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Author Topic: extention tube calculations? help needed.  (Read 1956 times)

hamada

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extention tube calculations? help needed.
« on: April 27, 2013, 05:58:57 AM »
hi, i bought a set of extention tubes for my macro work.

i need someone who can to explain to me how to calulate the new MFD and magnification.

for example when i put a 25mm extention tube on my 90mm macro that has 29cm MFD and 1:1 magnification... what is the new MFD and magnification?

or what if i put a 31mm extention tube on my 70-200mm f4.

is there maybe a good website that explains how to calculate this?

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extention tube calculations? help needed.
« on: April 27, 2013, 05:58:57 AM »

J.R.

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TW

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Re: extention tube calculations? help needed.
« Reply #2 on: April 27, 2013, 08:25:36 AM »
Simply divide the amount of extension by the focal length pf the lens. 25mm ext/ 50mm lens = 1/2x, or 50% magnification. Also, just take a pic of a ruler and do the math!
35+ years of Canon gear...good grief! Still have 2 FTb cameras in working order, too!

Canon-F1

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Re: extention tube calculations? help needed.
« Reply #3 on: April 27, 2013, 08:55:25 AM »
Also, just take a pic of a ruler and do the math!

yeah why not invent the wheel again.    ::)

sure much easier to do that for a dozend lenses * 3 extention tubes then searching a formular.  :P


Quote
http://www.cambridgeincolour.com/tutorials/macro-extension-tubes-closeup.htm

+1

was going to post that.
« Last Edit: April 27, 2013, 09:00:28 AM by Canon-F1 »

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Re: extention tube calculations? help needed.
« Reply #3 on: April 27, 2013, 08:55:25 AM »