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04-23-2012, 03:51 PM   #1
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Questions about DA* 55mm f/1.4 SDM

I'm an absolute beginner of DSLR. I own a k-r and recently got the 55mm 1.4 lens from B&H. I probably dont know how to use it at all and have a few questions:

1) when I move the camera after auto focusing (pressing half down), the focus changes. This doesn't happen with the 18-55mm kit lens. Is it normal?
2) when the subject of the shooting moves, the focus also shifts.

Am I doing something wrong or is this lens supposed to be only used for non moving objects?

Thanks. Would appreciate if anyone could give me some basic tutorial on this. If I need to test it thoroughly can someone tell me how to test it please? Thanks in advance.

04-23-2012, 04:02 PM   #2
axl
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One question for you:
Are you sure you don't have camera in AF-C mode?

There is no reason any lens should/would re-focus in AF-S mode regardless of whether you or the object move or not or whether.

my 2p
04-23-2012, 04:09 PM   #3
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It was on AF.A...
04-23-2012, 04:15 PM   #4
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It worked fine with AF.A when I use the kit 18-55mm lens

I think I'll choose AF.S for the 55mm 1.4 lens! Thanks!

04-23-2012, 04:33 PM   #5
hcc
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QuoteOriginally posted by junototoro Quote
It worked fine with AF.A when I use the kit 18-55mm lens. I think I'll choose AF.S for the 55mm 1.4 lens! Thanks!
For non moving object, you are better setting AF.S. AF.C is primarily for fast moving objects and it is less accurate IMHO.

Hope that the comment may help.

Last edited by hcc; 04-23-2012 at 09:39 PM.
04-23-2012, 04:35 PM   #6
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Hmm, I thought it was the other way around?

Difference between AF-A AF-S AF-C focus settings Nikon focus modes
04-23-2012, 05:39 PM   #7
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QuoteOriginally posted by hcc Quote
For non moving object, you are better setting AF.C. AF.S is primarily for fast moving objects and it is less accurate IMHO.

Hope that the comment may help.
The other way around The C in AF-C is for continuous.

04-23-2012, 09:39 PM   #8
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QuoteOriginally posted by Eberbachl Quote
The other way around The C in AF-C is for continuous.

Correct. mea culpa. Just edited the post.

04-24-2012, 03:15 AM   #9
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By the way, how fast is a fast object? Sports? Concerts/Dancing? Bird flying? Do you use AF.C then?
04-24-2012, 03:52 AM   #10
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QuoteOriginally posted by junototoro Quote
By the way, how fast is a fast object? Sports? Concerts/Dancing? Bird flying? Do you use AF.C then?
anything that moves is better done with AF-C if you want the camera to track the subject,
static objects are better off with AF-S (single)

I suspect the AF-A to be culprit here because of the thin DOF caused by fast lens.
04-24-2012, 08:52 AM   #11
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Imagine a sheet of paper held parallel to the front element of the lens, that's about how much DoF you have at 1.4. So yeah, the DA*55 when shot wide open is best for portraits or maybe product shots. Try shooting at f/8 and maybe bump the ISO up a bit to get the shutter speed you need. TAv mode is great for that.

Another thing you can do, though it takes some getting used to, is take the AF function off the shutter button, and move it strictly to the AF button. In AF-C mode as long as you hold the AF button the lens will focus, when you release it, it will lock, and pressing the shutter button will not cause it to change focus. That's what I have mine set to, and I love it now, but I missed a lot of shots while getting used to shooting that way.
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