yourself back and forth as you shoot.
12-21-2012, 06:53 AM   #21
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QuoteOriginally posted by jatrax Quote
The only way to get front focus when focusing manually is if the focusing screen is not shimmed properly. ...
This is the correct answer.
12-21-2012, 12:38 PM   #22
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QuoteOriginally posted by stevebrot Quote
But it is true. Using focus confirm or catch-in focus is only as good as the AF system in the camera and as we all know the AF systems are less precise (and usually less accurate) than a proper focus screen. As per the comments above, the stock focus screen in Pentax dSLR cameras is not a whole lot better than the AF system! DOF is equivalent to about f/4 regardless of how fast your lens is. As a result, critical focus is virtually impossible with the stock screen.

The solution is an aftermarket screen. I have the Katz Eye but others are probably quite serviceable as well. That screen made all the difference in the world.

In the mean time, Live View is your friend. Get a 4x loupe and you are set for VERY accurate focus.


Steve

What I meant is that backfocus-frontfocus issue is very relevant if you are using focus confirmation or catch in focus with your manual lenses. Let's not dispose of bf/ff issue as a problem exclusive to af lenses, because there are surely many of us who use af confirmation or cif focus with legacy lenses. And in my experience if you microadjust AF properly then AF confirmation with legacy manual lens is 100 percent reliable.

Katzeye is nice upgrade, although very expensive. For that price I think it would be nice to include shims in the package, which are absolutely necessary. As for liveview...this is safe method.....but not the fastest one .
12-21-2012, 03:03 PM   #23
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QuoteOriginally posted by thechumpen Quote
If I get a new focus screen is this just to provide better manual focus, or does it also improve AF as well?
AF is a completely separate system and does not use the focus screen in any way. So the short answer is that it allows for more accurate and consistent manual focus.

As for the comments regarding shimming, time was when the focus screens on all SLRs were properly colimated to the focal plane of the camera. If you do buy an aftermarket screen, it is easy enough to check by doing critical focus with live view (use a loupe and tripod) and comparing it to the split image in the viewfinder. I don't know how common colimation problems are since I only have experience with my K10D which did not require any adjustments. FWIW, if the stock screen was properly set up, the replacement should be too.


Steve

12-21-2012, 03:07 PM   #24
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QuoteOriginally posted by vrrattko Quote
And in my experience if you microadjust AF properly then AF confirmation with legacy manual lens is 100 percent reliable.
Even if properly calibrated, the AF systems are inherently imprecise with real-world subjects. That is the main issue with AF, IMHO.
12-21-2012, 11:32 PM   #25
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QuoteOriginally posted by stevebrot Quote
Even if properly calibrated, the AF systems are inherently imprecise with real-world subjects. That is the main issue with AF, IMHO.
That depends...in my experience once carefully calibrated to certain lens, focus indication is pretty reliable - my fastest lens is k85/1.8. The problem is that you cant calibrate AF for more than one K or M legacy lens. So I agree that if you own more lenses the eyecup magnifier and enhanced focusing screen are the best. Bigger and brighter viewfinder of FF body will surely help too
12-23-2012, 09:19 AM - 1 Like   #26
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What I do and it seems to help is I focus until I hear the beep, go past focus and reverse the focus until I hear the beep/see the green focus indicator light...micro adjust until it beeps again if I am unsure....my in focus shots have greatly improved. Sometimes the first focus point is different than the second... That is why I "fine tune" until it's right...takes more time but after you get used to the method you can get faster at it.

Hope this makes sense and helps

Thanks

Randy
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