# Your own definition of fast prime



## Dylan777 (Mar 6, 2017)

Describe in Your own definition of fast prime lenses. How and when do you use it.

Share a photo or two to show your points


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## midluk (Mar 6, 2017)

A fast prime lens is a prime lens that is faster than the fastest zoom I own at that focal length.
My 100 f/2.8L IS USM is a fast prime, since I only own the 70-200 f/4L IS USM with the same focal length.


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## AlanF (Mar 6, 2017)

Does my definition matter? In any case, it depends on focal length. An f/1.8 50mm is slow compared with an f/1.2 but an f/1.8 800mm would be quite spectacular. I would use it in conjunction with a small crane for far away birds at dawn and dusk.


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## rfdesigner (Mar 6, 2017)

Seeing as almost no zooms are faster than f2.8, I'd regard anything faster than f2.8 as fast, i.e. f2.0 and better.

but then with the lenses I have, I would, wouldn't I! :


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## mnclayshooter (Mar 6, 2017)

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.


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## Joe M (Mar 6, 2017)

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
> 
> ...



A fast prime is anything under f2.8. And off topic, speaking of fast, in my books at least, the absolute coolest jet ever. I never get bored of pouring over stats and pics of that bird. I can't imagine looking down from 26km at over 3,500km/h.


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## LonelyBoy (Mar 6, 2017)

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
> 
> ...



Awesome!

You may have already read this, but for anyone else who's interested, here's a big PDF about the U2 program:

https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/books-and-monographs/the-cia-and-the-u-2-program-1954-1974/u2.pdf

Fun story, I actually met an active U2 pilot at my now-wife's friend's wedding. Big Bengals fan, he was.


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## Dylan777 (Mar 7, 2017)

I have no words to describe. All I know it melts my heart every times I push that shutter 

85mm @ f1.4







35mm @ f1.4 - through the bed frame


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## slclick (Mar 7, 2017)

This post isn't going exactly as planned is it?


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## Dylan777 (Mar 7, 2017)

slclick said:


> This post isn't going exactly as planned is it?



I was hoping to see more photos from CR members, how they use fast primes.


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## beforeEos Camaras (Mar 7, 2017)

a 85mm 1.8 prime seems I have none to link to at the moment. I will fix that later infact 1.8 is my fastest non fd primes I have a 50 1.4 fd prime and a 135 3.5 fd prime so anything under 2.8 I consider fast


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## neuroanatomist (Mar 7, 2017)

It might not be the fastest prime, but in this context I'd suggest the best prime is 503, because upside down it's EOS. 

;D


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## Pookie (Mar 7, 2017)

In the words of Nick Nolte in Tropic Thunder... "I don't know what you call it, I only know the sound it makes when it kills a man..."

I use them whenever I damn well please... 

The 85 f/1.2 is a personal fav...




Or maybe a Summicron 50 wide open would work too...




In the MF world 2.8 is considered pretty fast...


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## drmikeinpdx (Mar 7, 2017)

I have lots of good wide aperture shots with the 50mm F/1.2 L and my trusty 85mm F/1.8, but they are too naughty to share in this forum.


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## applecider (Mar 7, 2017)

My definition of a fast prime is more intuitive than a dictionary definition. 

I'd say any normal length lens below f2.8 is a fast prime, but the 300mm f2.8, 500mm f4, and 600mm f4 are all also fast primes.

Below are photos of my three fast normals, a zeiss 55mm f1.4, a rokinon 24mm f1.4 and a canon 35mm f2.0 IS all on the same subject but with size controlled by foot action. BTW illumination is provided by an LED panel to the left. 
http://www.canonrumors.com/forum/index.php?action=gallery;sa=view;id=114

http://www.canonrumors.com/forum/gallery/0/57161-070317021520-1121588.jpeg

http://www.canonrumors.com/forum/index.php?action=gallery;sa=view;id=112

I'm not in love with the new way of adding photos BTW


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## Zv (Mar 7, 2017)

Since I own f/4 zooms anything faster than that is what I'd call a fast prime. I rarely shoot faster than f/2.8, had to really dig around on my Flickr page but found one taken last spring using the 135L @ f/2. The cyclist was a bit accidental but I decided to keep the shot. 

https://flic.kr/p/F19zHs

Edit - found another one from that time period with the 135L. This tree was gorgeous but the background was busy so f/2'd it away!

https://flic.kr/p/F1iKUa


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## slclick (Mar 7, 2017)

*A test of the new way to attach an image, from the Abstract Gallery *

Killing two posts in one here....





