Question with regards to fast lens.


TWmilkteaTW

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May 30, 2011
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#1
i understand that lens with f2.8 are the better and more expensive 1.. for example 2470. 70200. f2.8
i know the wide aperture will be very useful for night shooting and with it.. enable us to use a faster shutter speed.

However..im confused.. after i read the photography books.. in daylight..nobody shoots at f2.8 even they uses those lens.. they probably shoot at 5.6 or higher n up to 22 for landscapes. Err.. so what happen if i shoot at f2.8 in daylight? n why people generally dont use it.
(isit because during the day.. its too bright.. to use wide aperture? even if im on aperture priority mode it will turn overexposed?)
isit something to do with "sweet spot" i read about?
 

Last edited:
Aug 16, 2010
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#2
For landscapes rule of thumb is not to have such big aperture as the DOF will be too thin.

In daylight if you shoot f2.8 you will have a faster shutter speed lo. People might not want to use it because they don't want such a thin DOF for that specific shot?
 

Irvine

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Jan 1, 2010
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#3
i understand that lens with f2.8 are the better and more expensive 1.. for example 2470. 70200. f2.8
i know the wide aperture will be very useful for night shooting and with it.. enable us to use a faster shutter speed.

However..im confused.. after i read the photography books.. in daylight..nobody shoots at f2.8 even they uses those lens.. they probably shoot at 5.6 or higher n up to 22 for landscapes. Err.. so what happen if i shoot at f2.8 in daylight? n why people generally dont use it.
(isit because during the day.. its too bright.. to use wide aperture? even if im on aperture priority mode it will turn overexposed?)
isit something to do with "sweet spot" i read about?
it depends on what kind of shots they want. the dof can be too thin for the types of shots they want, n it can also be because that it's too bright in the open n the camera's shutter speed can't go any faster.
 

kei1309

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Apr 12, 2010
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#4
(isit because during the day.. its too bright.. to use wide aperture? even if im on aperture priority mode it will turn overexposed?)
isit something to do with "sweet spot" i read about?
in aperture priority, your camera will always fight to get you a good and standard exposure. UNLESS it's too bright. and then your shutter speed can't go fast enough to get that standard exposure, then it'll be overexposed.

and exposure has nothing to do with the sweet spot. it depends on the lens, and it's a range of aperture value or a single aperture value using that lens that gives you the sharpest image.

i suggest you read up on Aperture, ISO and Shutter speed before throwing wild guesses here and confuse yourself, and every other newbie that reads this thread
 

kei1309

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#5
By the way, it is the sharpness that is much more important than the "aperture".. And that is the reason why more people choose fixed lenses.. just like what "KEI" meaned
the glass used in the lens determines the sharpness. but the width of the aperture (i.e. aperture value) plays a part too. Aperture is not just about DOF.

and a thicker DOF doesn't equate to exposure. a thicker DOF means more can be in the focus area i.e. more things can be in focus.

you need to read up more on the trinity of exposure too, 5D MkII user or not.
 

bonrya

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Dec 16, 2010
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#6
i understand that lens with f2.8 are the better and more expensive 1.. for example 2470. 70200. f2.8
i know the wide aperture will be very useful for night shooting and with it.. enable us to use a faster shutter speed.

However..im confused.. after i read the photography books.. in daylight..nobody shoots at f2.8 even they uses those lens.. they probably shoot at 5.6 or higher n up to 22 for landscapes. Err.. so what happen if i shoot at f2.8 in daylight? n why people generally dont use it.
(isit because during the day.. its too bright.. to use wide aperture? even if im on aperture priority mode it will turn overexposed?)
isit something to do with "sweet spot" i read about?
you can shoot at f2.8 for landscapes, no problem, but why would you do that? maybe you like your shutter speed to be very fast, or you put a nd110 filter in front? :dunno: bu ming bai...

what is aperture? i think i have to read up again...
 

kei1309

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Apr 12, 2010
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#7
you can shoot at f2.8 for landscapes, no problem, but why would you do that? maybe you like your shutter speed to be very fast, or you put a nd110 filter in front? :dunno: bu ming bai...

what is aperture? i think i have to read up again...
you can use f2.8 for landscapes, but at shorter focal lengths. but f2.8's more suited for night, and you can focus to infinity for that.

focal length also affects DOF.

