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  1. #41

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    yes there was a booklet for the camera and each lens
    the descriptions were simpler than on this thread
    there was also a soft focus lens

  2. #42
    MattKing's Avatar
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    Flat field performance refers to the ability of the lens/camera system to record flat items sharply on the film.

    Think of copying something like artwork. You need to have excellent contrast and resolution across the entire negative, revealing all the details of the artwork.

    You cannot have the centre of the artwork in focus, with the corners of the artwork (which are farther away) out of focus.

    The plane of sharp focus needs to be flat, not curved, and that performance needs to be possible at different distances.

    Good flat field performance also requires being able to render an image without distortion - rectangular subjects need to be rendered as a rectangle, not a barrel or pincushion.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  3. #43
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    Ah right! Will try shooting something like that for the exercise!

    - via tapatalk.

  4. #44

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    Quote Originally Posted by MattKing View Post
    Flat field performance refers to the ability of the lens/camera system to record flat items sharply on the film.

    Think of copying something like artwork. You need to have excellent contrast and resolution across the entire negative, revealing all the details of the artwork.

    You cannot have the centre of the artwork in focus, with the corners of the artwork (which are farther away) out of focus.

    The plane of sharp focus needs to be flat, not curved, and that performance needs to be possible at different distances.

    Good flat field performance also requires being able to render an image without distortion - rectangular subjects need to be rendered as a rectangle, not a barrel or pincushion.
    two queries
    a) if you want e.g. to copy art work you would use a process lens?
    b) a RB67 open aperture performance may be limited by film flatness as well as lens performance if the film retains a memory from the film feed roller path...

  5. #45
    MattKing's Avatar
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    Quote Originally Posted by Xmas View Post
    two queries
    a) if you want e.g. to copy art work you would use a process lens?
    b) a RB67 open aperture performance may be limited by film flatness as well as lens performance if the film retains a memory from the film feed roller path...
    Are you sure those are queries?

    A process lens is good for artwork, but the process cameras are a bear to use on location.

    And process lenses aren't particularly flexible for general photography - especially the fixed aperture lenses.

    While it is true that RB67s may, like other roll film cameras, have some issues with film flatness when shooting wide open, the RB67 lenses probably don't exhibit their best performance when wide open anyways.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  6. #46

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    Quote Originally Posted by Rudeofus View Post

    Even Mamiya seems to be aware of this, since they market a 140mm macro lens with is supposedly optimized for close range.
    The RB67 140mm has a floating element which has a scale for no, one or both extension rings.

    If you are poor it is a reasonable sub for the 127 and 180.

  7. #47
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    Quote Originally Posted by Xmas View Post
    yes there was a booklet for the camera and each lens
    the descriptions were simpler than on this thread
    there was also a soft focus lens
    Hmm I see. I shall try looking it up, see if any are being sold on ebay!

  8. #48
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    Quote Originally Posted by stradibarrius View Post
    The scale on the rail seems so imprecise??? Probably it's that I just don't really know how to use it...
    It did seem like that to me, today, when I was trying out what polyglot suggested

    Quote Originally Posted by polyglot View Post
    Not just flat field, but correction of aberrations that cause radial smearing in the corners. The ground glass is too low-resolution to perceive it, but the difference is quite apparent in a good print. Try a closeup composition that has sharp corner details with the adjustment set to infinity for the first frame and set correctly for the second frame. Print them both and look in the corners.

    oh wait. sharp corner detail. Hmm, I dont think it had that, will try again. :| But I did do this, set floating to infinity and then to whatever distance scale said and shot of two snaps. Lets see how those turn up...

  9. #49

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    Quote Originally Posted by Xmas View Post
    yes there was a booklet for the camera and each lens
    the descriptions were simpler than on this thread
    there was also a soft focus lens
    I apologize this was abstract - from memory...

    My camera came with two booklets for the:-

    - camera
    - interchangeable lenses

    but the latter booklet references further specific booklets for the
    37mm, 140mm, 150mm and 500 mm which booklets I never had

    The rules in 2nd booklet for the 50mm and 65mm were focus and set the floating ring to distance from focus scale, and a note
    '* the floating ring may be turned to set the distance either before or after focusing' which I fair copy.

    Except and I fair copy again

    'When placing emphasis on spur-of-the-moment snap shots set the infinity mark (red) of the floating ring to the center mark (red) when the distance is from infinity to approximately 7 ft (2m), and if the distance to subject is less than approximately 7ft (2m)m a sufficiently sharp image can be obtained merely by setting 3.3 ft/1m (red) to the index.
    * In the case of close up photography nearer than 3.3 ft (1m), set the floating ring to 3.3 Ft/1m, then stop down the lens as much as possible.
    * The distance to subject implies the distance from the film plane to the subject'

    Except in the same booklets depth of field tables for each of the 50mm and 65mm fair copied again,

    'When using the 50mm (sic or 65mm) lens closed then 3.5 feet (1 meter) it is necessary to use a lens aperture of f/16, or smaller, in order to obtain satisfactory lens performance.'

    In first bookelt - when using the 360mm the (a) filter needs to be between the rubber hood and lens, either position may be used with the other lenses.

    Lastly there is a warning that only the 127mm will be reasonably free from from vignetting when both the type I and II tube are used together on 6x7, but some vignetting will be obtained with the 127mm on the polaroid packs larger image... The other lenses may vignette with two (both) tubes, but will be ok with either one alone.

    Note the 140mm would be better than the 127mm, but I don't have the handbook for it... The 140 is a double Gauss (7 element - the rear inner group floats) the 127mm a triplet (5 elements), I'd say the 90mm is already a inverted telephoto.

    I don't want to scan the handbooks cause of copyright, although the handbooks don't claim copyright

    I find my lenses pretty good the only precaution I take is to shoot all 10 (or 20) exposures over a short interval, for critical work at large apertures, if I'm dong long intervals or cold weather I use the 6x6 TLR Mamiya for film flatness risks,

    I do sometimes forget the floating rings, in snapshot mode... even with a warning Avery label on the back caps, it does not help that the 90mm has a similar depth of focus (only) ring.

    Noel

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