Aperture


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desertstrike

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#1
hi guys
i am reading this: http://en.wikipedia.org/wiki/Aperture
and i have a few questions...


the article states that "The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number, which in turn corresponds to a factor of 2 change in light intensity." and states that there are got f1.4 f2 f2.8 f4 f5.6 f8...

Q1. (dslr) which means when we up 1 stop f2 becomes f2.8? correct?

Q2. (dslr) my nikkor len is f3.5 - f5.6, how come the f3.5 is not anywhere on that scale? there is only f2.8 and the next stop is f4, how does f3.5 comes in?

Q3. (pns) there are 2 f stop, one is on the len, Maximum aperture f/2.8 - f/3.5, but on my pns camera, the f appears from f3.2 - f8... how come got this difference? and which one is accurate? does that means anything from f3.5 onwards, it is non existence for that camrea?

Q4. (pns) Focal length 5.8 - 58 mm (35 mm equivalent: 38 - 380mm). So for this PnS, do i need to multiply the crop factor to get the actual mm? or 38 is already factor in the crop factor?

thanks!
 

J-Chan

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#2
1. correct, though the correct term should be stop down 1 stop..

2. the f/2,2.8,4 are full 1 stop scales, f/3.5 is 1/3 stop from f/4..

3. if your PnS has a manual mode, it should be able to open up fully, some modes don't allow it..

4. 5.8-58mm is the actual physical focal length, the 35mm eq is already calculated for you so that it as that to approximate the angle of view..
 

desertstrike

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#3
1. correct, though the correct term should be stop down 1 stop..

2. the f/2,2.8,4 are full 1 stop scales, f/3.5 is 1/3 stop from f/4..

3. if your PnS has a manual mode, it should be able to open up fully, some modes don't allow it..

4. 5.8-58mm is the actual physical focal length, the 35mm eq is already calculated for you so that it as that to approximate the angle of view..
hmm... for question 2... does the camera follows f/2, f/2.8, f/4 or should it follow the lens f/3.5? or how should it be? i am a bit confused, can't test with my dslr for now, cos in office...

for question 3, yup, only the camera, i can open up max 3.5 and min 8... but i thought the len is only from f3.5 - f5.6, so what happens outside this range? as in if the lens state f5.6... and in the camrea, i set f/8... so do i get f/5.6 or f/8?

thank you for helping out :)
 

giantcanopy

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Feb 11, 2007
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#4
hmm... for question 2... does the camera follows f/2, f/2.8, f/4 or should it follow the lens f/3.5? or how should it be? i am a bit confused, can't test with my dslr for now, cos in office...
it will follow the widest aperture setting labelled on the lens. Labelled at f3.5, you cannot make it shoot at any larger aperture e.g f2.8. ( yes the camera can bring the aperture to smaller sizes such as f4, f5.6, f8 etc .. the limit of the smallest size of the aperture is lens dependent )

for question 3, yup, only the camera, i can open up max 3.5 and min 8... but i thought the len is only from f3.5 - f5.6 , so what happens outside this range? as in if the lens state f5.6... and in the camrea, i set f/8... so do i get f/5.6 or f/8?

thank you for helping out :)
The f3.5 - f5.6 tells you what are the widest apertures available for the range of your zoom lens. For example if a zoom lens is 18-200mmf3.5-f5.6, it means widest aperture at 18mm is f3.5, and widest at 200mm is f5.6 (the rest of the focal lengths have their widest aperture sizes somewhere in between, this u need to refer to the lens manual ). But you can stop down the aperture even smaller, the limits of how small ur aperture can go for a particular lens u gotta check with the manual.
( alternatively u can try shooting and adjusting to see how small it can get )

