'Cone' and 'Soap bubble' bokeh?

Started 2 months ago | Discussions thread
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AGscience New Member • Posts: 8
'Cone' and 'Soap bubble' bokeh?

I recently got SMC Pentax 30mm 2.8 (badly damaged) from sale and tried to repair it, including replacing some glass. It is a well regarded lens known for its 3D-pop performance. The 'repair' led to multiple unexpected effects:

1. 'Soap bubble' bokeh. First time seeing it on a wide angle lens.

2. 'Cone' bokeh for highlight areas. An exact bright point in the center with gradualy decreasing highlight.

3. Light leaks. Probably a result of the 'Cone' bokeh effect. Highlights leak into dark objects. It results in a 'soft glow' effect when objects are in focus (looks different to diffusion filters, see pictures).

All these effects are only present when wide open. At apertures 5.6-8 the lens gives images as usual, with some softness in corners. The bubble bokeh is regarded as poor lens performance and the lens is unusable soft wide open.

So the question: can these properties have any value? Or just sell this lens for the same price I bought it and forget about it?

Highlights when objects are in focus, wide open aperture.

Almost a Trioplan) Notice the 'Cone' bokeh at highlights (it gives the image a soft glow look).

Overall, the lens gives a soft glow effect for objects in focus and bubble bokeh for objects on the background.

See video tests:

Lens test #1

Lens test #2

And comparison shots at F2.8 and F8.



Light leaks (see how highlights leak into dark objects):

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