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08-05-2009, 09:56 PM   #1
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Severe front focus: k-7 and FA 50/1.4

Hi All,

Finally I got my K-7. Just played for a hour and found the shutter is real good, firing like a machine gun. The AF speed is nice too, slightly faster than D90 in good light. Low light will test later. But there is a severe problem with AF accuracy with AF 50/1.4.

It front focus much. I tried fine tune but still not very comfortable with -10. Have you ever have this problem? If so, any hint to fine tune?

Many thanks,
Tony

08-05-2009, 10:01 PM   #2
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How are you testing it, are you using a stable platform (tripod)? Are the camera and lens both new or were you using the fifty with another lens? Do you have other lenses and are they ok? Does it MF ok?
08-05-2009, 10:17 PM   #3
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Had a similar issue with my DA* 16-50. I suspect it's the lens though, as it was somewhat soft even on my K20D. I sent in the lens for repair.

My other lenses, which include the a FA 50 f/1.4, DA* 50-135, DA 10-17 fisheye, and 90mm f/2.8 macro, all look great on the K-7, following various AF adjustments.

Do you have any other lenses to try? Have you tried using a focus chart?

Any sample images?

- Jason
08-05-2009, 10:20 PM   #4
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Does your 50mm 1.4 works perfectly with another body?

Have you tried another lens on K7 to test whether its the overall sensor alignment or its the FA 50mm lens aligment.

I know my Gx20 got a sensor alignment issue. I almost have to use -10 for all my lenses and the same lenses need no adjustment on my K20.

08-05-2009, 11:22 PM   #5
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Hi All,

I don't have other body or lens to test. Will use a chart to test tomorrow.

inferno10, what is your setting for 50/1.4?

mcjm78, so if it's the body, should I send it to Pentax? Maybe I can order a replacement from Amazon to compare the two.

Thanks,
Tony
08-06-2009, 12:08 AM   #6
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What was your light source?

Pre-K-7 cameras would front focus with incandescent light. I'm wondering if your K-7 is doing that also.
08-06-2009, 12:23 AM   #7
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It is late afternoon sun light. How to solve that?

Thanks,
Tony
08-06-2009, 12:30 AM   #8
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Post some pics of your test as well please.

08-06-2009, 04:51 AM   #9
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QuoteOriginally posted by KungPOW Quote
What was your light source?

Pre-K-7 cameras would front focus with incandescent light. I'm wondering if your K-7 is doing that also.
K-7 is supposed to fix that. It has additional sensor to measure wavelength. Therefore Safox VIII+.
08-06-2009, 05:57 AM   #10
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The FA 50 f/1.4 was one of the first lenses I tried out on the K-7 - under tungsten lighting.
Its always been a sharp lens, but it previously tended to front focus at large apertures and tungsten lighting.
Its "perfect" with the K-7 - no more front focusing under even severely yellow sodium lights.
08-06-2009, 06:19 AM   #11
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Premature speculation before the facts are known breeds frustration. Test before you speculate its the camera.
08-06-2009, 08:47 AM   #12
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Right. If you haven't used a chart designed specifically for the purpose, you haven't tested - you've just taken a picture where the focus wasn't where you wanted (and that could be caused by any of a dozen or more different things).
08-06-2009, 10:06 AM   #13
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Well, it is not good to speculate people either. The feel is very important when you take a picture.

Here comes the proofs:
From up to down: AF tune, -10, -5, 0.
You can see the difference focuses on ~4, ~10, ~13 mm, which shows the tuning effects, but they all focuses in the front.

Thanks,
Tony
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08-06-2009, 10:08 AM   #14
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Hi, Kittykat,

I am not quite understanding. How did you solve the front focus issue? Why it is "no more front focusing under even severely yellow sodium lights"?

Thanks,
Tony

QuoteOriginally posted by kittykat46 Quote
The FA 50 f/1.4 was one of the first lenses I tried out on the K-7 - under tungsten lighting.
Its always been a sharp lens, but it previously tended to front focus at large apertures and tungsten lighting.
Its "perfect" with the K-7 - no more front focusing under even severely yellow sodium lights.
08-06-2009, 02:56 PM   #15
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Update:

I found my viewfinder/AF sensor is not consistent with the image sensor. I can see the focus is right in viewfinder but the photo taken is just not right. I also can see the fine tune effect on the viewfinder. LV focus is right on.

Tony
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