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

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

  1. bob

    dj_nme Guest

    I know all this, I have been participating in the discussion here.
    Perhaps my reply to "nospam" should have been worded to make it clear
    that I was after his solution (by writing "I am asking how would you
    [nospam] make..."), rather than making it so open sounding.
    I know how to get around the problem: ND filters.
    It ain't rocket surgery. :)
    It's just that nospam seems to want to turn it into an obtuse 4/3 format
    bashing exercise.
     
    dj_nme, Jun 15, 2011
    #41
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  2. bob

    Bruce Guest


    What you have missed, Rich, is that the equivalent Four Thirds lens
    would be a 150mm f/2.8. In this case "equivalent" means "same angle
    of view".

    Olympus has made some truly stunning lenses for Four Thirds including:
    150mm f/2 (300mm f/2 equivalent)
    14-35mm f/2 (28-70mm f/2 equivalent)
    35-100mm f/2 (70-200mm f/2 equivalent)
    90-250mm f/2.8 (180-500mm f/2.8 equivalent)
    300mm f/2.8 (600mm f/2.8 equivalent).

    I have used the first and third of these.

    All these Zuiko Digital lenses give superlative performance. Sadly,
    due to the failure of the E System, they are not widely used.
     
    Bruce, Jun 15, 2011
    #42
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  3. bob

    Guest Guest

    if you can't lower the iso on the 4/3rds you raise it on the full
    frame. it doesn't matter which (or even a little on both), as long as
    there's a 2 stop difference. it's really quite simple.
     
    Guest, Jun 15, 2011
    #43
  4. bob

    Guest Guest

    the ff camera has less noise than the 4/3rds camera (basic physics) so
    to match it, you raise the iso of the larger sensor. very simple.
    it's not a bashing of anything.
    except that's not what this is all about.
     
    Guest, Jun 15, 2011
    #44
  5. Sure, you're correct of course, but I'm afraid it's a waste of time with
    Nospam. As you mentioned in one post, he skips from one thing to another,
    from exposure value to noise to DOF, as if all of those could somehow be
    equivalent at the same time for different formats.

    The argument really should begin and end with: the same f-number means the
    same exposure regardless of format, all else being equal. Noise, etc., are
    separate issues and while important in themselves, should not be brought in
    to this.

    The notion that f/2.8 in full frame is "equivalent" to f/1.4 in Four Thirds
    is simply bizarre.
     
    Neil Harrington, Jun 15, 2011
    #45
  6. Well, I don't want to try to speak for "all photographers",
    because that's "always" a losing proposition. But I see
    that I'm far from the only person who has trouble
    understanding the way you explain this.

    I think I understand what you're trying to convey now, and
    it's true. But what you say above simply does not convey
    it to me.

    It may make perfect sense to people whose primary
    photographic experience is with astronomical photography; I
    don't know, since I've never done that. It's wrong,
    misleading, sends people off into crazy land, if they think
    like photographers.

    It's also just plain false if taken literally -- a high-key
    image will have more photons hitting the sensor total than
    a low-key image, but that doesn't mean high-key images
    inherently have higher image quality! But a literal
    reading of "the total photons in the image is what affects
    total image quality" says it does.

    Noise level is inversely proportional to number of photons
    hitting a pixel (sensel). All technological variables
    being equal, bigger pixels produce lower noise. The sensor
    size is irrelevant technologically; it's the pixel size
    that matters.

    As a marketing decision, most camera sensors (for sale new
    at a given point in time) have roughly the same number of
    pixels on them; when that is true, then pixel size tends to
    relate to sensor size. But that's not a technological
    rule, it's just a current marketing principle.

    So; the choice of a modest-size-sensor camera like my
    Olympus E-PL2 at 12MP is inherently accepting a higher
    noise level at any given ISO than with a larger-sensor
    camera of the same pixel count and vaguely similar
    technology like my Nikon D700 (also 12MP, full 35mm frame).
    True.

