• Please use real names.

    Greetings to all who have registered to OPF and those guests taking a look around. Please use real names. Registrations with fictitious names will not be processed. REAL NAMES ONLY will be processed

    Firstname Lastname

    Register

    We are a courteous and supportive community. No need to hide behind an alia. If you have a genuine need for privacy/secrecy then let me know!
  • Welcome to the new site. Here's a thread about the update where you can post your feedback, ask questions or spot those nasty bugs!

Some time ago in Murano

Asher Kelman

OPF Owner/Editor-in-Chief
Michael,

Of course, it's no mystery to you, but allow me to ponder Ben's experience of some weirdness with your arresting picture.





Michael Nagel: Bresaggio

Original



The format suits the feel of the building, is it me or is there some weird distortion going on there?




Buildingwith lines.jpg


Michael Nagel: Bresaggio

Original - Marked Up for geometry and orthogonality


Ben,

Your sense of geometry is well-tuned. The slight distortions are important clues. The converging horizontal lines are perfect, except in the markings on the road. There there's an unexpected bend!

However the verticals at the sides of the building are bowed, as in a barrel distortion. My guesses are

1. Lateral distortion of a 24mm or much wider lens which, maybe, has been partially corrected.

2. Stitching perhaps, especially as the EXIF data is missing entirely and stitching programs can do that.

3. The road slopes in the front? Rather unlikely as then it is sloping away from the building.

4. A corrected fisheye: I don't think so.

It's intriguing to try to work backwards and determine how a picture was taken. Of course, michael can let is in to his secrets!

What really is so distinctive is the pretty perfect converging horizontal parts of the building. That also is the basis for sensing the distortion of the verticals. That makes me think of a stitching program with rectilinear projection.

Asher :)
 

Michael Nagel

Well-known member
Ben - thanks.

Asher - thanks and thanks for digging deeper.

A few words on the making:

The picture is stitched from several shots taken with a APS-C camera and a focal length of 18mm (which makes a 27mm FoV equivalent for 36x24mm negative/sensor). There were taken in portrait orientation and stitched together in one line.

Concerning the distortion: There might be a little left in the picture, but the walls/corners on the left and right of the building are far from being perfect. I invite you to examine both sides and have a look at the height determined by the upper end of the lower row of windows. The crack and the offset on the left is very well visible, the one on the right can also be seen. So I am ready to take a part of the blame, but not all.

I optimized the stitched picture for rectilinear projection (others would have been possible) and put the main focus on the building and the sky. I did not touch the street level.

On distortion in general: Take a view which is larger than the FoV of your eyes and turn your head. If you apply a thought grid on every section you will experience a lot of distortions. It is just the amazing error correction of our brain which makes up the view we expect in a photo.

Best regards,
Michael
 
Top