1. ## Macro magnification

I'm trying to get my head around magnification factors using a bellows and either a Schneider 80mm or 120mm macro lens. This is all new to me, and I'm not sure I understand everything. Google is not my friend in this instance...as crawling the internet has only got me more confused.

Here's my question. Using a camera at its maximum bellows extension of 250mm, what would be the largest magnification factor I could expect of the subject on the film/sensor plane with each lens?

My rudimentary numerical skills have come up with 2.08:1 for the 120mm and 3.125:1 for the 80mm.

Am I close?

Thanks in advance, and pass the tylenol.

Jim

2. ## Re: Macro magnification

Looks correct to me.

At such high magnifications you can often use high-quality 135 small-format lenses with larger formats. At 2:1 a 135 format lens will cover 6x7. At 4:1, 4x5. Chances are you already have a suitable lens...

3. ## Re: Macro magnification

you need 160mm bellows draw for the 80mm to be 1:1 (80mm for the lens and 80mm for the bellows)
and 240mm bellows draw for the 120mm to be 1:1

if you are using a large format camera you can actually measure it on the screen.

here is a formula you can use: Ext=(m+1)F
Ext is extension
m is the magnification
F is the focal length

4. ## Re: Macro magnification

Thanks folks.

Greg - rearranging your formula gives M = (E/F) - 1.

So, using E=250mm (my maximum bellows extension) and F = 80mm, then M = 2.125

Likewise, keeping E constant (250mm) and F = 120mm, then M = 1.08

So, if I've got this right...with a maximum bellows extension of 250mm, the 80mm will get me to 2x lifesize, while the 120mm will only get me to 1x lifesize (i.e. lifesize) ?

This all reminds me of math tests back in high school (groan).

5. ## Re: Macro magnification

Originally Posted by f8orbust
Thanks folks.

Greg - rearranging your formula gives M = (E/F) - 1.

So, using E=250mm (my maximum bellows extension) and F = 80mm, then M = 2.125

Likewise, keeping E constant (250mm) and F = 120mm, then M = 1.08

So, if I've got this right...with a maximum bellows extension of 250mm, the 80mm will get me to 2x lifesize, while the 120mm will only get me to 1x lifesize (i.e. lifesize) ?

This all reminds me of math tests back in high school (groan).
Yep....

Now you're now getting me "cornfused"....

I'm referring to large format camera use where the bellows is at zero and so is the lens.

6. ## Re: Macro magnification

Thanks for your help - I'm going to go and lie down in a darkened room for a bit and mull this over.

7. ## Re: Macro magnification

All the math and some practical examples here:
http://www.captureintegration.com/20...extreme-macro/

Doug Peterson (e-mail Me)
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8. ## Re: Macro magnification

Thanks Doug - very informative. I'm weighing up the 80 vs 120 Schneider macros at the minute. As with your observations, the 120 is a great lens - but with only 10" (maximum) of bellows to work with it will only just get me to 1:1. If I want to dabble in higher magnifications I'll need to go with the 80. But, I prefer the longer focal length of the 120. Decsions, decisions.