Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,714   Posts: 1,483,032   Online: 767
      
Results 1 to 9 of 9
  1. #1
    fhovie's Avatar
    Join Date
    Mar 2003
    Location
    Port Hueneme, California - USA
    Shooter
    Large Format
    Posts
    1,246
    Images
    92

    To Stain or not to Stain ....

    I have been learning a lot from my 361t - Things I would not have otherwise known. Making sure that both ortho and uv calibrations are correct, I have been eveluating my pyrocat negs and my xtol negs. For the same ortho density areas, UV density is often twice the density. I have been limiting my experiments to FB Grade 2 paper. J&C Classic for now (which seems to have a nearly identical tonal scale as Forte - which is now harder to get.) My enlarger uses a Condenser head with a standard 150W light bulb. (Omega 6 pro series.) I have used development times (for pcat) that I have tweeked over the years to print a tonal scale for a EV range of approximately 7 for TRI-X and 5 for FP4. My paper can print a density range of approximatly 1.35.

    The unanswered questions are: How significant is the UV share of total light passing through my negatives? What is the Grade 2 paper response to the UV component?

    I know that UV has a significant impact intuitively. Visually thinner stained negs print with the same contrast as denser non-stained negs. It stands to reason that for equivalant ortho densities - the contrast will be significantly greater for the stained negatives - as I have seen.

    AZO and other alt processes use UV and contrastier negatives - 1.7 or more. This makes pyro clearly better for those process and these negs should probably be evaluated in the UV channel almost exclusively. But what is the benefit for Grade 2 FB paper? If my light source contains UV as part of its emission (guess maybe 35%) and an XTOL negative is the same density at UV and Ortho - The image is simple and the process of matching the scene contrast range to a negative range that fits the paper range is straight forward. But if the highlight densities of a stained negative block 20% more total light - that adds a complexity to the process.

    There are many good reasons to use staining developers on enlarging negatives - I wonder if a blocking UV source filter would simplify and improve or if it would increase the grainieness because the stain has a smoothing effect on the image. One of the differences between Pyrocat and PMK has been the overall stain (PMK has overall stain and pcat doesn't). Such an overall stain might equalize the UV and Ortho densities giving it an advantage (simplification) for enlarging. (Much less desirabel for alt processes.) The p'cat negs are much finer grain making it better for roll film as well. I am not sure what the conclusion is to all this - so I am looking for the comments from the brain trust here for insight - or correction - If I simply got it wrong - Thanks
    My photos are always without all that distracting color ...

  2. #2
    fhovie's Avatar
    Join Date
    Mar 2003
    Location
    Port Hueneme, California - USA
    Shooter
    Large Format
    Posts
    1,246
    Images
    92
    Thanks for the note Jay - In my mind - I create a negative for a particular paper. Although I have other papers I can use - I try to make a negative that will print well on the Grade 2 FB paper I have. I know from printing a step wedge what the range of my paper is and I know that I want to develop my film to take the range of values I see and spread them out over the paper I use. (Unless I want a falt image on purpose)

    I have a color head that has UV filtering in it - I choose the Condenser head for the advantages of increased sharpness and contrast. (it has no filter) I see the entire process as one system that includes the film choice - developer choice and time/temp/agitation - enlarger type and paper type and to some extent brand. - If I miss - well - there is always VC paper or water bath or toning or reducing -- etc. But for the most part I want to be standardized so I can create images rather than chase technique.

    My materials (other than for AZO - alt processes - which I do frequently) are optimized for grade 2 paper - a condenser enlarger and TRI-X for high contrast scenes and FP4 for low contrast scenes. So far - this simplification increases my odds of having an easy to use negative. - BTW Jay - I will be trying your Pyro 510 - for roll film. This in itself will not simplify anything - but xtol is a pain and I need full emulsion speed for hand held. - Most of what I am discussing here is for 4x5 sheet film. - (8x10 is always aimed at AZO and I am completely happy with pcat for that.)
    My photos are always without all that distracting color ...

  3. #3

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Quote:

    "The unanswered questions are: How significant is the UV share of total light passing through my negatives? What is the Grade 2 paper response to the UV component?"


    In checking Oriental Seagull graded material, the paper that I use, the spectral response indicates that it is sensitive to light in the 400-500nm range. With it's peak being 450nm. That is just slightly higher then Azo. Which has a sensitivity ranging from 365-450nm. So Azo is more sensitive to UVA then Seagull graded paper.

