Canon 70-300mm L with extension tubes

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Mark
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Hi - Has anyone any experience of using the new Canon 70-300mm L with extension tubes. Principally, does the AF work OK (at all focal lengths) with tubes attached. Many thanks in anticipation.
 
Based on a quick test with 65mm of Polaroid tubes, it just hunts in normal mode. Live view focuses OK. I'll experiment more in better light (fat chance!) at the weekend.

But it's an impressive macro performer even without tubes. This is a 100% crop, shot at 4ft range.


70-300-bee by griddle7, on Flickr
 
OK, I've done a bit more testing.

With 13 and 21mm tubes, it will focus at 150mm and longer.
With 31 and 34mm tubes, it will focus at 200mm and longer.
With 44mm or longer tubes, it will only focus in live view.

The focus feels a bit sluggish with any length of tubes on, and occasionally it oscillates slightly a few times before settling down.


Here's a test shot with 34mm tubes, 300mm, just above MFD. The EXIF says the subject distance is 1.37m, but it was actually about 1m.


5p by griddle7, on Flickr
 
Brilliant, many thanks, just what I wnated to know. I will be using a 25mm Canon tube mostly at 300mm, which drops the MFD to about 1m as you say (the EXIF cannot recored the actual MFD, only what the lens reports). I did suspect that AF would fail at some point as the tube loses light pushing the effective aperture passed the f5.6 max.
 
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