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Fast lenses
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PostPosted: Fri Dec 17, 2010 4:32 pm    Post subject: Fast lenses Reply with quote
http://www.mflenses.com/gallery/fast-lenses


PostPosted: Fri Dec 17, 2010 5:19 pm    Post subject: Reply with quote
At what point does a lens become fast? I always think that this depends on FL.


PostPosted: Fri Dec 17, 2010 5:22 pm    Post subject: Reply with quote
martinsmith99 wrote:
At what point does a lens become fast? I always think that this depends on FL.


Faster than usual in it's focal lengths.

for example in 135mm F2 and below, in 50mm below 1.4 etc


PostPosted: Fri Dec 17, 2010 6:57 pm    Post subject: Reply with quote
Attila wrote:
martinsmith99 wrote:
At what point does a lens become fast? I always think that this depends on FL.

Faster than usual in it's focal lengths.
for example in 135mm F2 and below, in 50mm below 1.4 etc

Then we must decide what is 'usual' in any focal length. To me, the usual is f/2.8 in 24-28-35-90-100-135mm, f/2 at 50-55-58mm, f/4 at 15-20-200mm. Then, 'fast' is 1/2 or 1 stop faster than usual, and 'super-fast' is beyond that. That is my personal mental map.

But like any line-drawing, these lines are arbitrary, and shift with changes in lensmaking. We may be near absolute limits in commercial optics. But lens matrices and arrays, active controls of malleable shapes, extensive image processing, may change our standards of judging optics and speed.


PostPosted: Fri Dec 17, 2010 7:51 pm    Post subject: Reply with quote
Ah, but what happens when discussing older lenses when the usual was f3.5 or more???????
So f1.8 was superfast back then eh??


PostPosted: Fri Dec 17, 2010 9:49 pm    Post subject: Reply with quote
It was....and still is, based on percentage of available lenses.


PostPosted: Sat Dec 18, 2010 12:25 am    Post subject: Reply with quote
This seems to me to be a rather subjective call and format dependent.


PostPosted: Sat Dec 18, 2010 12:40 am    Post subject: Reply with quote
cooltouch wrote:
This seems to me to be a rather subjective call and format dependent.

+1


PostPosted: Sat Dec 18, 2010 12:48 am    Post subject: Reply with quote
Attila wrote:
cooltouch wrote:
This seems to me to be a rather subjective call and format dependent.

+1


+2

For example (but there are many) 300/4.5 is fast for an 8x10 lens, slow for 35mm.

JJ


PostPosted: Sat Dec 18, 2010 2:01 am    Post subject: Reply with quote
Attila wrote:
martinsmith99 wrote:
At what point does a lens become fast? I always think that this depends on FL.


Faster than usual in it's focal lengths.

for example in 135mm F2 and below, in 50mm below 1.4 etc

Usually thats right. But not always right.
Based on my test, 50/1.4 only very slight slower than 50/1.2 lens. I mean smc M 50/1.4 vs Nikkor 55/1.2 & FD 55/1.2 SSC
My camera metering same speed with those 3 lenses.


PostPosted: Sat Dec 18, 2010 10:32 am    Post subject: Reply with quote
Quite agree with the last post...........I have canon fd 50 1.4 and 1.8 lenses and theres bugger all difference between them regarding light gathering properties........half a stop difference barely registers in camera


PostPosted: Sat Dec 18, 2010 5:12 pm    Post subject: Reply with quote
There are differences. Many meters may not notice a mere 2/3 of a stop, but film/sensors do.


PostPosted: Sat Dec 18, 2010 5:41 pm    Post subject: Reply with quote
jjphoto wrote:
Attila wrote:
cooltouch wrote:
This seems to me to be a rather subjective call and format dependent.

+1


+2

For example (but there are many) 300/4.5 is fast for an 8x10 lens, slow for 35mm.

