Quote:
Originally Posted by Martin Pugh
Thanks for the comments and the tip there. I was actually on the understanding that those stop-down covers did eliminate the diffraction spikes created by the lens diaphragm....obviously not!
cheers
Martin
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Martin, perhaps I didn't express myself clear enough - external apertures do not create spikes, but they may introduce other problems to your 50mm lens (which is designed to have iris where it is at the moment).
However, don't feel like I am attempting to stop you from trying - the simple, carefully cut hole in the black paper over your lens will indicate if the external diaphragm is worth the effort or not.
Of course, with external diaphragm you will have to open the internal iris of your lens to the max (F1.2) otherwise you will still have spikes. However you may have additional problems with vignetting and possibly CA and/or coma (both of them are nicely gone at F4.5 from you photo - BTW, I am using my modified Canon FD F1.4 at the same aperture (F4.5) and the behaviour is similar to yours).