I own an Elan IIe with 28-105 USM. Im going to buy Canon 250D close-up lens, but I know it may have some problems (vigneting at wide end) with my lens.

I want to know what focal length vignetting starts, or better: what 'vignette-free' magnification range will I achieve?

-- Michal Araszkiewicz (arasz@mech.pw.edu.pl), August 24, 2000

Answers

Michal, using a close-up lens on a wideangle doesn't give you much, IMO. Most of the magnification effect will be achieved when your lens is zoomed to a longer focal length. Therefore, I would not worry about vignetting. Also, for some optical reasons (you are at the Technical University so may know better) vignetting with a close-up lens is not as pronounced (i.e. starts "later" when zooming down) than with filters of equal (or even smaller) thickness. Please, somebody correct me if I'm wrong.

I can say the following: I have used a 62mm closeup lens (2-element achromat, thick ring) on a 24-85 Canon lens having the 67mm filter thread. I purchased a 67-62 step-down ring. I haven't noticed any vignetting but, to be honest, I haven't used it much at the extreme 24 mm setting. For one, it defeats the purpose (poor magnification). Secondly, the closeup lenses are designed for moderate telephotos (70- 200 range) so I use the close-up diopter on my telephoto zoom where it performs great. But I shot a few wideangle frames with big foreground flowers at 24mm and there was no vignetting. So your 28mm should be even safer.

By the way, I didn't get Canon diopters, I got Nikon 2-element achromats, 5T and 6T (hence the non-Canon 62mm diameter). Half the price of Canon's (even if you add a 58-62mm step-up ring) and also great performers. Plus, you'd have an oversized dioppter which would make vignetting even more unlikely at 28mm. Had to order them from BH, never seen them at the Warsaw Photo Fair.

Good luck,

Piotr

-- Piotr Mikolajczyk (mikolaj@pcwarsaw.waw.pl), August 25, 2000.

Thank you for your answer, Mikolaj. I know that using wide-angle CU-lens doesnt _usually_ make much sense. I don't want to use this close-up lens with wide end!

But I don't want to end up with magnification range limited by vignetting. At 105mm this lens with 250D magnifies 0.43x Although it's far away from 1:1 it seems enough and sometimes more than enough for my purposes. I would like to have possibility to zoom down a little to approx. 0.20x (which is, BTW close to max. magnification of this lens without accesoris)

As for Nikon CU-lenses I wanted to order it from B&H but they were out of stock.

I got one more question To what extent one can change magnification just by changing distance to the subject? (when using CU-lenses)

-- Michal Araszkiewicz (arasz@mech.pw.edu.pl), August 25, 2000.

ups, sorry Thank your for your answer, Piotr

-- Michal Araszkiewicz (arasz@mech.pw.edu.pl), August 25, 2000.

I have the 250D and a 28-105. Vignetting ( from the thickness of the diopter) will begin to appear around 35-40mm.and wider range. I have a Nikon 6T but, haven't used it on this lens so I'm not sure about vignetting with it. You can buy a set of Kenco extension tubes for about the same price as the 250D and you won't have any vignetting problems with them, and they work fine on this lens.

-- Clay Prescott (prescott@lib.uwo.ca), August 25, 2000.