There's no question I'm an opinionated sonofagun, but most of the time my opinions are developed over time, thru experience, and by reading the subject at hand! Amazing, huh? <g> Informed opinions instead of guesses. And after that, keep an open mind, and really listen when someone comes back at you. More below
Mark Erickson wrote: > > Keith wrote: > > > >Mark Erickson wrote: > >> > >> Bob wrote: > >> >This has to be baloney. Light *has* to strike the sensor at an oblique > >> > angleor an image will not be formed! Only light along the axis of > >> > the lens willbe perpendicular to the array, and of this light, only the > >> > ray on axis will be perpendicular. > >> Turns out that the light doesn't have to "strike the sensor at an oblique > >> angle" to form an image. > >Turns out that in a practical world of consumer photography, it does. > >If the object you're photographing is any larger than about 2", it does. > >Read this excerpt form that first site below: > > > >"A telecentric lens "sees" a cylindrical tube of space of diameter equal > >to that of the front lens element. It is limited to photographing > >objects whose lateral dimensions do not exceed the diameter of the lens." > > > >The use for such a lens is so limited, it's pertinence in this > >discussion is relegated to merely one of a curiosity. > > > >keith whaley > Keith, > > In practice I agree with you (how many of us have telecentric > object-inspection lenses at home?). Thing is, Bob didn't qualify his > statement with, "in a practical world of consumer photography." > > My bigger picture point is that in the practical world of modern > multi-element lens design, lens designers can control the angle of arrival > of light rays. I refer again to the retrofocus designs of very short focal > length lenses (like the Pentax 15mm F3.5). That's something _else_ I have to read more about, so I can better understand the design. Can't knock it OR praise it if you know nothing about it. Wellll, you shoudn't anyhow! <g> > If the Pentax lens designers are > as good as we think they are, I'll bet that they're designing their latest > lenses to accomodate the "quirks" of focal plane arrays. > > Anyway, thanks for actually reading the links and not just blasting away.... > > --Mark Yup. keith
