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MP-E at 10X

Started 5 months ago | Discussions thread
OP Victor Engel Forum Pro • Posts: 20,968
Re: MP-E at 10X

Pansottin wrote:

Victor Engel wrote:

SigmaTog wrote:

Can the MPE65 be used with an electric extension tube ?

Extension tubes work fine, but the lens is basically a built in extension tube lens anyway, so you'd need a lot of length to make much difference.

Hi, what if it's a bellows with a maximum extension of 192mm like the Novoflex BallPro1? How will the MP-E 65mm perform?

Thanks.

An approximation is to use the lens equation: 1/d0 + 1/d1 = 1/f where d0 is the sensor distance to the lens and d1 is the subject distance. At 1:1 d0 = d1 = 2f
I think the magnification is basically d0/d1.
So the MPE at maximum extension would be 1/5D + 1/D = 1/f
Solving for D,
1/5 + 1 = D/f
f/5 + f = D
So at full extension, the distance from lens to focal plane is 5(6/5 f) or 6f.
The focal length f = 65mm so the extension is 6*65 = 390mm
So how much difference will a 192mm extension tube make? (192 + 390) * 5 / 390 = about 7.5x
The MP-E is not a simple lens, but I think this formula is close enough for this question.

Derivations were done while I was in a meeting, so there could be an error.

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Victor Engel

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