Difference between 18-55mm and 17-50mm


Dec 17, 2007
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#1
Hi all,

I'm super new to DSLR, aiming to buy Canon 550D soon. As I know Kit I is with 18-55mm lens.
But having reading some posts in the forum, I noticed there are so many other kind of lens out there with different specs like, 17-50mm, etc.

So can I say that 17-50mm is able to shoot a wider angle at 17mm compare to 18mm. But cant zoom as far as 55mm. ?

Also, 18-55mm for example, 55mm is like equilvalent to how many times zoom as in a Compact Digital Camera?.

Thanks.
Iven
 

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android17

New Member
Sep 27, 2009
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#2
Well, this is simple maths lol.

Smaller number = wider angle

Bigger number = larger magnification

For zoom, just take the biggest focal length divide by smallest, so for ur example it'll be 55 divided by 18 = 3x

However do note that dslr users don talk about focal length in zooms.
 

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kokfann

Deregistered
Aug 2, 2009
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#3
for your question "18-55mm for example, 55mm is like equilvalent to how many times zoom as in a Compact Digital Camera?", 55/18 = 3x zoom
but you got it all wrong, 55mm is only the focal length, not times of zoom.

between 17mm and 18mm, i feel that the difference is very minute. but of course the IQ is better than 18-55mm. dont forget that 550d is a cropped body with factor of 1.6x, ie 17x1.6=27.2mm and 18x1.6=28.8mm
 

gibss

New Member
Nov 17, 2009
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#4
The focal length differences are minute, but if the two lenses that you are comparing are the 18-55 f3.5-5.6 and the 17-50 f2.8, then the largest difference is the aperture at 50mm. That's f5.6 vs f2.8, a total of around 2 stops difference, thus performing far better in low-light situations.

Regards,
gibss.
 

yc2005

New Member
May 14, 2009
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#5
Hi all,

So can I say that 17-50mm is able to shoot a wider angle at 17mm compare to 18mm. But cant zoom as far as 55mm. ?

Also, 18-55mm for example, 55mm is like equilvalent to how many times zoom as in a Compact Digital Camera?.

Thanks.
Iven
To calculate zoom level, you simply divide the longer focal length by the shorter one. Thus it doesn't mean that a 18-55mm (3X) can reach further than say a 70-200mm (2.8X)

Anyways, 17-50 has constant aperture across its entire zoom range, compared to 18-55 which is variable. IQ is also much better as well.
 

madmartian

Senior Member
May 2, 2009
20,218
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Outer Space
#6
To shoot 1mm wider & 5mm longer is not much of a difference. The difference between the two lenses you mentioned is a kit lens & a third party lens.
For the kit lens, the widest aperture is f3.5 at the wide end & f5.6 at the far end if you zoom out. Whereas, the 17-50mm gives you a constant aperture of f2.8 throughout ;)
 

edlimym

New Member
Feb 24, 2010
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#8
hi all. i believe the price difference is like 'Heaven' and 'Hell' right? :)
 

johndoe161

New Member
Apr 16, 2010
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Ang Mo Kio
#9
The focal length differences are minute, but if the two lenses that you are comparing are the 18-55 f3.5-5.6 and the 17-50 f2.8, then the largest difference is the aperture at 50mm. That's f5.6 vs f2.8, a total of around 2 stops difference, thus performing far better in low-light situations.

Regards,
gibss.
:thumbsup: TS, i think gibss explanation is the best, the 17-50 has an aperture of f2.8, therefore it works well in low light (with zoom), unlike the 18-55. 'Zoom'-wise, 17 to 50mm or 18 to 55mm is actually up to your preference though. Main reason ppl get the 17-50 is because of its low light capability. Thats my 2-newbie-cents worth, cheers! :)

PS. the 17-50 is also more ex than the 18-55 ;p
 

krazyman

New Member
Apr 13, 2010
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#10
Is there a Canon 17-50mm?

I only know there are EF-S17-55mm f/2.8 IS USM and EF17-40mm f/4L USM.
 

Apr 23, 2010
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#14
Is there a large difference in image quality between the 18-55mm IS and the tamron 17-50mm non VC? Or in other words, is it better to not get the kit lens and jump straight to the tamron for better IQ? Thanks! :)
 

kokfann

Deregistered
Aug 2, 2009
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#15
Is there a large difference in image quality between the 18-55mm IS and the tamron 17-50mm non VC? Or in other words, is it better to not get the kit lens and jump straight to the tamron for better IQ? Thanks! :)
if you have the budget, then just get the tamron.
 

Octarine

Moderator
Staff member
Jan 3, 2008
12,477
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Pasir Ris
#16
Is there a large difference in image quality between the 18-55mm IS and the tamron 17-50mm non VC? Or in other words, is it better to not get the kit lens and jump straight to the tamron for better IQ? Thanks! :)
Sure, try shooting at 50mm f/4 and compare the quality .. oops.. kit lens can't do that :bsmilie:
Basically: the Tamron is sharper and is a f/2.8 lens, usable already at f/2.8 for sharp pictures. The kit lens always needs some step-down (at least 1 stop) which gives you f/8 at 50mm. Using f/8 is not really helpful for subject isolation (shallow depth of field) and it requires higher ISO or more light.
Personally, the weight of the Tamron balances the camera much better than the kit lens.
 

Apr 23, 2010
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#17
Sure, try shooting at 50mm f/4 and compare the quality .. oops.. kit lens can't do that :bsmilie:
Basically: the Tamron is sharper and is a f/2.8 lens, usable already at f/2.8 for sharp pictures. The kit lens always needs some step-down (at least 1 stop) which gives you f/8 at 50mm. Using f/8 is not really helpful for subject isolation (shallow depth of field) and it requires higher ISO or more light.
Personally, the weight of the Tamron balances the camera much better than the kit lens.
Thanks for your very comprehensive answer! :)