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Thread: f64

  1. #201

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    Re: f64

    Quote Originally Posted by Drew Wiley View Post
    My mistake was assuming I logged into the Flat Film Society, when it really turned out to be the Flat Earth Society.
    Think of it as a Black Swan event. An event very hard to predict that could not have been anticipated, so rare that we could not see it coming.

    A lens is compared to other quality lenses of similar vintage and type, using sound methodology devoid of any possibility of flaw. And the results reveal that this lens is hugely superior in rendering an image at f/64 than any of the other lenses. This result could not be anticipated because it did not reveal itself, so far as we know, in any comparative testing provided by the manufacturer. Nor had the specific superiority been observed in empirical observations extending over more than two or three decades.

    Sandy
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  2. #202

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    Re: f64

    Quote Originally Posted by sanking View Post
    A lens is compared to other quality lenses of similar vintage and type, using sound methodology devoid of any possibility of flaw.
    Sandy
    While the Nikkor W 300mm is indeed a stellar performer, and Sal has performed the test as well as can be done outside a test lab, there are a couple of caveats:

    The 420mm f/8 Fujinon L and the 300mm f/5.6 Fujinon W (single-coated version) are of much older vinatge than the Niikkor W 300mm. One also does not know if the 250mm f/6.7 Fujinon W used was the older version in the Seiko shutter, or the later Copal 1 version. I have one in a Copal 3 shutter that appears to have been factory modified or least professionally modified to accept this specific lens, which has the Seiko shutter threads. Perhaps the owner liked its performance so much that he went to the expense of getting a Copal 3 shutter modified. The 250mm f/6.7 lens was/is reputed to be great for portraits, where absolute sharpness is perhaps less important than a certain roundness and tonality. This lens was also superseded by the 6.3 NW version (marked W on the outside) and then the CM-W version.

    Kumar

  3. #203

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    Re: f64

    Quote Originally Posted by B.S.Kumar View Post
    ...The 420mm f/8 Fujinon L and the 300mm f/5.6 Fujinon W (single-coated version) are of much older vinatge than the Niikkor W 300mm...
    And their performance at f/45 and f/64 was on par with the modern 450mm f/8 CM-W, not to mention in line with typical expectations for sharpness degradation at the smaller aperture. No differences that I can attribute to age of design or manufacture. And better than the 300mm f/9 A.

    Quote Originally Posted by B.S.Kumar View Post
    ...One also does not know if the 250mm f/6.7 Fujinon W used was the older version in the Seiko shutter, or the later Copal 1 version...
    It's a very late sample in Copal shutter. There's no evidence it had been tampered with or re-shuttered before I bought it.

  4. #204
    Drew Wiley
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    Re: f64

    I do covet a Fuji 420L, even though its a bit of a beast, or even a 300L. I want this for its distinct Tessar "look" in older multi-bladed Copal 3s shutter. But there is absolutely no way on earth, except in the estimation of one individual, that this lens will have the resolution or coverage, RELATIVE TO focal length, equal to an A series lens. People do use strong tilt and rise at times, even at f/64, or perhaps especially at f/64, since it's those strong movements which often demand a small aperture to avoid mechanical vignetting. There's a reason that, unless you a very lucky, any 300 or 360 A typically sells for triple the cost of a 300 or 420 L in equal condition. Even a 240A is sharper and more apo-corrected than the 250/6.7, and even has virtually an equal usable image circle. And the 250/6.7 is one damn fine lens! Sal likes fine lenses just like I do, and I hope he enjoys them to the fullest. But hundreds of big prints have given me a somewhat different take on the specifics.

  5. #205

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    f64

    Aside the normal bickering, a few thoughts.

    Sal it's great you followed up and did your own tests.

    Drew, to truly have a scientific analysis of lenses, you need to have digital technology to analyze it, one persons view through the loupe or a print done by a particular printer introduces new variables.

    To both, this is a great amateur test.

    To be more scientific you would need ...

    30 or more lenses of each type tested for a legitimate sample size before introducing a confidence interval which from a sample size of 1 which would be a very poor confidence.

    Tests performed in a lab on a solid stand with a vibration monitoring device to ensure lack of camera shake as a variable for each exposure's sharpness characteristic.

    A batch developing system that is completely machine automated to reduce the variable of batch to back processing differences.

    digital aperture measurements of all f/stop measurements for all lenses before and after each image was taken.

    Consistent lighting to avoid and account for contrast changes and potential flare variables.

    1:1 digitalized scan sections for examples of each sample

    Center as well as edge to edge images, in other words, using just rise and fall to get to the edge doesn't account for center sharpness or falloff of each lens as you get farther out.

