White easel discovery... problem?

Discussion in 'Enlarging' started by paul ron, Sep 28, 2004.

  1. paul ron

    paul ron Member

    Messages:
    1,896
    Joined:
    Jan 22, 2004
    Location:
    NYC
    Shooter:
    Medium Format
    I have a white easel I have been using for enarly 30 years. Well recently I drew some composition lines on it, a simple thirds grid using a magic marker.

    Last night I was making some prints and noticed faint white grid on my prints. It seems the light is passing thru my paper and reflecting back up thereby fogging my pics but I have never realized or noticed this before.

    I am painting my easel flat black tonight but I'd like to know if anyone has ever had anything like this?... any thoughts about it?

    I'm using Polymax DW Fiber, cold light 23C, 6x7 BTW...
     
  2. gma

    gma Member

    Messages:
    793
    Joined:
    Mar 10, 2004
    Location:
    Texas
    Shooter:
    Multi Format
    This is a really good discovery to share. Fogging like this could go undetected or attributed to other sources. I suppose single weight and RC are more translucent and maximize the effect. My easel is bright yellow and I am not aware of paper being fogged by reflected light, but I will place a black tape stripe on it to check for a reflected image. Thanks for posting your discovery.
     
  3. Dave Miller

    Dave Miller Member

    Messages:
    3,894
    Joined:
    Dec 22, 2003
    Location:
    Middle Engla
    Shooter:
    Medium Format
    This is not neccesarily a problem since normally you are only reflecting back the image that you are printing. However I have always covered the enlarger base with black card to eliminate the effect.
     
  4. TPPhotog

    TPPhotog Member

    Messages:
    3,042
    Joined:
    Jul 15, 2004
    Shooter:
    Multi Format
    I glad this post is here as mines getting a little scratched and the one I got with the enlarger is about the same. It never occurred to me to think about reflected light (Doh). Think I'll follow Dave's idea and get some black card before my next encampment in the darkroom.
     
  5. noseoil

    noseoil Member

    Messages:
    2,898
    Joined:
    Oct 6, 2003
    Location:
    Tucson
    Shooter:
    Multi Format
    I guess you could always put anti-halation backing on all of your paper. I think you may find that your contrast will change a bit when you go to a black background.

    This may be one reason why my azo prints have a bit more contrast than my enlarged prints (aside from the nature of the paper itself). Azo is a single weight paper and I use a sheet of black neoprene as a cushion for contact printing. My enlarging easel is also yellow. Will try printing with a sheet of black interleaving paper under 1/2 of the print, but I don't think a double weight paper lets much of the light through.
     
  6. titrisol

    titrisol Member

    Messages:
    1,671
    Joined:
    Aug 2, 2004
    Location:
    Rotterdam
    Shooter:
    Multi Format
    never thought of that bfore....
    I guess enlarging times will change, same as contrast and sharpness?
    I have a few stains in mine I'll have to look clooser
     
  7. David Ruby

    David Ruby Member

    Messages:
    203
    Joined:
    Sep 17, 2003
    Location:
    Boise, Idaho
    Shooter:
    Multi Format
    Thanks for bringing this up. I think I better do a test as well. I purposely bought a white backed easel because it was easier for me to see the image, but I can see that this could cause problems, especially with single weight paper.
     
  8. Ed Sukach

    Ed Sukach Member

    Messages:
    4,518
    Joined:
    Nov 27, 2002
    Location:
    Ipswich, Mas
    Shooter:
    Medium Format
    Hmm... I have, in my portfolio, a print from my "Carpe Errata" series. This was produced as a result of placing the color paper "wrong side up" on the easel. On exposure I immediately knew it ... color paper emulsion is gray - this was white. I came extremely close to dumping the print without development ... and out of curiosity, put it back on the easel "right" - emulsion side up and, exposed it again, and processed it.
    *Interesting* effect - there are a number of diagonal lines in the image... and there is a "cross-hatching" effect.... another "tool in the box" for the future.

