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Author Topic: Sigma 18-50mm f/2.8-4.5  (Read 880 times)


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Sigma 18-50mm f/2.8-4.5
« on: December 02, 2012, 09:34:56 AM »

Hi everybody.

I was looking forward to buy an afordable wide lenses, and I read I good review on the Sigma 18-50mm f/2.8-4.5, and want to know your opinion.

I have a Canon 50D, with the 28-135mm lens. I am looking for a wider lens now, and I find out about the Sigma 18-50mm f/2.8-4.5.

But I'm confused about the Angle of View. Se below the angle of view acording to the specifications:

Canon 28-135mm: Angle of View 76 - 18
Sigma 18-50mm: 69.3 - 27.9

Isn't the 28-135mm wider? But this angle of view, for the Canon lens, is not based on a full frame?

Here are the links for the two lenses:



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Re: Sigma 18-50mm f/2.8-4.5
« Reply #1 on: December 02, 2012, 09:53:13 AM »

  Somebody smarter than me ( and that won't take much  :)  )  will explain the math better than I can, but the confusion is the Canon is a full frame lens whereas the Sigma is a smaller, DX format lens only.    On a DX format camera a 18mm lens is still wider than any 28mm lens, regardless if that lens covers FX or DX.    So if you want the "most wide angle" lens for your camera, the choice between the two is the Sigma.

    One question to ask yourself, are you ever going to upgrade to a full frame camera some day?  If so, stick with lenses - any brand - that cover full frame only.

good luck




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Re: Sigma 18-50mm f/2.8-4.5
« Reply #2 on: December 03, 2012, 05:31:48 AM »

On your 50D...

28mm x 1.6 ("crop" factor) = 44.8mm = not very wide :( More of a "standard" really.
18 x 1.6 = 28.8mm = quite a bit wider :) you'll see the difference :)
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