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  1. #1
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    General advice about SLRs and Lenses - help needed,

    Hello all,

    I've decided to buy my first DSLR, (for reasons discussed below), the Sony A350. My question concerns the use of other lenses, and which lenses I should consider buying.

    I already have 2 lenses from a Konica Minolta Dynax 7000i, which I know work with the Alpha range (I took them to Jessops yesterday to have them checked out). The lenses I currently own are

    - A standard Konica Minolta 35 - 80mm zoom lens
    - A Sigma 75 - 300mm telephoto lens

    I also own a converter (M-Afi 2x Teleplus MC7 - I'm pretty sure it will work with the Sony, but I forgot to have it checked yesterday).

    The Alpha 350 ships with an 18-70mm zoom lens.

    From my amateur viewpoint, I have a full range from 18mm to 600mm (due to the converter), which seems sufficient. However, the staff at Jessops told me something about a multiplier, or something, built into the camera that would increase the zoom by 1.5, so the Sony lens would actually be 27 - 105mm, the KM 52.5 - 120mm, and the Sigma 112.5 - 450, plus the option of multiplying all those by 2 with the converter.

    Basically, is my interpretation of this correct? That the minimum zoom I'd have would be 27mm. If so, should I also buy a very wide angle lens, considering I won't be using it for professional shots. The staff seemed to imply that the 1.5 multiplier only applies to the lenses from my 35mm SLR. Is this true?

    If I've completely missed the point, could someone explain the fundamentals to me please?

    Many thanks.

  2. #2
    Color me obvious dumpy's Avatar
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    Re: General advice about SLRs and Lenses - help needed,

    It all comes down to sensor size vs. film size. 35mm film is 1.5x the size of the sensor in that camera. Consequently, (for example) a 50mm lens when mounted on this camera looks like a 75mm lens on a 35mm camera. This is common in DSLRs, only "full frame" models (see mucho $$) offer a sensor the size of 35mm film.

    For telephoto fans, this works out well as lenses become longer. If you like wide angle, it means the lens isn't as wide as it would be on a film or full frame camera.

    I hope this makes sense.


    Should you pony up for an even wider angle lens? Only you can answer that.
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  3. #3
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    Re: General advice about SLRs and Lenses - help needed,

    Does that mean that any lens I mount on the A350 is actually 1.5x its zoom, due to it having a smaller sensor than the film? And that only full frame cameras will use the true zoom (i.e the one printed on the lens)?

  4. #4
    Senior Member Dylan8i's Avatar
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    Re: General advice about SLRs and Lenses - help needed,

    yes

    18mm becomes 27mm
    100mm becomes 150mm
    200mm becomes 300mm
    etc
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  5. #5
    project forum co-moderator Frog's Avatar
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    Re: General advice about SLRs and Lenses - help needed,

    I got along with an 18-135 for some time with a Nikon which has the same crop factor.
    This year I sprung for a Tokina 12-24 and it has been quite useful when I need a wider shot, which, for me, happens more frequently than I thought it would.
    Keep Shooting!

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  6. #6
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    Re: General advice about SLRs and Lenses - help needed,

    Although the 18 - 70 is a highly regarded "kit" lens, it is less than stellar on the 14.2 megapixel Sony A350, not poor by any means, but not to be compared to the more expensive Zeiss lens. At $699.00 USD the 16 X 80 F3.5 / 4.5 CZ lens will show remarkable improvement. This issue of poorer performance from kit lens on high megapixel cameras is not just Sony. Canon is experiencing the same thing. It seems the more capable of high resolution the camera, the more lens quality is needed. What you get though is better overall performance.

    The lens you already have will prolly render some very pleasing images. Beware though if you ever try the Zeiss line on that camera. You will be amazed.

    Having said all the above, I think the Sony 100mm macro is also stellar, as well as the 70 - 200 F/2.8 G lens. Make yourself a list of the lens you are interested in and then seek every review of each one. It will help you make a better informed decision when considering purchase.

    Personally, I have several lens purchases planned over the next couple of years for my A350. They are all Zeiss.

    For the time being, take lots of images with what you have. That will also help you know what you expect from any lens.

  7. #7
    Member gryphonslair99's Avatar
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    Re: General advice about SLRs and Lenses - help needed,

    Quote Originally Posted by Dandavies87
    Does that mean that any lens I mount on the A350 is actually 1.5x its zoom, due to it having a smaller sensor than the film? And that only full frame cameras will use the true zoom (i.e the one printed on the lens)?

    Actually, NO. You do not get a magnification or a zoom, you get a crop factor. While it sounds the same they are actually different. What you are getting on the sensor is a smaller representation of the area the lens covers. That is a crop of that representation.

    18mm is cropped to resemble 27mm
    100mm is cropped to resemble 150mm
    200mm is cropped to resemble 300mm
    etc

    Lens Focal lengths have certain characteristics. Lenses below 50mm tend to exagerate features. Focal lengths above 50mm tend to compress features. Some wide lenses, fisheye lenses, are designed to greatly exagerate features. That is why a 50mm lens is considered a Normal lens. The visual characteristics of that lens most closely resemble how the human eye sees. It is also the reason that the classic portrait lens range is from 80mm to 120/135mm.

    What crop factor does do is change working distances because of that crop factor. If you are used to shooting head and shoulder portraits with a 100mm lens at a certain distance, to get the same shot you have to move back, or just get a head shot.

    It may seem like a small thing and to a lot of photographers it is irrelevent, but if you are trying to get a certain look, it is good to know the characteristics you need in a lens to accomplish the task.

    ______

  8. #8
    Be serious Franglais's Avatar
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    Terminology

    Quote Originally Posted by Dandavies87
    Does that mean that any lens I mount on the A350 is actually 1.5x its zoom, due to it having a smaller sensor than the film? And that only full frame cameras will use the true zoom (i.e the one printed on the lens)?
    I think it would help if we used the correct terms:

    Focal length = optical characteristic of the lens which determines the view it gives, measured in millimetres. Wide-angle lenses have short focal lengths and telephoto lenses have higher numbers. A "normal" focal length giving a view approximately the same as a human has a focal length equal to the diagonal of the sensor (or film frame)

    Zoom = ability to change the focal length of a lens by mechanically shifting the elements (a "prime" lens has a fixed focal length).

    Your question should be:

    "Does that mean that any lens I mount on the A350 is actually 1.5x its focal length, due to it having a smaller sensor than the film? And that only full frame cameras will use the true focal length (i.e the one printed on the lens)?"

    Answer: No the focal length of a lens does not change by mounting it on a A350 or on your Minolta. The image produced by the lens is exactly the same. HOWEVER the sensor on the A350 is smaller than a piece of film, so the sensor is only taking the center part of the image. The view becomes more telephoto. The focal length required to give a "normal" view = the diagonal of the sensor size = 28mm in the case of the A350 and 42mm in the case of your film camera (1.5x greater).

    The 28-80 designed-for-film lens will work on the A350 - the unused image area is just lost. However the designed-for-digital 18-70 will not work on a DSLR with a film-sized "full frame" sensor. The lens is designed to supply an image that only covers the smaller sensor and if you put it on a "full-frame" DSLR you will find that the edges of the frame are dark or even black.
    Charles

    Nikon D800, D7200, Sony RX100m3
    Not buying any more gear this year. I hope

  9. #9
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    Re: General advice about SLRs and Lenses - help needed,

    Thanks for all the help, everyone. Franglais - thanks for clearing that up.

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