why favor 2.8 lens??


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camerax

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Apr 19, 2008
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#1
okay, this is really what i wanna know about 2.8 lens.

FIRST POINT

okay i know its faster. simple explanation: as you can go down to lower aperture (2.8 compared to 2.5 and above) , you can use higher shutter speed to freeze the motion.

HOWEVER, i have 3.5-5.6 lens and its fast enough to stop the motion. i can use speed up to 1/500 in the afternoon and it can freeze the motion of taxi.
so why do we need 2.8??? like freezing the speed of sport car?? and how much faster is 2.8 really??



SECOND POINT

i am also confused about 2.8 aperture VS VR (vibration reduction).

people said, with VR, we can shoot objects in low light situation. okay, i get the logic.
because when there is low light, you want to make your shutter speed lower to allow more light to come in. but as you lower your speed, and if you shake your hand while the camera taking pics, then you will blur the image. in this case, VR will negate your hand movement. okay, i got it.

but technically 2.8 can do the same thing then but in a different way ofcourse.

2.8 can allow you to have lower aperture so that you have more light to come in.

so in low light situation, which one is better then?? 2.8 or VR?? this is so freakin confusing.


please enlighten me everybody as i really need to know this to upgrade.

thanks.
 

ahbian

Senior Member
May 23, 2006
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#2
I'll try to answer part of your questions.

HOWEVER, i have 3.5-5.6 lens and its fast enough to stop the motion. i can use speed up to 1/500 in the afternoon and it can freeze the motion of taxi.
so why do we need 2.8??? like freezing the speed of sport car?? and how much faster is 2.8 really??
If your shooting needs are to capture a moving vehicle (or slower objects ) in broad daylight , then yes, you do not need a faster lens. However, in the afternoon, the harsh lights are usually not flattering to photographs, will that be acceptable to you?

I can't say why you would need f2.8, for me, I need 1.8 and faster for my shoots are mainly indoors shots of stage dancers.

To be straightforward, if you find that your lens suits your shooting purposes, that'll be great. And in that case, it's doesn't really make sense for us to try to justify your buying a faster lens.
 

attap seed

Senior Member
Feb 16, 2006
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#3
prime lens go faster.

zoom lens, the biggest is 2.8 (only tokina got 2.6-2.8, but the difference is minimal).

so, many times, its not ppl's favourite. but if u use zoom, tats the fastest f the moment.

even cheapo 50 f1.8 is much faster than 2.8
 

Big Kahuna

Senior Member
Dec 15, 2004
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#4
f2.8 in low light allows faster shutter speed to be used in given scene compared to f3.5....where else VR merely compensate the handshake but the exposure time is still longer....so in low light....VR might not able to freeze a motion....besides....a brighter lens should helps in auto focus because the sensor is able to read the scene better :think:
 

attap seed

Senior Member
Feb 16, 2006
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#5
fast lens and VR are only part of the equation.

ISO and tripod completes the story.

do u understand how these 4 are interlinked?

why upgrade before u are sure wat to get?

go shoot more.

***paiseh, jus thought of flash. so, 5 variables altogether. anyone, anymore to add?
 

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giantcanopy

Senior Member
Feb 11, 2007
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#6
2.8 lenses have a larger aperture not a lower / smaller aperture.

In cases where light is not readily available, short of stepping up your ISO really high, shooting at larger aperture helps.

Here is a little article i came up with on stabilization vs larger aperture

Ryan
 

kcuf2

Senior Member
Dec 29, 2005
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#7
why f2.8 is so popular and always advertised as fast lens, ALTHOUGH there are even more fast lens like f1.0, f1.2.


The MAIN reason is that the f2.8 lens offers the best COMPROMISE of WEIGHT and FAST apeture.

Compare the 70-200 f2.8 size and the 200mm f2.0 size, the latter is easily double its weight.

likewise, why is it that the telephoto zooms like the 500mm, 600mm dun come in the f2.8 versions and instead all only f4? the answer is again COMPROMISE of WEIGHT and FAST apeture.

look at the weight of the sigma 200-500mm f2.8, it is more than 15kg while a 600mm f4 is at most 5kg (A dumbbell)


that is why u MUST always ignore wat advertisement says, they always say f2.8 is fast or f4 is fast. In the end, u must know wat are the fast apeture available for ur shooting range, then u decide the weight that u can handle..
 

woolman

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Feb 1, 2008
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#9
Camerax there is one point you may have left out about having f2.8 or bigger...

