Extension tubes on a 500 f4

Anyone tried this to reduce the MFD ?
I like to get the odd dragonfly/butterfly when i'm out shooting birds but sometimes they are just a little to close.

It depends on how much reduction you want. They work on a long lens but keep in mind that there will be light loss and the reduction in MFD won't be huge.

Canon EF12 II Extension Tube let me decrease the MFL on 400mm f/5.6 from 3.5m to around 3m.

Yes, you can use extension tubes on the 500mm. I did for this shot...

I picked a set up cheap so will give them a go, thanks for the help.

NeilB0147 wrote in post #16273211
I picked a set up cheap so will give them a go, thanks for the help.

I just hope they aren't too cheap...

A lot of the cheap ones are plastic and I wouldn't trust them on a big, heavy and expensive lens. Examples: Zeikos, Rokinon, Samyang, Polaroid, Vivitar, Bower, Rainbowstudio, Cowboystudio, Meike, Fotodiox, PLR, Xit, etc. The same ones show up under a bunch of different brand names and they sell for about $50 US (really plasticky, even the bayonet mounts) to under $75-100 US (plastic tubes with metal bayonet mounts). All those sets have rather odd size tubes: 13mm, 21mm, 31mm. Opteka now sell a similar quality set for a bit less than $100 US, that has more traditional length tubes, same as the Kenko: 12mm, 20mm, 36mm.

The ridiculously cheap ones ($25 to under $10 US) show up under some ot the same brand names and more, in various combinations of lengths, but don't have any electronic contacts so you lose both autofocus and the ability to control the aperture directly from the camera. Loss of autofocus isn't too big a deal, IMO. OTOH, inability to control aperture is a big problem.

With the really cheap ones that lack electronic contacts there's a work-around to change the aperture setting, but it's a real pain in the arse: 1. Put lens on camera without the extension tube. 2. Set the aperture. 3. Use depth of field preview to stop down lens. 4. While holding DOF button engaged, remove the lens, and it should stay stopped down. 5. Install extension tube and then the lens. 6. Focus manually (sorry, the viewfinder will be dimmer since the lens is stopped down) and take the shot. Ooops! Wrong aperture or need to change aperture? Remove lens and extension tube and follow steps 1 through 6 all over again. Repeat any time you want to change the aperture.

Frankly, with a heavy super tele that's worth some thousands of dollars I wouldn't trust any less than the Kenko. Those are available new for $200 US for the set... Or track down a used set for less. The older version marked "CA/AF" is be "EF only", won't work with EF-S lenses but are fine with all EF lenses and should sell at a significant discount now. The current version marked "CA/AFs" is usable with both EF and EF-S lenses.

The Canon tubes are also fine, but are only available individually in 12mm and 25mm lengths, and work out to be rather pricey (around $95 for the 12mm, and about $150 US for the 25mm). If you buy used, Canon tubes "II" are usable with both EF and EF-S lenses. The older version not marked "II" are EF only, which of course would be fine with your 500mm.

I haven't calculated how much effect the various lengths of tubes would have with the 500mm. However, to give you some idea, the lens on it's own will do 0.15X magnification and focus to about 12 feet MFD. With a 25mm extension, it will do about 0.22X and should have an MFD of roughly 8 feet.

Extension tubes are very versatile. After discovering them a few decades ago I've made a point of always having a set handy and over the years have used them with lenses ranging from 20mm to 500mm. The following was done with a 25mm tube on a 70-200/2.8 IS...