11-03-2010, 06:30 AM
[quote name='Brightcolours' timestamp='1288706873' post='3918']
According to me there is only one thing worthwhile to understand about diffraction: For a given sensor size, diffraction softening at a certain f-value is always the same, no matter what pixel density.
[/quote]
Hmm... this is starting to sound more and more like the typical "f/2 is f/2 regardless of the sensor size"-type arguments that [url="http://forums.dpreview.com/forums/read.asp?forum=1041&message=36804039"]you often hear in Olympus forums[/url] <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='B)' />
Yes, diffraction is an optical thing... plain and simple. But that's not a complete model of the system... the system also includes the sensor.
And yes, what you said about diffraction effects being the same regardless of the pixel density, for a particular sizes sensor is true... but you forgot to mention one important thing (or maybe you did but it wasn't highlighted enough): reproduction magnification also has to be the same.
What I think the other party is trying to get at is, to obtain the highest possible amount of information (image detail) from a particular sensor, you need to also take in to consideration the size of the airy disks (and by extension the f-number, because they're closely related).
In practice, it's not easy to say which f-number gives the best results for all lenses on a particular sensor. Just that line itself sounds wrong... different lenses behave differently when stopped down. Maybe the supposed optimal f-number for the maximum theoretical resolution might unfortunately also be the f-number where the lens exhibits the highest CA. So, as I said, this is a system... we have to think about all variables as much as we can (including the side of the bed you got off on the day you went out shooting <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' /> )
GTW
According to me there is only one thing worthwhile to understand about diffraction: For a given sensor size, diffraction softening at a certain f-value is always the same, no matter what pixel density.
[/quote]
Hmm... this is starting to sound more and more like the typical "f/2 is f/2 regardless of the sensor size"-type arguments that [url="http://forums.dpreview.com/forums/read.asp?forum=1041&message=36804039"]you often hear in Olympus forums[/url] <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='B)' />
Yes, diffraction is an optical thing... plain and simple. But that's not a complete model of the system... the system also includes the sensor.
And yes, what you said about diffraction effects being the same regardless of the pixel density, for a particular sizes sensor is true... but you forgot to mention one important thing (or maybe you did but it wasn't highlighted enough): reproduction magnification also has to be the same.
What I think the other party is trying to get at is, to obtain the highest possible amount of information (image detail) from a particular sensor, you need to also take in to consideration the size of the airy disks (and by extension the f-number, because they're closely related).
In practice, it's not easy to say which f-number gives the best results for all lenses on a particular sensor. Just that line itself sounds wrong... different lenses behave differently when stopped down. Maybe the supposed optimal f-number for the maximum theoretical resolution might unfortunately also be the f-number where the lens exhibits the highest CA. So, as I said, this is a system... we have to think about all variables as much as we can (including the side of the bed you got off on the day you went out shooting <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' /> )GTW