Ever seen a portrait shot where the backgorund is a silky smooth blur? it's call bokeh... it helps to isolate your main subject, make it have a 3D "pop-up" effect which will draw viewers moe to the main subject and generally makes the photo look more pleasant...

many pros go for such fast lens not just for low-light situation but also to get that nice silky bokeh...

yes, a f3.5-5.6 zoom can also give you that bokeh depending on the lens focal length, the working distance and background to subject distance... but a f2.8 or bigger makes the DoF so narrow that you almost always are guranteed a nice bokeh...

so unless you don't mind having sharp background where you can see many distracting things together with your main subject and thus take away the focus on your main subject and you know how to make use of your f3.5-5.6 to get the bokeh in more challenging wider DoF situations then stick to the f3.5-5.6 zooms

but if you really want that silkly smooth bokeh then consider f2.8 and above consatnt apertures
 

ngck12

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Dec 4, 2007
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#10
Do note that be it f2.8, 5.6, 11 or 22, you can achieve silky smooth bokeh. Its dependant on the roundness of aperture blades. Having bigger aperture helps in backgrd isolation, and not silky bokeh. It just happens that a lot f2.8 lenses use circular aperture, like tamron 17-50 f2.8 and canon 70-200 f2.8, thus the silky smooth bokeh.



*not that woolman is wrong, just to prevent confusion.
 

camerax

New Member
Apr 19, 2008
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#11
why f2.8 is so popular and always advertised as fast lens, ALTHOUGH there are even more fast lens like f1.0, f1.2.


The MAIN reason is that the f2.8 lens offers the best COMPROMISE of WEIGHT and FAST apeture.

Compare the 70-200 f2.8 size and the 200mm f2.0 size, the latter is easily double its weight.

likewise, why is it that the telephoto zooms like the 500mm, 600mm dun come in the f2.8 versions and instead all only f4? the answer is again COMPROMISE of WEIGHT and FAST apeture.

look at the weight of the sigma 200-500mm f2.8, it is more than 15kg while a 600mm f4 is at most 5kg (A dumbbell)


that is why u MUST always ignore wat advertisement says, they always say f2.8 is fast or f4 is fast. In the end, u must know wat are the fast apeture available for ur shooting range, then u decide the weight that u can handle..


well, there is one flaw from your statement. you forgot to think about 50mm 1.8.

this is a mini lens and faster lens compared to lets say 70-200mm 2.8 : )

what do you say about this?
 

camerax

New Member
Apr 19, 2008
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#12
Do note that be it f2.8, 5.6, 11 or 22, you can achieve silky smooth bokeh. Its dependant on the roundness of aperture blades. Having bigger aperture helps in backgrd isolation, and not silky bokeh. It just happens that a lot f2.8 lenses use circular aperture, like tamron 17-50 f2.8 and canon 70-200 f2.8, thus the silky smooth bokeh.



*not that woolman is wrong, just to prevent confusion.

ahh, i c. then what about prime lens 50mm 1.8??? is the bokeh good?

and is it better than 17-55mm 2.8 lens?? very curious about this
 

ngck12

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Dec 4, 2007
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#13
the 50mm f1.8 gives you horrible and rough bokeh, but more dof. the 17-55 f2.8 gives better bokeh, 7 blades as compared to the 50 prime 5 blades.
 

deklan

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Feb 28, 2007
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#14
the 50mm f1.8 gives you horrible and rough bokeh, but more dof. the 17-55 f2.8 gives better bokeh, 7 blades as compared to the 50 prime 5 blades.
doest the F1.8, give u less depth of field compared to the 17.55 F2.8?

and why a F2.8 rather then a F4, for instance the 14-24mm comparing the the significantly cheaper 12-24 F4?
cause i can also shoot F4 with the 14-24, but not F2.8 with the 12-24 F4...
i rather have it and not need it then, need it and not have it.
 

