Is fast lens necessary?


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cwtan12

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Jan 25, 2007
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#1
I have got a copy of magazine (Japanese translated to Chinese) about Nikon's lens. There are a lot of photos there taken with each type of Sigma, Tokina, Tamron and of course Nikkor lens.

1 thing I don't really understand is why most of the pictures taken with fast primes are more than f4? So does it make any sense to get a 85mm f/1.4 if most of the photos I take is f/1.8 and above?
 

Artosoft

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#2
I have got a copy of magazine (Japanese translated to Chinese) about Nikon's lens. There are a lot of photos there taken with each type of Sigma, Tokina, Tamron and of course Nikkor lens.

1 thing I don't really understand is why most of the pictures taken with fast primes are more than f4? So does it make any sense to get a 85mm f/1.4 if most of the photos I take is f/1.8 and above?
1) Fast lens focus better than slow lens.
2) Max quality usually not on max aperture. It is about 1 or 2 stop down from maximum aperture.

Regards,
Arto.
 

jdredd

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Mar 30, 2006
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doesnt mean that just because that particular magazine the pictures were taken at F4 or above that that is actually the case normally..

much will always depend onthe preference of the photographer and the nature of the scene..

in a studio for example, you dont need to shoot wide open because you have lighting and theres not really any background to blur out.

it could also be that they wanted to get the sharpest possible picture... most fast lenses tend to be a little softer wide open than when stopped down to F4 or F5.6.

or if theres a few people in the photo and u want more depth of field etc...

personally, every time ive used fast primes, i tend to shoot pretty much wide open or within 1 or 2 stops of wide open.
 

mcn

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Oct 6, 2005
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#4
i can see from your signature thet you have a 17-55mm f2.8; i assume u bot it after yor 18-55mm f3.5-4.5; so do u usually take at the large aperture of the kit lens that make u buy the f2.8

u can tell me about it if u want to
 

Rashkae

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Nov 28, 2005
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#5
There's a good reason why f/1.8 (or 1.7) lenses are usually called the "poor man's f/1.4". Especially in the case of the Canon 50mm f/1.2 L which actually turned out to be a pretty bad lens.

The thing to consider is that these lenses are manufactured to much higher standards than the 1.7/1.8 counterparts. So the overall sharpness achievable at, say, f/2.0 or f/2.8 is better than what you could achieve with an f/1.8 lens at the same aperture.

For f/5.6 and up, there's not going to be too big a difference anymore, but depending on the lens manufacturer there still can be, as they may have a circular aperture, better engineered lenses, add extra coating, dispersion-glass elements, etc that you will not get in the "budget" 1.7 or 1.8 lenses. This can reduce flare, improve bokeh and reduce CA.
 

zj2000

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Mar 10, 2007
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Because all lenses work best when stopped down by 1 / 2 stops. Generally when stopped down you'll get sharper images, less vignetting, better contrast etc. V seldom will you use a fast prime at wide open since at f1.4 or f1.8 even the dof shallow to the point of being impractical. ie model's face in focus but ears are out of focus / if model's face is at an angle to you 1 eye is in focus but the other is not....
 

cwtan12

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Jan 25, 2007
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#7
i can see from your signature thet you have a 17-55mm f2.8; i assume u bot it after yor 18-55mm f3.5-4.5; so do u usually take at the large aperture of the kit lens that make u buy the f2.8

u can tell me about it if u want to
The pics taken with 17-55mm f2.8 is sharper than 18-55. I havent really compare these 2 lens but use 18-55 most of the time not at wide open.;p
 

Rashkae

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Nov 28, 2005
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#8
Let's try to keep the kit lenses out of this discussion... Kit lenses are usually pretty bad anyway, and comparing a kit lens to a good lens, even in the same focal range, will never be objective. The better comparison are NOT kit lenses, such as 50mm 1.4 vs. 1.7/1.8
 

Artosoft

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Aug 31, 2005
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#9
Let's try to keep the kit lenses out of this discussion... Kit lenses are usually pretty bad anyway, and comparing a kit lens to a good lens, even in the same focal range, will never be objective. The better comparison are NOT kit lenses, such as 50mm 1.4 vs. 1.7/1.8
I agree with you kit lens are usually pretty bad. But some are excellent like nikkor 18-70mm f3.5-4.5 DX.

Regards,
Arto.
 

Rashkae

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Nov 28, 2005
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#10
I agree with you kit lens are usually pretty bad. But some are excellent like nikkor 18-70mm f3.5-4.5 DX.

Regards,
Arto.
Well, the Sony kit lens is pretty good as well, but I still think we should keep this to a "prime vs. baby prime" discussion.
 

ortega

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Nov 2, 2004
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#12
I have got a copy of magazine (Japanese translated to Chinese) about Nikon's lens. There are a lot of photos there taken with each type of Sigma, Tokina, Tamron and of course Nikkor lens.

1 thing I don't really understand is why most of the pictures taken with fast primes are more than f4? So does it make any sense to get a 85mm f/1.4 if most of the photos I take is f/1.8 and above?
to answer your question

it is because the lens work best stopped down 1 or 2 stops

so, if you get the fast lens would normally depend on your fast money
 

cwtan12

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Jan 25, 2007
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#13
I get it now. Seems like I may need to spend more.
 

Rashkae

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Nov 28, 2005
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#16
I think he meant prime of the same focal length but different apperture size e.g. 50mm f/1.4 vs 1.8. No :confused: ?
Correct. Almost-prime aperture but at a baby price compared to full prime. ;)
 

Artosoft

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Aug 31, 2005
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#17
I think he meant prime of the same focal length but different apperture size e.g. 50mm f/1.4 vs 1.8. No :confused: ?
In my understanding, prime lens mean not-zoom lens. Prime lens only have one/fixed focal length. It might f/1.4 or f/1.8 or even f/4, it is still called prime lens regardless the maximum aperture.

Regards,
Arto.
 

Artosoft

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Aug 31, 2005
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#18
Correct. Almost-prime aperture but at a baby price compared to full prime. ;)
Oh, please. Don't make your own definition. We already confused by many standard definitions. Just called them fast (prime) lens or slow (prime) lens will do.

Regards,
Arto.
 

Canonised

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Aug 27, 2003
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#19
Let's try to keep the kit lenses out of this discussion... Kit lenses are usually pretty bad anyway, and comparing a kit lens to a good lens, even in the same focal range, will never be objective.
Oh PLEASE! What utter nonsense! .... a "wise" guy once said :bsmilie: :sweatsm:
 

Canonised

Senior Member
Aug 27, 2003
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#20
Correct. Almost-prime aperture but at a baby price compared to full prime. ;)
This really takes the cream of the cake! ....:bsmilie::sweatsm:
What's almost-prime, full prime, baby prime??? ....Bro, try harder next time!:sweatsm:
 

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