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Thread: Is there any real utility to ULF?

  1. #221

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    Re: Is there any real utility to ULF?

    Quote Originally Posted by bglick View Post

    Sandy, when I read your lppm, I assumed it was a typo, and assumed lines per mm. I should have mentioned that. I hate the way these lpmm, lppmm, lp/mm is tossed around so loosely. Assuming the author truly meant line pairs per mm, then I would suggest his assessment is pretty high compared to most data i have read. What is the copyright of the book?

    I can assure you, the eye can not resolve 20 lp/mm, even under the best of circumstances. Grab a test chart and try it, you can't fathom how tiny these targets are. Again, you can double the target size, and double the viewing distance to 20" to test yourself assuming you can't close focus.
    The use of lppm is mine. John Williams uses "lines per millimeter" throughout the text. Not lpmm or lp/mm. I meant the term to mean one white line and one black line in every mm, thus line pairs per millimeter, or lp/mm.

    There appears to be a lot of confusion on this with photographers, because many use lpm for lines per millimeter. But lines per millimeter in Williams' text is understood to mean line pairs per millimeter.The book was published in 1990, in the very early days of digital imagery. But it is still a good read.

    Frankly there would be no need for me to get out a chart and try to resolve (pun) the issue with my eyes. I used to have 20/20 vision but now have very severe astigmatism in one eye, and the other is myopic and has a cataract that will need to be removed in a year or so. Also, I had a retinal tear last year in the myopic eye that caused some loss of vision. Fact of the matter I should probably quite talking about high resolution imagery and start working wth one of these "artsy fartsy" Holga cameras, or even the mythical Diana if I could afford one of those plastic marvels.

    Sandy King

  2. #222

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    Re: Is there any real utility to ULF?

    > The use of lppm is mine. John Williams uses "lines per millimeter" throughout the text. Not lpmm or lp/mm. I meant the term to mean one white line and one black line in every mm, thus line pairs per millimeter, or lp/mm.


    OK, but I assume you did not divide his values by 2, as I did.... if you divide his numbers by 2, things make more sense with other data, that used the more conventional lp/mm.



    > There appears to be a lot of confusion on this with photographers, because many use lpm for lines per millimeter. But lines per millimeter in Williams' text is understood to mean line pairs per millimeter.The book was published in 1990, in the very early days of digital imagery. But it is still a good read.


    Huh, that is interesting...the optical community often does use lpmm. (i.e. lines per mm) Then, when used in terms of test targets, they simply disregard the white line between the black lines, and still use lpmm. I think the photographic community began counting the white lines also, as we were always making comparisons to cc... i.e., one cc is the black line, and one cc is the white line. (which there is not a simple relationship)


    I hear ya about vision.... astronomers suffer the most from vision degradation. It ruins the hobby for many...and its very unfortunate, because its the Sr.'s that have the time and money to pursue the hobby. Photography does not punish us as severely when our eyes degrade some. But gosh, what a battle just to read the damn f stops and ss's on the lenses.... how I miss those days when everything was always in focus...

    > I have a 450mm Nikkkor M and a 600mm Fujinon-C that have a circle of illumination large enough

    I have these two lenses also, interesting, I never knew they had that kind of coverage. Hmmmm, maybe I will add a 1100 XXL and I will have a nice 16x20 kit. But, I still prefer color film, and to my knowledge, no one makes ULF color film, do they?

    Very impressive line up of cameras...I would love to see this line up one day.....do you happen to have a web site showing you under the hood of these?

  3. #223

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    Re: Is there any real utility to ULF?

    Quote Originally Posted by bglick View Post
    Very impressive line up of cameras...I would love to see this line up one day.....do you happen to have a web site showing you under the hood of these?
    In a few minutes I am going to drift out of cyberspace for a week or so. When I return I will send you some images of me working with the big cameras, and sites where you can see my work also if interested.

    Sandy

  4. #224

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    Re: Is there any real utility to ULF?

    Ole has the nomenclature correct. We should use lp/mm (line pairs per millimeter). It refers to one white or clear line beside one black or opaque line. As bglick has pointed out the contrast ratio between the black and white line in an aerial image is intimately related to the MTF of the lens. 1 lp/mm then means 1 black line 500um wide and 1 white line 500um wide within 1 mm (1000um). For reference the average human hair width is taken as about 75um or 3 mils (.003 inch). 3 mils represents about 7 lp/mm. So a black human hair is an approximate guide to what 7 lp/mm looks like. By the way I think recently there was a dandy guide to all this written by a UMass professor in View Camera - don't have the issue handy though.

    Nate Potter

  5. #225

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    Re: Is there any real utility to ULF?

    Um, Nate, when I look at a single black line on a white background I can't see the edges of the white lines on both sides of it. If there are n black lines, n-1 pairs of lines can be discerned.

  6. #226

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    Re: Is there any real utility to ULF?

    Yes, my example of 1 lp/mm is a poor example. I takes at least 2 lp/mm to determine the width of a white line as you point out.

    Nate Potter

  7. #227

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    Re: Is there any real utility to ULF?

    bglick, I think if you are willing to pay Kodak for the minimum order they will still cut to size. But you're talking about quite an investmant. Of course you can always get creative and start doing tri-color gum. ( just a little humor there). robert

  8. #228

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    Re: Is there any real utility to ULF?

    I think the Ebony 20x24 is probably the only one that can focus that 1100 xl at 1:1. I think it has 70" of bellows. The new Canham 20x24 may have that much extension also. Of course that's not required for landscapes. But if you're going to spend that much on a lens you may as well buy the camera that can handle it in every situation. robert

  9. #229

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    Re: Is there any real utility to ULF?

    The Ebony 20x24 has 78" of bellows and the Ebony 16x20 has 66". So the 20x24 will almost get you close to 1:1. Let's see...you'd need about 86-87" maybe. Ah hell you might as well buy both the 550 and the 1100.... lol... robert

  10. #230

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    Re: Is there any real utility to ULF?

    Nate, nice analogy....but, only very fine human hair is 75um (.003").... I think avg. human hair is 200um. Interestingly enough, I think standard copy paper is .003" thick. If you buy black and white sheets and interlace them, you will have a very nice 7 lp/mm target. (looking at the edges)

    BTW, if you can resolve this target, its said, you can resolve 7 lp/mm, as the white line counts as a line.

    I think Kodaks min. order is $15k for cut-to-size? too steep for me....

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