Bob YILDIRAN wrote:
Not true.. A good 180mm lens designed for 35mm format generally resolves up to double (if not triple) as much as the best 180mm lens for 4X5 format (including the Apo-Symmar-L) .. 50 lines/mm is stratospheric for 4x5 format. Great deal of the 50mm lenses for the 35mm format resolve better than the 50mm Distagon or 80mm Planar for Hasselblad. Just check the Zeiss site as an example; the MTF curves of the FF lenses vs the MF format ones; from the same manufacturer. (You can also refer to the lens test standards of the old Modern Photography for example.)
Bob, you are confusing cause and effect. MF lenses don\'t have to have the same resolving power as 135 format lenses and large format lenses don\'t have to have the same resolving power as medium format lenses to get equivalent high contrast in the fine detail. You can easily enough find examples where they\'ve maintained the same quality for different formats.
Here\'s an example from two same generation lenses The Zeiss 35/1.4 Distagon (CY) and the Zeiss 35/3.4 Distagon (Hasselblad V). The FF 135 lens is in red:
Of course, if we equalize the angle of view there\'s an endless supply of examples such as the 50 Sonnar (135) vs 110 Planar (mf). FF135 in red:
For any given focal length, the circle of illumination counts as one determining factor for the resolution power of a lens. That\'s why some microscope objectives from Leitz or Zeiss are specified of resolving more than 1000 lines/mm.
No it does not and this is basic optics. A difference in maximum image circle will of course affect the lens design and subsequently performance. But apart from diffraction which will limit lens performance as you go towards lenses with smaller image circles there is no optical relation between image circle and lens performance. You\'ll need a higher quality lens for a smaller format than for a larger format to get the same results and that is also subsequently reflected in the lens designs. But don\'t confuse the cause and the effect.
Anyway, the record holder for a photographic production lens, regardless of format is the Zeiss 25/2.8 Biogon ZM. It becomes diffraction limited on FF at f/4 when it resolves 400 lp/mm (center frame). On m43 an equivalent lens would have been diffraction limited at f/2..
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kwalsh wrote:
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.
No, that\'s not true. Although this is really basic, I don\'t really know where to start. I could simply give you a screen shot from lens design software that shows you the effect of linearly scaling a lens. The answer is that there isn\'t much of an effect in terms of what you\'ll see in an MTF chart but there will be a very large difference in weight and size. As volume increases in a cubic fashion, you very quickly end up with a lens that would be both too heavy, large and not to mention expensive (optical glass isn\'t free).
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.
Compact cameras have nothing close to the resolving power to 4x5 cameras. With a 4x5 with a digital scanning back you can get a gigapixel+ image with a much higher per pixel sharpness than what you get from a P&S.
Why do you think that for resolution critical stuff people use larger formats? The most fundamental requisite for there being a point in using a larger format is that lens performance is relatively constant regardless of maximum image circle. Otherwise there would be no difference between a tiny mobile phone cam and a full blown digital medium format camera.
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:
You\'re comparing simulated MTF charts from two different manufacturers for different focal lengths and apertures?
You might as well compare a graph of zoos/capita compared to the domestic gross product of France in the years 1844-1848. These are in no way comparable.
I was going to write more, but I\'m sorry - it would be too much. I\'ll just end up being impatient. I\'ll let somebody else take over.
Bob YILDIRAN wrote:
Not true.. A good 180mm lens designed for 35mm format generally resolves up to double (if not triple) as much as the best 180mm lens for 4X5 format (including the Apo-Symmar-L) .. 50 lines/mm is stratospheric for 4x5 format. Great deal of the 50mm lenses for the 35mm format resolve better than the 50mm Distagon or 80mm Planar for Hasselblad. Just check the Zeiss site as an example; the MTF curves of the FF lenses vs the MF format ones; from the same manufacturer. (You can also refer to the lens test standards of the old Modern Photography for example.)
Bob, you are confusing cause and effect. MF lenses don\'t have to have the same resolving power as 135 format lenses and large format lenses don\'t have to have the same resolving power as medium format lenses to get equivalent high contrast in the fine detail. You can easily enough find examples where they\'ve maintained the same quality for different formats.
Here\'s an example from two same generation lenses The Zeiss 35/1.4 Distagon (CY) and the Zeiss 35/3.4 Distagon (Hasselblad V). The FF 135 lens is in red:
Of course, if we equalize the angle of view there\'s an endless supply of examples such as the 50 Sonnar (135) vs 110 Planar (mf). FF135 in red:
For any given focal length, the circle of illumination counts as one determining factor for the resolution power of a lens. That\'s why some microscope objectives from Leitz or Zeiss are specified of resolving more than 1000 lines/mm.
No it does not and this is basic optics. A difference in maximum image circle will of course affect the lens design and subsequently performance. But apart from diffraction which will limit lens performance as you go towards lenses with smaller image circles there is no optical relation between image circle and lens performance. You\'ll need a higher quality lens for a smaller format than for a larger format to get the same results and that is also subsequently reflected in the lens designs. But don\'t confuse the cause and the effect.
Anyway, the record holder for a photographic production lens, regardless of format is the Zeiss 25/2.8 Biogon ZM. It becomes diffraction limited on FF at f/4 when it resolves 400 lp/mm (center frame). On m43 an equivalent lens would have been diffraction limited at f/2..
Aug 08, 2011 at 03:31 AM
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