From: http://www.tcinternet.net/users/nmolson/lenses.htm
"Many inexpensive zoom lenses offer a variable aperture. For example, a 70-210mm f/4-f/5.6 lens has a maximum aperture of f/4 at the 70mm setting but a maximum aperture of f/5.6 at the 210mm setting. This effect is also evident at all focal lengths and aperture settings. For example, f/8 may provide the proper exposure at 100mm, but will result in a slight underexposure at 180mm. Always re-meter the subject when changing focal lengths with a variable aperture zoom lens." Also http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=001tCK is Pentax specific. Christian On Tuesday 09 April 2002 12:37, you wrote: > Yes, you are missing something but I don't feel like going through the > whole, long, involved explanation here at the office. I have other things > to work on. > > Len > --- > > -----Original Message----- > From: Christian Skofteland [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, April 09, 2002 11:24 AM > To: [EMAIL PROTECTED] > Subject: Re: Using external lightmeter with a Zoom lens... > > > If that's the case why doesn't the maximum aperture stay constant? > > In other words if I have a 60-300 f4-5.6 and I set it to 5.6 and zoom to > 300 > > am I still at 5.6? No, I need to set it at 4 to be at 5.6. Likewise if I > set it at f8 and zoom to 300mm will I still be at f8? I don't think so. > I'd > be at f11 right? > > The question is: what is my f-stop when it is set at f8 and I'm zoomed to > 200mm? Answer: ?????? > > or am I missing something again? > > Christian > who doesn't like variable aperture zoom or zooms in general.... > > On Tuesday 09 April 2002 12:08, you wrote: > > Well, as long as you are using an aperture smaller than 3.8 (in this > > case) say f4 or smaller, you won't have a problem using an external > > meter. If you are trying to shoot at full aperture, you may be forced to > > compensate > > a > > > bit. For example, if you set the aperture at f/8, it will remain at f/8 > > throughout the zoom range. > > > > Len - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
