Full Frame vs APS-C

Discussion in 'Digital Photography' started by measekite, Sep 18, 2008.

  1. measekite

    Guest Guest

    | Archibald wrote:
    |> On Thu, 18 Sep 2008 14:21:12 -0700 (PDT), Scott W
    |>> A larger sensor will use less expensive lenses, not more. For example
    |>> the Canon 50mm f/1.8 lens is cost around $70, to get the same field of
    |>> view on a cropped sensor camera you would need something around 28mm,
    |>> a 28mm f/1.8 costs far more then the 50mm one.
    |>> Scott
    |> That's because there isn't a 28mm f/1.8 made for the small sensor. If
    |> there was, and once it was mass-produced, it would probably be cheaper
    |> (and lighter) than the 50mm f/1.8.
    |> Archibald
    | But a 28 mm f/1.8 lens will not
    | duplicate the image of the 50 mm f/1.8 on the full frame camera.
    | To get the same image you need the same apparent entrance pupil
    | diameter, which means a 28mm f/1.2 lens.

    It's the exit pupil that matters for this. The real issue is the distance
    the lens mounts from the sensor plane. If a 28mm lens could be closer by
    a 50/28 times, compared to the 50mm lens, then it represents a true scaled
    down model. If the mirror on the APS-C is further back, then the APS-C
    lens could be made with a protuding exit and achieve this, within the limit
    of the mount diameter. The full size 28mm lens, though, has to be mounted
    at the distance for a full size camera with a full size mirror. And that
    means its _absolute_ exit pupil will be larger than it would otherwise be.
    Think of a cone emerging from a pixel on the sensor (or a grain on film)
    forward to the back of the lens. The f/NN defines the angle of this cone.
    This is one reason why there is a slight drop in effective f/NN value when
    a lens that moves all elements together, when it focuses closer. This drop
    is more significant in macro work because lenses are moving quite far away.

    The design of a 28mm full size lens has to consider its "unnatural" distance
    away from the sensor plane. It has to have a larger absolute exit pupil to
    do this, compared to a 28mm lens that gets to mount closer (trying to mount
    such a lens on a full size camera would impact the mirror).
    Guest, Sep 21, 2008
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  2. measekite

    Guest Guest

    | I understand about low light but not about lens cost. Most of the EF-S
    | series of lenses cost less then the newer IS enabled EF lenses. Plus most
    | people who have a 5D or better will usually get a L series lens and they
    | for the most part cost more.

    Lenses for a smaller image system generally are cheaper, though there is some
    cost because the mounting point is still at the same distance as a full size
    image system. The cost benefit will be mostly in cheaper zoom lenses for some
    technical reasons, but more for market reasons.
    Guest, Sep 21, 2008
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  3. measekite

    Guest Guest

    | Who cares? The real question is which is more important to *you*. If you
    | go with the bigger sensor, you will have greater wide-angle capability, more
    | low-light sensitivity, and more options for selective focus. If you pick
    | the smaller sensor, you will have greater telephoto capability, more options
    | for extended depth of field, and more money in your pocket, in exchange for
    | which you will have to sacrifice some of that wide-angle and low-light
    | capability.

    One can always crop the image from a full frame sensor to make the effect of
    a crop frame sensor. Then it's just a matter of cost (paying for full frame
    pixels you are going to throw away). OTOH, if you have other reasons to get
    a full frame (e.g. wide-angle, more light gathering), you will not be at a
    loss with the telephoto (the sensors are about the same pixel density).
    Guest, Sep 21, 2008
  4. I haven't been able to google up any other references to that
    test. Can you supply any more specific details to help me find it? I'd
    be interested to know which models were involved in the test.

    The original hoohah about Quad and Naim amplifiers happened when the
    first Naim amplifiers came out. It wasn't difficult to hear how much
    better they were at driving the Quad ELS speakers of the day than the
    Quad 33/303 of the time. After having claimed for many years that
    their 33/303 was audibly indistinguishable from a piece of straight
    wire with gain Quad then went on to produce improved amplifiers and
    Chris Malcolm, Sep 21, 2008
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