Please answer reasonably -- What entities in a single stationaryimage of a B&W film's negative are m

Discussion in 'Australia Photography' started by GreenXenon, May 8, 2009.

  1. GreenXenon

    GreenXenon Guest

    Hi:

    What entities -- excluding wavelength of light [or any EM radiation
    for that matter] -- in a single stationary image of the negative of a
    B&W film are measured in Hz?

    What will the image look like if I downshift the frequencies of those
    entities to 0.1 Hz?

    Hz is commonly used to measure cycles-per-constant-time [usually in
    seconds] but could also be used to measure cycles-per-constant-
    distance [as in the cycles-per-meter in spatial frequency]. Right?

    If a single stationary image is low-pass-filtered it will look duller.
    If it is high-pass-filtered it will look sharper. This is an example
    of frequency-processing in which Hz is *not* the reciprocal of the
    period with respect to time.

    In this case Hz measures the reciprocal of the period with respect to
    distance. Right?

    What other than spatial frequency would be measured in Hz in my above
    scenario?

    No offense but please respond with reasonable answers & keep out the
    jokes, off-topic nonsense, taunts, insults, and trivializations. I am
    really interested in this.


    Thanks
     
    GreenXenon, May 8, 2009
    #1
    1. Advertisements

  2. GreenXenon

    Dan M Guest

    In this case Hz measures the reciprocal of the period with respect to
    "Hertz" is, by definition, "cycles per second". If the frequency of
    recurrence is measured for a unit of comparison other than 1 second of
    elapsed time, Hertz cannot be used to expressed the measurement.
     
    Dan M, May 8, 2009
    #2
    1. Advertisements

  3. GreenXenon

    GreenXenon Guest

    http://en.wikipedia.org/wiki/Spatial_frequency

    "In mathematics, physics, and engineering, spatial frequency is a
    characteristic of any structure that is periodic across position in
    space. The spatial frequency is a measure of how often the structure
    repeats per unit of distance. The SI unit of spatial frequency is
    cycles per meter."
     
    GreenXenon, May 8, 2009
    #3
  4. GreenXenon

    Scott Dorsey Guest

    Meters and seconds are not the same thing, no.
    --scott
     
    Scott Dorsey, May 8, 2009
    #4
  5. GreenXenon

    J. Clarke Guest

    With light, spatial frequencies occur in the context of interference
    patterns.
     
    J. Clarke, May 9, 2009
    #5
  6. GreenXenon

    GreenXenon Guest


    Lets say there is a single stationary image black image with white
    lines in it.

    Higher spatial frequency = smaller lines, more lines in the image,
    more lines per area in the image.

    Lower spatial frequency = bigger lines, less lines in image, less
    lines per area in image.
     
    GreenXenon, May 9, 2009
    #6
  7. GreenXenon

    GreenXenon Guest


    Ok, lets say there is a single stationary image black image with white
    lines in it.

    Higher spatial frequency = smaller lines, more lines in the image,
    more lines per area in the image.

    Lower spatial frequency = bigger lines, less lines in image, less
    lines per area in image.
     
    GreenXenon, May 9, 2009
    #7
  8. That's what you deserve for feeding the troll. I hope that headache
    will last all weekend!

    noyb
     
    Sir None Of Your Business, May 9, 2009
    #8
  9. Don't feed the GreenTroll

    noyb
     
    Sir None Of Your Business, May 9, 2009
    #9
  10. GreenXenon

    Doug Jewell Guest

    So if I'm understanding your question, which doesn't make a
    lot of sense, you are asking what would happen if the
    spatial frequency on the piece of film was .1 cycles/metre?
    (which you are incorrectly calling .1 Hz).

    Well assuming that is what you are asking, one cycle would
    require 10m of film.

    Assuming that the intensity of the image changed from Dmin
    to Dmax over the course of the cycle, the intensity at any
    point along the piece of film would be:
    Da=(Dmax+Dmin)/2 + (Dmax-Dmin)(sin a)/2
    Where a = the phase angle at that position
    a (in degrees) = x (in mm) / 10,000mm * 360 deg.

    The variation in brightness across the space of a 35mm film
    would then be
    dD=(Dmax-Dmin)((sin a)-(sin a+1.296))

    The maximum variation would be at the points where the
    waveform crosses the midpoint. At these points, in the space
    of 36mm the density would vary by 2.2% of Dmax-Dmin.

    Therefore for a "waveform" with a cycle of .1 cycles/metre,
    the maximum variation across the space of a single frame of
    35mm film is so small that it would be barely noticeable.

    I hope this answers your question and you'll now STFU.
     
    Doug Jewell, May 9, 2009
    #10
  11. GreenXenon

    Mr.T Guest

    "Doug Jewell" <
    Vain hope I'm afraid.

    MrT.
     
    Mr.T, May 10, 2009
    #11
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.