    I'll check it out ... I've estimated that the paper itself (Ilfocolor) will attenuate approximately one - one and a half stops. I'll check it with the ColorStar.
     
  9. gma

    gma Member

    Messages:
    793
    Joined:
    Mar 10, 2004
    Location:
    Texas
    Shooter:
    Multi Format
    Does the white easel cause the print darker tones to bleed into adjacent lighter areas as a result of reflecting from the easel? The reflected image would pass through the paper at a different angle than the original projected image incident angle and the effect would be more pronounced at the borders than at the center where the projected image is straight down into the paper. Very interesting. This could explain loss in edge sharpness that has been attributed to poor lenses.
     
  10. titrisol

    titrisol Member

    Messages:
    1,671
    Joined:
    Aug 2, 2004
    Location:
    Rotterdam
    Shooter:
    Multi Format
    I have to try the black background!

    How did you compensate for focus?
     
  11. Ed Sukach

    Ed Sukach Member

    Messages:
    4,518
    Joined:
    Nov 27, 2002
    Location:
    Ipswich, Mas
    Shooter:
    Medium Format
    Here I go ... quoting myself again.

    I've found that Ilfocolor paper attenuates light coming through it from the "wrong side" 1.31 LogD ... or approximately 2 1/2 stops.

    I've got to try this on more images with distinct diagonal lines. I'd give exposure times more thought, though, based on the density above.
     
  12. gma

    gma Member

    Messages:
    793
    Joined:
    Mar 10, 2004
    Location:
    Texas
    Shooter:
    Multi Format
    Maybe "Carpe erratum" should be the slogan of APUG. I know I have made plenty of mistakes in my sixty years.
     
  13. Dave Miller

    Dave Miller Member

    Messages:
    3,894
    Joined:
    Dec 22, 2003
    Location:
    Middle Engla
    Shooter:
    Medium Format
    I don’t make mistakes; I create learning opportunities! :D
     
  14. TPPhotog

    TPPhotog Member

    Messages:
    3,042
    Joined:
    Jul 15, 2004
    Shooter:
    Multi Format
    Whenever I open a new box of paper I always write off the first sheet to use the back in the easel to focus on. Then when I take the sheet out I know the sheet I'm going to expose it is focused at the same point. Also if the new batch is of a different thickness my focus is still at the same level not that it should vary by much. The black background stays on the easel :smile:
     
  15. gma

    gma Member

    Messages:
    793
    Joined:
    Mar 10, 2004
    Location:
    Texas
    Shooter:
    Multi Format
    I think there will always be enough depth of focus at the paper plane to cover variations in paper thickness. Why not simply use a piece of extra bright white bond paper for the target? I can't bear the thought of wasting a whole sheet from every fresh box of paper. My Scandinavian frugality, I suppose.
     
  16. glbeas

    glbeas Member

    Messages:
    3,307
    Joined:
    Sep 25, 2002
    Location:
    Roswell, Ga.
    Shooter:
    Multi Format
    I just save a wasted sheet, you know, bad contrast or exposure, and turn it backside up for a focus sheet. If you use a grain focuser it generally recommended to use a sheet under it for accurate results.
     
  17. paul ron

    paul ron Member

    Messages:
    1,896
    Joined:
    Jan 22, 2004
    Location:
    NYC
    Shooter:
    Medium Format
    What bothers me is...

    yes the DOF of the lens is enough to compensate for the thickness of the paper but the image was also filtered through and very much difused by the paper. SO relections or this feedback through the paper is causing nothing more than fog in my image. I really never noticed and always thought I was going blind. My grain scope says it's perfectly focused, it looks good but not razor sharp as I once was able to get. I atributed it to the cold light softening my prints.

    I have noticed my few prints I made last night look cleaner now that I am using a black paper under the print. I think my pix are sharper but that is probably just my imagination working hard to justify my observations.

