How APO is the 50 APO?

[enboe]

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Just curious, has anyone experimented with IR photography with the 50 APO? At what wavelength does it begin to have noticeable backfocus?

 

Thanks.

 

Eric

[enboe]

Received an email to my query today, "We would recommend starting with a shift of 1mm to the right of infinity for instance, and testing alternate measurements if necessary."

[farnz]

Just curious, has anyone experimented with IR photography with the 50 APO? At what wavelength does it begin to have noticeable backfocus?

 

Thanks.

 

Eric

Eric,

 

Without a variable IR-pass / visible light-blocking filter, which doesn't exist, how would you ever know? Trial and error with a selection of IR-pass filters may provide a clue but it's unlikely to be precise.

 

Apochromatic correction is designed to focus radiation in the 400 nm to 720 nm band (ie blue through to red) in the same plane so logic dictates that you're likely to find the 'best' IR corrected performance close to 720 nm using a Tiffen or Hoya 'deep red' R72 filter.

 

Pete.

[jaapv]

An interesting point Erwin Puts made to me on APO correction in general: Most manufacturers determine APO correction in two points of the spectrum: Red and Green. Leica uses three, adding a Blue benchmark. Most, if not all, "APO" lenses exhibit non-APO behavior on parts of the spectrum that fall outside these points, so you can still get chromatic aberrations on an APO lens, albeit less.

[tobey bilek]

I would be more concerned over the reported flare issues. They can keep it until this issue is resolved.

[jaapv]

According to LaVida Leica the issue IS resolved.

[120]

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An interesting point Erwin Puts made to me on APO correction in general: Most manufacturers determine APO correction in two points of the spectrum: Red and Green. Leica uses three, adding a Blue benchmark. Most, if not all, "APO" lenses exhibit non-APO behavior on parts of the spectrum that fall outside these points, so you can still get chromatic aberrations on an APO lens, albeit less.

 

is 19th century tech.