don't mind me if my sentences aren't coherent. flu bug's going around :bsmilie:
 

bonrya

Senior Member
Dec 16, 2010
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#8
During the day, it would be too bright when you shoot at f/2.8 ==> this is right

And actually, it is because of the purpose of the cameraman, guess they would want a thicker DOF...or else they don't want the "model" shot overexposured :)

By the way, it is the sharpness that is much more important than the "aperture".. And that is the reason why more people choose fixed lenses.. just like what "KEI" meaned
i actually shoot alot of f2.8 during the day.. most come out ok leh... :dunno:

don't think people choose their lens based on sharpness of aperture... :sweat: :sweat: you might need to check that again...
 

fmeeran

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Nov 5, 2010
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#9
i actually shoot alot of f2.8 during the day.. most come out ok leh... :dunno:

don't think people choose their lens based on sharpness of aperture... :sweat: :sweat: you might need to check that again...
Have a friend who uses his 50mm at f/1.8 most of the time including the day. Works perfectly well.
Aperture is just to change DOF. If you like having a razor thin DOF, you can use larger apertures even during day time. As long as you go down to ISO 100 and fast shutter speeds, there shouldn't be any problem of overexposure.
 

Cowseye

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Mar 7, 2010
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#10
Now TS is confused. Kei says aperture is not just abt DOF while fmeeran says aperture is just to change DOF. While both bros are right but I feel we should explain this.

Aperture changes DOF, yes. But as you change it, it affects the amt of light entering and hitting ur sensor. Hence you will need to change shutter speed to compensate the loss of light or else your picture will be under exposed.

Large aperture also have another advantage. If u do notice, you aperture always opens to the widest when you look thr ur viewfinder (unless you are using some old lenses or press down the DOF preview button). This means more light will be able to enter thr the lens to assist in auto focus due to the large aperture. The brighter the place, the easier to AF (unless it's too bright till u see only 1 colour with no contrast at all). Hope this helps.
 

edutilos-

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Dec 28, 2010
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#11
i understand that lens with f2.8 are the better and more expensive 1.. for example 2470. 70200. f2.8
i know the wide aperture will be very useful for night shooting and with it.. enable us to use a faster shutter speed.

However..im confused.. after i read the photography books.. in daylight..nobody shoots at f2.8 even they uses those lens.. they probably shoot at 5.6 or higher n up to 22 for landscapes. Err.. so what happen if i shoot at f2.8 in daylight? n why people generally dont use it.
(isit because during the day.. its too bright.. to use wide aperture? even if im on aperture priority mode it will turn overexposed?)
isit something to do with "sweet spot" i read about?
Yes, wide apertures allow you to use a faster shutter speed. Do read up on the relation between ISO/aperture/shutter speed and how you should adjust them accordingly to obtain optimal exposure.

Why people use a smaller aperture for landscapes:
1) Greater DOF (which aperture also affects)
2) As you point out, it may have something to do with the sweet spot, or the point of optimal sharpness. Most lenses (Majority, in fact) are soft wide open and require at least 2 stops down to hit the sweet spot. Do note that as you stop down more, you will eventually experience diffraction (pls google). Technical explanations aside (which you don't really need to understand, frankly), it just means that when you use smaller apertures there is a tendency of softening. For most people, F/8-F/11 will give you good sharpness while avoiding diffraction. Best not to go beyond F/16 unless you have no choice.
 

fmeeran

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Nov 5, 2010
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#12
Now TS is confused. Kei says aperture is not just abt DOF while fmeeran says aperture is just to change DOF. While both bros are right but I feel we should explain this.

Aperture changes DOF, yes. But as you change it, it affects the amt of light entering and hitting ur sensor. Hence you will need to change shutter speed to compensate the loss of light or else your picture will be under exposed.

Large aperture also have another advantage. If u do notice, you aperture always opens to the widest when you look thr ur viewfinder (unless you are using some old lenses or press down the DOF preview button). This means more light will be able to enter thr the lens to assist in auto focus due to the large aperture. The brighter the place, the easier to AF (unless it's too bright till u see only 1 colour with no contrast at all). Hope this helps.
Oops. Yes, aperture not just about DOF. :D
 

edutilos-

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#13
you can use f2.8 for landscapes, but at shorter focal lengths. but f2.8's more suited for night, and you can focus to infinity for that.

focal length also affects DOF.

don't mind me if my sentences aren't coherent. flu bug's going around :bsmilie:
You should not, because most of the time, you would want reasonable sharpness for landscapes.

