More bokeh? 200mm @ f/2.8 or 100mm @ f/2.0?

[Jeff Lucia]

I wish I could keep up with this thread because it's a fascinating subject. Maybe one of you guys who understands it in detail could post some images that illustrate your points? Speaking on behalf of the "no question too stupid" contingent [], it would be much easier to understand if we could see it.


Thanks and I hope someone can come up with a way to illustrate this.


Jeff

[powers_brent]

[View:http://farm3.static.flickr.com/2682/4234224849_ff11394af8.jpg]


XS with Canon 100mm f/2.0 @ 2.0, 1/200 sec, ISO 100. Kodak P20 shot thru @ 1/16 camera right and Canon 430EXII bare @ 1/64 left behind snowman. (http://www.flickr.com/photos/brentpowers/4234224849/in/photostream/)





XS with Canon 300mm f/4.0 @ 4.0, 1/200 sec, ISO 100. Kodak P20 shot thru @ 1/4 camera right and Canon 430EXII bare @ 1/16 left behind snowman. (http://www.flickr.com/photos/brentpowers/4234227817/in/photostream/)





If the framing is not exact does the test not count? They are framed almost the same, just slightly different. The OOF blur seems more diffused with the 100mm lens. Or is it just me? What may I have done wrong? Or is that what I should expect?

[Jon Ruyle]

The OOF blur seems more diffused with the 100mm lens.

Looks that way to me, too.


I think that is because the background is pretty close to the focal plane. If I understand things right, when the background is close, f number matters more. When the background is far, aperture matters more.

That's not the impression I get. Bob says:
<p style="padding-left: 30px;"] "While the quality of blur - bokeh - is in itself a "fuzzy" concept and
something that's quite difficult to predict or control, the quantity of blur can be
calculated quite easily and it's something over which the photographer has control through
choice of focal length and aperture."


To me it seems like he treats bokeh as quality only.

Yup, I agree with your interpretation of that quote. But he also says: "While "Bokeh" is a measure of both the quantity and the nature or
quality of background blur, this program only calculates the quantity."


Perhaps he is taking the precise definition of the word less seriously than we are []

[Daniel Browning]

The OOF blur seems more diffused with the 100mm lens.

I agree with Jon. If you repeated the test with human-sized focus distances, I think you would get different results.

Perhaps he is taking the precise definition of the word less seriously than we are

I see now, thanks. You're right.

[powers_brent]

Perhaps he is taking the precise definition of the word less seriously than we are

I see now, thanks. You're right.

Well everybody on this forum knows that the both of you (quite specifically you two) delve into the technicals of photography. But I ask these questions hoping that you two will answer and set all my mistakes, misconceptions, etc. correct. I literally post these questions and think in my head, "what will Daniel and Jon have to say?" I learn a lot by your exchange. Thanks for all the information.