denoir wrote:
No, not quite. The relation between the focal length and the diameter of the circle of illumination is angle of view. The resolving power of a lens is independent of the image circle and will depend on the materials used in the lenses and the optical design of the lens.
So the fundamental relationship with resolution while scaling focal length and image circle size (that is taking a given lens prescription for one image format and perfectly scaling it to another image format by multiplying all dimensions) is that the relationship for resolution scales perfectly linearly.
That is identical prescriptions for a 20mm lens with a 20mm circle and a 40mm lens with a 40mm circle will result in the 20mm lens have exactly double the resolution of the 40mm. No resolving advantage to the larger format. This is because scaled prescriptions have identical *angular* resolving power but the focal lengths have scaled with a resulting difference in linear resolving power at the image plane. This is why compact cameras have surprisingly similar resolving power to 4x5 despite the ridiculously large difference in format size.
Your assumptions are failing to consider that comparing a FF 20mm lens to a m43 20mm lens is neglecting the fact that the prescriptions are in fact wildly different because of the different image circle size, different distance to the rearmost element and different exit pupil distance as a result of the different sensor formats.
So designing a lens for a smaller image circle won\'t per se increase its resolving power.
Except that it does for the reasons outlined above and clearly shown in the MTF curves for two UWA zooms for FF and m43 - note the higher resolving power of the m43 lens compared to the FF lens as a direct result of the smaller image circle:
And no, I\'m not saying bigger isn\'t better! It sure is, I\'m just saying as far as resolving power and micro-contrast goes it is a second or third order effect at best. Both the practical examples and the theory clearly indicate resolving power and micro-contrast are weakly correlated to sensor size.
I think you are on the right track that as we go bigger we have access to more lenses designed with \"no compromises\" that just aren\'t supported by the market for smaller sensor cameras. The nice thing with Panasonic is that while not doing anything like a Zeiss prime they have gone all out on some of their m43 lens designs (like the 7-14). It is nothing at all like the selection of insanely expensive primes available for FF, MF and LF though.
denoir wrote:
No, not quite. The relation between the focal length and the diameter of the circle of illumination is angle of view. The resolving power of a lens is independent of the image circle and will depend on the materials used in the lenses and the optical design of the lens.
So the fundamental relationship with resolution while scaling focal length and image circle size (that is taking a given lens prescription for one image format and perfectly scaling it to another image format by multiplying all dimensions) is that the relationship for resolution scales perfectly linearly.
That is identical prescriptions for a 20mm lens with a 20mm circle and a 40mm lens with a 40mm circle will result in the 20mm lens have exactly double the resolution of the 40mm. No resolving advantage to the larger format. This is because scaled prescriptions have identical *angular* resolving power but the focal lengths have scaled with a resulting difference in linear resolving power at the image plane. This is why compact cameras have surprisingly similar resolving power to 4x5 despite the ridiculously large difference in format size.
Your assumptions are failing to consider that comparing a FF 20mm lens to a m43 20mm lens is neglecting the fact that the prescriptions are in fact wildly different because of the different image circle size, different distance to the rearmost element and different exit pupil distance as a result of the different sensor formats.
So designing a lens for a smaller image circle won\'t per se increase its resolving power.
Except that it does for the reasons outlined above and clearly shown in the MTF curves for two UWA zooms for FF and m43 - note the higher resolving power of the m43 lens compared to the FF lens as a direct result of the smaller image circle:
And no, I\'m not saying bigger isn\'t better! It sure is, I\'m just saying as far as resolving power and micro-contrast goes it is a second or third order effect at best. Both the practical examples and the theory clearly indicate resolving power and micro-contrast are weakly correlated to sensor size.
I think you are on the right track that as we go bigger we have access to more lenses designed with \"no compromises\" that just aren\'t supported by the market for smaller sensor cameras. The nice thing with Panasonic is that while not doing anything like a Zeiss prime they have gone all out on some of their m43 lens designs (like the 7-14).
Ken
Aug 08, 2011 at 03:24 AM
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