    The proportional stain from a pyrocat negative will add appr. .20-.30 density at the upper density regions when evaluated on the basis of blue light transmission. Thus this proportional stain does have an effect on printing graded materials.

    Now is this a desireable thing? That depends on what you're wanting. I personally like the effects that this proportional stain induces. Being proportional it provides better highlight tonal separation.

    Obviously the same density range can be gained with a non staining developer. It is just a matter of how you want the tonal information rendered.

  4. #4
    fhovie's Avatar
    Join Date
    Mar 2003
    Location
    Port Hueneme, California - USA
    Shooter
    Large Format
    Posts
    1,246
    Images
    92
    "The proportional stain from a pyrocat negative will add appr. .20-.30 density at the upper density regions when evaluated on the basis of blue light transmission."

    The blue channel data is interesting - but the UV channel on the 361t shows densities almost double that of the ortho channel - 1.45 on the ortho channel may be as high as 2.6 on the UV channel - I checked the calbration when I started seeing these differences and the x-rite traceable step wedge agrees.
    My photos are always without all that distracting color ...

  5. #5

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Quote Originally Posted by fhovie
    "The proportional stain from a pyrocat negative will add appr. .20-.30 density at the upper density regions when evaluated on the basis of blue light transmission."

    The blue channel data is interesting - but the UV channel on the 361t shows densities almost double that of the ortho channel - 1.45 on the ortho channel may be as high as 2.6 on the UV channel - I checked the calbration when I started seeing these differences and the x-rite traceable step wedge agrees.
    Yes the stain would be more actinic to UV then blue...almost double in a lot of cases. But the light spectrum most involved in exposing graded papers is probably more blue then UVA

  6. #6

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    [QUOTE]Quote:

    "The unanswered questions are: How significant is the UV share of total light passing through my negatives? What is the Grade 2 paper response to the UV component?"


    No, the first real question is "How much UV light is generated by my enlarger, and is it significant when compared to the spectral response of my paper?"

    Your standard 150W lightbulb produces a very little amount of UV light.
    I'll refer you to Sandy King's nice article on light sources for alt printing - http://unblinkingeye.com/Articles/Light/light.html and then check out this really nice applet http://webphysics.davidson.edu/Apple...l?textBox=3200 for calculating black body radiation - enter about 2800K for the temp of your 150W bulb. I hope you will see after playing around with it, incendescent bulb do not put out much UV.
    Kirk - www.keyesphoto.com

  7. #7

    Join Date
    Dec 2004
    Shooter
    Multi Format
    Posts
    1,670
    What little UV light an incandescent bulb puts out is further attenuated by any glass in the light path. Ordinary crown glass (used in condensers) is only good out to 350 - 360 nm and is totally opaque to UV at 310 nm. Then the glass in the enlarging lens must also be considered.

  8. #8
    fhovie's Avatar
    Join Date
    Mar 2003
    Location
    Port Hueneme, California - USA
    Shooter
    Large Format
    Posts
    1,246
    Images
    92
    It sounds like for enlarger printing - the blue channel is more telling for results - I specifically got the 361t for the UV channel after reading about its use with pyro for several years now. I am just learning how to use it as another tool in my arsenal. Maybe for enlarging decision making I'll stick to the ortho channel and let the UV charicteristics work their serendiptous effects. The UV info will be more pertinent for AZO and a real benefit for dual purpose negatives. I have been using mostly pyro (of several varieties) for years. So I am a fan. Thanks for all the good feedback.
    My photos are always without all that distracting color ...

  9. #9

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Quote Originally Posted by fhovie
    It sounds like for enlarger printing - the blue channel is more telling for results - I specifically got the 361t for the UV channel after reading about its use with pyro for several years now. I am just learning how to use it as another tool in my arsenal. Maybe for enlarging decision making I'll stick to the ortho channel and let the UV charicteristics work their serendiptous effects. The UV info will be more pertinent for AZO and a real benefit for dual purpose negatives. I have been using mostly pyro (of several varieties) for years. So I am a fan. Thanks for all the good feedback.

    Frank,

    Bob Herbst has an article posted on unblinkingeye about the effects of pyro stain when determined by the 361T...as I recall he also has the curves for blue channel densities...it may be that this will help you draw some correlation if you are interested.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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