4

In the photos at the links below there seems to be a diagonal, low front to high rear focus plane. In the first photo note the turf, feet and lower legs of the players in the foreground are in focus while their bodies from the thighs up are not. The QB behind them in the center of the photo is in focus from about the thighs up but his knees to the turf less so. He is also leaning slightly backward.

In the second photo the turf in front of the four players is in focus but their bodies are only in focus from about the thighs up.

Why isn't there a consistent vertical focus plane?

Jay

Nikon D500, Sigma 120-300mm, f2.8, SS 1/640 (#1) and 1/320 (#2), dynamic 72 point focus points, 300mm focal length (#1) and 155mm focal length (#2), ISO 4000 (#1) and 1800 (#2).

http://www.attorneyjaysportspics.com/2016-Sports/Football/October-28-2016-Bermudian/i-JswH9c9/A

http://www.attorneyjaysportspics.com/2016-Sports/Football/October-28-2016-Bermudian/i-Vq27RSb/A

5

Your lens is demonstrating tilt. In addition to the bottom to top negative tilt (the bottom is in focus closer that the top of the frame) there also appears to be a little positive tilt left to right (the left is in focus slightly closer than the right). Sometimes the lens gets out of alignment due to a hard blow or fall. If that is the case the lense will demonstrate the same characteristic, to one degree or another depending on focal length, focus distance, and selected aperture, in every shot. Sometimes the image stabilization components (VR in the Nikon nomenclature) can create tilt that is more variable in terms of how often and in what direction it occurs.

Do note that if you are shooting at an angle from an elevated position, which doesn't seem to be the case in your examples, a lens with a proper flat plane of focus will show the lower part of the frame in focus in front of subjects standing straight.

The lens needs to be adjusted by a service center qualified to do so, and if the lens is in warranty by one that is authorized to do such repairs by your lens' manufacturer. How effective such a repair will be can vary greatly from one instance to the next. Roger Cicala, the founder and lens guru at lensrentals.com, has addressed the frustration of having a misaligned lens returned to a customer and labeled "within specification" at this entry to his blog.

  • Would a loose lens mount cause the problem? After posting my question I noticed that all the screws on the lens mount were loose (camera mount is fine). So, the lens was slightly wobbly on the camera. I tightened the screws and will now test it under conditions similar to those in the photos I posted and let you know what happens. Thank you for your input! – Jay Kalasnik Oct 31 '16 at 23:26
  • Yes. Anything that changes the alignment of the lens' optical axis so that it is not perpendicular to the image sensor will cause tilt. – Michael C Oct 31 '16 at 23:43

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