Why use all other aperture sizes other then f2.8?


SpyGlass

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Jan 21, 2008
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#1
Just a noob question.

Money, IQ and zoom length aside, why do people prefer to use lens with aperture of f3.5, f4, f4.5, f5.6?

For me, i find that the f2.8 on the Tamron 17-50mm is perfect for every occasion, esp when it becomes dimly lit. I can get a sharper picture obviously when i stop down to f4.

Since money aside, wouldn't everyone prefer a F2.8 lens ? its fast enough and can stop down as well?

Hypothetically speaking, people prefer lens such as 18-200mm f3.5-5.6 for the ability to stop down?

In that case, if there is a 18-200mm F2.8 manufactured, would be optimum?

Just a curious thought, hope the seniors can enlighten.
 

sinned79

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Jun 18, 2009
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#2
if u are doing landscape (when u need more details), u will definitely need f8. f2.8 is too shallow to do any landscape (mountain scapes for example)

Below is a photo I took at Beijing (Great Wall of China) at f8.



Can you imagine how the shot will turn out at f2.8?
 

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huatman

Senior Member
Nov 27, 2010
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#3
If there is a 18-200mm F2.8 .. think it will be super huge, n too heavy to bring ard.
Beside more light to go in, larger aperture (smaller aperture value, eg f2.8) give shallow depth of field (other factor including distance of subject and focal length etc), so if u need more area to be in focus, normally u will use aperture (eg for landscape photo).
The nos only indicate the larger aperture, think most lens can have smallest aperture of f22.
(small aperture value = large aperture opening)
 

SpyGlass

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Jan 21, 2008
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#4
erm..help me understand.

the Tamron 17-50mm f2.8 is throughout f2.8

but i can still stop down to f8.

Are you saying that its different with a f2.8 lens when stopped down to f8 as compared to a normal zoom lens stopped down to f8?
 

Irvine

Senior Member
Jan 1, 2010
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#5
Just a noob question.

Money, IQ and zoom length aside, why do people prefer to use lens with aperture of f3.5, f4, f4.5, f5.6?

For me, i find that the f2.8 on the Tamron 17-50mm is perfect for every occasion, esp when it becomes dimly lit. I can get a sharper picture obviously when i stop down to f4.

Since money aside, wouldn't everyone prefer a F2.8 lens ? its fast enough and can stop down as well?

Hypothetically speaking, people prefer lens such as 18-200mm f3.5-5.6 for the ability to stop down?

In that case, if there is a 18-200mm F2.8 manufactured, would be optimum?

Just a curious thought, hope the seniors can enlighten.
18-200 f/3.5-5.6 is there for people who r looking for an all-in-one package. it's more for convenience, where ppl do not wish to change lenses on the go while traveling and also wish to travel light with juz 1 lens to do everything. the overall weight u will be holding with a camera body + 18-200 lens is lighter compared to when u carry a camera body + 18-55 kit lens + 55-200 kit lens. wouldnt it be worse if u bring only f/2.8 zooms when u go overseas? imagine a camera body + tamron 17-50 f/2.8 + sigma 50-150 f/2.8 or tamron/sigma 70-200 f/2.8? the amount of space these equipment take up in the bag matters also. camera + 18-200 attached takes up the least amount of space among all the other setups. for low light work? grab a flash to go along with ur setup n u r fine.

f/2.8 is definitely great, but haf u thought of the weight factor, especially f/2.8 tele zooms? compare canon's 70-200 f/4L and their own 70-200 f/2.8 L USM IS. see the weight and size difference. if not, u can use nikon's own 70-300 f/3.5-5.6 and compare with 70-200 f/2.8 vr II. these smaller aperture tele zooms r also lighter than tamron's and sigma's own 70-200 f/2.8. look at ultra wide f/2.8 zooms as well, they r also heavier than the smaller aperture ultra wide zooms. compare 17-40 f/4L and 16-35 f/2.8 L II, and also nikon's own 16-35 f/4 and 14-24 f/2.8.
 

