Kodak Wratten Gelatin filter no.12 ??????

Discussion in 'Kodak' started by simon3000, Dec 1, 2004.

  1. simon3000

    simon3000 Guest

    I'm even more confused than ever now with all this technical talk.

    I used to work with a Professor of Ophthalmology who used to use a
    piece of Kodak Wratten gel filter no.12 - it looked like a very flimsy
    square (i'd guess approximately 3 x 3 inches in size) of yellow
    plastic material which he held in front of the patient's fluorescein
    stained eyes whilst viewing them through a slit-lamp biomicroscope
    using a cobalt blue illumination source.

    Recently I came across a medical review article by my now-retired Prof
    whcih states:
    "Fluorescein staining is the standard method used to demonstrate
    ocular surface damage. This orange dye, which fluoresces green when
    excited by blue light, is applied to the eyes. Optimal results are
    obtained by viewing through a yellow barrier filter, such as a Kodak
    Wratten 12 absorption filter, used in combination with the standard
    blue exciter filter of the slit lamp. This technique reveals surface
    damage on both the cornea and conjunctiva. Usually, staining has a
    characteristic distribution and is confined to the exposed
    interpalpebral area of the ocular surface. In the absence of a yellow
    filter, staining is poorly seen on the bulbar conjunctiva. With
    regular use of a yellow filter and routine examination of the upper
    bulbar conjunctiva, the clinician is unlikely to miss the diagnosis of
    SLK in a symptomatic patient."

    I guess I'll have to email him to see where he gets them from.

    Thanks

    Simon
     
    simon3000, Dec 2, 2004
    #21
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  2. Ah! You're in luck. Almost any photographic filter described as "medium
    yellow" (comparable to Wratten 12 or 15) will work just fine. It sounds as
    if an exact equivalent is not needed.

    Since the size of the filter is not critical, as long as you can hold it up
    to your eye and look through it, I'd suggest checking secondhand filters at
    a store that sells used cameras.
     
    Michael A. Covington, Dec 3, 2004
    #22
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  3. Yeah, that's what we have been trying to tell you!

    Wratten #12, 3x3", B&H New York, ~$27, they ship internationally

    or

    Deep Yellow filter, 49/52/55 mm, ~$10-20, _any_ competent camera store.
    Filter is glass and comes in a metal ring. This is
    probably your best choice.

    or

    Roscolux #12, 20x24", B&H or any theatrical supply, ~$6

    How is this confusing?
     
    Nicholas O. Lindan, Dec 3, 2004
    #23
  4. simon3000

    friend® Guest

    yellow filters cuts off all blue radiation from your cobalt glass
    filtered light source, but transmitt green radiation of excited dye.
    it imroves contrast of an image, making it easier to detect fine
    hairlines of a damage.

    Wratten 12 is quite popular, was used as standard filter in color
    infrared photography. many other filters from various suppliers will
    work as well. Lee filters are of very good quality, I used them in IR
    photography with great success.


    On 2 Dec 2004 15:35:12 -0800, (simon3000) wrote:

    *I'm even more confused than ever now with all this technical talk.
    *
    *I used to work with a Professor of Ophthalmology who used to use a
    *piece of Kodak Wratten gel filter no.12 - it looked like a very flimsy
    *square (i'd guess approximately 3 x 3 inches in size) of yellow
    *plastic material which he held in front of the patient's fluorescein
    *stained eyes whilst viewing them through a slit-lamp biomicroscope
    *using a cobalt blue illumination source.
    *
    *Recently I came across a medical review article by my now-retired Prof
    *whcih states:
    *"Fluorescein staining is the standard method used to demonstrate
    *ocular surface damage. This orange dye, which fluoresces green when
    *excited by blue light, is applied to the eyes. Optimal results are
    *obtained by viewing through a yellow barrier filter, such as a Kodak
    *Wratten 12 absorption filter, used in combination with the standard
    *blue exciter filter of the slit lamp. This technique reveals surface
    *damage on both the cornea and conjunctiva. Usually, staining has a
    *characteristic distribution and is confined to the exposed
    *interpalpebral area of the ocular surface. In the absence of a yellow
    *filter, staining is poorly seen on the bulbar conjunctiva. With
    *regular use of a yellow filter and routine examination of the upper
    *bulbar conjunctiva, the clinician is unlikely to miss the diagnosis of
    *SLK in a symptomatic patient."
    *
    *I guess I'll have to email him to see where he gets them from.
    *
    *Thanks
    *
    *Simon
    *
    *
    *
    * (RWatson767) wrote in message *> Simon3000
    *> >Kodak Wratten Gelatin filter no.12 ??????
    *>
    *> I am a medical doctor looking to purchase a Kodak Wratten Gelatin filter Number
    *> 12 for use in assessment of patients with dry eye using fluorescein tear
    *> staining.
    *>
    *> What size? There are or were several sizes. Some round ones also.
    *>
    *> Bob AZ
     
    friend®, Dec 3, 2004
    #24
  5. simon3000

    prep Guest

    A 12 is a blue cut filter, normal use was in IR false colour work.
    Good luck getting one out of the yellow bird... Can't remember the
    cutoff wavelength. Any of the good filter supliers should be able to
    supply a glass one that will do the job. If all else fails, try Zeis.


