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Close Up Lens Combination


ni_gentry

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Question for you techies...<p>

Which lens will give the highest magnification factor when used with a Nikon 6T close up filter... the

Canon 50mm f/1.4 or 85mm f/1.8 ?

<p>

I'll also ask the same question but using the Canon 500D filter (which I do not own) instead of the Nikon

6T (which I do own). I know the 6T has a higher diopter.

<p>

Does this look right?<p>

Nikon 6T, diopter 2.9 ---> focal length 345mm<br>

magnification ~= .15 on a 50mm lens<br>

magnification ~= .25 on an 85mm<p>

 

Canon 500D, diopter 2.0 ---> focal length 500mm<br>

magnification ~= .10 on a 50mm lens<br>

magnification ~= .17 on an 85mm<p>

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Yes, at that level of precision. That's with the lenses focused at infinity, of course. At closest focus you have to factor in both different native near-focus capability and the fact that the 50/1.4 is linear-focusing (maintaining focal length) whereas the 85/1.8 is internal-focusing (reducing focal length). Exercise for the reader.
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It sounds as if you need a <a href="http://www.imaginatorium.org/stuff/cufilter.htm">close-up filter calculator</a>. For a subject at the same distance, the 80mm will give higher mag, but you might not get the 50mm and 80mm lenses to focus at the same distance. I keep a 500D in my small waist bag (along with a CP filter, lens/body cap, CF cards, pen, paper & business cards) for use on my 70-200/2.8 L IS when I don't happen to have a true macro lens with me. It works well, but the subject distance at which it can focus is only from about 10" to 20".
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