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07-08-2019, 02:05 AM   #1
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Brick wall diagnosis

I never thought I'd end up taking photos of brick wall. But here we are. Look at the left side. Is there something wrong with my DA 18-135 or is it a not so great copy and within spec?
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07-08-2019, 03:06 AM   #2
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This kind of 8x zooms beyond 85mm still works for subjects in the center with blurred background.= (portraits, macros etc). I had the DA 18-250 it was still sharp in the center from about 100mm to 180mm, not sharp at the edges+corners at those focal length, and even the center started to suffer from 180mm to 250mm, especially wide open, it had to be stopped down to at least f8 to be reasonably sharp in the corners even from 50mm to about 100mm.
07-08-2019, 04:02 AM   #3
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The 18-135 isn’t very sharp on the edges at the long end. This does look a little decentered though. Were you perfectly perpendicular to the wall? Does it look better at f8?
07-08-2019, 04:11 AM   #4
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QuoteOriginally posted by Kozlok Quote
This does look a little decentered though.
Did take a big knock when my son ran right into it on his scooter as I was taking action shots. I might get it checked out.
'Objects in the viewfinder are closer than they appear'

07-08-2019, 07:24 AM   #5
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I wouldn't accept that result from my 18-135.
Whether or not it can be fixed is another issue.

---------- Post added 07-08-19 at 10:26 AM ----------

QuoteOriginally posted by Kozlok Quote
The 18-135 isnít very sharp on the edges at the long end. This does look a little decentered though. Were you perfectly perpendicular to the wall? Does it look better at f8?
What I was more concerned with was the centre sharpness, which should be excellent.
07-08-2019, 01:12 PM   #6
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Could you try it on a tripod with manual focus? See if you can get the left side to focus better. Perhaps focussing on the centre and then seeing if the scale on the lens moves when the left side is improved.
Is the problem the same at various focal lengths? A grid pattern, even a chain link fence might be better than a brick wall.
07-08-2019, 01:47 PM   #7
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To make sure you are exactly perpendicular to the wall you might want to use a measuring tape to make sure you have equal right triangles to the wall.
07-08-2019, 08:58 PM   #8
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You can also try a different test- get good focus using center-only spot focus, on a more distant solid stationary object with a good sharp edge and which has elements of good detail. Then carefully switch to MF to hold the focus. (or simply use MF if you are good at it) Do this when using a tripod with SR turned off. Then reposition the camera and take additional shots so the object is placed at various areas in your frame: at and near the right edge, at and near the right upper and right lower corners, then the same for the left side. Then do the same for central upper edge and lower central edge. You can refocus and do the same over again. You should get a good comparison of central performance vs. right and left edges, corners (which matter less), and central edge performance.

07-09-2019, 03:22 AM   #9
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I'm with those who question your perpendicularity. Looks to me that the right side is closer to you than the left (which would indicate that you were pointed towards the left when you took the shot), and that's the most likely reason the focus is different. It looks to me that the horizontal lines in the concrete converge slightly as you go from right to left (though I'd have to measure to be certain), further evidence of non-perpendicularity.
07-09-2019, 07:32 AM   #10
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Looking at the bottom of the photo shows a line of mortar which is missing on the right hand side. If more is showing of the left end of the wall, then it must be further away.
A retest is needed, get an assistant to hold something against the wall which has a square edge, such as a sheet of board or a rafter square, so you can align the camera axis dead square.
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