.. I used this image to illustrate it http://tinyurl.com/flengths and note I say in it "bearing in mind the perspective is different for each focal length used" - meaning I have moved the camera .. perspective is your position relative to the subject was something covered earlier in the lessons. (the images were explained in class, so it made more sense there!) a second part to this was a series of photos shot from the *same* perspective using different lenses, with the center portion enlarged to show aside from the graininess the image - perspective and all - remained the same irrespective of lens choice. I was intending to also do a followup using a wide angle shot photo and compare this to a sequence of images shot with a longer focal length lens (narrow field of view) collaged together which would have illustrated that a wide angle isn't magical.. it just has a wider field of view. I made do with comparing a panoramic made with composite images using a 100mm lens and showing that relative to a shot taken with a 24mm lens - they looked the same. As a fun aside to these series, something I discussed years back here was fooling with focal lengths in making panoramas - the plan resulted in a half built swing lens panoramic camera that used a zoom to automatically change from a long focal length at the sides to a short in the middle.. but it was abandoned when digital came along and I just autostitched individual frames for the same effect. Again it was an interesting play on lens choice, easily explained to students with simple geometry.. with a camera mounted chest high atop a tripod on a straight beach, traditional fixed focal length panoramas create a U shaped beach scene.. the variable focal length straightens out the beach and it looks more normal and much more appealing. Drawing angles and filling the whiteboard with geometry equations had most of the students getting the point :) k
