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Optical zoom questions

Discussion in 'General Technical Discussion' started by DFRI, Jul 29, 2007.

  1. DFRI


    Jul 21, 2007
    Rhode Island
    Sorry for such a novice question. How would I figure out what the optical zoom is for a lens? I am very new to cameras in general, and looking to get my first SLR.
    Currently I have a Canon A70 with 3X optical zoom. Then I bought a tele-converter lens for it (TC-DC52) 2.4x. What does that lens change the zoom to?? 7.2????

    I am most likely going to buy a D50 body only and a seperate lens, but how does one figure out what the zoom is on a lens?

    Thanks, and sorry for the novice questions to you people who know so much. Trying to learn.
  2. Baywing


    Feb 22, 2005
    CT USA
    Zoom ratios are usually not used when referring to SLRs and DSLRs. In this area, only the focal lengths are used as they are a much more accurate way of communicating the properties of a lens. A 3x zoom only tells us that the long focal length is 3 times the short focal length, but doesn't tell us what those are. The consumer digicams (and camcorders) seem to like to tell us how much zoom range they have, versus what actual focal lengths they have.
    As an example, a Nikon 75-300 AF zoom would be a 4x zoom (75mm x 4= 300mm), a 70-210 would be a 3x. But! A 35-105 is also a 3x, so to say a zoom is 3x could apply equally correctly to the 70-210 or the 35-105. This is why DSLR lenses are referred to by their focal length, that way we know exactly what we are talking about.
    As for your question about your camera, no, adding a TC doesn't change the zoom ratio (3x), it just changes the focal lengths by the amount of the TC. If your camera's lens is 12mm-36mm, then using the 2.4x TC will give you effectively a lens of 28.8mm-86.4mm, still a 3x lens.
  3. According to the review at DPR, the A70 has 3X zoom of 35-105 in 7 steps.

    Were you to buy a used Nikon 28-105, you would have more than 7 steps (the zoom on a DSLR does not have preset stops for zooming, it is much more flexible).

    So to help you choose a lens, I would suggest that:

    1. Do not go anywhere near the lens lust forum.
    2. Stay away from the lens lust forum.
    3. Ignore any advice you receive in the lens lust forum.

    Think about what most of the photographs you take are about, and look at the EXIF on your A70 to see where most of your shots were actually taken. That can help you with your first lens choice. From there, you can

    1. Avoid the lens lust forum.
    2. Stay away from the lens lust forum.

    Not knowing your photography style, you might consider something in the same range as your A70, for example the 18-200.

    Hope this helps. Stay away from the lens lust forum. You have been warned.
  4. Mark forgot to mention:
    Stay the heck away from the lens lust forum!

    Don't got there, not now, not never.
  5. DFRI


    Jul 21, 2007
    Rhode Island
    Thank you for the explanations. I will look at the EXIF on the camera tomorrow. And it's too late, :wink:, I have already been to the lens lust forum. And reading about them at slrgear.com

    The 18-200 VR is the one I have been thinking about.

    Thanks for the help.
  6. Help is still possible. Surrender your credit card.

    Kidding aside, for all I have read and heard, the 18-200 is an excellent lens. There are lotsa folks here with some excellent advice on how to get the best out of it.

    However it does leave you lusting for more.

    Looking forward to seeing some posts.
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