> "Paul Brecht" <nowayidontthinkso.net> wrote in message
>>Just keep in mind that you need to multiply 1.6 to the effective focal
>>length to understand what you're getting in focal length...
>>28-100mm = 45-180mm (aperture stays the same...)
> The Focal Length stays the same too. It's only the Field of View that gets
> changed. (the area that the lense sees)
> At 28mm then 10D will have the same Field of View as a 45mm Lense. And at
> 100mm it will have the same Field of View as a 160mm lense would have. But,
> the actual Focal Length does not change.
> The reason being that at the focuse point the CMOS sensor(being smaller)
> will only see the middle part of the image being focused on it using a lense
> designed for 35mm Film cameras.
> It is the same as cropping an image in Photoshop. The image is no larger,
> unless you enlarge the cropped image.
> Too many people think the conversion that is mentioned( most say 1.6 for the
> Canon Sensor, but, if I remember correctly it's 1.58 according to Canon)
> somehow causes the lense to become a longer lense( increased focal length)
> which is not so. It makes a newbie think that they are somehow getting a
> longer , more powerful lense even though they are buying one with a smaller
> focal length. The only way to increase the focal length of any given lense
> is to use
> an extender tube or a tele converter like a 2X tele converter. Which works
> pretty good, but, can cause the Auto Focuse to be a bit slower.
>>"Ron" <rfranksadelphia.net> wrote in message