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  1. #31
    markbarendt's Avatar
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    Michael,

    Depth of field and depth of focus are in practical and geometric terms, absolutely linked; if one is right, so is the other. The only difference is where you decide talk about it or do the measuring.

    Getting "perfect" lens swing and tilt simply allow you to use larger apertures, a shorter depth of field, and still get everything you want in focus.

    In the situation you describe, where you have plenty of DOF, a 1 or 2 degree swing or tilt will have little to no effect on the quality of focus on the facade. I'm not saying you should ignore it completely, just that when you are fitting a facade that is a few inches think into say a 5-foot DOF range, a little swing or tilt won't matter.

    Where a 1 degree swing or tilt will make a difference is where you have a very short DOF and a very long or tall subject. On a 10 story building, using front rise, shot from across the street, 1 degree means something, same when you lay the plane of sharp focus on the ground for a landscape that stretches miles into the distance. For a 2-story building when it's getting dark out, not so much.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  2. #32

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    Quote Originally Posted by markbarendt View Post
    On a 10 story building, using front rise, shot from across the street, 1 degree means something
    This is what I'm often dealing with. Not 10 stories, but significant front rise, from a vantage point not too far away from the subject. Parallelism definitely helps.

    Anyhow, I guess I'll have to just continue to do the best I can with the tools I have. Perhaps one day I'll be able to invest in something better, but I really wonder if I'll be happier or just slightly less disappointed albeit with a substantially lighter wallet...

  3. #33

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    Quote Originally Posted by Michael R 1974 View Post
    This is what I'm often dealing with. Not 10 stories, but significant front rise, from a vantage point not too far away from the subject. Parallelism definitely helps.

    Anyhow, I guess I'll have to just continue to do the best I can with the tools I have. Perhaps one day I'll be able to invest in something better, but I really wonder if I'll be happier or just slightly less disappointed albeit with a substantially lighter wallet...
    Unless you yourself verify that the standards are indeed parallel, you will never be happy. If you do not have the tools and the skills to do this, you're truly in a fix. If you learn to limit your concern to real problems and ignore the imagined ones, you'll be in a better place on many levels. I've been using the same 4x5 for a couple decades. I've never verified the parallelism because I've never needed to. Use your groundglass to verify things, it's what it's there for. Do you have a grid on the GG?

    I'm curious, how much do you worry about the front-end alignment of the vehicle you drive? You can have it aligned, and drive it out of the alignment shop only to hit a pothole which will destroy the alignment just done. This is a bit more significant than a camera....

  4. #34

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    The roads where I live destroy any possibility of maintaining any semblance of front end alignment. But that is hardly a relevant comparison with camera alignment in any case.

    I have a grid on the groundglass, but again, squaring the back to the subject is not the issue.

  5. #35
    markbarendt's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    This is what I'm often dealing with. Not 10 stories, but significant front rise, from a vantage point not too far away from the subject. Parallelism definitely helps.

    Anyhow, I guess I'll have to just continue to do the best I can with the tools I have. Perhaps one day I'll be able to invest in something better, but I really wonder if I'll be happier or just slightly less disappointed albeit with a substantially lighter wallet...
    I thought of a tool that might help, when I was a kid I had a drafting tool that was essentially two rulers attached with two arms that kept them parallel. Don't remember what it as actually called but it would allow you to square up real quick.

    "Better" cameras can make certain things easier (like making your wallet easier to carry) but that won't necessarily make your life easier.

    The later Sinars with the way they can measure for lens tilt can make that task considerably quicker and more accurate, that doesn't mean I'll be trading my Toyo 45A for one. My 45A with 6 holders can fit in a Domke F2 bag with my light meter a Nikon speed light and the other normal SWAG. The Sinar is tougher to lug around and takes more room. Different strokes for different folks.

    Even though the Sinar is stiffer I'd bet that my 45A, just as it opens, is within about 1 degree of parallel.

    So after thinking on this a bit I made a few educated guesses and did some math, and I gotta ask: Are you really seeing a focus problem on your negatives?

    Here's my math, maybe a 90mm lens (wide for 4x5) at F/5.6 (wide open or close to it on LF lenses), focused at about 39-40' (across a small street, 2 parking lanes and 2 travel lanes), I used the circle of confusion for 35mm to make the tolerance real tight and allow for a large print and the calculator shows that everything in the scene from about 32-53 feet out, should be in focus. That tells me that for a 40' tall facade, the plane of sharp focus could be tilted or swung up to about 25 degrees away from vertical and you could still get the whole facade nicely into focus.

