# Help in Selecting Canon Extesion Tube



## Old Swede (Jun 10, 2012)

Do you have experience that might guide my decision regarding choice between Canon’s Extension Tubes (EF 12 II or EF 25II). I will probably use the extension tube for semi-macro work and birding. Some of my lenses that it might be used with are 50 mm f/1.4, 85 mm f/1.8, 400 mm f/5.6L, 
70- 200 mm f/2.8L IS II, 24-105 mm f/4L IS, and 16-35 mm f/2.8L II. I suspect that my major use of the extension tube will be with the 70- 200 mm f/2.8L IS II and the 400 mm f/5.6L. I am leaning towards the EF 12 II, because of working range, but recognize that I will give up magnification to achieve that. Cost is not an issue. My Canon bodies are the 50D and the 5D Mark III.


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## neuroanatomist (Jun 11, 2012)

Old Swede said:


> I suspect that my major use of the extension tube will be with the 70- 200 mm f/2.8L IS II and the 400 mm f/5.6L. I am leaning towards the EF 12 II, because of working range, but recognize that I will give up magnification to achieve that.



Neither will be very effective in the 200-400mm range, since additional mag is tube length / focal length (so, a gain of 0.03x with a 12mm tube on a 400mm lens). Also, you lose infinity focus. Generally, for semi-macro work a 500D Close-Up Lens is better for use with a telephoto lens. I've used one with my 70-200 II and it's hard to tell the difference from my 100mm L Macro.


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## Old Swede (Jun 11, 2012)

Thanks Neuroanatomist. I have read a number of your past posts in this forum and very much respect you. 
Getting to the point: I had seen the rough ratio formula for predicting magnifcation and knew that these extension tubes would afford little benefit in that respect. What I have not found are tables regarding the minimum and maximum focal distances for different extension/lens combinations. My greatest interest is attaining the ability to move in a few feet closer with my 400 mm f/5.6L lens. On the other hand, I need to know what the impact of the extension tube will be on maximum focal distance. For pictures of birds in my back yard, cropped pictures acquired with the 400 mm lens are generally OK. However, birds sometime land just a tad short of the minimum focal distance for this lens. I would be delighted if an extension tube would afford a working range of 8 to 40 feet with the 400mm lens. My mention of macro photography was probably an inadvertant "red herring". A more casual interest is to use the extension tube for macro. In this latter case, I would probably experiment with some of the other lenses in my kit.


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## neuroanatomist (Jun 11, 2012)

Ahhh, I see. In that case the tube is better - the 500D restricts you to focusing at a 50 cm (~20 inch) distance. 

You do lose a little light with a tube (longer tube means more light lost), can be a concern with an f/5.6 lens, but an auto-exposure mode (Av, Tv, M with Auto ISO on a recent body) handles that from a practical perspective. 

To your question: Natively, your 400mm f/5.6L has a working range (front element to subject distance) of ~11 feet to infinity. With an EF 12mm tube attached, the working range is 8.5 feet to 43 feet. With the EF 25mm tube, it's 7 feet to 20.7 feet. 

Hope that helps!


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## Bennymiata (Jul 5, 2012)

The best tubes to get are the Kenko tube set.
You get 3 different sizes, and you can mount them together in any combination, including all 3, and they work well on Canon lenses and are cheap as chips.


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