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Fotophilic

Senior Member
Jun 18, 2006
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#16
FIRST POINT
i have 3.5-5.6 lens and its fast enough to stop the motion. i can use speed up to 1/500 in the afternoon and it can freeze the motion of taxi. so why do we need 2.8??? like freezing the speed of sport car?? and how much faster is 2.8 really??


why don't u try indoors, with less "ideal" amount of light? u don't have to shoot a car indoor, u can just try it on a kid playing around. u should be able to feel the difference and the need for speed, without me even telling u.

SECOND POINT
people said, with VR, we can shoot objects in low light situation. okay, i get the logic.
but technically 2.8 can do the same thing then but in a different way ofcourse.
2.8 can allow you to have lower aperture so that you have more light to come in.
so in low light situation, which one is better then?? 2.8 or VR?? this is so freakin confusing.


VR lenses with smaller apertures (e.g. 3.5-5.6) could counter handshakes but not freeze motion of the subject u are taking. F2.8 lenses on the other hand, could "somehow" counter handshake (by increasing the shutter speed a little) and could freeze motion better (also by virtue of faster shutter speed). But I tell u the truth: In real low light situation, 2.8 or VR are of little help; tripod is the best. Of course, good technics in holding ur camera plays a role as well.

please enlighten me everybody as i really need to know this to upgrade.

A word of advice: If u think ur current setup is gd enough, don't look for reasons to upgrade. Money don't come easy (for most people).
 

night86mare

Deregistered
Aug 25, 2006
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#17
HOWEVER, i have 3.5-5.6 lens and its fast enough to stop the motion. i can use speed up to 1/500 in the afternoon and it can freeze the motion of taxi.
so why do we need 2.8??? like freezing the speed of sport car?? and how much faster is 2.8 really??
it allows you half a stop faster. for sports and candids it can mean the difference between having motion blur and not having motion blur.

also note that shooting WIDE OPEN tends to give you softer shots on most lenses, more often than not. there are exceptions actually, but these are few and far between.

if you find that you're doing fine with your 3.5-5.6, stick with it. i firmly believe in knowing what you need instead of blindly following the crowd and others' advice because everyone has their own unique needs.

2.8 can allow you to have lower aperture so that you have more light to come in.

so in low light situation, which one is better then?? 2.8 or VR?? this is so freakin confusing.
depends. do you want the depth of field to be as shallow at 2.8? my camera has in-body stabilisation and i thank my lucky stars everytime i want extreme depth of field and handshake-introducing speeds are required.. and a tripod is not easy to use.

you speak as if your lens is stuck at f/2.8 or wide open. what of f/8? if i shoot at say, 18mm and i need a speed of about 1/10 seconds coupled with f/8 and iso 200.. then the vr lens will do it, your f/2.8 lens will not.

it's all about YOUR needs. think about which situations you'd be more likely to be in. then figure out what you need.
 

attap seed

Senior Member
Feb 16, 2006
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#18
well, there is one flaw from your statement. you forgot to think about 50mm 1.8.

this is a mini lens and faster lens compared to lets say 70-200mm 2.8 : )

what do you say about this?



do compare banana to banana.

wats the size of 50 1.8 relative to 50 1.2 ?

wats the size of 70-200 2.8 relative to 70-210 4-5.6 ?
 

Aug 20, 2007
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#19
I think you need to read & shoot more with your lens to learn about aperture...:dunno:
 

ricleo

Senior Member
Mar 13, 2004
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#20
well, there is one flaw from your statement. you forgot to think about 50mm 1.8.

this is a mini lens and faster lens compared to lets say 70-200mm 2.8 : )

what do you say about this?
The reason why the 50mm F1.8 is so small compared to 70-200 F2.8 is because of the different focal length as well. the 50mm is a prime while the 70-200 is a zoom. To get a fixed F2.8 aperture across 70-200mm requires a bigger front element to let light in. The 50mm on the other hand is a simple design that does not have to take into account the zoom range.

This is why if u look at the 3rd party or less expensive canon non constant aperture zoom lens, eg the Sigma 17-70 F2.8-4.5 and the canon 18-55 F3.5-5.6, they are small, but they offer only the "big" apertures at the widest angle (17mm/18mm), and at the full zoom, the apertures are smaller.

So as what the previous poster has mentioned, compare like with like. Take a look at the 50mm F0.95 announced by Leica, or the old one by canon...they are huge!


 

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