Someone please explain MACRO lenses to me

Discussion in 'Digital Photography' started by greg, Aug 13, 2004.

  1. greg

    greg Guest

    Hi folks, I feel a bit like an idiot because I don't know this, but it's
    never come up. I'm not sure I understand the idea of macro (close-up)
    lenses. A bit of searching on the internet always turns up the same info:

    "Continuous focusing from infinity to life-size"
    "Maximum Reproduction Ratio (Macro Setting): 1:1"
    "high resolution from infinity to close-ups down to x.x inches"

    ..but I'm honestly not sure what this means. Don't all lenses have
    "continuous focusing"?

    In other words, what's the difference in the photo? For example, they always
    seem to show a picture of a flower. What is the difference between shooting
    with, say, a 105mm macro lens and a 105mm non-macro lens? I assume you can
    get quite close to the subject to shoot with these lenses, but what's the
    benefit? Is there any reason to choose a 60mm macro lens to shoot something
    closeup, versus a 200mm non-macro lens a bit further away?

    Thanks in advance,
    G
     
    greg, Aug 13, 2004
    #1
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  2. No. For example, on the Minolta A2 there is a restricted range at which
    its macro settings work. In fact, there are two ranges, one for
    wide-angle and one for telephoto. I don't have the figures in front of
    me, but it mean that (for example) you could only take pictures from 3
    inches to 4 inches, 7 inches to 8 inches, and 15 inches or further
    (Non-macro).
    In theory, none, but the non-macro lens may not allow you to focus close
    enough (some 28 - 200mm zooms can only focus down to 2 metres), and it may
    not be as sharp. The macro lens will be designed to wrok close up, and
    may focus better over the whole subject (i.e. it has a flatter field).

    [Cross-posting trimmed]

    Cheers,
    David
     
    David J Taylor, Aug 13, 2004
    #2
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  3. Macro is one of those terms which has been misused by lens manufacturers, so
    it's not surprising you are confused. So, to clear things up, a true macro
    lens generally focuses to life size, or 1:1. That means that the object is
    reproduced actual size on the film. The image of one centimeter object in
    real life will measure one centimeter on the neg or slide.

    Not all lenses have continuous focusing, no. Some specialized lenses don't
    focus to infinity, for example, like the old Minolta macro zoom, which went
    to 3 times life size.

    Hi resolution is meaningless in differentiating a macro from anything else.
    More marketing babble. You can have a high resolution non macro lens too.

    The difference between a 100mm macro and non macro will be the minimum
    focusing distance. A non-macro may get to you within several feet. A 100mm
    macro with lifesize capability (1:1) will get you to 100mm, more or less,
    probably less due to lens oddities.

    Most lenses claiming macro anymore are consumer zooms which will focus down
    to 1/4th life size. Nice, but hardly macro.

    Mike
     
    Mike Lipphardt, Aug 13, 2004
    #3
  4. greg

    Ian Riches Guest

    greg () wrote...
    Yes, all lenses have continuous focusing, as you put it, but all
    lenses also have a minimum focus distance - that is a point where if
    you move any closer to the subject you will not be able to focus on
    it.

    Some specialist macro lenses, however, are so tuned to macro
    photography that they will not focus out to infinity (e.g. the Canon
    MP-E65mm)
    Nothing, except with a proper Macro lens you will be able to get
    closer to the flower (and thus get more of it to fill your frame)
    than with the non-macro lens.

    It gets a bit confusing because "Macro" as a term is often abused.
    My 28-70mm zoom lens has a "macro" end of the focusing scale, but is
    only capable of 0.22 x lifesize.

    Life size (or 1:1) means that the size of the subject on the film is
    the same size as in real life. So, assuming you have a 35mm film
    camera, at "life size" an object 35mm across will fill the frame.

    So my "macro" setting on my lens will mean that at the minimum
    focusing distance an object 35mm / 0.22 = 160mm wide will fill the
    frame. In other words, if I want a frame-filling photo of a bumble
    bee, this is not the lens to do it!
    The advantage of a longer focal length macro lens is that you have
    more working distance between you and the object in question. This
    can make lighting it a bit easier, as you are less likely to be
    casting your own shadow over it.

    Ian
     
    Ian Riches, Aug 13, 2004
    #4
  5. greg

    Robert Barr Guest

    No. I can recall aftermarket lenses in the late 70's / early 80's that
    required the user to move a 'shift cam' to select the macro range. Some
    of the Vivitar Series 1 were like this.
     
    Robert Barr, Aug 13, 2004
    #5
  6. A 100mm lens at 1:1 reproduction ratio will have a subject to lens
    (front nodal plane) distance of 200mm and a lens (rear nodal plane) to
    film distance of 200mm. (Bear in mind, though, that some complex designs
    will have the nodal planes outside the physical limits of the lens.)
     
