12-10-2010, 12:01 AM
[quote name='Lars' timestamp='1291887332' post='4899']
So, a question for the optics-specialists:
As I assume, the position of the aperture blades in the lens ist important for the IQ.
What do you think?
Is the IQ degraded if you close this aperture within the adapter?
[/quote]
Moving the aperture further to the back of the lens moves the exit pupil closer to the sensor. There are several layers of flat glass on typical digital sensors (for IR-cut, AA-filter, dust removal, etc.) that are thick enough to cause refraction of light (and introduce their own aberrations like CA). So putting the exit pupil further back will make the exiting light rays hit the sensor more angled than they would if the lens was using its own aperture which is further away from the sensor. I'll leave it at that <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />
GTW
PS: But didn't anyone notice how nice and round those apertures are? Wish they made apertures like that in modern lenses.
So, a question for the optics-specialists:
As I assume, the position of the aperture blades in the lens ist important for the IQ.
What do you think?
Is the IQ degraded if you close this aperture within the adapter?
[/quote]
Moving the aperture further to the back of the lens moves the exit pupil closer to the sensor. There are several layers of flat glass on typical digital sensors (for IR-cut, AA-filter, dust removal, etc.) that are thick enough to cause refraction of light (and introduce their own aberrations like CA). So putting the exit pupil further back will make the exiting light rays hit the sensor more angled than they would if the lens was using its own aperture which is further away from the sensor. I'll leave it at that <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />GTW
PS: But didn't anyone notice how nice and round those apertures are? Wish they made apertures like that in modern lenses.