Help a newbie buy a lens

Discussion in 'Digital Discussion & Q&A' started by redu, Feb 2, 2009.

  1. redu

    redu TPF Noob!

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    I am a beginner into the technical side of photography and I have been having trouble figuring out which lens to buy, so I found this forum I thought there might be someone here who can help.

    I have a Canon 400D and a Canon EF-S 18-55mm F3.5-5.6 and I am looking for a wide-angle lens with a large aperture. I need something around 20mm, but I am getting confused about the whole EF/EF-S thing.

    Is 18-55mm on the EF-S the same as on a EF lens or are the numbers adjusted to the smaller sensor, so that it appear as 18-55mm would on a EF, or is it just the mount that is the only difference between Ef and EF-S?

    So to get a circa 20mm on the 400D, what lens should I buy, considering I need an aperture of F1.4 or F1.8?

    I have been thinking about the Sigma 20mm f/1.8 EX DG Aspherical RF, but that won't be a 20mm on the smaller sensor, right?

    Thanks in advance, I really hope someone her can help!
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Welcome to the forum.

    The focal length of a lens is a constant...18mm is always 18mm, it doesn't change from one camera to another. However, the field of view changes if you go from a crop camera (like yours) to a full frame camera.

    Now, EF-S lenses have a slightly different mount and a smaller image circle than EF lenses. EF-S lenses are for crop bodies only. EF lenses can be used on either crop or full frame bodies.

    On you camera, the EF-S 18-55mm lens will give you about the same wide view as the EF 17-40mm F4 lens. The 20mm lens won't be as wide.

    If you want a wider angle of view on your camera, you need to look at something like the EF-S 10-22mm. Another option is the Sigma 10-20mm. If you really need a wide aperture, then the Tonkina 11-16mm F2.8 is an option.

    Do you really need F2.8 on such a wide lens though?
     
  3. AlexColeman

    AlexColeman TPF Noob!

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    If you are looking for something wide, you can check the Sigma 10-20.
     
  4. redu

    redu TPF Noob!

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    I dont know much, but why wouldn't I need a big aperture on a wide angle lens?

    I am leaning towards the Sigma 20mm f1.8 because it has the big aperture, and I dont really need it to me a zoom, like the 10-20mm. But is there something I dont know about wide angle and big apertures?

    Thanks
     
  5. LarryD

    LarryD TPF Noob!

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    Maybe we could help you better if you could tell us what you intend to use the lens for that you don't get with your 18-55.

    A wide angle lens has a broader field of view and therefore has more light overall entering so a larger aperture is not always needed to get a decent exposure...

    Wide angle lenses also tend to distort the image so if you want that effect, go wide.......otherwise, step back some more..
     
  6. weddingguy

    weddingguy TPF Noob!

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    Probably the most expensive part of my equipment are the lenses that I bought that ended up not doing the job for me. I shoot Canon . . bought canon's cheaper lenses . . sold them and lost $$$ . . . bought Sigma . . sold them and lost $$$ . . bought Tamron . . sold them and lost $$$. Learned my lesson the hard way and bought Canon "L" glass. No matter how many cameras Canon dangles and talks me into buying I will always have the good glass! Best investment you can make, and much cheaper than trial and error!
     

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