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You are here: Home / The Last Word / Bokeh, can you see? — cat’s eyes

Bokeh, can you see? — cat’s eyes

December 22, 2016 JimK Leave a Comment

This is a continuation of a series of posts about bokeh and lenses that are designed to optimize it. The series starts here.

We’ve seen that in the Zeiss 135 mm f/2 Apo-Sonnar ZF.2, and to a lesser extent in the Nikon 135 mm f/2 DC-Nikkor, that out of focus (OOF) point sources are rendered as disks with approximately the same illumination across the disk. The Sony 135 mm f/2.8 STF lens has a different rendering, one with more of the energy concentrated towards the center of the blur circle.

All that is true when the point sources are near the center of the image. However, when the points are at the edges or corners, their view of the lens aperture is from the side, and the bourred area can cease to be circulat, ans assume the shape that some bokeh aficionados call “cat’s eyes”.

In this post, I’m going to look at point source rendering at the edges and corners with all three lenses when they are wide open, which is the worst-case setting.

First, the Apo-Sonnar:

Zeiss

 

Zeiss

 

Zeiss

Ignore the dark lines and bands; they are artifacts of the way the LED light works. The Zeiss cat’s eyes are gone at f/4 and narrower apertures.

Now the Nikon lens with the defocus control set to off:

Nikon no DC

 

Nikon no DC

 

Nikon no DC

With the Nikon, the cat’s eyes are almost gone at f/2.8. 

Now the Nikon with the defocus control turned on:

Nikon DC

 

Nikon DC

 

Nikon DC

 

The defocus control makes essentially no difference  with respect to cat’s eyes.

Now the Sony STF lens:

 

STF

 

STF

No cat’s eyes. But the Sony STF is only a f/2.8 lens, so it has an easier time with cat’s eyes than the other two lenses, which are a full stop faster. Only the Zeiss lens shows significant feline characteristics at f/2.8.

 

 

 

The Last Word

← Bokeh, can you see? — closely defocused images Bokeh, can you see? — greatly defocused images →

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