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Stopping down a mirror lens

Started Jan 14, 2021 | Discussions thread
petrochemist Veteran Member • Posts: 3,619
Re: Stopping down a mirror lens

Karl Persson wrote:

Mirror lenses have fixed apertures, they can´t be stopped down.

Well, they actually can. I´ve seen examples where a section of the front has been covered.
But I have a better idea.

I made a 5mm wide ring (in plastic) to fit inside the filter thread and put it on my Samyang 300/6,3 mFT lens.
Not only did it stop the lens down by ~2/3 stop, it transformed the lens from unusable to nearly usable

So, if you have a better mirror lens, that is close to usable, you might be able to make it usable with the discribed method.

I've done similar things with black card/thick paper, but for projector lenses rather than a mirror lens.

I found my 300/6.3 to be quite good straight out of the box, I think I actually prefer it to the 100-300 I subsequently got!

It's probably worth the investment to try the trick on my other mirror lenses

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