Voigtlander APO-Lanthar 125mm f/2.5 SL - Review / Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)

Distortion

As to be expected from a moderate tele lens the level of distortion is very low (very slight pincushion distortion).

The chart above has a real-world size of about 120x80cm.

Vignetting

On the EOS 350D with its reduced format (APS-C) the (full format) lens exhibits slight vignetting at f/2.5 which shouldn't be problem in most scenes. At f/2.8 the issue is already negligible.

MTF (resolution)

The 125mm APO Lanthar exhibited an excellent performance straight from f/2.5 up to f/8. Beyond diffraction effects are the limiting factor but it remains easily usable till about f/16. The lens showed a very even performance across the frame without any obvious centering issues.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

The Voigtlander is virtually free of lateral chromatic aberrations (color shadows at harsh contrast transitions). An exceptional and also very rare characteristic these days.

Longitudinal Chromatic Aberrations (LoCA)

LoCAs (greenish to reddish halos in front and behind the focus field) are practically absent as you can see below - a positive side effect of the (true) apochromatic design.




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