# Extension tubes + macro lenses; how to measure?



## ScottyP (Aug 23, 2015)

Hi,

I see extension tubes at different lengths (12mm, 20mm, 25mm, etc.) but how does that work in terms of the macro power as is normally expressed in 1:1 true macro. The Canon MPE-65 gives up to 1:5 enlargement. 

How do I add up the extra magnification from extension tubes in those terms? I never see that, and I was thinking of getting a 100MM macro but maybe tubes to get big snowflake images, etc....

Thanks.


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## tolusina (Aug 23, 2015)

The formula for determining magnification increase with extension tubes is;
Extension tube length divided by the lens' focal length.

In use, add the calculated increase to the lens' native magnification.

Using the three tubes together that you've listed adds up to 57mm extension.

57/65=0.877

Add the 65 macro's 1:5 to 1:0.877 gets you to 1:5.877

Additional magnification with extension tubes increases as focal length decreases.


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## ScottyP (Aug 23, 2015)

Ah, that clears it up. Thanks.

The tubes would add some magnification to the 100mm macro but not as dramatic as I would have guessed.


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## dcm (Aug 23, 2015)

Here's a page that helps explain them and has some tools to help you determine the effect of each.
http://www.cambridgeincolour.com/tutorials/macro-extension-tubes-closeup.htm


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## LDS (Aug 23, 2015)

ScottyP said:


> The tubes would add some magnification to the 100mm macro but not as dramatic as I would have guessed.



Another option to obtain larger magnifications without a dedicated lens is to use a bellows, but Canon never made one for EF lenses, introducing instead the specially designed 65mm.
Novoflex manufactures some, including one designed specially for EF lenses. On a bellows you can use almost any lens, but usually macro ones yield best results. Mounting the lens reversed is also an 'old trick', but requires an adapter.
Anyway, for subjects you can get very close shorter focal lengths will deliver higher magnifications using the same extension (but proper lighting becomes trickier, because the lens front may be very close to the subject). Longer macro lenses are usually designed for subjects you can't get close enough easily.


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## danski0224 (Aug 23, 2015)

A "close up" filter is an option. 

If you get a good one like the Canon 500D or other apo designated filter, it will not impact image quality. You can use one on almost any lens with a step down ring as required. 

A bellows or MP-E 65 will be quite difficult to use hand held. 

I'd look at legacy Nikon lenses and bellows if you want to go that route. Almost any manual lens for reversing, or enlarge lenses. Canon EF lenses don't work so well due to the electronic aperture... unless you futz with it.


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## LDS (Aug 23, 2015)

danski0224 said:


> A bellows or MP-E 65 will be quite difficult to use hand held.



At larger magnifications DOF becomes so shallow, and vibrations amplified so much, handheld shooting becomes quite difficult - a tripod and a focusing rail are usually needed. Moreover effective aperture decreases, and ambient light often is not enough.
Macro beyond 1:1 usually becomes quite a complex and expensive task.

Novoflex also makes an EF adapter for reverse mounting, which transmits the lens-camera signals, I tried it at a wildlife photography fair last year, shown at the Canon stand, and it works well enough.


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## Deleted member 91053 (Aug 23, 2015)

Another thing to consider is that extension tubes may allow you to use extenders on your macro lens. I have tried a 13mm extension tube with my Canon 100 F2.8 macro and 1.4 or 2 x Mk3 extenders - works surprisingly well though not perfect.
My extension tubes are 3rd party ones so the subtle application of a knife was needed to allow the use of the extenders.


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