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Archive 2005 · 50/1.8 front focus
  
 
Eishi
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p.1 #1 · p.1 #1 · 50/1.8 front focus


I just bought a used 50/1.8 MK I from B&S forum and it is consistently focusing 1-2 inches in front of the focus point. Is this common or does this lens need to be calibrated? I single-point focused on the "7" of the tape measure but it focused between "9" and "10" (tape set at 45 angle):
http://img.photobucket.com/albums/v296/gofast33/IMG_0685.jpg

100% crop:
http://img.photobucket.com/albums/v296/gofast33/IMG_0685-100.jpg
(I hope you can see the sample photos, this is the first time I tried posting pictures)



Feb 20, 2005 at 07:05 AM
Eishi
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p.1 #2 · p.1 #2 · 50/1.8 front focus


Anyone have any advise for me? I should mention that I shot 5-10 shots at each aperture between 1.8 and 4.0 (re-focused each shot) and the shot was consistently focusing near the 10" mark on the tape measure.


Feb 20, 2005 at 08:52 AM
IronHelix
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p.1 #3 · p.1 #3 · 50/1.8 front focus


IMHO- thats not really the best target to use, mainly because of the shadow above the stove control. There is no huge FOCUS HERE line that the camera cannot miss- there is many things it could be trying for there. If i were using such a thing, i'd put a checkerboard pattern paper next to the tape measure, or print out a real focusing chart (there are a few PDFs floating around here) or grab one here http://www.photo.net/learn/focustest/ . Then tripod your cam, place the chart at a 45 angle and make sure that you have the auto focuspoint selection turned off. Focus and shoot, do 3-4 refocusing each time (go to MF mode, turn the focus all the way out one way, AF on again and shoot). See if focusing full in or full out makes a diff. Then post your results, you will get much more help.


Feb 20, 2005 at 09:15 AM
Eishi
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p.1 #4 · p.1 #4 · 50/1.8 front focus


Thanks for the help, IronHelix. I will re-evaluate using your suggested method.


Feb 20, 2005 at 09:23 AM
Eishi
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p.1 #5 · p.1 #5 · 50/1.8 front focus


OK, I used the test chart suggested by IronHelix and here is my result:

AF:
http://img.photobucket.com/albums/v296/gofast33/IMG_0739AF.jpg

MF:
http://img.photobucket.com/albums/v296/gofast33/IMG_0748MF.jpg

Shot 5 AF and 5 MF with similar results. Would you consider this acceptable for AF performance?



Feb 20, 2005 at 10:29 AM
Gijs
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p.1 #6 · p.1 #6 · 50/1.8 front focus


I would consider that acceptable.


Feb 20, 2005 at 10:38 AM
riokid
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p.1 #7 · p.1 #7 · 50/1.8 front focus


Eishi,

I share the views of IronHelix and Gijs.

I have used this lens in question with no problems on my 20D. However, I am offering to refund your money in full if you can send the lens back as quickly as you can. The only cost to you will be the return postage.

I am sorry this did not work out for you.

dan



Feb 20, 2005 at 04:13 PM
 

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c08as2
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p.1 #8 · p.1 #8 · 50/1.8 front focus


Eishi could you post the link from Ironhelix where you printed the focus chart. I can't seem to find one. Thanks in advance.


Feb 20, 2005 at 05:17 PM
DaveEP
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p.1 #9 · p.1 #9 · 50/1.8 front focus


http://www.photo.net/learn/focustest/scale45.jpg


Feb 20, 2005 at 08:12 PM
RDKirk
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p.1 #10 · p.1 #10 · 50/1.8 front focus


That's good performance. Keep the lens.


Feb 20, 2005 at 10:13 PM
nutek
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p.1 #11 · p.1 #11 · 50/1.8 front focus


Looks good to me too, I would say it is within operating specifications.


Feb 20, 2005 at 11:40 PM
trtagawa
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p.1 #12 · p.1 #12 · 50/1.8 front focus


Looks acceptable to me. My MKII did the same thing with my DRebel at close range; didn't have the problem with subjects at longer distances because of the wider DOF. To compensate in close distance and wide aperture shots, I just got into the habit of focusing in the lower half of the focus box.


Feb 21, 2005 at 12:01 AM
Eishi
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p.1 #13 · p.1 #13 · 50/1.8 front focus


Thanks to all who responded! This site is the best! I've decided to keep the lens. Thanks, Dan (seller: riokid), for sticking with me.

I am fairly new to SLR's as this is only my third lens ever. I think I am just not used to such a shallow DOF at f/1.8. I took a bunch of shots of real subjects today in better lighting with good results, especially at f/2.2 and up. Thanks again, everyone!



Feb 21, 2005 at 12:38 AM







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