Ryan
 

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J-Chan

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#5
just to add, the 1/3 stop scale goes something like f/2, 2.2, 2.5, 2.8, 3.2, 3.5, 4, ie finer steps
 

zcf

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Apr 10, 2005
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#6
there is an 1.4x different between each stop for f/ value. e.g.
f/1.4 (x1.4) = f/2
f/2.0 (x1.4) = f/2.8
f/2.8 (x1.4) = f/4.0
f/4.0 (x1.4) = f/5.6
f/5.6 (x1.4) = f/8.0
etc,
do for f/3.5 the one stop different is f3.5 (x1.4) = f/4.9 (or roughly around this value). 2 stops is f/7 (or roughly around this value)
 

desertstrike

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#7
it will follow the widest aperture setting labelled on the lens. Labelled at f3.5, you cannot make it shoot at any larger aperture e.g f2.8. ( yes the camera can bring the aperture to smaller sizes such as f4, f5.6, f8 etc .. the limit of the smallest size of the aperture is lens dependent )



The f3.5 - f5.6 tells you what are the widest apertures available for the range of your zoom lens. For example if a zoom lens is 18-200mmf3.5-f5.6, it means widest aperture at 18mm is f3.5, and widest at 200mm is f5.6 (the rest of the focal lengths have their widest aperture sizes somewhere in between, this u need to refer to the lens manual ). But you can stop down the aperture even smaller, the limits of how small ur aperture can go for a particular lens u gotta check with the manual.
( alternatively u can try shooting and adjusting to see how small it can get )

Ryan

okie, so i should only follow what is printed on the lens rite? no matter is smallest or largest
hmm...

i roughly remember that for PnS, my len biggest aperture is f2.8, however on camera, i can only step up to f3.2... maybe i need to double check...

on the other hand, if the len on my PnS state smallest aperture at f3.5 but i can step down to f8... so any aperture smaller than f3.5, i.e. f5.6 do i get f/5.6(camera) or f3.5(on len)?
 

desertstrike

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#8
just to add, the 1/3 stop scale goes something like f/2, 2.2, 2.5, 2.8, 3.2, 3.5, 4, ie finer steps
okie, so do all camera able to adjust to this finer steps or only certain brand can?
 

giantcanopy

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#9
on the other hand, if the len on my PnS state smallest aperture at f3.5 but i can step down to f8... so any aperture smaller than f3.5, i.e. f5.6 do i get f/5.6(camera) or f3.5(on len)?
You mean your lens aperture is largest at f3.5 not smallest.
f4 / 5.6 / 8 etc are smaller apertures.

At f3.5, you can step down to even smaller apertures to f8 for example.

The aperture is an attribute of the lens, not the camera

Ryan
 

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desertstrike

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#10
You mean your lens aperture is largest at f3.5 not smallest.
f4 / 5.6 / 8 etc are smaller apertures.

At f3.5, you can step down to even smaller apertures to f8 for example.

The aperture is an attribute of the lens, not the camera

Ryan
er.. the range is f2.8 - f3.5...

so i mean my aperture is smallest at f3.5 correct? or wrong? haha
largest is ar f2.8 rite?

so if the scale is:

f1.4 ----- f2 ----- f2.8 ----- f4 ------ f5.6 ----- f8

my aperture(len) is:

____________________2.8 - f3.5_____________________

but my camera setting can go from:

_______________________f3.2 --------------------- f8__

so which one should i follow?

sorry for the confusion...
 

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zcf

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#11
an example of the lens as Tamron AF 18-270mm f/3.5-6.3
Maximum aperture F3.5-6.3
Minimum aperture F22-40 (not stated on the lens)
so it means at the widest 18mm, the aperture is range from f/3.5-22, at most tele range 270mm, the aperture is range from f/6.3-40.

so your f/2.8 - f/3.5 mean the lens has Maximum aperture f/2.8 at it widest end and Maximum aperture f/3.5 at it most tele end, while the minimum aperture is not stated.
 