    Given that calculation, I am going to hazard a scientific wild ass guess that a lens misalignment of 5 degrees, maybe more, away from parallel shouldn't give you a focus problem.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  6. #36

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    Depends on how big something needs to be printed, and how all the other variables in the system add up. You're only as good as your weakest link. I'd personally consider 5 degrees off with any lens
    to be catastrophic; but then, I often print large and expect extreme detail. Even trusting the groundglass image shouldn't be taken for granted unless you've critically tested it or measured it on
    each dimension with a depth micrometer. Then film itself does not sit dead flat in a typical holder.
    You can shrug your shoulders and ignore all this, or you can isolate each variable and see how many
    you can realistically control. I place a priority on the film plane itself, and then critically focus relative to that. Which elements in a composition to place in the most acute focus is really an esthetic decision. I don't believe in any of that normal viewing distance or circle of confusion BS
    (it might work for others, but not for me - I prioritize the elements, at least till diffraction kicks in.)

  7. #37
    markbarendt's Avatar
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    I am not suggesting ignoring issues or settling for just so so stuff, but, and its a big but, all systems have tolerances, slop. Even our highfalutin super fancy computer systems use rounding in calculations. Precision has real practical limits beyond which little is gained.

    My example above is offered to suggest that in normal use, normal camera gear can get well within workable tolerances.

    A five degree misalignment in my camera is visible to my naked eye, I can get much closer to parallel than that without any aids.
    Eliminating the last 1 degree of alignment error though, is tough, even with aids.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  8. #38

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    That's just one more reason I love 8x10, Mark, and dread a 6x9 roll film back on my 4x5 - everything
    just gets way way more fussy both mechanicallly and in terms of visual focus to achieve a comparable print as the equipment scales down. And you're right - trying to achieve one degree accuracy in a detent is pretty damn difficult, esp in a field camera.

  9. #39
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    I use two methods to set the detents and double check each.
    1) Laser Method: you actually can use any laser pointer, you don't need a Versalab but if you have it you can use it.
    a) Set camera on tripod and remove the lensboard. The camera does not need to be level or plumb, but all the movements need to be at the zero detents. Shine the laser at the film back. Horseman has a shiny side of the fresnel there so it bounces the light back and make note where in your room the laser beam is shining. (other cameras require a piece of optical glass at the film plane). You can move the camera around on the tripod so the beam shines back at a convenient place (it does not have to point exactly back at the Versalab center unless you want it to).
    b) Now mount the lens with a microscope slide on the front rim of the lens. Zero the detents so the beam bounces off the microscope slide and shines to the same place as before. Double and triple check, mounting and un-mounting the lensboard, etc. until happy.
    2) Optical test for wide angle lenses: Put a piece of tape on your focus knob. Focus an object on the horizon at the far right of the ground glass with a high power loupe (this will be very challenging with some cameras and some loupes and very wide lenses but the wider the lens you can use, the better you can set the detent). Note exactly where the focus knob is. Swing the camera on axis until the same object is now on the far left of the ground glass. Re-focus on the object. Now check the focus knob to see if it is back in the same place. Repeat as needed to get a good idea if the front lens swing detent is indeed correct. If not re-adjust it. Keep notes of which way you swung the detent because it is a little non-intuitive to know which way the detent needs to be swung to rectify the focus being a little too far in or out on one side.

    Anyone that needs to know where the detent adjustments are on a Horseman FA, let me know.

  10. #40
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    Quote Originally Posted by dlin View Post
    Sounds like you'd be best served by a monorail camera with clear detents on the zero positions and good levels on both front and rear standards. If you're working with primarily wideangle lenses, a bag bellows would be necessary. There are a number of good options available: Sinar, Arca Swiss, Linhof. You'd be trading off portability/compactness for this level of precision, but it sounds like a solution to your frustrations.
    Add Horseman L-series monorails (LE, LB, LS, LX, LXC) to this list, as well as the Toyo 45GX.

    http://lensfielders.com/2011/06/hors...ew-camera-kit/
    This site has the OMG top-of-line Horseman LXC in a full kit for $895, and Calument lists the LXC camera only for $5600!

    In 2003 the bottom-of-line LE was selling for $1440 new at B&H! And this site has a used LE for $400. http://montreal.en.craigslist.ca/pho/3265196511.html
    Last edited by wiltw; 09-27-2012 at 09:22 PM. Click to view previous post history.



 

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