[wim]

@ Wim:  You are hardly the one I would challenge when it comes to macro work!  Not if you run around with the 65mm MPE!

 

I did forget to mention in the above comment that you are indeed correct, many lenses do no focus correctly with tubes attached.  What makes this tolerable is the fact that your higher magnification at least allows you to see more details, if you have good lighting.

 

The same thing could be expected with anything changing depths of field, such as close-up lenses.  Which is why (Just guessing) close-up lens work better further away from the subject.  Because the size of the focus steps will be off, hence Canon's advice, that AF even using their doublet closeup lenses is not recommended.  Now, it comes down to scale.  Is there enough difference to make a difference.

 

Let me throw in one example why I think the answer is maybe yes.  Even decent quality adapters from Pentax, Nikon, M42, and Tamron Adaptall-2 to EOS.  Often loose infinity focus.  This is regardless of the quality of the lens in question.  It can only be the adapter, and the adapter is not off by very much!  One that looks identical to the eye, might give perfect results.  So, it just makes me wonder, that's all. 

 

Of course I don't need to understand perfectly how the system works.  But one speculates on one's hobby.  It's human nature.

I actually literally run around with the MP-E, often with an extender added, with a triple ring flash, and a bracket so I can hold it with both hands. Works well, actually.


I always recommend extension tubes for shorter lenses, and close-up lenses for longer ones, as tubes have a greater effect on shorter lenses and close-up lenses on longer ones.


AF with tubes or close-up lenses is not recommended because at close distances the distance to the rear nodal point of a lens increases drastically, and is often larger than the change in distance to the front nodal point when focusing. This also the reason why one often sets a magnification and then moves the entire setup, and also why macro focusing rails are popular (no need to move the camera and tripod continuously).


Close-up lenses effectively shorten the FL of a lens, and with the nodal point at the back staying in a position for a longer FL this results in a larger magnification. This is the simplified version .

I have always used a Canon 500D close-up lens (the doublet, anachromat), with my 100-400L, old and new. On the old one by zooming from 100 to 400 you went from a 1:4 magnification to 1:1, while keeping a good distance from the subject. Since the Mk II lens focuses a lot closer, I expect even better results magnification wise, but I haven't tried the limits yet.


With the doublet you could try AF, as long as you stay within the focusing range, but you're talking cms here, so not easy. Best is always to set a magnification and move the entire setup, camera and lens, for focusing. You still need to adjust anyway, for optimal sharpness.


Cheap adapters, and even more expensive ones, have not necessarily the correct mount tolerances, if at all possible of course, and in addition have only very limited space or depth available for allowing infinity focus, while fitting all the mechanisms and/or electronics required as wel, and maintaining a stable mount.


I have recently given up completely on those for Canon bodies as they were not satisfactory to me. IOW, all my non-Canon and non-MFT lenses have left the house now , except a few high quality enlarging lenses (for macro work ).


I only adapt lenses now for systems with much shorter flange distances, such as EF lenses adapted for MFT , and only with first rate adapters. That works well enough for me . I have also given up on old analog lenses - they just don't cut it on digital, optically, and I am not interested in any "special effects" they may or may not provide .


Kind regards, Wim