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Thread: Is there any real utility to ULF?

  1. #211

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    Re: Is there any real utility to ULF?

    Quote Originally Posted by Kirk Gittings View Post
    Along with this, are there any figures about what resolution the eye can perceive at various viewing distances?

    Kirk,

    John Williams has a chapter on this in his book, Image Clarity: High Resolution Photography.

    He says basically this. And it is based on optimum viewing distance of about ten inches, and is related to studies of the actual fovea of the eye which process light.

    1. 5-7 lppm has traditionally been accepted as about as much detail as the eye can appreciate, but that this figure is based on a false premise.

    2. Studies which show that the eye can resolve from 40 seconds to one minute of arc suggest that the resolving power of the eye is really in the 15-20 lppm range.

    3. Some differences in perceived quality may be seen by persons with very good eyesight in the 20-25 lppm range.

    4. Resolution beyond 25 lppm can not be appreciated by the human eye.

    Sandy King
    Last edited by sanking; 23-Jan-2008 at 14:28.

  2. #212

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    Re: Is there any real utility to ULF?

    > 5-7 lppm has traditionally been accepted as about as much detail as the eye can appreciate, but that this figure is based on a false premise.

    lpmm must be converted to lp/mm, for most photographic discussions..... it somehow became the norm. So this represents 3 lp/mm avg,. which seems to still be an accepted norm, using black and white targets. My eyesight for most my life was 20/10 in each eye... and yet, by 40, the most I could resolve was 2 - 3 lp/mm....very hard, grab a chart and try it..... you can double the view distance and double the size of the chart to compensate for our un-accommodating eyes, for us 40+.




    > 2. Studies which show that the eye can resolve from 40 seconds to one minute of arc suggest that the resolving power of the eye is really in the 15-10 lppm range.

    or, 6 lp/mm avg.... and yes, this has been stated as the very best human vision.




    > Some differences in perceived quality may be seen by persons with very good eyesight in the 20-25 lppm range.

    IMO, this is the significance of the Ctein study I quoted above... truly the best test to date that I have read - on human vision as it relates to sharpness of photographic prints. Quite impressive results, and really supports the value of tack sharp prints. The other interesting study looked at edge sharpness in the 3 - 5 lp/mm range as having a higher perceived sharpness than much higher targets with slightly less edge sharpness, also explained above.


    Sandy, what ULF sizes do you shoot? Do you have both the 550 and 1100?

  3. #213

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    Re: Is there any real utility to ULF?

    Quote Originally Posted by bglick View Post
    > 5-7 lppm has traditionally been accepted as about as much detail as the eye can appreciate, but that this figure is based on a false premise.

    lpmm must be converted to lp/mm, for most photographic discussions..... it somehow became the norm. So this represents 3 lp/mm avg,. which seems to still be an accepted norm, using black and white targets. My eyesight for most my life was 20/10 in each eye... and yet, by 40, the most I could resolve was 2 - 3 lp/mm....very hard, grab a chart and try it..... you can double the view distance and double the size of the chart to compensate for our un-accommodating eyes, for us 40+.





    Sandy, what ULF sizes do you shoot? Do you have both the 550 and 1100?

    You mean lpm, right? lppm is lp/pm.

    I use 7X17, 12X20 and 20X24 formats. But by far 7X17 has been my favorite over the course of many years. I just got a RR 20X24 and plan to use it a lot this year.

    I only have the 550/11 XXL, not the 1100.

    Sandy

  4. #214
    All metric sizes to 24x30 Ole Tjugen's Avatar
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    Re: Is there any real utility to ULF?

    Quote Originally Posted by sanking View Post
    You mean lpm, right? lppm is lp/pm...
    It should have been lppmm, Line Pairs Per MilliMeter.

    "lpm" as an abbreviation doesn't make sense in any case - is that "linepair-meters", or "lines per meter"?

    lp/mm is probably the least ambiguous notation.

  5. #215

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    Re: Is there any real utility to ULF?

    Quote Originally Posted by Ole Tjugen View Post
    It should have been lppmm, Line Pairs Per MilliMeter.

    "lpm" as an abbreviation doesn't make sense in any case - is that "linepair-meters", or "lines per meter"?

    lp/mm is probably the least ambiguous notation.
    Ole,

    Thanks for the clarifcation. lp/mm clearly makes the most sense. I have been using lppm for a long time and I can now see why that might be confusing.

    Sandy King

  6. #216
    Kirk Gittings's Avatar
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    Re: Is there any real utility to ULF?

    4X 16X20" 20 lppm
    from 4x5

    Some differences in perceived quality may be seen by persons with very good eyesight in the 20-25 lppm range..... Resolution beyond 25 lppm can not be appreciated by the human eye.

    Sandy King
    Interesting, whether traditional or digital prints, I have always considered a 16x20, from a good 4x5, the maximum size enlargement before obvious degradation of the sharpness set in on close inspection.
    Thanks,
    Kirk

    at age 73:
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  7. #217
    Zebra
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    Re: Is there any real utility to ULF?

    I have not felt the need to use a center filter on the 550 XXL and I use this lens for both 16 x 20 and 20 x 24. I only shoot for Pt/Pd and Wet Plate Collodion out put and to be honest I have noticed as a much more limiting factor in terms of fall off to be my NuArc 26 1KS uv unit (Amerigraph here we come!) which is significant as it moves out towards the edges. The negatives don't show near that drop off. Admittedly I haven't put them under a densitometer to confirm this as I cleary have more passion than skill when it comes to the vast majority of the contents of this thread. Pure and simple the lens is better at its job than I probably ever will be handling my end of the bargain! It is a phenomenal lens and is the only lens I have for the formats that is in a shutter. I would love to have the 1100 but damn there has to be a line drawn somewhere and my wife used a big boot to scrape it out in the dirt so I wouldn't mistake it for anything else. The 1100 is just on the other side of that line!

    Monty
    aka Zebra


    Quote Originally Posted by sanking View Post
    I am not finding that the 555/11 on 20X24 needs a center filter. There may be some light fall off toward the edge of the, but this is often a good thing when we contact print.

    However, I should remark that to this point I have not used the 550/11 very much on 20X24, though I plan to do so a lot in the future. Zebra may have something to say about the light fall off issue.

    Sandy

  8. #218

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    Re: Is there any real utility to ULF?

    > I would love to have the 1100 but damn there has to be a line drawn somewhere and my wife used a big boot to scrape it out in the dirt so I wouldn't mistake it for anything else. The 1100 is just on the other side of that line!

    this is just too funny..... gosh, what we do for the right glass, huh.....



    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.

  9. #219

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    Re: Is there any real utility to ULF?

    > I just got a RR 20X24 and plan to use it a lot this year.

    Sandy, what lenses do you have that covers this?

  10. #220

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    Re: Is there any real utility to ULF?

    Quote Originally Posted by bglick View Post
    > I just got a RR 20X24 and plan to use it a lot this year.

    Sandy, what lenses do you have that covers this?
    Depends on critical you are for coverage on the edges.

    I have a 450mm Nikkkor M and a 600mm Fujinon-C that have a circle of illumination large enough for the 20X24" coverage. But to get acceptable definition on the edges of the field you must stop down to f/64. Even them the far corners are just a bit soft.

    Then I have the 550/11 XXL, which covers 20X24 with some movement.

    I also have a 30" Red Dot Artar, which covers 20X24 nicely, but again you need to stop down to f/32 or f/45for good performance on the far eddges.

    Sandy King

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