Advantage of Fast Lens eg: 2.8


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eurox

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#1
I'm a newbie, may I know what is the advantage using a fast lens eg: 2.8 over a 3.5-5.6 lens

Please spare me, I'm really a newbie :embrass:

any links or explanations would be appreciated

thanks!
 

AReality

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#2
Wah... u newbie since April 2002 leh.

Fast lens can focus better in lower lighting, can use the larger aperature also.
 

KNIGHT ONG

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#3
Hmm ... :think:

Eg 1. 70-200mmf2.8, constant aperture throughout the lens. Expensive also.

Eg 2. 70-200mmf3.5-5.6, the aperture at 70mm will be f3.5 and when zoom to 200mm will be f5.6 with a drop of two stop.

Depending on what you shoot, indoor will normally required fast lens under low light condition and that f2.8 came in very handy and useful unless you step up ISO setting.
 

eurox

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#5
AReality said:
Wah... u newbie since April 2002 leh.
hehe I didnt continue my interest since that time coz I got no money to follow up .. now I'm working and have some money to spare :bsmilie:
 

eurox

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#6
what is the difference of shooting with 2.8 lens and 5.6 lens under normal daylight condition ?

Is it true to say that the difference will be only under low light conditions ?
 

dkw

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#7
eurox said:
what is the difference of shooting with 2.8 lens and 5.6 lens under normal daylight condition ?

Is it true to say that the difference will be only under low light conditions ?
The aperture size affects the speed of your lens. So f2.8 aperture is 1 stop faster than an f4 aperture, that is, it allows twice the amount of light to come though at the same shutter speed. So, for the same exposure, you can shoot at twice the shutter speed. i.e f2.8@1/100s = f4@1/50s. Got it? It is an advantage at low light because with a slower lens, your shutter speed may be so slow as to be intolerable. A faster lens buys you shutter speed.

Aperture size also affects depth of field (DOF), but that is a much longer tutorial, and I hope you will dig around a bit on the web and learn it for yourself. For one, a long list of photography resources on the web is listed in the sticky at the top of this forum. --> http://forums.clubsnap.org/showthread.php?t=37569

Cheers,
 

zekai

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#9
my pro friend shared with me.

a lens regardless of brand is normally not that sharp at its widest. They only perform optimally 1-2 stop lower.

example.

f2.8 ~ optimal sharpness @ f3.5 onward
f3.5 ~ optimal sharpness @ f4/ 5.6 onward

with a zoom lens F2.8 through out, you have more range of lighting to play with.
 

showtime

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#11
eurox said:
what is the difference of shooting with 2.8 lens and 5.6 lens under normal daylight condition ?

Is it true to say that the difference will be only under low light conditions ?
2.8 will give shallower dof as compared with 5.6
good for nice blur backgrounds and photography with selective focus...
 

zaren

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#14
i love my 32-96mm/ f2.8 lens! ;p
 

Prismatic

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#15
zekai said:
my pro friend shared with me.

a lens regardless of brand is normally not that sharp at its widest. They only perform optimally 1-2 stop lower.

example.

f2.8 ~ optimal sharpness @ f3.5 onward
f3.5 ~ optimal sharpness @ f4/ 5.6 onward

with a zoom lens F2.8 through out, you have more range of lighting to play with.
True, usually, only portrait lens are designed to be sharp at wide apertures.
 

Ah Pao

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#16
In practical terms, a f/2.8 (fast) lens enables you to use faster shutter speed in low light conditions. Most noticably the benefits of a fast lens come in for indoor sports or stage photography, when you need a fast shutter speed without flash to freeze the motion without unexposing your subject.
 

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