Forum: Pentax SLR Lens Discussion
09-14-2015, 08:19 PM
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Uh, huh...actually, it is the diameter of the entrance pupil, but close enough, I fancy. For a 50mm lens, that is only 25mm to make f/2.0. I have a couple of very petite 50mm f/2 FF lenses with a barrel diameter of only about 45mm and an overall length about the same. Both are very well corrected and quite sharp too. That being said, they were made for use of 35mm rangefinder film cameras.
I am not saying that maximum aperture is not a factor. It is, but it is not the entrance pupil size that is driving the increase in size, nor is it those pesky tiny pixels. The huge front elements have more to do with allowing a mirror box that is deeper than the lens focal length and while also providing a decent sized entrance pupil while providing flat field and excellent optical correction.
Steve
(...has a 28/2.5 that is three times the volume of the FA 77/1.8 Limited and which takes a 77mm filter. The FA 77 takes a 49mm filter...go figure...)
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Forum: Pentax SLR Lens Discussion
09-14-2015, 08:05 PM
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I expect it will make the new FF look like petite. If they had shrunk the range by a few millimeters (28-70/2.8), much of that pain might have been averted.
Steve
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Forum: Pentax SLR Lens Discussion
09-14-2015, 08:01 PM
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Those darned smaller pixels! :p
No way! :eek:
Well...I guess there might be something to it.
Steve
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Forum: Pentax SLR Lens Discussion
09-09-2015, 10:10 PM
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They are getting larger, but not on an apples-to-apples comparison with older models. The problem, of course is finding the older lens with the same specs as the new. A good example would by the current crop of 70-200/2.8 internal focus zooms with built-in AF motor. The FA* 80-200/2.8 is both lighter and smaller than the yet-to-be-released D FA* 70-200/2.8, but the latter has more glass and that nice quiet motor.
My most compact FF lens is a Tamron Adaptall-2 28/2.5 that dates to about 1980. I would expect that a modern 28mm f/2.8 lens for 35mm format might have similar size/weight if it were manual focus. If you add in a requirement for AF and faster maximum aperture, you have something closer in size to the FA 31/1.8 Limited and even larger if it must hold a DC motor.
Steve
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