[OM] m.4/3 extension tubes, was: Re: C-U Lenses [was Color... At last!]

[Chuck Norcutt]

I have a set of these with metal mounts
<http://www.dxomark.com/lenses/brand-canon-olympus/mounted_on-Canon_EOS_5D-176/mount_type-Canon_EF/sensor_brand-Canon#hideAdvancedOptions=false&viewMode=list&yDataType=global>
as opposed to these which are all plastic
<http://www.ebay.com/itm/Meike-Auto-Focus-Automatic-Macro-Extension-Tube-10-16mm-Olympus-Micro-4-3-Camera-/271844929948?hash=item3f4b38719c:g:KbYAAOSwNSxVNc2T>

They're the same part number except the metal mount has an "A" suffix 
and the plastic mount has a "B" suffix.
Take all of this with a grain of salt since I don't use the 75-300 very 
much (little field experience) and have never used the extension tubes 
other than trying them out in the house with a few different lenses.
Anyhow, I mounted the 75-300 onto both tubes together (10mm + 16mm) and 
tried using the lens in the house at both 75 and 300.  The tubes give a 
very slight rotary motion which allows the assembly to rotate perhaps 
1/2mm on the mount circumference but that's all.  There doesn't seem to 
be any looseness that would produce a gap between lens mount and camera. 
 I think the mount flanges are some sort of hard aluminum (certainly 
not stainless steel) but they seem reasonably sturdy.
My only other comment is that they'd be horribly difficult to use in the 
field.  At a distance of about 6 feet or so with the lens at 300 mm and 
both tubes mounted the total range of focus was about 2-3".  At first I 
thought there was something amiss about the tubes using autofocus until 
I thought a bit about what I was actually trying to do and realized how 
restrictive the focusing range would be.  It took a lot of trial and 
error to find the focusing range.  A flutterby shooter I am not.  :-)
Chuck Norcutt


On 4/20/2016 6:05 PM, Moose wrote:
> > I have not seen anyone report on the Panny/Leica 100-400 use on
> > extension--perhaps it behaves very well.
> Entirely possible, likely, even, given my excellent experience with the
> 75-300. I just haven't gotten around to trying that. As you know, I'm
> not much for careful, formal testing. The lens arrived on a Wed
> afternoon, I took one shot, to make sure it worked, then it was off the
> next morning to the wilds, where I tried out several things, keeping no
> notes . . .
>
> I'm pretty convinced it wouldn't be safe the way I use the lens in the
> field with the plastic mount tubes I have. Even the smaller, lighter,
> shorter 75-300 causes a small gap to appear at the top of the tube to
> body or lens to tube connection. I suspect that's just the springs of
> the mount compressing, but those tubes just don't strike me as up to the
> mechanical challenge of the 100-400. I hadn't checked recently, but now
> see that metal mount tubes with good reviews are available much cheaper
> than when I last looked.
>
> So I guess I'm to have some sort of C-U lens vs. extension tube shoot
> out. :-)
--
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