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09-24-2012, 09:27 AM   #1
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It's been a month since I bought my 40XS, what gives?

I'm talking about the focusing. Once I'm at a fair distance away from the subject (people), focusing is really inaccurate and unreliable. I provided some samples in the Lens Sample forums that focused well, probably because of the close distance and good contrast between the foreground and background.

This is my first auto focusing prime lens. If you check out the lenses that I reviewed, I own manual prime lenses and the DC auto focusing super zoom (18-135).

This lens seems to backfocus often and when it's not backfocused, it's slightly off focused. What's happening?

Oh and even my manual lenses can focus better than this, daylight or low-light.


Last edited by Vicboy; 09-24-2012 at 06:18 PM.
09-24-2012, 09:40 AM   #2
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what camera do you have, the lens might need some AF adjust using the body.
09-24-2012, 09:50 AM   #3
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How far is this distance? Are you sure its the lens and not just AF point focusing on something else?
09-24-2012, 09:54 AM - 1 Like   #4
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And, how can your manual prime lenses "focus better"?

09-24-2012, 10:10 AM   #5
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QuoteOriginally posted by Deimos Quote
what camera do you have, the lens might need some AF adjust using the body.
From the link I provided, I find that, it does find the correct focus. Maybe it's because there's a lot of contrast. (lighted subject, dark background)

QuoteOriginally posted by Na Horuk Quote
How far is this distance? Are you sure its the lens and not just AF point focusing on something else?
2 meters away, etc. I made sure the red blinking focusing dot hits the subject. Actually, manually focusing this lens is better than the unreliable and inaccurate focusing experience.

QuoteOriginally posted by Giklab Quote
And, how can your manual prime lenses "focus better"?
Because of me.

Last edited by Vicboy; 09-24-2012 at 06:20 PM.
09-24-2012, 10:23 AM   #6
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1. Try to focus on something static using Live View AF (which will nail it if it's focusing where you want it to) and then defocus and focus with PDAF (viewfinder AF).

2. Report back with results

3. Take it easy on your eyes, so you can use your manual lenses till they fall apart

(4. ????? 5. Profit)
09-24-2012, 01:51 PM   #7
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QuoteOriginally posted by Vicboy Quote
I made sure the red blinking focusing dot hits the subject.
The actual AF sensor area may be larger than the red dot area,
so if there was a contrasty object near your subject,
the lens might end up focused on that instead.
09-24-2012, 02:24 PM   #8
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Huh, I dunno, my experience with the 40mm XS is that it focuses very quickly and accurately, both with the K-01 and the K-r. But maybe you should look at some other general AF threads on here to see the advice given there. Its mostly lens correction adjustment (for Phase detect AF) and learning to use the AF points (the central one is especially large, as big as the ( ) area, not just the red square)

09-27-2012, 07:15 PM   #9
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Af sensor is always much larger than the red dot. Focus is not ecessarily at that exact point, but only somewhere "near" that point (near o the viewfinder; might be very far in front or behind of course).

Without seeng pictures you are unhappy with, though, it's impossible to mroe than speculate that this is your problem. It is a pretty common msitake, though, so I'm giving it about a 90% chance.

Last edited by Marc Sabatella; 10-01-2012 at 10:44 PM.
09-27-2012, 08:29 PM   #10
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It can't be the AF points, I use my DC 18-135 and it works pretty well. Maybe it's because the SDM is too slow and the aperture is too wide open...
09-28-2012, 06:45 AM   #11
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The 40XS' focus is adjusted by the camera's own motor. Try shooting at f/4 to have something comparable to your 18-135 DOF-wise (as you said, it is a faster lens), and then you'll see if it's the lens or the camera (and you only notice it on the faster lens.
09-30-2012, 02:55 PM   #12
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QuoteOriginally posted by Vicboy Quote
It can't be the AF points, I use my DC 18-135 and it works pretty well. Maybe it's because the SDM is too slow and the aperture is too wide open...
The 40 XS has no SDM.
10-01-2012, 08:16 PM   #13
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QuoteOriginally posted by Blue Quote
The 40 XS has no SDM.
What do you call it then?

I'll go try shooting with the XS soon enough, it's thinness gives it another chance, anyway.
10-01-2012, 08:26 PM   #14
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QuoteOriginally posted by Vicboy Quote
What do you call it then?

I'll go try shooting with the XS soon enough, it's thinness gives it another chance, anyway.

They don't have a motor. They are ran by a motor in the body by screw drive.
10-01-2012, 10:46 PM   #15
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QuoteOriginally posted by Vicboy Quote
It can't be the AF points, I use my DC 18-135 and it works pretty well. Maybe it's because the SDM is too slow and the aperture is too wide open...
Much more lilkely the wider DOF of the zoom is simply masking errors caused by failure to control the focus points well enough. But until ypu post the controlled tests shots that lead you to beleive a problem exists, all we can do is guess.
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