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dandantheadminman
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 Posted: Fri Oct 20, 2006 11:53 am Post subject: F-Stop? |
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Hi, bit of a noobish question, but o well, I'm still relativey new to photography
whats teh f-stpo thing mean? is it the rating given with teh lense? like, 50mm, f-2.6-3.6 or whatever? what does it mean? what does it do? how does it affect the pictures,etc..?
thnx
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duncan_g
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Location: Glencoe, Scotland
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| Posted: Fri Oct 20, 2006 12:56 pm Post subject: |
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The f/stop regulates how much light is allowed through the lens by varying the area of the hole the light comes through.
Good ol' google! http://www.uscoles.com/fstop.htm |
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dandantheadminman
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| Posted: Fri Oct 20, 2006 3:35 pm Post subject: |
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oo thnx, now this is dif to aperature right?
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Hamish
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| Posted: Fri Oct 20, 2006 4:41 pm Post subject: |
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No. The f-stop is a measure of the aperture. Big aperture = small f-stop = shallow DOF & vice versa. Confusing at first but you'll get used to it.
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dandantheadminman
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| Posted: Fri Oct 20, 2006 4:43 pm Post subject: |
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yeh i know all abotu aperature, and coresponding f/so and so, but what does this mean when quoted on the lense describition?
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Hamish
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| Posted: Fri Oct 20, 2006 4:50 pm Post subject: |
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?????????
It means that the maximum aperture of the lens is what is quoted.
50mm f1.8 has a maximum aperture of f1.8 and will go down to f22, as will most lenses (some go down further but you won't ever use that taking biking pics)
Where there's a range quoted, such as 18-70DX f3.5-4.5, then it means that the maximum aperture changes as the focal length increases. At 18mm you'll get f3.5 but at 70mm you'll only be able to use f4.5.
In order to buy a zoom lens with a constant maximum aperture ( e.g. 70-200 f2.8 ) then you need to spend a lot of money.
Does that help?
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dandantheadminman
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| Posted: Fri Oct 20, 2006 5:06 pm Post subject: |
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oo thnx,
yeh that cleared it up for me 
thnx buddy
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duncan_g
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| Posted: Fri Oct 20, 2006 7:44 pm Post subject: |
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| Same! I had little knowledge too |
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Roo
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Joined: 16 Aug 2006
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| Posted: Fri Oct 20, 2006 9:12 pm Post subject: |
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As one of the links says, the numbers do actually mean something, say you have a 50mm f2 lens, 50 divided by 2 = 25, so the actual size of the aperture is 25mm, not very useful but good to know. Also as you may have noticed, there is a patten in the main apertures you double the number and you get the next but one, aperture, so they go
f1.4 f2 f2.8 f4 f5.6 f8 f11 f16 f22 f32 f45 f64
if you are serious about photography you should know those off by heart as well as the shutter speeds, e.g.
4" 2" 1" 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 etc...
the gap between every one of those shutter speeds and apertures is known as a "stop" and stops work on the doubling and halving scale, so f4 is half the light of f2.8 and double the light of f5.6. ISO of course also comes into this
100, 200, 400, 800, 1600, 3200
each gap again is a stop, this may seem overly complicated but can be very useful. if you are given an exposure of 1/60 @ f5.6 @ ISO200 and for some reason you get told to use f16 but you have no exposure meter or TTL then you work out the exposure by stops, the gap between f5.6 and f16 is 3 stops, so you need to open up 3 stops on the shutter speed, so 3 stops brighter on the shutter speed from 1/60 is 1/8. Alternatively, you could leave the shutter speed at 1/60 and up the ISO by 3 stops, from 200 it is then 1600.
Oh, one last thing to confuse you in case you use a light meter f4.8 is exactly the same thing as f4 1/2 or maybe shown as f4.0 5.
As I said, if you are serious, that should all make sense.
Lesson over  |
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fozzybear
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| Posted: Fri Oct 20, 2006 11:23 pm Post subject: |
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| Hamish wrote: |
In order to buy a zoom lens with a constant maximum aperture ( e.g. 70-200 f2.8 ) then you need to spend a lot of money.
