Olympus Lens Cap 15mm f/8 - Review / Cap Test - Analysis
Lens Reviews - (Micro-)Four-Thirds

Distortion

The distortion characteristic of the Lens Cap is actually pretty decent at ~1.7% (barrel type). Usually distortion is auto-corrected in the micro-four-thirds system but since the lens does not communicate any EXIF data, the camera doesn't 'know' what to do so this is the original quality of the lens here.

Vignetting

Despite the fixed aperture, there's quite a bit of light falloff (~0.9EV). This is not dramatic but it'll be visible in many scenes.

MTF (resolution)

The resolution characteristic of the Lens Cap is either surprisingly good or downright bad depending on how you look at it. The dead center is pretty sharp. However, this is where the glory ends. Usually we only provide MTF readings at the borders and extreme corners but this time we also included the mid-field. As you can see below, the resolution drops dramatically here already. The borders are extremely soft. There's a minor improvement in the extreme corners but the quality is nothing to write home about really. The image contrast is also just soso and we have some doubts whether Olympus applied any coating to the lens elements.

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)

Lateral CAs (color shadows at hard contrast transitions) aren't bad but still visible with an average pixel width of 1.7px at the image borders.




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