    --
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    +61 (08) 9257-1001 Kalamunda.
    West Australia 6076
    comp.os.vms,- The Older, Grumpier Slashdot
    Raw, Cooked or Well-done, it's all half baked.
    EPIC, The Architecture of the future, always has been, always will be.
     
    prep, Dec 3, 2004
    #25
  6. Funny, works here, Calumet has a ton (well, a few ounces) of them.
    Maybe it is one of those UK things. Are they still on ration?

    Using google and entering:

    wratten 12 uk

    One finds:

    http://www.silverprint.co.uk/acc6.html

    I am not sure this has not all been a troll...
     
    Nicholas O. Lindan, Dec 3, 2004
    #26
  7. If they are lighting filters they are not gelatin but
    plastic and may not be suitable for use in an image forming
    optical system. If the filter is used in a light source
    plastic filters have the advantage of being cheaper and more
    rugged. I am not sure how the original poster is using the
    filter. Kodak publishes transmission charts and curves for
    its filters.
     
    Richard Knoppow, Dec 3, 2004
    #27
  8. After reading the description of the use of the filter
    and looking at the transmission curves in the Kodak filter
    manual it seems to me that a plain No.8 (K-2)or No.15 (G)
    might do. The No.8 transmitts somewhat more green than the
    No.12 but cuts off blue pretty well. The No.15 cuts off more
    green but has a somewhat lower tranmission in its passband,
    probably not significant for the use. These are very
    commonly used filters for black and white photography and
    should be easily available.
    Unless the filter is being used in an image forming
    optical system where the light is fairly convergent or
    divergent a gelatin filter is not necessary. Both the No.8
    and No.15 are available as glass filters (actually gelatin
    sandwiched between optical glass blanks) and in plastic
    sheets. Glass filters have very good optical properties and
    are a lot more rugged than unprotected gelatin. Plastic
    filters are not as satisfactory as gelatin for use in
    optical systems because they are less homogenious and have a
    higher index of refraction but this is significant only for
    critical use in image forming beams as described above. For
    visual use any form will do and the precise spectral
    transmission is probably of no consequence.
     
    Richard Knoppow, Dec 3, 2004
    #28
  9. simon3000

    Travis Porco Guest

    [/QUOTE]
    Not to butt in, but you all may have seen <a href="http://msp.rmit.edu.au/Article_02/02d.html">http://msp.rmit.edu.au/Article_02/02d.html</a>. Apparently
    some people do use the Wratten 15 for what looks like a similar purpose; I
    suppose it depends whether or not there is a calibrated measurement of some
    sort involving a standard light source with the Wratten 12 filter.

    You might wish to try http://www.filterfind.net in looking for these. **I
    hasten to add that I'm not connected with the site and profit in no way by
    it**. Other possibly useful sites are Edmund Optical http://www.edmundoptics.com , who sell Wratten 12 filters (I found them on the UK version of their site,
    priced in pounds sterling). Another place to find them is Lumicon, http://www.lumicon.com , who sell both specialty minus-violet filters for astrophotography
    as well as Wratten 12 in certain sizes.

    HTH, --travis
    standard disclaimers, etc.
     
    Travis Porco, Dec 3, 2004
    #29
  10. I'd be willing to bet that a piece of cleared photographic film dyed
    with yellow Easter egg or fabric dye would do the trick.
     
    PATRICK GAINER, Dec 4, 2004
    #30
  11. simon3000

    simon3000 Guest

    Hello everyone,

    Thanks for all the advice.
    I found a Kodak Wratten 12 on one of the websites suggested for a
    price of 29.75 euros which seems pretty steep especially if its a
    flimsy peice of gel which may not last long in clinical use, so the
    possibility of buying a cheaper/more durable glass or plastic filter
    is obviously very attractive to me as long as it does the required job
    (in this case, demonstrate green fluorescence from the surface of the
    eye).

    From what I gather in medical textbooks:
    "Excitation of fluorescein occurs when exposed to blue wavelengths
    between 465 and 490 nm, resulting in emission of yellow-green
    frequencies (520-530 nm).
    Because various structures within the eye are capable of reflecting
    incoming light, a barrier filter that transmits only yellow-green
    fluorescent wavelengths, indicating the true position of fluorescein
    dye, is required. Because the excitation and emission spectra of
    fluorescein are relatively close in position, and may even
    overlap—pseudofluorescence, transmission curves of the filters should
    be carefully chosen to insure minimal overlap."

    so does that mean the plain No.8 (K-2)or No.15 (G) mentioned would do
    the trick - I'm not sure what this means - is that the name of a
    specific filter - if so, what exactly should I ask for if a visit a
    photographic shop?

    Thanks

    Simon
     
    simon3000, Dec 5, 2004
    #31
  12. simon3000

    Tom Phillips Guest


    Get some filter frames or make a frame to sandwich the
    gel between and handle carefully. It should last quite
    a while.
    Yes, #8 Yellow, #12 Yellow, #15 Yellow are the correct names.

    If the suggestion is to carefully choose the transmittance
    probably best to stick with #12, the minus blue. Both the 15
    and 12 block all transmission in the 400 nanometer range, but
    the 12 allows more of the yellow green at 520-530 (which is I
    gather what you want and is why 12 is commonly used.) A #8
    likely passes too much cyan/blue for the purpose.
     
    Tom Phillips, Dec 5, 2004
    #32
  13. simon3000

    simon3000 Guest

     
    simon3000, Dec 7, 2004
    #33
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