Originally posted by stevebrot Dave,
Thanks for providing some hard numbers for the Raynox. I had done the calculations before, but could not find them or the "how-to" articles. Looking at your numbers and the Raynox images on this site, it is easy to see why they are so popular.
Steve
Steve, I made a serious typo on the magnifications. They should read:
Originally posted by newarts: A Raynox 150 on your DA 77 will yield about 0.56x at a working distance of about 208mm.
A Raynox 250 on your DA 77 will yield about 0.84x at a working distance of about 125mm.
My statement that a modest enlargement is needed to get to an effective 1:1x was also wrong... for the DCR 150 case an enlargement of 1.78x will be needed - not "modest" but do-able.
Sorry,
Dave
PS On the matter of "natural vignetting" limiting image circle (or angle) a variety of means are used to compensate for it, including radially graded and filters in the lens. The links I gave discuss strategies.
Originally posted by SteveBrot: I own two large format camera lenses, a 90mm and a 150mm. The 90mm has an advertised image circle of 221mm (102 degrees) at f/22 and the 150mm has an advertised image circle of 231mm (75 degrees). ....
Those are very large illumination circles indeed; 9 inches! How large is this camera? How far are the lenses from the film plane when in use?
You are certainly correct about the egregious hijack of the thread. I apologize to all.