On 3 Jan 2004 at 21:12, Andy Chang wrote: > If you remember, I have asked about losing F stops using teleconverter. > I'm just wondering if it also applies on the extension tubes. By adding > extension tubes behind the lens, do I have to adjust the exposure > accordingly?
Yes, consider the way the tubes work. When using tube the image projected on the film plane is only a sub section of the image that would appear if the lens were closer (hence the effective magnification). You can then assume that the available illumination in that projected image is less over the area of the film as it is spread over a wider area. You can calculate the losses but it's difficult and lens dependent to an extent, this is one of the areas where TTL meters reign supreme. Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