    If I'm running my Nikon D700 above base ISO, I may be able
    to match its noise level on the E-PL2 by selecting a lower
    ISO. Doing this this will necessitate either a wider
    aperture or a longer shutter speed. True. (This isn't
    very useful to me in practice, because for an awful lot of
    photos where noise matters a whole lot, I'm running the
    D700 at base ISO to begin with; the E-PL2 has the same base
    ISO, so I can't run it at a lower ISO in an attempt to
    match the noise. The rest of the time, I'm running at the
    widest aperture I have and the slowest shutter speed the
    subject motion will allow, and using whatever ISO is needed
    to make that work out; again, no room for opening up any
    apertures or reducing the ISO.)

    A 6MP E-PL2 would be a lot more valuable to me than the
    12MP one they actually make! But apparently I'm not normal
    (I've kind of gotten used to that over the years).
     
    David Dyer-Bennet, Jun 15, 2011
    #46
  7. Lucky dog :) .
    And they're all for 4/3, not Micro 4/3, right? (The adapter looks
    relatively expensive, but if I were buying those lenses, that would
    just be noise.)

    In theory, the smaller sensor would make it easier to design and build
    such lenses. 35mm vs. medium format shows that in practice, as does
    Super-8 vs. 16mm over in motion picture film (or I guess 16mm
    vs. 35mm, but I've never worked with 35mm motion picture gear). I'm
    sad only Olympus has taken much advantage of it.

    And since my E-PL2 is my "toy camera", the small one that lives in my
    shoulder bag all the time (with the Panasonic 20/1.7 pancake lens, so
    it's just about 1/8" thicker than an LX3), I'm not investing that kind
    of money in lenses for it (or carrying that kind of weight).
     
    David Dyer-Bennet, Jun 15, 2011
    #47
  8. The complete post of yours I was replying to was:
    _______________

    ... and half the length, and one eighth of the weight! Doesn't seem to be
    so in practice, though. You also use the word "equivalent". To be
    equivalent in light gathering power an f/2.8 full-frame lens would need to
    be replaced by an f/1.4 half-frame lens. Somewhat more costly to make, if
    possible at all.
    ____________________

    While you're correct WRT "light gathering power" as the term is generally
    used in astronomical telescopes, that isn't something that photographers are
    usually concerned with. You seem to be saying that f/1.4 on the smaller
    format would somehow be equivalent to f/2.8 on the larger, which is
    obviously not true.
    "Half frame" is generally taken to mean 18 x 24 mm, or one-half the area of
    "full frame" whereas Four Thirds is about one-fourth. You are not correct in
    using "half frame" and "Four Thirds" to mean the same thing, which is what
    you seem to be doing.
     
    Neil Harrington, Jun 15, 2011
    #48
  9. You cannot correct this by making the lens aperture larger, though. Your
    claim that it would take an f/1.4 lens on a Four Thirds camera to make the
    "equivalent" of an f/2.8 lens on full frame is obviously wrong: you'd get
    four times the photons (in the same time) all right, but you'd have to
    reduce exposure time proportionately in order to keep exposure correct, so
    the total number of photons would remain the same. You would gain nothing.
     
    Neil Harrington, Jun 15, 2011
    #49
  10. It wouldn't be too surprising to see some of them appear in m4/3 though. I
    just recently bought an Olympus 9-18 in m4/3 (superb lens by the way!) and
    it sure looks to me like they basically just took the original 4/3 9-18 and
    adapted it to m4/3. Better than using a separate adapter, which I understand
    has some drawbacks in AF.
     
    Neil Harrington, Jun 15, 2011
    #50
  11. []
    Except in terms of light gathering power, and possibly other aspects such
    as depth of field (but I've not done those sums).

    []
    Half of 36 x 24mm is 18 x 12mm, approximately the size of the four-thirds
    frame (in area). Approximately on quarter of the area, yes. I was not
    using "half frame" in any specialised meaning, so sorry for any confusion.

    Cheers,
    David
     
    David J Taylor, Jun 15, 2011
    #51
  12. []
    As the sensor area is one quarter on 4/3, you would get the /same/ number
    of photons - one quarter of the area with four times the photons per unit
    area.

