on 16/12/02 9:27 am, Shangara Singh wrote: >> In view cameras there is a streaching of an object as it gets nearer the >> edge of the frame. This can be seen if you look at a circular object near >> the edge of a wide angle shot. It becomes an elipse. > > Ian, aren't elipsing and perspective distortion different phenomena? One > caused by the design of the lens while the other is caused by the angle of > the light hitting the film/sensor?
I have not had a chance to look at the text books, but I think they are the same. Its not so much caused by the design of the lens, it is a law of optics. You would get the same effect with a pinhole. >> In Photoshop, what is called perspective in the transform menue is in >> reality just a crop. > > Ummm...not so sure about that. <G> As I understand it, a crop cuts up an > image but perspective distorts it. If anything, Adobe have confused the > terminology by giving the crop tool the option of not only correcting > perspective but also resizing the image. Imagine being able to put your > image on a cutting board and being able to stretch it and also make it > appear bigger! Can't be done - can it? Perhaps I could have phrased that better!. By using the Transform> Perspective tools. You get a similar result, but with less control, as using the Crop tool and checking the Perspective tick box. As I then went on to repeat :) >> The same effect is produced by using the crop tool, and >> selecting an area of the picture. Then with the perspective tick box checked >> on the task bar you can move the corners of the frame as you want. > > See above...you're not cropping any more but distorting your image to look > the way you want it to. You get the impression that you're un-distorting but > in fact you're doing the exact opposite. Yes in the exactly same way that using movements on a view camera distorts an image, to make it look the way I want it to! Ian -- Ian Goodrick, Ian Goodrick Photography, Gravesend, Kent, UK =============================================================== GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
