Because with a variable aperture lens, the aperture changes as you zoom, and you'd never know exactly what the aperture is at the time of the exposure unless you have a new, high tech camera that will read out or record the aperture. So, let's say you measure the exposure to be XX sec @ f4.0, and you set the lens at 4.0, and then zoom in/out to frame, while zooming the aperture will change.
Shel > [Original Message] > From: frank theriault <[EMAIL PROTECTED]> > To: <pentax-discuss@pdml.net> > Date: 5/19/2005 5:17:53 AM > Subject: Re: Understanding exposure? Recommendations? > > On 5/18/05, Shel Belinkoff <[EMAIL PROTECTED]> wrote: > <snip>Do not use a > > variable focus zoom lens when learning exposure. <snip> > > Why would you give that advice, Shel, when talking about exposure? > > I would think that when learning composition, eliminating as many > variables as possible means that one can concentrate on the task at > hand, rather than fiddling with focal length. > > But what does it have to do with exposure? > > I'm not taking you to task WRT your statement, or or questioning the > validity of it, I just don't understand it. > > thanks, > frank > > > -- > "Sharpness is a bourgeois concept." -Henri Cartier-Bresson
