Telephoto how much in "x"?

Discussion in 'Photography Beginners' Forum' started by pcouturier, Sep 1, 2008.

  1. pcouturier

    pcouturier TPF Noob!

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    I have just ordered a new digital camera (Canon EOS Rebel XTi), will have a telephoto 75mm-300mm with it. But how much x is that zoom? 50x, 100x???

    Please help me!
     
  2. Sandspur

    Sandspur TPF Noob!

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    4x

    It's simple ... 300 divided by 75 = 4
     
  3. Big Mike

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

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    Welcome to the forum.

    That's correct. The 'X' factor is the range of the zoom. So a 12x zoom isn't neccesarily longer than a 10X zoom...is just has more range.
    The zoom 'x' factor is commonly used in digi-cams with a built in lens...but not SLR lenses.
    For SLR lenses, they use the focal length and that should give you a pretty good idea of 'how much zoom' you will get.

    A greater zoom range is more convenient but compromises must be made. As a general rule, the greater the range, the lower the image quality. Top quality SLR lenses usually don't go over 4 or 5X.
     
  4. Battou

    Battou No longer a newbie, moving up!

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    I have had this question posed to me a time or two IRL and I found my self unable to answer for this very reason...or a variation of it atleast. Personally I wish manufacturers would stop with this 10/12 X zoom on those damn superzoom class P-Shooters and just give OLE numbers, it would eliminate a lot of this confusion.
     
  5. Big Mike

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

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    The problem is that if they list the focal length range, say 4mm to 40mm...it won't really mean anything. They could convert that to 35mm equivelent, which would mean something to us, but not to most of the people who are buying these things.
     
  6. Battou

    Battou No longer a newbie, moving up!

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    This is true, prolly unfixable now but if they had started listing the 35mm equivalent from the get go people would better understand it now. It's really not that hard for the people buying these things to get the idea that a 36-432mm 2.7/3.5 (Canon S5) is a whole hell of a lot bigger than a 37–111 mm f/2.7–4.8 (Kodak C-743). Then if they decided to move up to the SLR they actually have some semblance of what a focal length is instead of asking about focal range in X amounts. I had a guy ask me what my 400mm prime was in the X zoom factor after I told him it was a 400mm fixed focal length lens....I facepalmed.
     
    Last edited: Sep 2, 2008
  7. mrodgers

    mrodgers No longer a newbie, moving up!

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    Ok, so now that the question originally asked has been answered, and answered in a more helpful way than the 2nd post, I have a question stemming from this quoted post....

    Is SLR lenses are not described in 35mm equivalent, correct? I ask because I had a dSLR in my hands this past weekend and had a quick look at it (it was a D40x and I was amazed at how quickly it autofocused over my superzoom). It had a 200 mm lens on it, though I'm not sure exactly which lens. I noticed it was approximately the same as my superzoom which is 38-380 mm.

    So, why aren't the dSLR lenses described in 35mm equiv. numbers? You can usually find the focal lengths of the superzooms if you look on the lens or in the manual, and they are always in 35mm equiv. format.

    So, even with getting rid of the X factor of point and shoot cameras, people moving up to a dSLR would still be confused as it would be possible for someone to think I have more zoom capability with my 380 mm over say, the kit lenses of 200 mm.

    I wonder this because not even all dSLR cameras are the same. Wouldn't the 200 mm on an Olympus be different than 200 mm on a Nikon or Canon because the sensor is different? If I recall, I remember reading that Olympus is 4:3 format, but most others are something else of which I can't remember the number. Would that have anything to do with the focal length or crop factors? I do semi-understand that the 35mm equiv. and the described mm of most dSLRs have to do with the crop factor, unless I am wrong about that. I have no idea if the crop factor has anything to do with ratio format though.
     
  8. Big Mike

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

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    These lenses are described with their actual focal lengths. This makes sense, especially because many of them can be used on 35mm film SLR camera, DSLR 'Crop' cameras and 'full frame' DSLR cameras. So it's FOV would depend on what camera it's mounted on. Digicams don't have that problem because they are attached to the camera.

    Yes.
     
  9. Battou

    Battou No longer a newbie, moving up!

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    Big mike beat me to the punch so I'll just disregard that as he said the same thing, and skip on to the next part. Iron Flatline I think it was wrote some thing up on crop factors once that I think could be useful to your question....I just have to find it.

    *EDIT*

    Crap, I can't find it, it was written some time last year and it explained quite a bit, but I was not paying enough attention to it to know for sure who wrote it, I thought it was IF but I was wrong.
     
    Last edited: Sep 2, 2008

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