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06/13/2005 10:25:37 PM · #1 |
I am trying to track down a focusing problem with my equipment.
I think its my 18-70mm lens, but I am not sure, maybe its my D70, maybe its user error. I hope you guys can help judge.
I conducted the following lens test:
//www.photo.net/learn/focustest/
here are the results from all 3 of my lenses, shot on a tripod in raw mode, converted to jpg.
//photopickles.smugmug.com/share/f9L6ALiQQUbOg
What do you guys think?
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06/13/2005 11:28:23 PM · #2 |
It appears to me that two of your three test lenses focus slightly further from the camera than optimum, that is the center of focus is beyond the target focus point. The second tested lens appeared to focus pretty much on target. This leads me to believe that there may be some minor backlash in the lens focusing drive, or more likely, the focusing algorithm is just a bit on the sloppy side to reduce focus 'hunting'.
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06/13/2005 11:31:44 PM · #3 |
So what should I do? Send the camera for repair or the lenses? or is it not bad enough for worrying about it?
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06/13/2005 11:57:07 PM · #4 |
If possible, compare your camera to another of the same type and see if the same effect is present. I don't believe the problem is bad enough to warrant repair, but that is your call. For critical applications where focus is paramount I always use manual focus anyway so auto-focus doesn't mess up my composition!
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06/14/2005 12:50:24 AM · #5 |
This is not the best test of focusing. You want to be able to focus on a flat surface not a diagonal one. Lay that bunch of lines on the paper next to a book and focus on the book instead.
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06/14/2005 12:59:03 AM · #6 |
I say set up the domino one...each domino 1mm in front of the otherfor about a total of 11 and focus on the middle one...from straight on. The contrast of black and white should be very good to get autofocus a good lock. And oh what fun to set it up!! (C:
With the paper one...not sure how well it is locking onto such a tiny line.. You didn't have it on Dynamic Focus right? That may cause a problem.
Message edited by author 2005-06-14 00:59:30.
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06/14/2005 01:02:53 AM · #7 |
Originally posted by dacrazyrn:
I say set up the domino one...each domino 1mm in front of the otherfor about a total of 11 and focus on the middle one...from straight on. The contrast of black and white should be very good to get autofocus a good lock. And oh what fun to set it up!! (C:
With the paper one...not sure how well it is locking onto such a tiny line.. You didn't have it on Dynamic Focus right? That may cause a problem. |
good idea.
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06/14/2005 05:11:55 PM · #8 |
Originally posted by kyebosh:
This is not the best test of focusing. You want to be able to focus on a flat surface not a diagonal one. Lay that bunch of lines on the paper next to a book and focus on the book instead. |
If you focus on a plane that is normal to the lens then you have no indication of where that plane falls in the focus depth. The 45 degree plane provides exactly that information with a qualitative representation of how the auto focus performs.
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06/14/2005 08:17:41 PM · #9 |
Of course since you're focusing on the centre of the frame, this completely ignores the loss of focus you may get towards the edges of your shot, especially at widest aperture on inexpensive lenses. This has the potential to skew your results somewhat.
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06/14/2005 08:24:49 PM · #10 |
Would diopter adjustment affect this?
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06/14/2005 08:26:04 PM · #11 |
Originally posted by faidoi:
Would diopter adjustment affect this? |
Diopter adjustment modifies the amount of eye relief you have in the viewfinder...
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06/16/2005 11:52:13 PM · #12 |
I really don't have dominos. Can you guys tell at all if the 18-70 lens is worse then the others? You might be able to see it in the original size better (available at the link above). I can probably take the 18-70 to B&H for waranty repair in the next couple of weeks, after that, its gonna be out of warranty.
I've found that lately on my photographs with the 18-70 the focus seems a bit off. I've mostly noticed this at close to minimum focus distance, wide open with full zoomed in, trying to use this lens for macro type photography. I find that the 18-70 is more often not in good enough focus then my other lenses, so that is why i descided to conduct this test. I am wondering if its simply user error, lens problem, or is the lens simply not sharp enough?
Message edited by author 2005-06-16 23:53:45.
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