    I'll be playing with this more during the weekend when I have more time.

    Thanks for the feedback.
     
  18. gainer

    gainer Subscriber

    Messages:
    3,725
    Joined:
    Sep 20, 2002
    I'm responding from my own experience. Some time ago I wrote the article "Hazards of the Grain Focuser" for Photo Techniques. I tested red, green and blue separation filters to determine if the spectrral sensitivity of the paper or the eye made a difference. I did a number of trials with each color and without any filter to find mean and standard deviations of focusing errors. I focused for each trial by moving the enlarger head until sharpest visual focus was obtained because movements of the lens carrier would have been too small to measure accurately. I measured focus distance from negative carrier to baseboard.

    You might expect only a difference in standard deviation due to change in focusing color, but there was also a different mean error for each color. The exception was that white and green gave the same result: smallest random error as well as smallest mean error.

    The question of which color was absolutely closest to true focus was answered by making greatly enlarged prints from each mean focus distance. This i did by first making a print on ortho lith film, then using that as a negative to square the enlargement from 10 to 100. The grain in the final photos was convincing: the sharpest focus was obtained at the point of least mean error.

    The conclusion I reached was that the ancient reason for using blue filters to focus telescopes was not applicable to modern enlarging lenses. The focusing error was more likely due to chromatic abberation of the human eye, which is easily demonstrated. This effect has been known to astronomers for a long time: the aberration of the eye increases the apparent aberration of a refracting telescope.

    Thus, the sharpest focus of an enlarger will be obtained by either white or green light because the acuity and sensitivity of the eye are both greater there. Modern enlarging lenses are achromatized very well over at least the blue and green, so the best strategy is to favor the optimum color for the eye.

    Now as to thickness of the paper, I used in my tests the optimum aperture for the lens I had, an El Nikor f/2.8. The visible grain was sharpest at the 5.6 aperture. The smallest average error in focusing was considerable more than the thickness of the printing paper, and the mean square deviation was greater yet.
     
  19. gainer

    gainer Subscriber

    Messages:
    3,725
    Joined:
    Sep 20, 2002
    I forgot to mention that one of the effects of halation is a decreas in contrast. It is not necessary to use black on the easel unless you are using panchromatic paper. A yellow easel or one that looks like the VC safelight should do the job and might still be bright enough for composition. The grain focuser won't see the color of the easel anyway.
     
  20. sergio caetano

    sergio caetano Member

    Messages:
    127
    Joined:
    Aug 16, 2003
    Location:
    sao paulo -
    Paul
    You did the right thing painting your easel black, otherwise there will be reflection in the back of paper. That is what I also did. I don't know until now why manufacturers make them white.
    "The usual white surface is excellent to focus upon, but..... an appreciable fogging effect..... (so) a back of dark cardboard should always be used ..." (AA ; The Print)
     
  21. bazz8

    bazz8 Member

    Messages:
    25
    Joined:
    Aug 9, 2004
    Shooter:
    35mm RF
    Easel discovery

    A phototeck showed me this earlier this year and it definately makes a difference to the base fog as for focus simply expose a sheet of paper for 1 or 2 minutes develop and fix ,dry etc for the size prints you are using eg 10x8
    11x14 to focus turn the paper over and focus on the white side when final exposure is ready turn the paper over and the black side up it works and is what i call a 10% er
    regards
    bazz8
     
  22. argentic

    argentic Member

    Messages:
    1,722
    Joined:
    Sep 7, 2002
    Location:
    Echandelys,
    Shooter:
    4x5 Format
    Hi,

    I've had this very same problem many years ago. I immediately painted my easel flat black, and exposure times increased !

    And yes, this paper backlighting makes for less sharp prints, because the reflected light is more diffuse than the direct enlarger light. Even if the difference was small, I could see it. (I still had young eyes back then.) It's another factor to eliminate if you want to produce topnotch prints.

    G.