A fixed focal length lens which allows a large amount of light to enter resulting in either interesting specular highlights or an acceptable image in a low light scene. YMMV.

Lensbaby Composer, Sweet 35 , Canon 60D


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## jeffa4444 (Mar 7, 2017)

Depends what you want a fast lens for a. bokah at maximum apertures or b. to shoot in lower light. Lower light is equally affected by the sensitivity of the camera sensor so a high sensitivity sensor may give you the same result at f4 as you would get with a lower sensitivity sensor at f2.8 or f2. 

Fast lenses to most manufacturers are 2.8 through to .95 etc. depending on whether they are fixed primes or zooms.


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## AcutancePhotography (Mar 7, 2017)

I don't know if the phrase "fast" is even an appropriate term to describe a lens. Fast in relation to what?

Faster and slower to me are more appropriate.

"Lens X is slower than Lens Y"

"I wish Lens A was faster."

"If you were not such a noob, you would know to use a faster lens" ;D

"For your type of photography a slower lens would be more cost effective"


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## slclick (Mar 7, 2017)

AcutancePhotography said:


> I don't know if the phrase "fast" is even an appropriate term to describe a lens. Fast in relation to what?
> 
> Faster and slower to me are more appropriate.
> 
> ...



It's slang... photog parlance. Nothing to be nitpicked, I think we all get it's meaning.


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## tolusina (Mar 7, 2017)




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## rfdesigner (Mar 7, 2017)

applecider said:


> My definition of a fast prime is more intuitive than a dictionary definition.
> 
> I'd say any normal length lens below f2.8 is a fast prime, but the 300mm f2.8, 500mm f4, and 600mm f4 are all also fast primes.
> 
> ...



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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## danski0224 (Mar 8, 2017)

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
> 
> ...



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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## [email protected] (Mar 8, 2017)

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. ...


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## Jopa (Mar 8, 2017)

Before I became lazy and spoiled by Canon's AF I use to shoot MF lenses. 1.4 is quite fast for me, and with some practice and patience sharp images are possible (but timing could be wrong  ). Like this one:





Taken with a fast lens but slow focus


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## AlanF (Mar 8, 2017)

danski0224 said:


> mnclayshooter said:
> 
> 
> > The one mounted in the underbelly of the SR-71 was pretty fast, relatively speaking.
> ...



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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## Fleetie (Mar 10, 2017)

danski0224 said:


> mnclayshooter said:
> 
> 
> > The one mounted in the underbelly of the SR-71 was pretty fast, relatively speaking.
> ...


Seeing something, and RESOLVING it are quite different things.
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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## Viggo (Mar 10, 2017)

My definition is f2.0 and faster, and I only own fast primes so I use them for everything and 99,9% of the time wide open.


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## Dylan777 (Mar 10, 2017)

Viggo said:


> My definition is f2.0 and faster, and I only own fast primes so I use them for everything and 99,9% of the time wide open.



That's not the way to shoot prime Viggo


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## AlanF (Mar 10, 2017)

Fleetie said:


> danski0224 said:
> 
> 
> > mnclayshooter said:
> ...



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:


> 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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## Viggo (Mar 10, 2017)

Dylan777 said:


> Viggo said:
> 
> 
> > My definition is f2.0 and faster, and I only own fast primes so I use them for everything and 99,9% of the time wide open.
> ...



I guess it's 100%, but sometimes when I carry my camera in the Black Rapid I bump the dial ;D


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## NancyP (Mar 10, 2017)

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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## StudentOfLight (Mar 10, 2017)

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.


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## sulla (Mar 10, 2017)

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.


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## sulla (Mar 10, 2017)

24mm at 1.4 and 1/80, ISO 640


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## sulla (Mar 10, 2017)

35mm at 1.4 and 1/160s, ISO 800


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## sulla (Mar 10, 2017)

50mm at 1.4 and 1/25s, ISO1250


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## sulla (Mar 10, 2017)

50mm at 1.6 and 1/60s, ISO400


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## sulla (Mar 10, 2017)

85mm at 1.2 and 1/800s, ISO100


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## sulla (Mar 10, 2017)

85mm at 1.2 and 1/80s, ISO250


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