    Comparable digital back scans of the same images for comparisons to notate differences between angles of light hitting pixels vs silver grains.

    A true scientific test would be extensive and not something we could do at home.

    I say this simply because the question was asked "what could be done to make this more scientific?" So those are some thoughts on why this isn't a scientific test.

    Side note, my 300 C is very contrasty.

    Anyway still an interesting set of comparisons. Thanks Sal for actually doing tests, but as I often have told Drew, showing your examples for us to view (like I believe Ken Lee did? Or someone else who was an early forum member) would greatly help us to see what you see. Yes this is a lot of work, but it would help your case. As they say, a picture is worth 1,000 words.

    Thanks for taking the time to read.

  6. #206
    Drew Wiley
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    Re: f64

    Not only how X versus Y versus V pixels compare, versus again X versus Y versus Z specific films, but about how the different kinds of aperture blades interact
    at small f-stops to create artifacts which might look different under a loupe than in an actual print. But like I already said, if the film plane isn't totally flat in the
    first place, all bets are off. And what some of you perceive as contention or opinion is just the tip of the iceberg in terms of what many practitioners already know and rely on to get predictable results. Not all the chatter on this given subject is on this venue, not by a long shot. And it still absolutely astounds me that everything is fair game for discussion except the elephant in the room. But I don't care. Sal does post at lot of things I genuinely appreciate. I'll continue to do what is necessary for my own needs or those seeking analogous solutions.

  7. #207
    Maris Rusis's Avatar
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    Re: f64

    I do lens comparison tests at various apertures which I reckon will unambiguously find which lens is better or worse or the same. The key is to look at the aerial image. I set up a couple of large format cameras side by side that have their backs replaced by telescope style focussing drawtubes. Telescope eyepieces, usually Plossls of various focal lengths, deliver selectable magnifications to highlight aberration and diffraction effects. A favourite infinity subject is the top of a power pole well above ground shimmer that has fine wires against the sky, insulators with specular highlights, and wood textures. By looking back and forth between eyepieces it's easy to pick lens quality differences. And it's downright gratifying to know which lens is best.

    BUT:
    The test shows only central image quality, not the edges of the image circle.
    Actual image quality on film will be worse because of film sag, film resolution limits, halation, flare, etc...
    Camera vibration, shutter vibration, wind vibration, tripod wiggle, etc will confound results.

    The net outcome is that I know the best lens but what I end up with in the final photograph is an accumulation of errors (they never cancel?) from every step in the production process.
    Photography:first utterance. Sir John Herschel, 14 March 1839 at the Royal Society. "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..".

  8. #208
    Drew Wiley
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    Re: f64

    The protocol for people using film for scientific purposes, or anything analogous requiring image optimization inherently demands certain variables get ironed out
    one at a time. True film plane is one of these. That is why Kodak continued making high-resolution glass plates for many decades after the invention of more practical but less precise film. In aesthetic photography, we can bend the rules any way we wish, and select lenses for net visual effect rather than precision if we
    prefer. I do both, depending on my specific project, degree of intended enlargement etc. But since this thread is about hypothetical lens performance and not image "look", I was merely pointing out one of the the most frequent major obstacles to objectivity which generally gets overlooked. I find the aerial image technique, which Maris just pointed out, to be most effective when using film somewhat undersized in relation to the image circle, where really only the center
    of the field generally comes into play. For example, roll film exposures using 4x5 gear and the same lenses I carry for full 4x5 film itself. This means greater
    enlargements, yet potentially photographed at slightly wider apertures. Quality of film tightness, whether or not the roll film back tugs the rear standard out
    of assumed position due to extra weight or bulk, etc - here again, true film plane becomes a misunderstood issue, where any given lens might get graded wrong
    due to a different problem completely.

  9. #209
    Vaughn's Avatar
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    Re: f64

    Quote Originally Posted by Maris Rusis View Post
    ...The net outcome is that I know the best lens but what I end up with in the final photograph is an accumulation of errors (they never cancel?) from every step in the production process.
    Photographing El Capitan from the meadow with the 11x14. Two exposures, same lens, nothing else moved. One dang negative is sharper than the other. Something must have happened to the lens! You turn your back on an Artar and they'll change on you! It's a Red Dot - must be a commie. It can't be the fault of the operator and his use of the lens-cap-as-shutter!
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  10. #210
    Drew Wiley
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    Re: f64

    The solution was simple, Vaughn. If El Capitan was out of focus, just move the monolith either forward or backwards a bit.

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