JJ


However, for those using smalelr formats, such as 35mm, most would have no problem using their lenses at full bore, but large format users would not want to do that. In fact Rodenstock specified their lenses to be used at f/22.

That being said, while I have no problem at all using my Protar V lenses, I still use a Grandagon-N, 65/4.5 Cool


PostPosted: Sun Dec 19, 2010 3:21 pm    Post subject: Reply with quote
I still wondering why lenses with large aperture called fast lens Rolling Eyes
It only lets more light passing through. The speed of light is constant exept if you are shooting near a blackhole Razz


PostPosted: Sun Dec 19, 2010 4:15 pm    Post subject: Reply with quote
kopimorning wrote:
I still wondering why lenses with large aperture called fast lens Rolling Eyes
It only lets more light passing through. The speed of light is constant exept if you are shooting near a blackhole Razz


It refers to the shutter speeds the lens allows...A fast lens allows faster shutter speeds to be used due to its wider/brighter aperture and a slow lens has to be used at slower shutter speeds because of it smaller/dimmer aperture...At least thats the story I'm sticking to Wink


PostPosted: Sun Dec 19, 2010 4:17 pm    Post subject: Reply with quote
DSG wrote:
kopimorning wrote:
I still wondering why lenses with large aperture called fast lens Rolling Eyes
It only lets more light passing through. The speed of light is constant exept if you are shooting near a blackhole Razz


It refers to the shutter speeds the lens allows...A fast lens allows faster shutter speeds to be used due to its wider/brighter aperture and a slow lens has to be used at slower shutter speeds because of it smaller/dimmer aperture...At least thats the story I'm sticking to Wink


I like this explantion thanks! In Hungarian we call them lens with light power.


PostPosted: Sun Dec 19, 2010 6:10 pm    Post subject: Reply with quote
DSG wrote:
kopimorning wrote:
I still wondering why lenses with large aperture called fast lens Rolling Eyes
It only lets more light passing through. The speed of light is constant exept if you are shooting near a blackhole Razz

It refers to the shutter speeds the lens allows...A fast lens allows faster shutter speeds to be used due to its wider/brighter aperture and a slow lens has to be used at slower shutter speeds because of it smaller/dimmer aperture...At least thats the story I'm sticking to Wink

It goes back to Aristotelean physics, where heavier objects fall faster than do lighter objects. So-called 'faster' lenses are usually bigger and heavier than 'slower' lenses; being heavier, they fall faster. Galileo proved this to be false when he dropped cannonballs and apples from the Tower of Pisa, but optical engineers still live in a pre-Galilean, pre-Newtonian world. Selah!


PostPosted: Sun Dec 19, 2010 6:14 pm    Post subject: Reply with quote
DSG's explanation sounds as good as any. RioRico's violates the principle of parsimony. Cool

I've always thought of the speed, whether fast or slow, as being the amount of time it takes to make an exposure at that particular aperture. Fast lenses allow fast exposure times, which amounts to the same thing as DSG's explanation in the end.


PostPosted: Mon Dec 20, 2010 5:56 am    Post subject: Reply with quote
cooltouch wrote:

I've always thought of the speed, whether fast or slow, as being the amount of time it takes to make an exposure at that particular aperture. Fast lenses allow fast exposure times, which amounts to the same thing as DSG's explanation in the end.


I like your explanation, that make your explanation sounds as good as any Laughing

Now I would like to call these lenses as: "fast shutter speed allowed lens" Laughing Laughing Laughing


PostPosted: Mon Dec 20, 2010 8:18 am    Post subject: Reply with quote
I always thought "fast" lenses were the ones that emptied your wallet quickly? Mr. Green


PostPosted: Mon Dec 20, 2010 5:08 pm    Post subject: Reply with quote
Scheimpflug wrote:
I always thought "fast" lenses were the ones that emptied your wallet quickly? Mr. Green


I like your explanation, the fast lens is the one that allows a lot of light in your pocket!
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