Sigma 10-20mm arpenture


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yuugi

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Oct 28, 2005
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#1
Hello to all bros out there

I recently bought Sigma 10-20mm lens. It was said that the aperture range from F4-5.6. However, when i try it on my d40, i could change the F stops to F 22. I test with f22 and f 5.6(as stated) to see if there is any difference, and i found out that there is a difference in the picture composition. Can anyone tell me if it is alright to go above f5.6?

Thanks!
 

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sulhan

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May 11, 2002
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#2
Hello to all bros out there

I recently bought Sigma 10-20mm lens. It was said that the aperture range from F4-5.6. However, when i try it on my d40, i could change the F stops to F 22. I test with f22 and f 5.6(as stated) to see if there is any difference, and i found out that there is a difference in the picture composition. Can anyone tell me if it is alright to go above f5.6?

Thanks!
Hi Yuugi,

The notation on lens (mormally non-constant aperture lens) liek the Sigma 10-20mm which is an f4-5.6 means that at the wide end (10mm) the aperture is f4 - at the widest aperture at this zoom position and at the zoomed in end(20mm) its aperture is equivalent to f5.6 - at the widest aperture at this zoom position.

Typically for zoom lens that physically change length when zoomed - their apertures values gets smaller.

Like the 75-300mm f4.5-5.6 - at 75mm its widest open aperture is at f4.5 & at 300mm its widest open aperture is f5.6.


As for the smallest aperture it can go, the F22 is the stopped down aperture at 10mm and at the 20mm focal length the smallest possible aperture is at f32.

Hope this helps...
 

Jul 22, 2008
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#3
hahaha f/4-5.6 means your widest aperture of your lens. which means it can be widest, f4 at 10mm, to f5.6 at 20mm. you can surely go beyond that aperture and it's nth wrong going above f5.6 where your aperture goes smaller.

i'm new too >_0.
 

darrrrrrrrrr

Senior Member
Sep 19, 2006
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#4
f/4 is the maximum aperture at 10mm zoom, while f/5.6 is the maximum aperture at the 20mm end, ie. the maximum aperture decreases by 1 stop when zooming from 10mm to 20mm.

of course you can stop down the lens at any of the zoom settings to f/6.7, f/8, f/11, f/16, f/22 for example. it will close down the aperture to a smaller hole when taking the photo compared to the max aperture of f/4 or f/5.6.

it's definitely alright to stop down your lens, you will get more depth of field (ie more objects in foreground and background will be in sharp focus), most lenses will become sharper around f/8 compared to wide open, but diffraction will set somewhere around f/16 and beyond causing softer photos.

the downside of stopping down is that shutter speed will have to be longer to get the same exposure, but i suppose if u're using yr 10-20 for landscapes on a tripod it shouldn't be an issue.
 

yuugi

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Oct 28, 2005
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#6
Thanks for the quick reply. I got the idea already! :D
 

#7
Hello to all bros out there

I recently bought Sigma 10-20mm lens. It was said that the aperture range from F4-5.6. However, when i try it on my d40, i could change the F stops to F 22. I test with f22 and f 5.6(as stated) to see if there is any difference, and i found out that there is a difference in the picture composition. Can anyone tell me if it is alright to go above f5.6?

Thanks!
Learn more here:

http://www.clubsnap.com/forums/showthread.php?t=309544
 

tjerome

New Member
May 24, 2008
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#8
hey guys i was thinking of buying a sigma 10-20mm aswell

i realised the lkens is f4-5.6 i just wanna ask if this would mean that i would have to shoot at a higher ISO/slower shutter speed as compared to a 18-55mm with f3.5-5.6. or is the small aperture size compensated by the wider angle of 10-20mm ask compared to 18-55mm, i f i;m making any sense
 

calebk

Senior Member
Jul 25, 2006
10,594
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Clementi
#9
hey guys i was thinking of buying a sigma 10-20mm aswell

i realised the lkens is f4-5.6 i just wanna ask if this would mean that i would have to shoot at a higher ISO/slower shutter speed as compared to a 18-55mm with f3.5-5.6. or is the small aperture size compensated by the wider angle of 10-20mm ask compared to 18-55mm, i f i;m making any sense
How does focal length possibly "compensate" for aperture size? Do you understand what it means when a lens is designated f/4-5.6?

It means that at its widest focal length, the largest its aperture can open to is f/4, and at its longest focal length, the largest its aperture can open up to is f/5.6.

f/4 is f/4 no matter what lens you are using.
 

#10
hey guys i was thinking of buying a sigma 10-20mm aswell

i realised the lkens is f4-5.6 i just wanna ask if this would mean that i would have to shoot at a higher ISO/slower shutter speed as compared to a 18-55mm with f3.5-5.6. or is the small aperture size compensated by the wider angle of 10-20mm ask compared to 18-55mm, i f i;m making any sense
Read this:

http://www.clubsnap.com/forums/showthread.php?t=309544
 

yuugi

New Member
Oct 28, 2005
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#12
Hey, sigma 10-20 lens is good! Feels solid and images look sharp. It has built-in motor too, so it suits my d40
 

edesign

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Mar 28, 2007
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#13
Hey, sigma 10-20 lens is good! Feels solid and images look sharp. It has built-in motor too, so it suits my d40
how i wish i have the money to get this fabulous lens.
you're a lucky person and shoot more to do justice!
 

Jul 2, 2004
489
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18
Singapore
#14
I've got the lens too. There's some barrel distortion you'll have to either accept or deal with at the widest angle, but for its low asking price it's hard to complain. I'm personally very happy with it.

Then again, if you're a Ken Rockwell follower, he'll tell you not to buy this lens and to go for the alternative UWA lenses.:)
 

calebk

Senior Member
Jul 25, 2006
10,594
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Clementi
#15
I've got the lens too. There's some barrel distortion you'll have to either accept or deal with at the widest angle, but for its low asking price it's hard to complain. I'm personally very happy with it.

Then again, if you're a Ken Rockwell follower, he'll tell you not to buy this lens and to go for the alternative UWA lenses.:)
IMHO this lens has very LOW simple barrel distortions, but it has distinct complex barrel distortions that only show up towards the edge of the frame at 10mm. Essentially you will see straight horizontals for most of the image, but they will curve near the edges.

In real life usage though, it is hardly noticeable.




I think the distortion to watch out for more is perspective distortion; it does tend to be unflattering to some subjects, especially people. In the latter picture, you notice the guy's hand looks a little abnormal, because of the perspective that this lens gives.

BTW, I no longer use this lens as I'm not on a 1.6x crop body anymore.
 

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