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Has anyone tried adding a filter holder to lens adapters?

Started Dec 31, 2018 | Questions thread
ProfHankD
ProfHankD Veteran Member • Posts: 9,147
Re: No, but trivial to do with 3D printing

SmoothOperator wrote:

Gato Amarillo wrote:

Since we're mainly adapting to mirroless cameras which focus from the sensor image focus shift should be accounted for and not be a problem - the one problem being if the shift prevented the lens reaching infinity focus.

Gato

The adapter should take that into account, drop-in filters in telephotos are included as part of the optical formula.

As I said in my post that started this sequence,

if the adapter is designed to have a filter with a specific optical thickness, you'd need one even for clear to keep the same rear focus distance, which would still degrade IQ a bit.

Of course you build the adapter a little thin compensating for the filter.

For example, if we assume a 2mm thick filter with a refractive index of 1.5, the filter is approximately the same as passing through 3mm of air. Thus, the adapter should be roughly 1mm shorter. If the adapter wasn't made shorter, you'd probably miss infinity focus by a significant amount -- especially using short focal length lenses.

Incidentally, a filter does the same thing on the other end of the lens too, but who cares about 1mm less when your focus is at 5 feet?

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