Extreme macro

Discussion in 'Beyond the Basics' started by prodigy2k7, May 3, 2008.

  1. prodigy2k7

    prodigy2k7 No longer a newbie, moving up!

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    Well I got a rebel XTi kit awhile back and I got a "wide angle" lens with it, a cheesey screw on (like filters) onto the end of a lens...

    As shown here http://www.epelmart.com/images/all/1458W/1458W-unit.jpg

    The lens is actually two pieces, one screws off,.

    I took my 50mm F/1.4 and screwed on like a filter, the thin piece of the wide angle lens, screw it on like a filter, and you can get extreme macro up close results.

    Note: It can ONLY be used for super up close, minimum focus length is like 1 inch, and maximum is like 2 inches haha...

    Its just something i noticed playing around, got some interesting looking shots of flowers up close...
     
  2. christopher walrath

    christopher walrath No longer a newbie, moving up!

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    I use a Macro Bellows with my Minolta sr-T101 and have made some cool shots. Big stuff, just small. the fibers on my camera bag's strap, my wedding ring (a focus thing), tip of a ball point pen (look like a floating ball bearing). Extreme macro is cool. There's another way to get it also. Here's how.

    Place a second lens, inverted, in front of the lens mounted on your camera body. This third method is the one that I will discuss in this article.
    When placing a lens in front of another and inverting it (that is to place the front elements against each other, the rear elements opposite) you effectively shorten the focal distance of your lens combination and the aperture remains the same as that of the smallest maximum aperture between the two lenses.
    To determine the focal length of the lenses together, you can use one of a few mathematical formulas. The one I used is

    F=(F1xF2)/(F1+F2)

    where F = combined effective focal length, F1 equals the focal length of one lens and F2 = the focal length of the other. Say you have a Mamiya medium format camera and two lenses, one that has a focal length of 150mm and another normal 80mm lens. By the formula above we determine the effective focal length of both lenses by dividing the product of the two focal lengths by their sum.

    F=(150x80)/(150+80)
    F=12,000/230
    F=52.2

    So, the effective focal length of the 150mm lens with the inverted 80mm lens facing it is 52mm.
    To determine exposure you can use your through-the-lens metering if your camera body comes so equipped. If not, then the exposure is rather simple to figure. I have searched exhaustively for an equation to determine this mathematically, but to no avail. But I have done some very simple tests to determine proper exposure.
    I wish to preface the next section by clarifying ahead of time a couple of terms I will use. Maximum aperture refers to the largest f-stop number on a lens. Maximum aperture diameter (which will be referred to as a lens’s MAD) refers to the actual size of that aperture in millimeters.
    We’ll say that the 150mm lens has a maximum aperture of f/3.5 and the 80mm has a maximum aperture of f/2.8. To rehash something you may know, a lens’s aperture relates to its focal length and aperture diameter.

    Av = F/d
    or
    d = F/Av

    where Av = aperture, F = focal length and d = aperture diameter.

    d = 150 / 3.5
    d = 43

    This shows that the 150mm’s MAD is 43mm.

    d = 80 / 2.8
    d = 28.5

    The 80mm’s MAD is 28.5mm.
    But here’s the twist. Even though the MAD is larger on the 150mm lens, the 80mm allows the most light to pass through it since its MAD is larger in relation to the focal length of the lens than the 150mm’s is. The 80mm’s MAD is 1/2.8 of its focal length because its maximum aperture is f/2.8. The 150mm’s MAD is 1/3.5 of its focal length because its maximum aperture is f/3.5. So we need to focus, no pun intended, on the smallest maximum aperture, f/3.5. This is on the 150mm.
    If you have a large enough viewing glass to meter through with a hand-held meter then face the camera toward a strong light near your infinity range of focus. The sun is ideal but do not stare at its image in the viewfinder as this can damage your vision. Meter the light coming through the viewfinder with the 150mm lens mounted, focused to infinity and stopped wide open (maximum aperture). Then meter it again through both lenses with the 80mm inverted in front of the 150mm and both lenses focused to infinity and opened up all the way (maximum aperture). The reading should be the same. If you meter the same light through the other lens, in this case the reading will indicate one zone higher for exposure than with both lenses. The 150mm chokes down the light coming through both lenses to the amount of light that it will allow, meaning that even though the f/2.8 aperture of the 80mm allows more light, only f/3.5 of that light will pass through that aperture on the 150mm.
    So once exposure is determined, aperture should be adjusted on the lens with the smallest maximum aperture, in this case, the 150mm lens. For this reason, it is simpler to keep that lens mounted on the camera body for adjustments in aperture, keeping the outer lens stopped wide open, both focused at infinity. If you were to adjust the aperture on the 80mm lens, it would not affect the exposure until it became smaller than that on the 150mm, in this case f/4 or smaller. Until that point, the 150mm’s aperture is the smaller of the two.
    Now, how do you go about attaching them together? All modern lenses have filter threads around the outer edge by the front glass. Most photographic equipment companies produce threaded adapters called filter coupler rings to connect the lenses in this manner. Excepting possession of a filter coupler ring, you can get creative. Zippy-ties, tape, Velcro straps, thick rubber bands, glue (if you don’t care about taking them apart again). Just make sure that the lenses are stable so as not to slip unexpectedly and ruin your focus. If one of the lenses has a lens shade, this can be very helpful in keeping the lenses aligned.
    Don’t allow finances to hedge your creativity. You need to inform yourself so that you can bring all of the tools you can to bear on your subject. Now go and make a memorable image that will impress you and your viewers for years to come.
     
  3. prodigy2k7

    prodigy2k7 No longer a newbie, moving up!

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    wow 5 minutes quick response with a lot of info
     

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