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12-14-2009, 02:06 PM   #1
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Autofocus with the kit lens?

I have so much trouble with my kit lens. Many of my shots are focused on the wall behind the subjects, instead of on their nose. I use center point AF, but even shots with the subject in the center come out mis-focused.

If I hand my camera to a friend and set it in auto mode the same thing happens.

I can see the appeal of face detection autofocus.

Any suggestions?

12-14-2009, 08:24 PM   #2
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QuoteOriginally posted by dragonfly Quote
I use center point AF, but even shots with the subject in the center come out mis-focused.
That shouldn't happen if the subject is larger than the center AF point (which is about the size of the inner etched bracket in the viewfinder), but if the subject is smaller than that, ten indeed, this can happen with any camera.

QuoteQuote:
Any suggestions?
Post an image demonstrating the problem.
12-15-2009, 02:47 AM   #3
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As Marc says "it should not happen," are you sure you are in single sensor only mode and the centre is selected not a sensor off to one side?
Which camera; which lens??
Post an image that is off focus maybe to look at?
Alistair
12-15-2009, 05:47 AM   #4
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Hope I'm not hijacking this thread, but I get some focus misses too. I've managed to figure out my mistakes in many of them, but several puzzle me.

In this one, I don't see anything in sharp focus. I have several similar.

Any ideas on what happened?



link to image and bigger sizes on Flickr
link to 100% crop

Kx DA 40mm
f/2.8
1/80s
ISO: 1600
focus: AF-s, fixed center point ( just left of mouth)
SR on and stabilized (according to EXIF)


Last edited by bnorikane; 12-15-2009 at 08:16 AM.
12-15-2009, 08:33 AM   #5
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Just a guess - you or she moved just enough between the time focus lock was achieved and when the shutter was fired to put her a bit behind the focus point. That combined with maybe a little motion blur as well as overenthusiastic NR.
12-15-2009, 09:46 AM   #6
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I would suspect motion blur which most of us neglect and don't put too much importance to since we are always emboldened by the SR.
12-15-2009, 11:07 AM   #7
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Thanks Marc!

Several good pointers to watch out for. I'm used to shooting with greater DOF and probably have some bad habits.

I'll check the NR. My NR is set at default. It starts at 800 ISO and this is at 1600. I can get sharp images at 1600 in similar conditions, but missed on this one.
12-15-2009, 11:12 AM   #8
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I have several shots in this sequence with motion blur, but I don't think this is one of them. At least I don't see it. I'm not an expert, maybe you see something that I don't.

Any pointer is welcome. I am going through my bad shots and trying to see how I can avoid repeating them.

12-15-2009, 12:03 PM   #9
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I agree it's not *obvious* motion blur, and that doesn't seem to be the *main* problem. Ditto with the NR. I think it's mostly a case of subject distance having changed between focus and the actual shutter release. But I suspect that NR and the small amount motion blur that is inevitable when shooting an living subject who is not holding perfectly still probably did rob you of a pixel or two as well. Without having actually been there, I don't know that anyone can say much more about this particular shot. Missed shots happen; the important thing is to try to avid the things that *might* have contributed.
12-15-2009, 12:10 PM   #10
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Yeah my gut feeling there is that the subject moved back a little (even a half inch) when the lens was pointed at her and bang, your focus is off.
12-15-2009, 03:46 PM   #11
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No motion blur there that I can see. Good old OOF, for what ever reason. Hope you don`t mind, ran small section through Focus-magic. That was 3 pixels of out of focus blur correction, correctable in PP to save the image.

Cheers, Mike.

Last edited by Ex Finn.; 11-11-2014 at 05:51 PM.
12-15-2009, 06:06 PM   #12
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Mike - that is great, thanks! I'd never heard of Focus Magic, and that's a good demo. With several blurry photos per session, I'll look into it.

Marc - Thanks for all your help. I'll work on my technique and watch for subject (or me) moving OOF.
12-16-2009, 07:09 AM   #13
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Here's Focus Magic applied in this situation. There was both motion & small focus blur:


Dave
12-16-2009, 01:23 PM   #14
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QuoteOriginally posted by newarts Quote
Here's Focus Magic applied in this situation.
I noticed you are using v3.01. Available for download is v3.02 which you are entitled to with a registration. Not sure if it is an improvement but one should think so.
12-16-2009, 04:03 PM   #15
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I must take a closer look.. Nope, can`t see motion blur, note to self, get eyes checked.

Cheers, Mike.

Last edited by Ex Finn.; 12-16-2009 at 04:33 PM.
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