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OVF & Bokeh

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Miranda F View Drop Down
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Topic: OVF & Bokeh
    Posted: 16 August 2017 at 08:06
Having just acquired a low shutter-count A900 in vgc (thanks, Cian!), I was interested to see the same behaviour I've had on film cameras like those in my sig, namely that the bokeh seen through the OVF is different from (and usually much worse than) that in the final image. Typical OVF cameras show donut or onion-ring bokeh at full aperture, often with dotted or striated (lines) microstructure that is hardly evident in the image.

Has anyone else noticed this?

What is the cause?

Is it manufacturing effects in the mirror, pentaprism, or diopter adjustment? I note the bokeh is affected by the diopter adjustment.
A900, A58, 5d, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras . . .
 



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SnowFella View Drop Down
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Post Options Post Options   Quote SnowFella Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2017 at 08:17
Don't have any other OVF cameras than my old A350 but best guess would be the ground glass in the focusing screen.
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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2017 at 17:25
Originally posted by Miranda F Miranda F wrote:

I note the bokeh is affected by the diopter adjustment.

Sure does - throw that way out of adjustment and the bokeh gets silky smooth.

Seriously though, focusing screens always have some sort of texture that gets imparted to the viewed image. In addition, the focusing screens designed for the brightest viewing also fail to represent DOF at very wide apertures correctly. There's typically some value beyond which they don't show any change.
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