Extension tubes

[Mack Hicks]

I know extension tubes decrease minimal focusing distance. Do they have any effect on depth of field or it that strictly a function of aperture?

[Daniel Cadieux]

DOF becomes VERY shallow with extention tubes (especially so when stacked). You will need to stop down plenty, but the good news is there is no noticeable loss of light. You also lose the ability to focus to infinity. I love using extention tubes for flower close-ups, or other "macro" subjects such as insects. A nice low-cost tool to have :-)

[Axel Hildebrandt]

I've used extension tubes on my 300f/4 with 1.4x TC which makes it a pretty good semi-macro lens. Since there is no glass, the real issue is DOF as Daniel mentioned and AF acquisition might take a bit longer.

[Alfred Forns]

With macro tubes you should focus manually, AF is not a good option. I carry three 25 mm tubes with me and stack when needed.

With the tubes you will gain some magnification and will loose light so increasing ISO is important. As mentioned dof is almost non existing so stopping down and accurately focusing is a must !!! Good luck with them ... fun to use with all sort of lenses including wide angle !!!!

btw Axel's set up is one fine dragonfly lens !!

[Kaustubh Deshpande]

Mack...the depth of field goes down because you the distance to the subject is so small.
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[Mack Hicks]

Thank you all.