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sinned79

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Jun 18, 2009
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#6
Hypothetically speaking, people prefer lens such as 18-200mm f3.5-5.6 for the ability to stop down?

there is a 70-200 f2.8

like huatman mention, if they built a 18-200 f2.8, it will be damn too heavy and expensive. Do you know how much a 70-200mm f2.8 cost? and a 14mm f2.8 cost? I guess if they really come out with a 18-200 f2.8, it will cost you at least $5000!
 

NoS77

Senior Member
May 19, 2008
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#7
erm..help me understand.

the Tamron 17-50mm f2.8 is throughout f2.8

but i can still stop down to f8.

Are you saying that its different with a f2.8 lens when stopped down to f8 as compared to a normal zoom lens stopped down to f8?
Technically, there is no difference if you stop down your tamron to f8, compared to a kit lens stopped down to f8 (other than IQ, but that depends on lens design, glass used etc). However, if money is not an issue, f2.8 wouldn't be enough. I would go for primes that can give me f1.2, f0.95 etc. They can also be stopped down as well when required. Zooms offering big apertures would also be heavier and bigger than their equivalent variable aperture counterparts. (Kit lens vs 17-50mm f2.8, 70-200 f4 vs 70-200 f2.8, possibly a poor example)

In conclusion, money IS an issue, that's why people still go for lens with variable and smaller apertures. It also depends on your wants and/or needs, eg, a landscape hobbyist (small aperture, UWA, WA usually) requires vastly different lens from a night event professional photographer (big aperture, good IQ).

Just my 2 humble cents.
 

Diavonex

Senior Member
Sep 23, 2008
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#8
Look at these two pictures and you'll know why we want to use other aperture at times.

First picture is taken with F2.8 and second picture taken with F22.





First picture taken with F2.8 and second picture taken with F16



 

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daredevil123

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Oct 25, 2005
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#9
If I buy a 2.8 lens but only shoot F16-F22 with it all the time, why not buy the alternative non-2.8 lens which is cheaper and lighter and less bulky?
 

catchlights

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Sep 27, 2004
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#10
Just a noob question.

Money, IQ and zoom length aside, why do people prefer to use lens with aperture of f3.5, f4, f4.5, f5.6?

For me, i find that the f2.8 on the Tamron 17-50mm is perfect for every occasion, esp when it becomes dimly lit. I can get a sharper picture obviously when i stop down to f4.

Since money aside, wouldn't everyone prefer a F2.8 lens ? its fast enough and can stop down as well?

Hypothetically speaking, people prefer lens such as 18-200mm f3.5-5.6 for the ability to stop down?

In that case, if there is a 18-200mm F2.8 manufactured, would be optimum?

Just a curious thought, hope the seniors can enlighten.
the bigger the aperture setting, the shallower the depth of field, not everything can shoot at wide open aperture, for examples, if you shoot f2.8 with landscape, only part of the scene is in focus, and if you shoot a group photo of people, only some of the people stand at the center of front row is sharp, these are not desired, not the right moment to use f2.8.

the bigger the aperture lens have, the larger the front element needed, the larger lens element needed, the higher quality of the glasses also needed, all these glass element need a larger housing, so eventually the weight of the lens also increase. All these translate into the cost of designing, materials used, and producing such lenses.

anyway, a optimized zoom lens usually only 3x or less, higher than these will have too much compromise on the quality. eg the pro quality zoom lens like 14-24, 17-35, 24-70, 70-200 are only 2x to 3x.
so designing a super zoom lens of 18-200mm f2.8 is impractical, not just only about the cost, size and weight.
 

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Clarenze

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Jan 27, 2008
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#11
In that case, if there is a 18-200mm F2.8 manufactured, would be optimum?
If there was a 18-200mm F2.8, all these lens manufacturer will be losing money .
Why don't Steve Jobs from Apple make a iPad which can be converted into a MacBook? Why don't Sony Ericsson make a 20 megapixel camera phone equipped with state-of-the-art audio, coupled with HD resolution screen and ultra slim feature?

