May 27, 2018, 09:53:11 AM

### Author Topic: extention tube calculations? help needed.  (Read 2955 times)

#### hamada

• EOS Rebel T7i
• Posts: 119
##### 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?

#### canon rumors FORUM

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

#### J.R.

• EOS-1D X Mark II
• Posts: 1749
##### Re: extention tube calculations? help needed.
« Reply #1 on: April 27, 2013, 08:13:34 AM »
I took a hiatus from CR for a year and a half. The discussions haven't changed much. Excellent information is still being shared while people bitching about Canon cameras are still bitching and haven't moved on to Sony

#### TW

• EOS Rebel 300D
• Posts: 69
##### 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

• Guest
##### 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.

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 »

#### canon rumors FORUM

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