What's the smallest aperture?
It's f45, but I don't have all day.
What's the smallest aperture? That's the one you want to use. I have a 1960s Soligor 5.6/350mm and it's actually rather sharp stopped down. I only paid $9 for it too.
f:45 will put you well into diffraction. Try f:8 or so.
F45 on 500mm is probably too large for diffraction to have much effect, the aperture would still be larger than f16 on 50mm.
Sorry. Diffraction depends solely upon the stop, it has nothing to do with focal length. The diffraction limit in LP/MM can be approximated by dividing the stop # into 1500. At f:45 the diffraction limit is about 30 LP/MM regardless of the focal length of the lens.
Sorry. Diffraction depends solely upon the stop, it has nothing to do with focal length. The diffraction limit in LP/MM can be approximated by dividing the stop # into 1500. At f:45 the diffraction limit is about 30 LP/MM regardless of the focal length of the lens.
And the F stop is a fraction of the focal length.f16 on a 500mm lens is a whole lot larger than f16 on a 50mm lens. It's the relation of the size of the hole to the wavelength of light going through it that causes diffraction.
It's the relation of the size of the hole to the wavelength of light going through it that causes diffraction.
I'm sure you know what I mean.
(in case you didn't: that diffraction is correlated to the size of the aperture, and the f stop number is a fraction of the focal length of the lens.)
I'm sure you know what I mean.
(in case you didn't: that diffraction is correlated to the size of the aperture, and the f stop number is a fraction of the focal length of the lens.)
So, that big chunk of light bending glass in front of the aperture makes no difference?
Technical Note: Independence of Focal Length
Since the physical size of an aperture is larger for telephoto lenses (f/4 is has a 50 mm diameter at 200 mm, but only 25 mm diameter at 100 mm), why doesn't the airy disk become smaller? This is because longer focal lengths also cause light to travel further before hitting the camera sensor -- thus increasing the distance over which the airy disk can continue to diverge. The competing effects of larger aperture and longer focal length therefore cancel, leaving only the f-number as being important (which describes focal length relative to aperture size).
The Cambridge In Colour site quoted above specifies that the f/number is relevant, not the absolute diametre of the diaphragm aperture. It says:
Technical Note: Independence of Focal Length
Since the physical size of an aperture is larger for telephoto lenses (f/4 is has a 50 mm diameter at 200 mm, but only 25 mm diameter at 100 mm), why doesn't the airy disk become smaller? This is because longer focal lengths also cause light to travel further before hitting the camera sensor -- thus increasing the distance over which the airy disk can continue to diverge. The competing effects of larger aperture and longer focal length therefore cancel, leaving only the f-number as being important (which describes focal length relative to aperture size).
A one time back in the 60s and 70s I worked for the world's largest news organization. Their photogs (including me) used the Takumar 500 for sports photography (Dodgers, Yankees, etc.) and it was a fine lens. We mounted 'em on Nikons and had a Mickey Mouse system like a car gear shift to instantly focus on first and third base, second, home, and the pitcher's mound. The photos were used in newspapers and magazines all over the country and it is one of my favorite lenses. Large, but a goodie. I think you bought a gem.
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