I'm looking for an extension tube for my DSLR. Any suggestions? I see a lot on the internet, but I cannot figure out which is the best.
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1\$\begingroup\$ It is worth pointing out that if you go for ones with electrical contacts, and expect AF to work just like it normally would, you will be disappointed. AF performance will be decreased and there will be a lot more hunting for the AF motor. For the price difference its more economical to go for tubes with no contacts and MF as they are usually many times cheaper. \$\endgroup\$– GaptonCommented Jan 21, 2013 at 2:40
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\$\begingroup\$ If speedy AF is critical, extension tube is not really an option. You will be better off using a dedicated macro lens with a good USM motor with good AF performance. \$\endgroup\$– GaptonCommented Jan 21, 2013 at 2:42
4 Answers
An extension tube doesn't have any optics in it, it's just a tube that is used to move the lens in relation to the sensor, because there's nothing but air in there all the extension tubes in the world will use the same air will give you the exact same image.
There are 3 ways extension tubes differ:
Electrical contacts
Tubes with no electrical contacts (the cheap kind) don't have a connection between the lens and camera, you don't have auto focus and don't have aperture control, the camera will only work in M and Av mode.
To control aperture switch camera to Av mode, set aperture, press DOF preview button and hold, while pressing detach lens
Tube with electrical contacts: those are easier to use because you have all the normal camera controls (but I don't think auto-focus will be useful here).
Thickness
Thicker tubes will increase magnification and move the focus plane closer - but remember if the tube is too thick the focus plane will move behind the lens's front element and nothing will be in focus.
You can buy a set of tubes with different thicknesses that you can combine to have a large number of options.
Build quality
Just don't put an heavy expensive telephoto on a thin plastic Chinese tube.
Even if macro extension tubes have no glass in them, with cheap ones reflections or play at the mounts can make a huge difference. I recently bought one set branded COMIX, sold by Commlite, from eBay. It is useless because of glare and play. Kenko seems a safe bet. I got so upset with the COMIX tubes that I wrote a review some days ago comparing three equivalent sets of tubes for MFT of different brands and prices. Have a look at the test images, and you will never ever again believe that bad quality or badly designed macro extension tubes will not affect image quality. The review is in instalments: part 1, part 2, part 3.
The air in my Kenko tubes has never let me down. :-)
This is one of my rare third party camera accessories. I can't think of any good reason to pay more for a set of tubes. I bought mine used. The air seems undamaged.
I've been using Kenko for 3 years now and they work well. You will notice some flex in them if you mount all three at once on a heavy lens but other than this they are well built and get the job done.