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Old Aug 8, 2009, 5:46 PM   #11
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This is correct. F-stops are an inverse relationship...the higher the number the smaller the f-stop. So f-18 is smaller than f/11 and you're test is correct. Lower f-stop numbers are larger apertures.
I didn't think that is what I said. I have understood the relationship of f-stop numbers for years. What the article indicated was that if you use it and f-stop smaller than 11 with a digital camera light diffraction becomes a contributing factor. And what I was trying to say is that my f/11 pictures seemed to be just as sharp (if not sharper) than the ones I look at f/18.
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Old Aug 8, 2009, 6:14 PM   #12
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I didn't think that is what I said. I have understood the relationship of f-stop numbers for years. What the article indicated was that if you use it and f-stop smaller than 11 with a digital camera light diffraction becomes a contributing factor. And what I was trying to say is that my f/11 pictures seemed to be just as sharp (if not sharper) than the ones I look at f/18.
Right!! Because of diffraction, I wouldn't expect an image shot at F18 to be sharper than one shot at F11, regardless of the lens used. Based on your post, you seemed to (and still seem to) indicate that f18 is a larger aperture than f11 and that you're suprised that the images aren't as sharp, hence my comment on fstops.
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Old Aug 8, 2009, 6:43 PM   #13
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Right!! Because of diffraction, I wouldn't expect an image shot at F18 to be sharper than one shot at F11, regardless of the lens used. Based on your post, you seemed to (and still seem to) indicate that f18 is a larger aperture than f11 and that you're suprised that the images aren't as sharp, hence my comment on fstops.
You and I really must be having some sort of communication breakdown. YES, I understand, f/18 is a SMALLER f-stop than f/11. I don't read anywhere where I've suggested otherwise. I have understood that principle for 50 years. I USED to assume that a smaller f-stop (i.e. a HIGHER number) will yield a sharper image. However, I am realizing more and more the adverse effect light diffraction has on smaller (i.e. higher number) f-stops.

And I was just saying that at "normal" f-stop settings I am not seeing any problem with dust on my sensor. And that is due, in large part, because I am using a LARGER f-stop, i.e. a LOWER number. It was only a comment. No need for further education at this point.
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Old Aug 8, 2009, 11:19 PM   #14
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You and I really must be having some sort of communication breakdown. YES, I understand, f/18 is a SMALLER f-stop than f/11. I don't read anywhere where I've suggested otherwise. I have understood that principle for 50 years. I USED to assume that a smaller f-stop (i.e. a HIGHER number) will yield a sharper image. However, I am realizing more and more the adverse effect light diffraction has on smaller (i.e. higher number) f-stops.

And I was just saying that at "normal" f-stop settings I am not seeing any problem with dust on my sensor. And that is due, in large part, because I am using a LARGER f-stop, i.e. a LOWER number. It was only a comment. No need for further education at this point.
I'm sorry if I offended you and I misunderstood you're posts. Diffraction has always been an issue, even with film. Based on your comments, I thought you were expecting smaller f stops to result in sharper images, which has never been the case beyond the point of diffraction.
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Old Aug 9, 2009, 7:14 PM   #15
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Okay, so now I have another question. How does one know at what point this light diffraction becomes a factor in image quality?
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