Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,288   Posts: 1,535,366   Online: 790
      
Page 4 of 18 FirstFirst 1234567891014 ... LastLast
Results 31 to 40 of 171
  1. #31
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Rhodamine may or may not work. IDK. The structure looks marginal.

    PE

  2. #32
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,418
    Images
    2
    Could you elaborate a bit on that Ron? It's kind of cryptic...

    How do you spell the guy's name whose responsible for J-aggregation, Jelly?
    If you are the big tree, we are the small axe

  3. #33
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Chris;

    With few exception (Erythrosine and Chlorophyll being two I can name OTOMH), emulsion sensitizing dyes have positively charged Nitrogen atoms in them.

    See attached. There is a resonance plus charge carried by one of the Nitrogens as the electrons resonate. Compare with Rhodamine.

    PE
    Attached Thumbnails Attached Thumbnails dye class vs wavelength.jpg  

  4. #34

    Join Date
    Apr 2005
    Location
    San Bernardino, CA
    Shooter
    8x10 Format
    Posts
    734
    Good morning Ron,
    While this subject is being discussed, I am running low on my stash of Sands 3057 . I hope that it is still availible to individuals. But if not, you mentioned another green and a red sensitizing dye you were getting for your own panchromatic work. Are they obtainible by individuals like me? Are they similar in price to the Sands Dyes.
    I would hate to have to go back to grinding spinach and little red beetles!
    BTW: Way back on the First day of your Workshop a t the Formulary, you warned me of the difficulty I would face in making a panchro emulsion. You were absolutely correct! Here it is, how many years later, and I am still working on it! But, If I had to do a color separation project today, I could do it with my current emulsion. It is just not as fast as I would like it to be. Filter factor for the blue separation filter is X22! That, coupled with the fact that I have stubournly refused to use gelatin, has made this a long project! Its a very good thing, for me, that I would rather do research than make art!
    Bill

  5. #35
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Bill;

    Red and Green dyes are available through Sands. The price is about $100 / gram or more.

    Blue sensitizers can be had from Honeywell in Germany for about the same price.

    AFAIK, neither list them on their web sites, but you can e-mail them or call and they will give you product numbers.

    But, don't use a blue filter. Since a plain raw emulsion is blue sensitive, no filter will give you much higher speed.

    Best of luck.

    PE

  6. #36

    Join Date
    Apr 2005
    Location
    San Bernardino, CA
    Shooter
    8x10 Format
    Posts
    734
    Quote Originally Posted by Photo Engineer View Post
    Bill;



    But, don't use a blue filter. Since a plain raw emulsion is blue sensitive, no filter will give you much higher speed.

    Best of luck.

    PE
    That is assuming that I am using 3 emulsions. 1 each with no spectral dye;a green sensitive dye;and a red sensitive dye. That is a possibility. But if I use a single Pan emulsion, I nead 3 negs. one each made with red; green and blue filters. No filter will give me a full spectrum negative.
    B

  7. #37
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Blue sensitizing dyes do not impart much speed to an emulsion. They just give an intense band at one end or the other of the blue region. If you have such low blue speed, you may be adding too much green or red dyes. After all, sensitizing dyes are desensitizers as well, if used in too high quantity.

    That is why most companies use one broad dye for pan sensitization. You might inquire about that at Sands.

    PE

  8. #38

    Join Date
    Apr 2005
    Location
    San Bernardino, CA
    Shooter
    8x10 Format
    Posts
    734
    Thank you PE,
    I knew of pan sensitizers. I think that you have mentioned them on your Forum here. But I believe that you also indicated that they tend to be secrets of individual Companies ( like Kodak).
    But I will enquire about this with Sands.
    Early on, I cut my leval of 3057 from your recommended 200mg/ per mole of Ag to 150mg. Then I got the cyan colored emulsion instead of a red color.. But this is highly dependent on Ag/halide grain size. And my grain size is smaller than it used to be. But I do get the bright cyan color that I am supposed to get. My leval of 3008 green sensitizing dye has remained at 100mg/mole of Ag. And I have not tried to reduce it yet
    I can live with the speed that I am getting now, as I can get a full gray scale at 1 second at f45. But I want more speed because my preffered subject matter requires bellows extention as well as small apature for macro photography.
    Good weekend,
    Bill

  9. #39
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Even with Sands, these dyes are considered proprietary in some cases, and they will not tell you the structure. They will only supply a suggested solvent and a curve of the spectrum.

    In any case, don't take ANY dyes containing Selenium. They are too toxic for home use and need industrial quality equipment for safe handling. Sands sent me one for a test, and it remains in their safe packing material in a refrigerator dedicated to chemicals. Paul Gilman saw the dye, knew what it was and told me to never use it due to its toxicity.

    PE

  10. #40

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    PE - Could you list some pan dyes - from Sands or otherwise?

    Bill - I think it's been 4 years since that fatefull first day of class.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

Page 4 of 18 FirstFirst 1234567891014 ... LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin