Your own definition of fast prime
- Thread starter Dylan777
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applecider said:
yup I'd go for that
Based on "fast primes are wider than the typically best zoom at that focal length", then your teles are wide primes.
I think my 1500mm f5 telescope counts too ;D
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mnclayshooter said:The one mounted in the underbelly of the SR-71 was pretty fast, relatively speaking.
http://www.wvi.com/~sr71webmaster/sr_sensors_pg1.htm
Anything sub f2.8 is fast, borderline specialty-use, IMHO.
Being able to resolve a 6" wide parking lot stripe from 81,000 feet and at speed, using stuff designed and made by hand in the 1960's is pretty damned impressive.
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Below 150mm, I consider f/2 and below fast. Above 150mm, I consider 2.8 to 4 to be fast.
I've taken lots of f/1.4 shots, but when I'm shooting that wide open, it's likely because it's significantly dark, and it doesn't seem fast at all. ...
I've taken lots of f/1.4 shots, but when I'm shooting that wide open, it's likely because it's significantly dark, and it doesn't seem fast at all. ...
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). Like this one:
danski0224 said:mnclayshooter said:The one mounted in the underbelly of the SR-71 was pretty fast, relatively speaking.
http://www.wvi.com/~sr71webmaster/sr_sensors_pg1.htm
Anything sub f2.8 is fast, borderline specialty-use, IMHO.
Being able to resolve a 6" wide parking lot stripe from 81,000 feet and at speed, using stuff designed and made by hand in the 1960's is pretty damned impressive.
Its resolution specs of 110lines/mm is about 50% of the top new lenses and lower than even a Sigma 150-600mm at 600mm. A 100-400mm II resolves about 140 l/mm. The focal length is equivalent to 1220mm. Without any diffraction limitation, it should resolve lines of rows of alternating black and white lines 7.2" wide.
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Seeing something, and RESOLVING it are quite different things.danski0224 said:mnclayshooter said:The one mounted in the underbelly of the SR-71 was pretty fast, relatively speaking.
http://www.wvi.com/~sr71webmaster/sr_sensors_pg1.htm
Anything sub f2.8 is fast, borderline specialty-use, IMHO.
Being able to resolve a 6" wide parking lot stripe from 81,000 feet and at speed, using stuff designed and made by hand in the 1960's is pretty damned impressive.
You can see a star (I mean not our Sun), with the naked eye, but you most certainly cannot resolve it.
It's just effectively a point source, but some of its photons still happen to impinge on our retinae.
I have little doubt that the SR71 camera could have "seen" 2-inch wide car-park stripes, if they'd been painted bright enough white. But if there'd been 2 parallel stripes, each 2 inches wide, separated by 6 inches, the SR71 camera would still only have seen 1, brighter stripe. That is "resolving", or in this case, NOT resolving, but just "seeing".
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Fleetie said:Seeing something, and RESOLVING it are quite different things.danski0224 said:mnclayshooter said:The one mounted in the underbelly of the SR-71 was pretty fast, relatively speaking.
http://www.wvi.com/~sr71webmaster/sr_sensors_pg1.htm
Anything sub f2.8 is fast, borderline specialty-use, IMHO.
Being able to resolve a 6" wide parking lot stripe from 81,000 feet and at speed, using stuff designed and made by hand in the 1960's is pretty damned impressive.
You can see a star (I mean not our Sun), with the naked eye, but you most certainly cannot resolve it.
It's just effectively a point source, but some of its photons still happen to impinge on our retinae.
I have little doubt that the SR71 camera could have "seen" 2-inch wide car-park stripes, if they'd been painted bright enough white. But if there'd been 2 parallel stripes, each 2 inches wide, separated by 6 inches, the SR71 camera would still only have seen 1, brighter stripe. That is "resolving", or in this case, NOT resolving, but just "seeing".
You are absolutely correct about "resolving" and "seeing", which is why I made my comments. However, two lines separated by 6" should just be resolved as being separate as they are pretty close to the theoretical distance apart for resolution, which is not a sharp cut-off.
AlanF said:
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My fastest "fast prime" is a vintage Nikon 50mm f/1.2 classic double Gauss design, which has a certain look when at f/1.2, and turns into an ordinary sharp prime by f/2.8. My AF fast prime is a Sigma 35 f/1.4. I have vintage manual focus Nikon 105 f/2.5 and a more modern (but still obsolete) Voigtlander 125 f/2.5 macro. I don't have any fast supertelephotos - still using my 400 f/5.6.
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For me, up to 200mm, any full frame prime faster than f/2.8 is fast.
I don't typically shoot longer than 200mm anymore, so when it comes to that class of lens I'll plead the 2nd
General rules:
1) Anything faster than f/1.8 is Super-Fast.
2) Anything faster than f/1.4 is Ultra-Fast.
I don't typically shoot longer than 200mm anymore, so when it comes to that class of lens I'll plead the 2nd
General rules:
1) Anything faster than f/1.8 is Super-Fast.
2) Anything faster than f/1.4 is Ultra-Fast.
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Up to 100mm my definition is: "at least 1.4". And prime.
For longer than 200mm lenses, I'd say 2.8 is fast, too. (I would not consider the 600mm 4.0 or 800mm 5.6 fast lenses, even if there are no faster ones at these lengths.)
Does that make some sense?
I like natural lighting, so I don't use flash too frequently outside a studio, and when I do, only as fill flash, and when lights get dim, I use fast primes, so I need a marked difference in speed over zooms.
Therefore I do not consider 1/f = 2.0 or 1.8 as fast primes, as the difference to 2.8 zooms is not great enough to justify the investment in such a prime for me.
Very very rarely I use fast primes to shoot wide open in bright light for their shallow DOF (I used the 24 1.4 for still life at close distances with some degree of success), even less frequently with ND filters. I generally find 2.8 to be enough.
For longer than 200mm lenses, I'd say 2.8 is fast, too. (I would not consider the 600mm 4.0 or 800mm 5.6 fast lenses, even if there are no faster ones at these lengths.)
Does that make some sense?
I like natural lighting, so I don't use flash too frequently outside a studio, and when I do, only as fill flash, and when lights get dim, I use fast primes, so I need a marked difference in speed over zooms.
Therefore I do not consider 1/f = 2.0 or 1.8 as fast primes, as the difference to 2.8 zooms is not great enough to justify the investment in such a prime for me.
Very very rarely I use fast primes to shoot wide open in bright light for their shallow DOF (I used the 24 1.4 for still life at close distances with some degree of success), even less frequently with ND filters. I generally find 2.8 to be enough.
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