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  1. #51

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    Quote Originally Posted by polyglot View Post
    then you're just going to get a smear unless the shape of the subject is extremely constrained so that no two parts at different depth image onto the same part of the film?
    You're still making a 2 dimensional image of a 3D object, so as you say, no two parts of the object are exposed onto the same piece of film. If light hits a part of the object underneath another which has already been imaged, the first piece is blocking the now illuminated part (from lens viewpoint), so it is never imaged.

    There are some issues with the technique:

    Because camera, light sheet (& focus) are all set, and the image is only made at that plane as the object passes through it, magnification is constant, and therefore perspective doesn't work as it normally would. "Leading lines" no longer exist, and objects look a bit flattened.

    A sphere would lose it's expected shape, I imagine.

    To create a light sheet, often two boards in the shape of a donut are sandwiched 1 or 2mm apart from each other (we used brass spacers), then 3 lights are placed 120deg from each other around the edge, directed into the centre.
    This works well, but if the object has holes or depressions in it, they may not be illuminated as it passes through the sheet - the end result is an object with a deep shadow in the said depressions.

    But, for a sphere, this isn't an issue.

    Not sure if that makes things any clearer or worse.

  2. #52
    polyglot's Avatar
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    Yeah, that helps; thanks. As you say, there is a loss of the perspective and my concern is that the change in projection could cause overlaps. Can't as I know for sure though.

  3. #53

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    My Sinar 4x5 has 28 inches of bellows, so I'd just grab the thing and be done with it. It would faster than reading thru all the foregoing.

  4. #54

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    Quote Originally Posted by DREW WILEY View Post
    My Sinar 4x5 has 28 inches of bellows, so I'd just grab the thing and be done with it. It would faster than reading thru all the foregoing.
    Drew, there's no way that either of us, with our antiquated gear, can get the infinite depth of field at any magnification that confocal techniques do. That said, confocal techniques can't be used in the situations where I've shot at high magnification.

    Around the turn of the century, one of my collaborators who was also chairman of a college biology department, scraped up $250 k and bought a shiny new confocal microscope. He remarked to me that his professors had better get a lot of good publications with it.

  5. #55

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    What you need Dan is a scanning electron microscope - no good for color, however. I don't think a mere
    250K will buy one of those, however ... perhaps a used one.... And confocal techniques per se won't resolve critical diffraction issues. Apochromaticity at high magnifications requires a very specialized kind
    of hybrid correction, way out of my $ league. I'd be happy just to have one of those Zeiss research microscopes like I used in college, along with a sheet film holder. They're common, but still in demand
    enough to be expensive. The Polaroid holders could be adapted to standard sheet film I think. Or the
    Sinar system itself can be adapted to high magnifcation work - you just need a very stable base column
    and a lot of rail sections and bellows. I don't really understand all this fuss, however ... unless someone needs 1:1 or some other fixed scale of reproduction, the larger film at smaller aperture will
    give better results, and in something printed small like publication, it won't matter anyway. Sometimes
    it's fun to look at images on Nikons "Small World" site. Most are false color and taken with expensive
    gear from their medical imaging division.

  6. #56

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    Drew, I got into photography to take portraits of unconstrained live fish in my aquariums. I'm not aware of anything that will beat an SLR (film, digital, who cares?) with flash illumination in that application. Studio and lab photography are one thing, shooting mobile subjects is another entirely.

    I also shoot small preserved fish, with emphasis on the bones in their fins. For this transmitted light is preferable to reflected and an SEM is pretty useless. This hasn't stopped some nut cases I know who had access to an SEM from trying, though. The shots they published weren't informative.

  7. #57

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    Do it like they do butterflies - freeze the fish first! You can always eat them afterwards (just kidding). The other day I bought my wife an amphibious 35mm because she likes to snorkel. Yeah, I know I guy who does bugs with an 8x10 ... but either dead or more often stuffed into the fridge a little while first. I've done macro with 8x10, and once enlarged, have had a few precisely-focused live bugs come to view, which I wasn't aware of when the shot was made. Wish I could find an underwater housing for
    my P67, but I don't do it enough to warrant the expense, and all the gaskets for those things have to
    be replaced at this point in history - probably been three decades since Pentax stopped making them.

  8. #58

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    Coming to this thread late, but I have been working on a project where I have been doing close-up photos of tattoos, looking at the interplay between the pattern of the ink and the texture of the skin. The subject is usually curved, and the total magnification to the final print is generally on the order of 10X. I have used 35mm, 6x6, and 4x5 and have gotten decent images from all 3 formats, but depending on the particular subject sometimes one system works better than others.

    If my subject is relatively flat (for example, a tattoo on a back), then I tend to prefer the 4x5 where I can adjust the plane of focus to have more control over what I have in focus vs what is thrown out of focus. Otherwise, I have tended to like using one of the smaller formats where more of my total magnification is coming during the printing stage.

    One of the other considerations that I have is the exposure time - since my subjects are alive, and don't remain completely still, faster shutter speeds are better, and when I am using L.F., because of more magnification to the negative, I am forced to longer exposures.

  9. #59
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    Photomacrography of spherical subjects

    Quote Originally Posted by BetterSense View Post
    I've been photographing some small but round objects, and running into DOF limits.
    I'm not sure how I missed this when it was first submitted... but... there is a means whereby one can reach the objective of 1:1 (and over) magnification of half of a spherical (or non-spherical subject) and have a 'sharp' image of the whole that is observed.

    Scanning slit photomicrography where the subject passes through a narrow beam of light from (usually) at least three light sources where the beam is horizontal 'flat and narrow' (via slits between two vertical "barn doors"that control the 'height' of the light beam) and the subject is raised up through the light beam at a predetermined speed (the room 'should be 'in the dark) with the shutter open (time exposure). The results can be 'magnificent'

    There should be information on 'the net'... but I'll see if I have a copy of the paper originally published in the Journal of Biological Photography... (Or may time to visit "JStor"... again).

    Ken
    There are holes in the sky where the rain gets in,
    But they're ever so small that's why rain is thin.
    Spike Milligan.

  10. #60
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    Well, Firstly gain complete knowledge about subject. Then Carefully use of Camera and macro.

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