Should 4/3 lenses be half the size of full frame lenses?

Discussion in 'Digital Cameras' started by bob, Jun 13, 2011.

  1. bob

    Guest Guest

    it exists.
    there you go again, picking only one item.
    Guest, Jun 17, 2011
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  2. bob

    tony cooper Guest

    Only if the pint glass has perpendicular sides, and I've never seen
    one like that. Beer glasses are either tapered, bowed out, or
    schooner-shaped so cutting the height in half would result in a
    container that would hold significantly less than a half-pint.
    tony cooper, Jun 17, 2011
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  3. []
    ... and the hole falls out of the argument. <G>

    David J Taylor, Jun 17, 2011
  4. bob

    Bruce Guest

    Pity the guy who got the top half ...

    .... a no-pint glass.
    Bruce, Jun 17, 2011
  5. It is indeed, and there's no need for you to try to complicate it.

    ISO simply has to do with the sensitivity of the sensor or film to light.

    That's all.

    For any given subject and light conditions, ISO defines the necessary
    exposure to get a properly exposed photo. Higher ISO = less exposure, etc.,

    The properly exposed photo may have more or less noise, depending on things
    such as sensor size, which does not change the ISO. There is no "normalize
    it for equivalency," whatever that is supposed to mean.

    ISO is ISO.

    Yes, "it's really quite simple."
    Neil Harrington, Jun 17, 2011
  6. Yes. Stop right there.
    You didn't stop where you should have stopped.
    Neil Harrington, Jun 17, 2011
  7. That depends on how you define "in half." No one said anything about
    "cutting the height in half."
    Neil Harrington, Jun 17, 2011
  8. Just so. :)
    Neil Harrington, Jun 17, 2011
  9. bob

    Guest Guest

    if you take a lens without a camera, there is no exposure. it's just a
    lens, sitting on the table.
    or more accurately, you're stopping prematurely, ignoring things that
    matter. why is that?
    Guest, Jun 17, 2011
  10. bob

    Guest Guest

    i'm not complicating it at all. for something to be equivalent, it must
    be equivalent in all aspects, not only the ones you feel like
    if a photo from one camera has more or less noise than a photo from a
    different camera, then the two cameras didn't produce equivalent
    images, did they?
    Guest, Jun 17, 2011
  11. I take your point, but in trying to make something "equivalent in all
    aspects" here, you are attempting the impossible.

    ISO is ISO. It has to do with exposure, that's all. Small sensors will have
    more noise than large sensors at the same ISO. There is no way you can make
    them "equivalent in all aspects."
    Obviously not, and the difference obviously has nothing to do with ISO.

    What you're trying to do is something like putting the same 300-hp engine in
    a small sports car and a big truck, and then saying the horsepower must be
    "normalized" (as you call it) because the two don't accelerate the same. The
    difference in performance has nothing to do with, and does not change, the
    fact that the engine is still the same 300 hp regardless of what vehicle
    it's in.

    It's the same with ISO. The fact that two different cameras produce
    different amounts of noise at the same ISO does not mean the ISO has to be
    "normalized" or otherwise tinkered with in either case.
    Neil Harrington, Jun 17, 2011
  12. Because they don't in fact matter in this connection.

    The f-number is the f-number. Period.
    Neil Harrington, Jun 17, 2011
  13. bob

    Guest Guest

    it's not impossible at all.
    yes you can, simply by raising the iso of the larger sensor which
    increases its noise to match that of the smaller and noisier sensor.
    nope. if you want to use a car analogy, put a 150hp motor in the
    smaller and lighter car and a 300hp motor in the larger and heavier
    car, and they both have the same 0-60 times.

    an engine without a car isn't particularly useful, just as a lens
    without a camera.
    it does if you want to call something equivalent.
    Guest, Jun 17, 2011
  14. bob

    Guest Guest

    only without a camera or photo.
    Guest, Jun 17, 2011
  15. Of course it does.

    Try this:
    To spread the light from a 1x1 area onto a 2x2 area quadruples
    the area lighted, quarters the light per area. Since the lens
    is unchanged (and since the transmission didn't change (much)),
    the f-stop must have doubled.

    Or, try this:
    To have the same angle of view (which you keep, after all) with a
    sensor of 2 times the linear dimension, (which the 2x teleconverter
    does) you need a lens twice the focal length. The teleconverter
    does that without changing the lens, so the aperture stays the
    same, but the effective focal length must have doubled. Since the
    f/stop is effective focal length/effective aperture diameter,
    the new f/stop value is doubled (as the focal length doubles).
    Same thing, different words. But I like the spreading and less
    light per area better.

    I must correct myself: s/80mm/70mm/
    The NASA had some built to photograph the dark side of the moon.
    Later, Kubrick used a lens for Barry Lyndon (where some scenes
    were lit only by candles).

    The 70mm was a German wartime night lens, btw., though the design
    is prewar.

    Wolfgang Weisselberg, Jun 17, 2011
  16. OK, then noone can help you :)
    OK, but then you are not looking at the photos, but at tiny details
    you need larger to properly edit them. And if it wasn't for the
    12 MPix, you'd need 141% and 283%.

    Wolfgang Weisselberg, Jun 17, 2011
  17. Changing the focal length while keeping the maximum aperture the same is
    what changes the f-number. For example, f/2.8 means the aperture is 1/2.8 of
    the focal length. If you double the focal length while keeping the same
    physical aperture, it is then f/5.6. That's what a 2x tele converter does.
    What you like better doesn't change the definition. The f-number is f (focal
    length) divided by aperture. That's the way it's written and that's what it
    means. Yes, obviously this does mean less light per unit area, just as
    anything else than increases the f-number does.
    Neil Harrington, Jun 19, 2011
  18. Fair enough. It's not, basically, a photographic problem,
    and hence outside the remit of this newsgroup.
    For both dust on the sensor, and actual image details,
    they'll be twice as big (in pixels; same size in physical
    on-sensor image dimensions) on the 6MP sensor, so I won't
    need to enlarge more to get my usual on-screen working
    David Dyer-Bennet, Jun 20, 2011
  19. bob

    Paul Furman Guest

    Yes they do give the lens a faster real f-stop.

    Equivalent DOF.
    Paul Furman, Jun 21, 2011
  20. Then "equivalent DOF" should be stated. I don't think "equivalent f/2.8"
    conveys anything about DOF to most readers.
    Neil Harrington, Jun 22, 2011
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