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No sheet... it does.. about £1200.. weighs a blooming tonne too (well nearly 2 kgs..)
as Hamish says you want higher F.stop lenes ideally for action photography but this comes at a cost.. that cost is price.. |
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Hamish
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| Posted: Sat Oct 21, 2006 8:03 am Post subject: |
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| Roo wrote: | Also as you may have noticed, there is a patten in the main apertures you double the number and you get the next but one, aperture, so they go
f1.4 f2 f2.8 f4 f5.6 f8 f11 f16 f22 f32 f45 f64
if you are serious about photography you should know those off by heart as well as the shutter speeds |
I've just remembered that for every 1 stop increase/decrease then you just multiply/divide the aperture by 1.4 wherease shutter speed & ISO are doubled/halved.
Does that mean that I'm serious as well? 
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dandantheadminman
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Joined: 01 Aug 2006
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| Posted: Sat Oct 21, 2006 10:48 am Post subject: |
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| Roo wrote: | As one of the links says, the numbers do actually mean something, say you have a 50mm f2 lens, 50 divided by 2 = 25, so the actual size of the aperture is 25mm, not very useful but good to know. Also as you may have noticed, there is a patten in the main apertures you double the number and you get the next but one, aperture, so they go
f1.4 f2 f2.8 f4 f5.6 f8 f11 f16 f22 f32 f45 f64
if you are serious about photography you should know those off by heart as well as the shutter speeds, e.g.
4" 2" 1" 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 etc...
the gap between every one of those shutter speeds and apertures is known as a "stop" and stops work on the doubling and halving scale, so f4 is half the light of f2.8 and double the light of f5.6. ISO of course also comes into this
100, 200, 400, 800, 1600, 3200
each gap again is a stop, this may seem overly complicated but can be very useful. if you are given an exposure of 1/60 @ f5.6 @ ISO200 and for some reason you get told to use f16 but you have no exposure meter or TTL then you work out the exposure by stops, the gap between f5.6 and f16 is 3 stops, so you need to open up 3 stops on the shutter speed, so 3 stops brighter on the shutter speed from 1/60 is 1/8. Alternatively, you could leave the shutter speed at 1/60 and up the ISO by 3 stops, from 200 it is then 1600.
Oh, one last thing to confuse you in case you use a light meter f4.8 is exactly the same thing as f4 1/2 or maybe shown as f4.0 5.
As I said, if you are serious, that should all make sense.
Lesson over |
thnx again roo, you've taught me alot there |
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sassycat11736
High User
Joined: 29 Nov 2006
Posts: 169
Location: Portsmouth
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| Posted: Fri Dec 15, 2006 8:51 pm Post subject: |
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| Roo wrote: | As one of the links says, the numbers do actually mean something, say you have a 50mm f2 lens, 50 divided by 2 = 25, so the actual size of the aperture is 25mm, not very useful but good to know. Also as you may have noticed, there is a patten in the main apertures you double the number and you get the next but one, aperture, so they go
f1.4 f2 f2.8 f4 f5.6 f8 f11 f16 f22 f32 f45 f64
if you are serious about photography you should know those off by heart as well as the shutter speeds, e.g.
4" 2" 1" 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 etc...
the gap between every one of those shutter speeds and apertures is known as a "stop" and stops work on the doubling and halving scale, so f4 is half the light of f2.8 and double the light of f5.6. ISO of course also comes into this
100, 200, 400, 800, 1600, 3200
each gap again is a stop, this may seem overly complicated but can be very useful. if you are given an exposure of 1/60 @ f5.6 @ ISO200 and for some reason you get told to use f16 but you have no exposure meter or TTL then you work out the exposure by stops, the gap between f5.6 and f16 is 3 stops, so you need to open up 3 stops on the shutter speed, so 3 stops brighter on the shutter speed from 1/60 is 1/8. Alternatively, you could leave the shutter speed at 1/60 and up the ISO by 3 stops, from 200 it is then 1600.
Oh, one last thing to confuse you in case you use a light meter f4.8 is exactly the same thing as f4 1/2 or maybe shown as f4.0 5.
As I said, if you are serious, that should all make sense.
Lesson over |
Mr teacher!
And what if you're serious AND have dyscalculia 
I try to memorise the numbers by asscociating them with images that i've taken in settings where i've used them.
Try taking a photograph of a scene using various settings and recognise how the images come out after they react to the different shutter speeds, ISO settings etc.
This is VERY helpful if you have problems with numbers guys, it might not be the most professional way to go about things but if you're retarded with figures try it- and if it helps do it. 
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dandantheadminman
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| Posted: Fri Dec 15, 2006 9:13 pm Post subject: |
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thnx for the tip nikki
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