Where have all the Focal-reducers gone? (with apologies)

Started Feb 3, 2014 | Discussions thread
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greypixelz
greypixelz Regular Member • Posts: 162
Re: speaking of blue dots...

Hi Tom and co.,

With the Mitakon Nikon to NEX focal reducer I had seen blue spots with the 1.8/50E, a lens know to be less capable than the regular AI-S, and the 2/40Voigt. However, with the 2/28AI-S not so much, in fact, none what so ever.

With the RJ EOS to NEX focal reducer, onto which I mount another Fujica M42 to EOS ring, I had only tried the 1.4/50EBC Fujinon on it and had seen biggerand more colorful blue spots than what I was used to with the Mitakon focal reducer.

Another thing is that with the Mitakon, the blue spot issue only became apparent starting with f/5.6-8. On the RJ focal reducer, however, the blue spots were visible starting with 1.4 on the Fujinon (truth be told, I was framing directly into the light bulb).

I will have to try some wide angles to see whether it is more pronounced on the RJ compared to the Mitakon.

Nevertheless, I am clueless as to what actually causes this behavior. My inital and best guess was the coatings or rather lack of in the focal reducer optical unit.

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