Every lens are made for different scenarios and genre of photography. Firstly, it is extremely big and heavy to have a 18-200mm with constant aperture. Secondly, if you were Nikon or Canon, would you sell 100 different kind of lens or just 1 "ultimate all-in-one" lens?
 

wdEvA

Senior Member
Sep 1, 2006
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#12
f2.8 vs non f2.8 zoom lens of similar range,
people choose the latter cause they do not need the fstop at 2.8, they want a lighter lens, they have a tighter budget
you won't want to know how heavy and costly an 18-200mm f/2.8 will be, also having good performance throughout the whole focal length would be another problem
 

madmartian

Senior Member
May 2, 2009
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#13
erm..help me understand.

the Tamron 17-50mm f2.8 is throughout f2.8

but i can still stop down to f8.

Are you saying that its different with a f2.8 lens when stopped down to f8 as compared to a normal zoom lens stopped down to f8?
Putting aside the brand, glass quality & built quality & price, zoom or fixed lens, stopping down to f8 is f8 across the playing field.
To answer your question, is that with a fixed aperture, be it f2.0, f2.8 or f4.0 for example, in a short or long zoom lens, when zoomed out to the maximum range, you are still able to shoot at the largest aperture.
For lenses that are f3.5-5.6, for example, when you shoot @minimum zoom you get f3.5 but once you pass a certain zoom range of that lens it becomes f5.6.
In other words, a fixed f2.8 lens allows you to shoot at maximum aperture regardless of your zoom range.
HTH :)
 

Sep 19, 2006
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#14
I hope the few replies have helped you understand the correlation between aperture opening and the depth of field. In sum, the smaller the opening (f/xx with the biggest number), the greater the depth of field. That is, the overall picture appears sharp. The bigger the aperture opening (f/xx with the smallest number), the shallower the depth of field. That is, only the subject (or focussed portion) is in focus while the rest is not.

To your question " . . .why do people prefer to use lens with aperture of f3.5, f4, f4.5, f5.6?", it would have to do with what is the best "fit for the purpose" lens in terms of cost, weight and size. I wouldn't say there is a preference for a slower lens and most if not all would go for a faster lens if the conditions are right.

"For me, i find that the f2.8 on the Tamron 17-50mm is perfect for every occasion . . .", you are absolute right to say this as you would have already shot with different aperture settings for different sceneries. The f/2.8 comes in handy in low light scene.
 

sumsum80

Deregistered
Apr 29, 2011
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#15
I am also using 17-50 Tammy lens. Just wonder if anyone use 2.8 to shoot low light portrait w scenary background.
 

May 20, 2009
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#16
Yes you can, but of course the background scenery would be rendered as blur or bokeh.
 

snowc

New Member
Jan 8, 2006
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#17
I am also using 17-50 Tammy lens. Just wonder if anyone use 2.8 to shoot low light portrait w scenary background.
Its not advisable to shoot at the maximum or minimum aperture of a lens if possible. This is because lenses are not at its sharpest at either end of their aperture range. If you shoot wide open, less details are resolved. If you shoot at the minimum aperture, you find that diffraction will affect the IQ badly.
 

Diavonex

Senior Member
Sep 23, 2008
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#18
Large aperture opening like F2.8 can be used to effectively isolate subject from distractive background.

 

huatman

Senior Member
Nov 27, 2010
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#19
F/2.8 = focal length(mm)/2.8 = opening of lens (mm)
This what I understand after reading online etc..
 

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giantcanopy

Senior Member
Feb 11, 2007
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#20
As you might have already noted, aperture also will affect the degree of depth of field of the photos.
Having a lens capable of having a larger aperture gives you more leeway in creativity with dof and also a little more space in shooting under dimmer lights.

Ryan
 

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