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

Started 6 months ago | Discussions thread
Tom Caldwell
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Re: Out taking photos with them? :-)
In reply to chakari, 6 months ago

chakari wrote:

Tom Caldwell wrote:

I have the FD in f1.2 but have not tried it in the Zhongyi. But I also have the FL in both models and also the f1.2 version. They all fit in the Zhongyi as long as the aperture rod had a small flat filed into it. There seemed no problem with the rear lens element which I know is right at the back of these lenses and quite vulnerable. The RJ version is a quite different internal design and has a lot more room at the front of the adapter.

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Tom Caldwell

Does the RJ show any difference in results, (i.e. IQ), from the Zhongyi, as far as you know? Also, is one of better construction?

Thanks! ..... and for all your very interesting posts!

As far as I know RJ (a metal shop) made the bodies for the Zhongyi and Mitakon supplied the optics (from tenuous but fairly reliable information). RJ then made their own completely different body design (obvious) - the lens block was fitted from the opposite direction, for example. Whether or not Mitakon supplied the glass for the RJ version I do not know but I suspect that might have happened. I have not pulled these adapters apart to try and discover if the elements are of different design but there seems to be a different light through each which may indicate different coatings at least. Both Mitakon and Metabones publish their lens diagrams and they are obviously very different and patented. I have not seen a lens diagram for the RJ version. That there is a certain amount of collaboration amongst the Chinese focal reducer industry can be shown by the latest "made for FF" electronic adapter from RJ which has "Techart" in raised lettering on the baffle. RJ tends to not always brand their products and they are sold through quite a few resellers in Hong Kong which makes identification harder.

It would be hard to tell the difference in results between these two brands. The Zhongyi has a lens fit problem with all FL lenses and some FD lenses which can be overcome with some minor surgery, but the RJ fits all of them easily except the FL 35mm f2.5 with the bulged lens end cover which will not mount at all.

Presumably the RJ being a later design has had running improvements. I would prefer the RJ if cornered but I have examples of both and I use them without fear or favour. There was some talk of blue spot problems especially on the first RJ Nikon adapter from my recollection. I have not bought any Nikon adapters but did try and get a layman's opinion on the blue spot and the related blue smudge.

As far as I can figure out these problems are the re-reflection of the sensor as a ghost image off a flat(ish) lens surface ~in the lens~ itself, it seems that even a lens filter on the front of the lens can do this. If the reflection is round and the aperture blades can be seen then the reflection comes from in front of the lens aperture. If it is a smudge then it is coming from behind the lens aperture. This is a lens problem and is caused from lack of attention to this type of ghosting in the lens design in the days of film where the film was less reflective than a sensor surface and was of a much lesser problem.

Presumably the very best lens adapter design might disperse these re-reflections but it would be extremely difficult without tuning each adapter for every lens design. Notably I cannot recollect any complaints of ghosts on the EF focal reducers whether from metabones or anyone else. Presumably either Canon sorted the problem out in their lens design or these adapters to a single lens type source did it for them (the former seems more plausible). Likewise perhaps the revered Nikon slr designs were less worried about these ghosts off film stock which like the real thing have come to haunt now that sensors provide the reflections.

The essence is that I don't know in any expert way but am interested enough to glean any information within my understanding. Any errors are mine and I wold welcome corrections by those with proper technical knowledge.

The blue spot issue seems worse on some lenses than others. I have not really seen "accidental" blue spot happening and had to be told how to provoke it to satisfy my incredulity. The best I could get at the time was a blue smudge. If you liken them to a form of len flare then you might learn to live with the occasional spots/smudges as much as flares are a sometime fact of photography and have to be lived with if they cannot be avoided.

Others seem to be able almost to dial up blue spots on demand.

Basically it seems that focal reducers enhance. If the lens is very good then the focal reducer improves but if the lens has faults then the focal reducer will obligingly make them seem worse. If anything goes wrong that was not wrong before then it is easy to blame the focal reducer.   For instance soft corners were probably unoticeably soft before or the aps-c crop conveniently left them out of the picture.

Pity there are no focal reducers for Leica glass.  But how does one improve on perfection?

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Tom Caldwell

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