Relation between dust and aperture setting

Started Mar 30, 2014 | Questions thread
jfriend00 Forum Pro • Posts: 11,444
Re: Relation between dust and aperture setting

Ernie Misner wrote:

Would it be so totally wrong to simply say that at smaller apertures everything (including the way close dust spots) becomes more in focus? Sure makes a working model for me anyway.

It isn't really the dust spots being in focus as they aren't being imaged.  It's more a matter of how sharply defined a shadow they form which is a product of how divergent an angle of light rays are being used.

An interesting real world effect that is somewhat similar is that you can shoot sports through a chain link fence and not see the fence at all if you use a large aperture, but if you use a small aperture, you will see the effects of the chain link fence.  It's the same concept.  If the light rays come from a narrow angle, then the obstacle in the way of the light rays has a more noticeable effect.

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