    David Littlewood, Aug 13, 2004
    #6
  7. With apologies if there is some overlap with other replies.

    1 With a normal (i.e. non-macro) lens, the closest focus may get you to
    a magnification of say 0.2 - that is, a subject 1cm in length will be
    0.2cm on film or sensor (referred to hereinafter as "film"). Now you can
    make any lens give a larger magnification by moving it further from the
    film. This can be done by using extension tubes - metal tubes which fit
    between lens and camera body - or bellows. However, this is
    inconvenient, as you have to keep stopping and switching bits in and out
    for differing magnifications. One of the advantages of a true macro lens
    is that it will go to 1:1 in one continuous rotation of the focus ring
    without you having to mess about with tubes. Hence "continuous focussing
    from infinity to life-size". Yes, all (well, most) lenses have
    "continuous focussing", but not down to life size.

    2 Reproduction ratio is the size of the image of an object on film
    divided by its true size. Thus 1:1 reproduction ratio, or 1.0
    magnification, is "life size". Note that in purist terms
    photomacrography only *starts* at magnifications of 1.0, and goes up to
    about 50 or 60x or so (beyond which you really start to need a compound
    microscope, and are in the realms of photomicroscopy). Also note that
    the words macrophotography and microphotography mean something else
    entirely (very big and very small photographs - like microdots -
    respectively). Not that you used these terms, but just FYI...

    3 All lenses have to be designed to give the best balance of the various
    aberrations - image faults - for a given size, maximum aperture, price
    and application. Aberrations will vary, and require different
    corrections, at different combinations of subject distance and image
    distance. Lenses for normal use are corrected to give best performance
    at a subject distance of typically about 20x focal length. To get decent
    performance down to M = 0.2 often requires things like aspherical
    elements, floating element groups (i.e. groups which move relative to
    other groups as you focus) etc.

    4 To get down to M = 1.0 in one lens, yet still have decent performance
    with a subject at infinity, is difficult. Something has to give, and
    that is usually price and maximum aperture. That is why a true macro
    lens will typically be 1.5-2x the price of a "normal" lens of similar
    focal length, and about 1-1.5 stops slower.

    5 The other thing which matters a lot more for a macro design than for a
    normal lens is field flatness. With an ordinary lens, if you focus a
    flat subject, the image plane of best sharpness will typically be
    slightly curved. This normally does not matter, as most subjects are not
    flat planes anyway. For a macro lens this is more important, as
    photographing stamps, documents or works of art is a common application.
    Thus a good macro lens will have a flat field, which also adds another
    constraint.

    6 The advantage of a longer length lens - say a 200mm macro - is that it
    places you further away from the subject. For example, with the 200mm
    lens at M = 1.0 the subject will be about 400mm away, compared with
    100mm away with a 50mm macro. With a nervous subject, or a nervous
    photographer of say venomous snakes, this can be an advantage. However,
    there are costs: first, such lenses tend to cost 2-4 times as much,
    second they tend to be 2-4 times as heavy, and third they are 2-4 times
    as long. Incidentally, I don't think the fact that they have a longer
    focal length in itself makes them significantly harder to hand-hold -
    camera shake is mostly* a function of image magnification, not focal
    length as such, and if you are working at 1:1 the magnification is the
    same. Perspective and depth of field will be different, which may be a
    plus or a minus under different circumstances.

    *I think it's a bit more complex than that, but this is going too far
    for this reply.

    David
     
    David Littlewood, Aug 13, 2004
    #7
  8. greg

    Alan Browne Guest

    While others give you technically specific answers, it is easiset
    to stick to a very simple definition:

    --fixed focal length (often called a prime)
    --50mm to 200mm (50, 90, 100, 180 are common)
    --reprod ratio of at least 50% (1:2) but usually 1:1 for the
    better macros. This means at the 1:1 end an object that measures
    10 mm in length will take 10mm on the negative or slide.

    Good macro lenses also tend to be very sharp (hi res) and have
    great contrast. Some say they have poor bokeh (poor bokeh =
    harsh out of focus highlihghts), but this is not always the case.

    I mention this because it is often the case that a macro lens
    stands in as a portrait lens as well and many feel that they
    render the out of focus background too harshly.

    Hope that helps along with the other replies.

    Cheers,
    Alan
     
    Alan Browne, Aug 13, 2004
    #8
  9. greg

    Jeremy Guest

    That extra distance from the subject affords the opportunity to better light
    up the subject. When shooting tiny insects at very close range, as an
    example, a normal focal length macro lens must often be right up against the
    subject. A longer focal length gives a little breathing room, so light can
    better fall onto the subject, rather than it being in the lens' shadow.

    Sometimes, a normal focal length lens is just TOO close for comfort.
     
