which lens?

Discussion in 'Photography Beginners' Forum' started by AndrewW, Apr 22, 2007.

  1. AndrewW

    AndrewW TPF Noob!

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    I have done a basic search but am did not find the answer to this question which I am sure has been answered before.

    Just purchased a Canon EOS350D with the 18-55mm lens. The pictures are produced are absolutely studding. However, I don’t seem to have much zoom.

    What can I expect from the 18-55mm lens?
    What sort of lens do I need for better zoom?
    Are there any standard Lens sizes which I should own ?

    How do I calculate zoom multiples?
    Is there an all in one lens; if so is it any good?



    Thanks
    Andrew
     
  2. Alex_B

    Alex_B No longer a newbie, moving up!

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    not sure what you mean by "not much zoom" .. do you mean the magnification from 18mm to 55mm? As a rule of thumb, the greater the difference, the more compromise in optical quality (sharpness, distortion, minimum aperture) ... and the more expensive!

    or do you want a lens which is more towards the telephoto lens? Then the 24-105 L might be an option, if you do not need wider lenses than 24.

    It is hard to cover all interesting focal lengths with just one lens (and that is the idea of an SLR, to swap lenses while shooting)

    There are no "standard" lenses, it all depends on what sort of photography you mostly do. The best value for money lens is the 50mm f/1.8.

    I never leave the house with one lens only.
     
  3. AndrewW

    AndrewW TPF Noob!

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    Thanks for the reply Alex, unfortunately, I don’t understand what you said.
    I have been used to camera with a fixed lins my old camera was a powers shot S70, and this gave a maximum optical zoom i.e x3.

    I am trying to understand the way an SLR works.

    When I said "not much zoom” I mean I can not zoom in a lot with the supplied lens.


    On order to be able to zoom in more, what do I need?

    Is there a beginners lens faq for SLR cameras?
     
  4. Alex_B

    Alex_B No longer a newbie, moving up!

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    ok, but when you talk about a zoom lens, then the x3 just gives you the factor by which you zoom in.

    A 18-55 lens gives you more or less a x3 zoom (55 divided by 18), but a 35-105mm lens also gives you a zoom factor of x3, the range is totally different though! Here you can see that the zoom factor alone is not sufficient to describe the zoom range and its usefulness for your kind of photography. If you do architecture, you would be happier with some room at the wide end (18mm) and when you want to photograph the occasional
    wildlife, then the 55 would be too short though and you would want something more telephoto-like.

    The powershot now has a lens which is equivalent to a 28-100mm on 35mm film, which is slightly more than 3x !

    Your dSLR with 18-55 is equivalent to 28.8-88mm on 35mm film.

    So your zoom range and also the maximum focal length equivalent is indeed longer on your powershot.
     
  5. Alex_B

    Alex_B No longer a newbie, moving up!

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    Forgot to mention something:
    I gave all focal lengths as 35mm film equivalents, since the part of the scene you will have inside your frame when pressing the shutter release depends not only on the focal length, but also on the size of your medium (35mm-film, APS-c digital sensors (which are smaller by 1.6 than the film) or the tiny sensors built into compact digital cameras).

    Since 35mm-film is larger than your APS-C sensor by a factor of 1.6, you have to multiply your actual focal length as written on the lens by 1.6 to get the 35mm-film equivalent (18x1.6=28.8 55x1.6=88, hence 28.8-88mm)

    Your Powershot has a 5.8 - 20.7mm lens, and a much smaller sensor, which translates into 28-100mm as the 35mm-film equivalent.
     
  6. EOS_JD

    EOS_JD TPF Noob!

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    The way you want to term this Andrew is that you need more range.

    I use the 24-105 f4L IS. A great lens with a nice focal range although I do sometimes miss a little at the wide end.
     
  7. RedDevilUK

    RedDevilUK TPF Noob!

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    This seems to be the biggest confusion when people move from compact point and shoot cameras to SLR/DSLR.

    basically your focal length is explained by the 2 numbers on the lens.
    18-70 for example.
    now lenses are complex and are designed to try and give the clearest sharpest image... and do this, but all lenses have a peak performance.
    as a rule... more so with the cheaper lenses, the closer the 2 numbers above are, the better image quality you will get.
    so if you want really good quality images at peak magnification/zoom.. say 300mm and you had 2 lenses
    28-300mm
    and
    100-300mm
    then the second lens 100-300mm would be better, because the first lens is trying to keep clearer images over too big of a range.
    in theory in your camera bag you would have a few lenses.
    18-55mm
    70-200mm
    200-300mm
    or something similar... 3 lenses that cover the range you want... and you will get better quality images than trying to do this with 1 lens

    i hope this makes sense
     
  8. Alex_B

    Alex_B No longer a newbie, moving up!

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    That is why I combine it with a 17-40 f/4 L :)

    for the long end I then use a 300mm prime.
     
  9. AndrewW

    AndrewW TPF Noob!

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    ReddevilUk
    Thanks for the information that really helps and makes sense. (Especially the tip about the two numbers being closer together, I’ll remember that one), except when I also read Alex_B comments about dividing the two numbers to get the factor by which your zoom in.
    i.e 55/18 = 3.05
    200/70 = 2.85
    300/200= 1.5
    This would mean that the 200:300 lens gives less range than the 18:55, and I think that is incorrect.
    I am guessing the size of the two numbers(i.e. bigger the number larger the magnification) and the f number (what ever that is? Also comes into the equation)

    Any place I can get an idiots guide to this area

    Thanks
    Andrew
     
  10. RedDevilUK

    RedDevilUK TPF Noob!

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    well yes, it still works.

    because with a 100-300mm lens, remember even at the closest range (100mm) you are technically already zoomed in, so to speak

    so swapping mid shoot from a 18-55 or a 18-70, to the 100-300 you are already going to seem closer to the target at your minumum focal length.

    the best thing to do is start with a lens you think you will use most, a 18-55 or a 18-70

    then save for your next lens while you are learning all the settings on your new camera... that probably seem difficult at the moment :)

    at the end of the day... with cameras there is always something you want, something bigger or better. well there is for me :D

    But its always handy to go out on a shoot, with as many options as possible.

    for instance if you dont like spiders... you will want a 300mm lens not a 55mm one were you have to sit next the spider :(
    (why of all the explanations for a bigger lens i thought of that i dont know :D...maybe its just me and BIG spiders LOL)
     
  11. EOS_JD

    EOS_JD TPF Noob!

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    Alex
    I do have a few other lenses but was trying to say how I felt about using just one on its own (which I never do) I have a great range of lenses

    10-22f3.5-4.5, Tamron 17-35f2.8-4, 28-75f2.8, 70-200 f2.8L IS and the 300 f4L IS as well as a few primes

    There's no "one" lens to do all.
     
  12. EOS_JD

    EOS_JD TPF Noob!

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    Focal length and zoom range are two different things.

    Focal length
    The higher the number the more magnification - The close the object will appear.

    This is what you are talking about. 17-55 is a short focal length. You want a telephoto zoom. Look at the 70-200f4L if too expensive look at the 70-300 range of lenses.
     

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