15-85mm or 18-200mm

[neuroanatomist]

I don't know, Mark... Looking at the first image of Big Ben, I see both perspective distortion (the lean in the clock tower) and barrel distortion (the curve in the clock tower).


Here's an example from my recent trip, shot with the 5DII and EF 24-105mm f/4L IS @ 24mm, which has what photozone.de refers to as 'massive barrel distortion' at the wide end (measured as 4.3%). The left image is a DPP conversion with no corrections applied, the right image is a DxO conversion which corrects for the barrel distortion(DxO also improves the lighting). You can see that the perspective distortion is present in both images, but in the uncorrected image on the left the lines on the ceiling appear to converge (yes, perspective causes convergence too, but not over a distance of 15 feet), the transverse beams on the ceiling 'frown', the vertical columns bow outward, and the altar and table in front appear to 'smile'. Those effects are all due to the barrell dostirtion of the lens, and the spatial correction applied by DxO removes those effects.


[img]/cfs-file.ashx/__key/CommunityServer-Components-UserFiles/00-00-00-35-15/Barrel-Distortion.jpg[/img]

[Mark Elberson]

John,


Your example is a much better one. What I

[neuroanatomist]

What I'd like to see is two pictures taken with lenses having different amounts of barrel distortion but in the example itself having zero perspective distortion. If you get bored maybe you could show us since I "think" you have two lenses that would apply

Yep, the 24-105mm @ 24mm vs. the TS-E 24mm which is about as undistorted as you'll find at that focal length. The only examples I have of the same scene shot with both are where the TS-E corrects for both (perspective corrected with shift), but I'll find a bit of time to shoot a straight-on comparison which will isolate the barrel distortion component in a 'real world' setting.

[neuroanatomist]

What I'd like to see is two pictures taken with lenses having different amounts of barrel distortion but in the example itself having zero perspective distortion. If you get bored maybe you could show us since I "think" you have two lenses that would apply

Yep, the 24-105mm @ 24mm vs. the TS-E 24mm which is about as undistorted as you'll find at that focal length. The only examples I have of the same scene shot with both are where the TS-E corrects for both (perspective corrected with shift), but I'll find a bit of time to shoot a straight-on comparison which will isolate the barrel distortion component in a 'real world' setting.

Comparison shot and posted in the Barrel Distortion thread.