Lens Talks


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erizai

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Sep 16, 2005
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#1
Hi there,

Having notice the lens with attributes like f3.5-5.6, or f4-XX and etc...

The price could be so much different if f2.8 and smaller...

Anyone can enlighten me on this?:dunno:
 

TMC

Senior Member
Sep 4, 2004
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Beyond Space-Time Continuum
#2
coz smaller f number need larger lens elements and they cost more. If you are talking about fixed aperture lens like the 70-200/2.8, they can maintain that aperture throughout the range instead of going from f3.5 to f5.6 as you zoom out.
 

erizai

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Sep 16, 2005
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#3
But the price different can be 4 to 5 times that the normal lens!

But anyway thanks for answering...:sweatsm:
 

Witness

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Mar 18, 2004
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#5
act its coz at 2.8, the relative size of the aperture is alot larger than say at 3.5 or above.... thus it lets in more light, and allows u to use the lens at a higher shutter speed (but wider aperture) in dim light conditions....

that's y 2.8 lenses (especially the constant ones) are in such high demand...esp for telezooms... with a longer focal lenght..if u stick by the 1/focal lenght rule for shutter speed, a wider aperture will help u achieve the faster shutter speed....

cheers...
 

Canew

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Jul 26, 2005
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#6
Witness said:
the 1/focal lenght rule for shutter speed, a wider aperture will help u achieve the faster shutter speed....

cheers...
For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens? :confused:

Thanks.
 

user111

Senior Member
Jul 27, 2004
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#7
Canew said:
For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens? :confused:

Thanks.
that rule is just a rough guide

use whatever shutter speed u can manage
 

#8
erizai said:
But the price different can be 4 to 5 times that the normal lens!

But anyway thanks for answering...:sweatsm:
at the telephoto end of that lens a f2.8 aperture instead of a f5.6 implies 2 f stops which translates into 4 times the amount of light ~ 4 times the cost ;)
 

tunster

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Oct 26, 2003
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#10
Witness said:
act its coz at 2.8, the relative size of the aperture is alot larger than say at 3.5 or above.... thus it lets in more light, and allows u to use the lens at a higher shutter speed (but wider aperture) in dim light conditions....

that's y 2.8 lenses (especially the constant ones) are in such high demand...esp for telezooms... with a longer focal lenght..if u stick by the 1/focal lenght rule for shutter speed, a wider aperture will help u achieve the faster shutter speed....

cheers...
Add on to this, for a bigger aperture (smaller F stop). The lens can focus faster. Because lens are focus wide open and stop down during shutter release.
 

Witness

Senior Member
Mar 18, 2004
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#11
Canew said:
For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens? :confused:

Thanks.
honestly this is debatable.... but if we take the censor size as a guide to the "real focal length" then i guess yes.... but i erhm dun follow this rule and still get great results hahaha

cheers..
 

#12
Canew said:
For the 1/focal lenght rule for shutter speed of telezooms, do we need to take the FOV multiplier into consideration? For example on a 1.6X FOV camera, will we need to set the shutter speed to 1/320 sec. or the usual 1/200 sec. when we are shooting using a 200 mm lens? :confused:

Thanks.
I think no need to take 1.6X multiplier into account. Just shoot at 1/200 sec will do...cos you're still shooting at 200mm...

It's just that the sensor is smaller, cropping the image to a smaller field of view.
 

Jul 31, 2005
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Bt Batok
#13
tincup said:
I think no need to take 1.6X multiplier into account. Just shoot at 1/200 sec will do...cos you're still shooting at 200mm...

It's just that the sensor is smaller, cropping the image to a smaller field of view.
as the image is cropped, so is the blur due to camera shake. steady hands with tripod and/or VR/IS/OS will give blur-free images most of the time. with my 70-200vr@200mm, i can handhold @1/20sec. of course VR/IS/OS lenses are considerably more expensive
 

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