desertstrike

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#12
an example of the lens as Tamron AF 18-270mm f/3.5-6.3
Maximum aperture F3.5-6.3
Minimum aperture F22-40 (not stated on the lens)
so it means at the widest 18mm, the aperture is range from f/3.5-22, at most tele range 270mm, the aperture is range from f/6.3-40.

so your f/2.8 - f/3.5 mean the lens has Maximum aperture f/2.8 at it widest end and Maximum aperture f/3.5 at it most tele end, while the minimum aperture is not stated.
oh, i think i am enlgihtened! thank you so much zcf! :thumbsup:

so how do u find the hidden minimun aperture if it is not stated?
 

zcf

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#13
you can either try to close down the aperture on your lens when using the camera, or search through the lens manufacturer website, or on the original box/insert of the lens.
 

desertstrike

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#14

Octarine

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#15
so how do u find the hidden minimun aperture if it is not stated?
Check the technical documentation of the lens, e.g. at websites of manufacturer. In real live the smallest aperture opening is irrelevant because is hardly used. Diffraction starts much earlier and will affect the sharpness of the image. If you need a smaller aperture to reduce the light further but you want to void diffraction then it's time for ND filters.
 

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desertstrike

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#16
Check the technical documentation of the lens, e.g. at websites of manufacturer. In real live the smallest aperture opening is irrelevant because is hardly used. Diffraction starts much earlier and will affect the sharpness of the image. If you need a smaller aperture to reduce the light further but you want to void diffraction then it's time for ND filters.
oh ic, thanks Octarine, just curious how come dpreview states that max/min aperture together for the nikkor 18-105mm compared to the tamron 18-270mm
 

zcf

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#17
i found out something:

zcf, the tamron has
Maximum aperture F3.5-6.3
Minimum aperture F22-40
on http://www.dpreview.com/lensreviews/tamron_18-270_3p5-6p3_vc_n15/

i compared with nikkor 18-105mm dx vr
Max/min aperture f/3.5-5.6
on http://www.dpreview.com/news/0808/08082701nikkor_18-105lens.asp

er... so max is 3.5 and min is 5.6? 0_o
confused again...
in this case, the website state wrongly or commonly f/3.5-5.6 as the max aperture for the wide to tele range, but didn't state the minimum aperture.
 

desertstrike

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#18
in this case, the website state wrongly or commonly f/3.5-5.6 as the max aperture for the wide to tele range, but didn't state the minimum aperture.
oh i see! okie thanks zcf! :thumbsup:
 

desertstrike

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#19
i found le, the specs for 18-105mm hahaha, so both zcf and octarine are correct! thanks a lot!!! :thumbsup::D

AF-S DX NIKKOR 18-105mm f/3.5-5.6G ED VR Specifications
Focal length 18-105mm
Maximum aperture f/3.5-5.6
Minimum aperture f/22-38

Lens construction 15 elements in 11 groups (with one ED glass element and one aspherical lens element)
Picture angle 76° - 15°20’
Closest focus distance 0.45 m/1.48 ft. (throughout entire zoom range)
Maximum reproduction ratio 0.2x (1/5)
No. of diaphragm blades 7 (rounded)
Filter attachment size 67mm
Focusing Internal autofocus with built-in SWM and manual focus
Diameter x length (extension from lens mount)
Approx. 76 x 89 mm/3.0 x 3.5 in.
Weight Approx. 420 g/14.8 oz.
Supplied accessories 67mm snap-on front lens cap LC-67, Rear lens cap LF-1, Bayonet hood HB-32, Flexible lens pouch CL-1018
http://www.nikon.com/about/news/2008/0827_nikkor_02.htm
 

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desertstrike

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#20
another question ar guys, bear me me, just trying to learn :p

i always thought that the aperture is on the len?

but on 50D specification
Aperture values
• F1.0 - F91
• 0.3 or 0.5 EV increments
• Actual aperture range depends on lens used
how come 50D has it aperture specs on body?
it may sounds silly, but is aperture suppose to be on len or body?
 

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