Macro magnification

[f8orbust]

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

 

[Jan Brittenson]

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...

 

[Greg Lockrey]

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

 

[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).

 

[Greg Lockrey]

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".... :bugeyes:

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

 

[f8orbust]

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

 

[dougpeterson]

All the math and some practical examples here:
http://www.captureintegration.com/2009/08/25/extreme-macro/


Doug Peterson (e-mail Me)
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[f8orbust]

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.