Help judging performance of my FE55z, FE35f2.8z horizon/infinity

Started Jul 5, 2016 | Questions thread
l_d_allan
l_d_allan Veteran Member • Posts: 5,087
Re: Help judging performance of my FE55z, FE35f2.8z horizon/infinity

holin wrote:

Here's an unverified idea for cheap aligment. Aligning to a wall is difficult, even with lasers it takes some work and there are multiple sources of uncertainty. However, floors (and ceilings) are level in modern buildings, usually done with a self leveling compound (think how water surface levels itself). My arca clamp has a bubble level that can be used to point the camera straight up or down, which should make it parallel to a level floor or ceiling. Maybe this would work, at least better than trying to align to a wall, if no specialist setup is available.

Mostly agree.

I've done AFMA indoors several times with a camera club loaned LensAlign, and there are definite advantages to being indoors. The location I used had tiled flooring that came out perpendicular to the wall. That provided a double check on the LensAlign mirror by using a tape measure.

However, lighting can be somewhat more difficult indoors. Building can vibrate more than you might realize from wind, HVAC cycling, nearby traffic (especially trucks), people walking around (even on a different floor),  etc.

The bigger problem I encountered was getting far enough away for longer focal lengths.

With shorter focal lengths, it can be difficult or impossible to get all four corners in the capture (which I understand to be at least partial justification for the "tilted horizon" approach).

My perhaps flawed impression is that the level of "attention to detail" for alignment is about the same for:

  • AFMA with LensAlign 
  • "good copy vs bad copy testing" with a brick wall.
  • ...
  • I found there was a definite learning curve with both.
  • I'm not claiming the "attention to detail" sufficient for brick wall testing is appropriate for the more demanding challenge of getting valid, repeatable +/- 100 numbers for MtfMapper tests.
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