You can, of course. People sometimes do F/2.8 landscapes when they want to shoot stars, but without the star trails. Or the Milky Way.
 

kei1309

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Apr 12, 2010
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#14
You should not, because most of the time, you would want reasonable sharpness for landscapes.

You can, of course. People sometimes do F/2.8 landscapes when they want to shoot stars, but without the star trails. Or the Milky Way.
yup. that's my thought. also for those who head out at night without their tripods, want to stick to a lower ISO yet be able to use a reasonably fast shutter speed to capture landscapes.

of course bro, you're the master of landscapes here :D

thanks for the advice.
 

TWmilkteaTW

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May 30, 2011
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#15
oh ok..thanks for the replies..
was confused because i always hear about bokeh and DOF..the bigger your aperture the more thinner n shallow the DOF. Then most people uses f2.8 lens but dont shoot at f2.8..unless at night..so im confused.. (yea i know u no need f2.8 to have bokeh effect but since they want the bokeh..shouldnt they shoot at the lowest f/stop available? kinda contradicting to me. well... own preferences huh..
 

#16
Its all a matter of how you want to use your lens. and how picky you are about image quality. I usually prefer more DOF in wide angle shots so even though my 17-35 goes to 2.8, i usually shoot at 5.6 (also cos iq isnt as good wide open). But i frequently shoot my 50 1.2 wide open even in the day. it might not be 'tack sharp', but i don't want it to be. also be aware of what output yr lens gives at different apertures. my 5.8cm 1.4 is a lil smudgy and 'old school' at 1.4, less so at 2. but once f4 and over it starts to look like any other lens and looses its charm so i shoot it st 1.4 or 2 most of the time.

In short, know what yr lens is capable of doing, and then work with that to get what you want.
OR, know what you want, and go with the lens that will help you get what you want.
 

edutilos-

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Dec 28, 2010
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#17
oh ok..thanks for the replies..
was confused because i always hear about bokeh and DOF..the bigger your aperture the more thinner n shallow the DOF. Then most people uses f2.8 lens but dont shoot at f2.8..unless at night..so im confused.. (yea i know u no need f2.8 to have bokeh effect but since they want the bokeh..shouldnt they shoot at the lowest f/stop available? kinda contradicting to me. well... own preferences huh..
If you are say, shooting a friend at night and you don't want to use flash, that's when the fast lens comes into play, DOF aside.
 

TWmilkteaTW

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May 30, 2011
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#18
If you are say, shooting a friend at night and you don't want to use flash, that's when the fast lens comes into play, DOF aside.
yea im aware about this.. they are excellent n most useful at night compare to those f3.5-5.6 etc lens.
but just curious why pple dont use f2.8 in the day when they uses those lens. Thanks for reply.
 

TWmilkteaTW

Senior Member
May 30, 2011
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#19
Its all a matter of how you want to use your lens. and how picky you are about image quality. I usually prefer more DOF in wide angle shots so even though my 17-35 goes to 2.8, i usually shoot at 5.6 (also cos iq isnt as good wide open). But i frequently shoot my 50 1.2 wide open even in the day. it might not be 'tack sharp', but i don't want it to be. also be aware of what output yr lens gives at different apertures. my 5.8cm 1.4 is a lil smudgy and 'old school' at 1.4, less so at 2. but once f4 and over it starts to look like any other lens and looses its charm so i shoot it st 1.4 or 2 most of the time.

In short, know what yr lens is capable of doing, and then work with that to get what you want.
OR, know what you want, and go with the lens that will help you get what you want.
alright.. Thanks. Helps alot. Peace.
 

kei1309

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Apr 12, 2010
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#20
yea im aware about this.. they are excellent n most useful at night compare to those f3.5-5.6 etc lens.
but just curious why pple dont use f2.8 in the day when they uses those lens. Thanks for reply.
they do.

just that they control their parameters well. don't make sweeping statements just because you've only come across people who don't.

people still do use f2.8 in the day. just that they change their shutter speeds, use ND filters etc etc.

like i said, go read up on Aperture and Shutter Speed. there're many stickies in the newbies section that'll help you
 

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