    If you reduce the exposure on the 4/3 camera, or are forced to because the
    sensor overloads, you will reduce the signal-to-noise. If you follow the
    argument through, it seems that you may be saying that any camera with an
    f/2.8 lens is as sensitive as any other, and we know that simply isn't
    true. Smaller sensors work less well at high ISOs.

    Cheers,
    David
     
    David J Taylor, Jun 15, 2011
    #52
  13. But in one-quarter of the time, changing the exposure. Correct exposure on
    4/3 is still the same f-number and shutter speed as it is on full frame, all
    else being equal. You can't just open up to f/1.4 to get all those extra
    photons.
    ISO is ISO, just as f-number is f-number. If f/2.8 at 1/250 is correct at
    ISO 100 on a full-frame camera, f/2.8 at 1/250 will still be correct at ISO
    100 on a 4/3 camera. Again, you can't just put an f/1.4 lens on the 4/3
    camera to collect otherwise missing photons and leave everything else the
    same.
    Of course.
     
    Neil Harrington, Jun 15, 2011
    #53
  14. Not by any ordinary, usual or reasonable way of looking at it.
    I am using "half frame" in the way it has always been used in 35mm still
    photography, e.g. the various models of Olympus Pen and several other
    cameras commonly called "half-frame," which used an 18x24mm format -- half
    of the conventional 24x36mm frame.
     
    Neil Harrington, Jun 15, 2011
    #54
  15. Yes, you can use a longer exposure on the smaller sensor camera to collect
    the same total number of photons (and hence potential image quality), but
    I would not describe the picture taking as "equivalent" in that case
    (longer exposure means more movement blur, for example). It comes back to
    what I asked in the first place: for the OP, exactly what does
    "equivalent" mean. If it's purely exposure, then the same f/number will
    do. If it's other factors like image quality at a certain light level, or
    the same depth of field, then the same aperture will not produce the same
    results.

    I hope that helps, and I think enough has been said now., at least by me!

    Cheers,
    David
     
    David J Taylor, Jun 15, 2011
    #55
  16. []
    Half of 36 isn't 18? A quarter of the area.

    Perhaps you would prefer "half the frame size, i.e. one quarter of the
    area"? I was using half in its common-day usage, nothing specifically
    photographic, and have already apologies for any confusion.

    Cheers,
    David
     
    David J Taylor, Jun 15, 2011
    #56
  17. bob

    Paul Furman Guest

    In my first reply to this thread, I wrote: "the usable print size scales
    down for a given ISO rating". If you've got soft bright studio lighting
    with no dynamic range challenges and can use a low ISO, your scenario
    holds mostly true but you do see the noise and lack of detail with ever
    larger prints. If light is low, if there's important detail in the
    shadows and/or ISO needs to be raised, the difference can be dramatic.
     
    Paul Furman, Jun 15, 2011
    #57
  18. bob

    Bruce Guest


    Yes, it is certainly true that raising the ISO has a more dramatic
    effect on image quality when using the smaller sensors.
     
    Bruce, Jun 15, 2011
    #58
  19. bob

    Paul Furman Guest

    You can't just squish the photons onto the sensor without changing field
    of view. Hmm, actually you can, but it takes more glass, and shortens
    the mount distance. Theoretically you could take a 50mm f/2.8 FX lens
    and add a relay lens to squeeze it onto micro 4/3 but it would likely be
    a large awkward expensive thing which was not very sharp. I believe it
    might be possible to use a lens like this with an telescope reducer lens
    to get a fast wide m4/3 lens:
    http://www.flickr.com/photos/edgehill/5129933204/
    http://www.celestron.com/c3/product.php?ProdID=359
    If you actually did that as described above, it would be an actual
    f/1.4, or equivalent f/2.8.

    Yep, just that the smaller format makes smaller prints without extra
    enlarging, which loses quality.
     
    Paul Furman, Jun 15, 2011
    #59
  20. bob

    Paul Furman Guest

    If you squish the photons down to the 4/3 sensor and drop the ISO, you'd
    get the same image. You'd still have a dynamic range problem though.
     
    Paul Furman, Jun 15, 2011
    #60
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