What's your top 5 MF lens (with Pics)

Started Feb 26, 2013 | Discussions thread
ProfHankD Veteran Member • Posts: 5,477
Swirly bokeh come from internal vignetting

Letsgokoulos wrote:

RezaTravilla wrote:

Swirly bokeh appear because there is some movements on the background (movement on the leaves because of the wind).

I don't think swirly bokeh is caused by the wind or background movement, it just does not make sense. The (rare) cases where I got this special optical effect, there was no wind or background movement.

Swirly bokeh are primarily due to internal (optical) vignetting due to the fact that the lens has thickness. It shows only with defocus. This same issue is what causes the image of an out-of-focus point to have a squashed shape near the edge of the frame. Sometimes, other optical defects like coma also contribute to the swirl.

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