    Jeremy, Aug 13, 2004
    #9
  10. Not quite... Many 50mm macro lenses are capable of "continuous
    focusing" only from infinity to 1:2 magnification. But to get to 1:1,
    you must insert an extension tube betweeen lens and camera body which
    gives 1:2 to 1:1 range magnification.

    -Dave
     
    Dave Herzstein, Aug 13, 2004
    #10
  11. This probably doesn't apply to the OP's problem, but at least one
    macro lense didn't have continuous focus. My father bought a Leica M3
    rangefinder camera about 60 years ago that had a macro-Summicron 50 mm
    F/2.

    It focused over the normal range like any other summicron. When you
    wanted to use the macro facility you had to move past a step of some
    sort and put a lens assembly in front of the rangefinder windows. Then
    you got a new focus range, all very close to the camera.

    I don't suppose anything for an SLR would be like that. I use a
    MicroNikkor 105 mm that is continuous focus.



    Rodney Myrvaagnes NYC J36 Gjo/a


    "Wanting to meet a writer because you like his work is like wanting to meet a duck because you like pate."
    Margaret Atwood
     
    Rodney Myrvaagnes, Aug 13, 2004
    #11
  12. greg

    Ed E. Guest

    Ed E., Aug 13, 2004
    #12
  13. greg

    DSphotog Guest

    Ah, finally someone who is aware of where true macro actually begins.
     
    DSphotog, Aug 14, 2004
    #13
  14. greg

    RSD99 Guest

    You've got the right idea ... but the details you have used in your example are a little
    off. You posted

    "...
    The difference between a 100mm macro and non macro will be the minimum
    focusing distance. A non-macro may get to you within several feet. A 100mm
    macro with lifesize capability (1:1) will get you to 100mm, more or less,
    ...."

    The first part of your statement is correct, but for a "simple" macro lens, a 1:1 image
    will be achieved when the rear node of the lens is extended to **twice** it's focal length
    from the film, and the subject will be at the same distance from the front node of the
    lens.

    So ... for your example 100 mm Macro lens ... if it is a "simple" macro lens (and most are
    *not*) ... "life sized reproduction" will be when

    Lens to film distance = lens to subject distance = 200 mm


    Note:
    The term "simple macro lens" implies a multi-element lens where the element-to-element
    distance(s) are not changed during focussing. MOST modern Macro lenses (such as those
    furnished by companies such as Canon and Nikon) creatively use changing the inter-element
    spacing(s) to improve the design, or to make the lens smaller.
     
    RSD99, Aug 14, 2004
    #14
  15. And I suspect that in some cases the movement of the elements changes
    the focal length (which in effect gets you greater magnification at a
    given lens/image distance, at the expense of a shorter working distance
    (subject to lens distance).
     
    David Littlewood, Aug 14, 2004
    #15
  16. greg

    Nostrobino Guest

    That would be true if a 100mm macro lens kept its actual 100mm focal length
    throughout its extension range. Many (perhaps most) do not, and a "100mm"
    macro at full extension may have an actual f.l. of 70mm or so. Lens element
    relationships are changed during focusing to effect a magnification increase
    in the lens itself.

    This is true of some 50mm macros as well. My Sigma 50mm macro for example
    has, at 1:1, an extension of only 37 mm, suggesting that the actual f.l. has
    shortened to 43mm or so.
     
    Nostrobino, Aug 14, 2004
    #16
  17. greg

    Nostrobino Guest

    All lenses have continuous focusing within their focusing range, but some
    macro lenses only focus down to 1:2 unaided. Such macro lenses require an
    adapter of some sort (either an extension tube or supplementary lens) to
    reach 1:1 (life size on the negative).

    A 200mm non-macro lens will not give you nearly as high a magnification at
    its closest focusing distance as a macro lens will. If you need something
    approaching 1:1 or even 1:2, you need a macro lens. If you don't need
    anything nearly that close, you may not need a macro lens.
     
    Nostrobino, Aug 14, 2004
    #17
  18. greg

    Nostrobino Guest

    [ . . . ]
    Often MISTAKENLY called a prime. Too often, too often.
     
    Nostrobino, Aug 14, 2004
    #18
  19. That is iindeed the case with my 105 MicroNikkor AF. It is not 200 mm
    away at closest focus. It is still a big heavy lens. I am glad it
    isn't even bigger and heavier and still F/2.8.



    Rodney Myrvaagnes NYC J36 Gjo/a


    "Wanting to meet a writer because you like his work is like wanting to meet a duck because you like pate."
    Margaret Atwood
     
    Rodney Myrvaagnes, Aug 14, 2004
    #19
  20. greg

    Alan Browne Guest


    Often gets the goat of people who care too much what it's called
    and too little about what to use it for. I personally don't
    care, and I know what a photographer means by "prime" and I won't
    spend any effort correcting him/her.

    Cheers,
    Alan
     
    Alan Browne, Aug 14, 2004
    #20
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