DP2m Lens Distortion Problem

Started Sep 3, 2012 | Discussions thread
Roland Karlsson Forum Pro • Posts: 27,984
RE:Optical illusion

adegroot wrote:

3. the sea water level line is 100% straight; I laid a large ruler over my monitor at the water level of your photo's original size. Straight as can be. Not one curve to be seen, not even a tiny one. Total optical illusion.

Measuring in Photoshop on the largest image gave me 0.8% distortion, which equals 4 pixels max deviation

0.8% is a moderately good normal lens. A good one can vary from 0.3 to 1.2%.

2nd photo: Put your camera on a tripod, put a dark cloth over your head and the back of the DP2M and recompose: make sure your camera's back is 100% parallel to the object you are shooting, and voila, your lines should be just fine. The path of the light going through the lens is to be 100% perpendicular. No camera would be that far off. You don't have a bad camera. The closer you get to an object, the more crucial it si to have this perpendicular/parallel alignment. This is elementary, my dear Watson.

If its the edge of a photo and it is laying 100% flat on the table, then it does not matter how you hold the camera. The edge will always be straight in a lens without distortion. That is what my program for fixing distortion measures. I promise you - it works.

There are three possible explanations.

  1. the image did not lay flat.

  2. the lens distorts when focussing closer

  3. the edge of the photo is not straight

 Roland Karlsson's gear list:Roland Karlsson's gear list
Sigma DP3 Merrill Sigma dp2 Quattro Sony RX100 III Pentax K-3 Pentax K-1 +14 more
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