Frans: I too was concerned about getting the proportions of the stretched photo as close as possible to actual size of the sundial. This can be done in two ways.
If a sundial is circular or has a circle drawn somewhere on it (my dial has a circle in the dial's center), the circle appears as an elipse in the original untouched photo. I simply stretched the photo until the elipse became a circle, and this automatically produced a photo of correct proportions of the sundial. Or, if you have a square or rectangular sundial of known height and width, just keep stretching or compressing until you get the correct proportions. You could have problems if you are photographing a non-circular or rectangular sundial which you can't measure, such as a vertical dial high up on a wall. If a dial is not square or circular, you'd have to guess its shape when strtetching. John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: <http://www.sundialsculptures.com> ----- Original Message ----- From: "Frans W. MAES" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, October 08, 2001 4:46 AM Subject: Re: Sundial Trick Photography > Hi All, > > John Carmichael wrote: > > > But I discovered that by using digital editing, you can stretch or > > compress a photo so that it appears that camara was directly over the > > dial! I discovered this while using the "perspective" and "distort" > > features of Adobe Photo Delux. > > I sometimes apply the same trick, using Paint Shop Pro. Starting > with a picture of a rectangular dial face taken at an arbitrary angle, > this involves 4 steps: the horizontal and vertical perspective tools are > used to make the sides parallel, then the horizontal and vertical > skewing tools are used to make them parallel to the picture frame. > > My question, however, is: does this procedure guarantee to yield the > correct result? That is: is the resulting height/width ratio equal to that > of the original? If not, angles between hour lines would be distorted. > As a consequence, it would be impossible to check the correctness > of the hour line layout, or to calculate the latitude for which the dial > was designed. > > Kind regards, > Frans > > ===================================== > Frans W. Maes > Peize, The Netherlands > 53.1 N, 6.5 E > www.biol.rug.nl/maes/sundials/ > =====================================
