Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,741   Posts: 1,515,567   Online: 939
      
Page 1 of 4 1234 LastLast
Results 1 to 10 of 37
  1. #1

    Join Date
    Apr 2011
    Location
    Denver, Colorado
    Shooter
    Medium Format
    Posts
    130

    Strange light leak from enlarger

    I am having a hard time identifying what is causing this light leak from my enlarger. I am using a LPL Saunders 6700 with color head. The picture below shows the light leaks which shows up around the image projected from a 6x4.5 or 6x6 negative. I have checked the bellows and negative stage but cannot seem to identify the leak path.

    Click image for larger version. 

Name:	light_leak_2.JPG 
Views:	163 
Size:	19.9 KB 
ID:	53003

    It doesn't seem like a reflection or light leaking out from any gap in the enlarger above the lens. The problem seems to be coming directly from the lens. I am using a Rodenstock Rodagon-S 80mm f/4 lens. I don't have another 80mm lens to compare with. But I did switch it to a Nikon 50mm lens. It causes vignetting on the 6x4.5 and 6x6 negative but I didn't see the lines of light leak.

    I could fix the light leaks by putting a dark skirt all around the lens or by hanging some black foam down from the negative carrier platform. But I am not very thrilled about this make shift fix as it gets in the way of reaching the lens aperture etc.

    I am still puzzled as to what these lines that are being projected by the lens? Is it some sort of internal reflection or flare from the lens? I would be hard pressed to believe that the Rodagon lens is the culprit. But could it be? I have put my head on the baseboard to look up through the lens and I don't see anything suspicious to cause these lines. The lens is also mounted securely to the lens board without any gap.

    Any tips or suggestions to help me identify the problem will be appreciated.

  2. #2
    Worker 11811's Avatar
    Join Date
    Jan 2010
    Location
    Pennsylvania, USA
    Shooter
    Multi Format
    Posts
    1,620
    Does your aperture plate or film holder properly mask the negative? Are you using the correct film holder for the negative you are using?

    Are you cropping in on the image, thus leaving some of the image (and some of the enlarger's light beam) outside the borders of the four-bladed easel you are using?

    'Cause here's what I see in the image.. I see that you are using a piece of paper that's larger than the blades as you have them set on your four-blade easel and some of that paper that's peeking out between the gaps in the blades is getting exposed by the "excess" light that comes from the lens because you are cropping too tight.

    Use smaller paper or readjust the blades of the easel so that they don't let some of it peek out.
    OR... Place a piece of cardboard masking on the easel around the blades where the paper peeks out.
    OR... Readjust and re-crop your picture so that light doesn't spill out.
    OR... Check to be sure you have the right aperture and/or film holder in place to match the aspect ratio and/or format of film you are using.
    Randy S.

    In girum imus nocte et consumimur igni.

    -----

    http://www.flickr.com/photos/randystankey/

  3. #3

    Join Date
    Apr 2011
    Location
    Denver, Colorado
    Shooter
    Medium Format
    Posts
    130
    I am using the standard glass less carriers made for LPL 6700 like here:

    Click image for larger version. 

Name:	220666.jpg 
Views:	35 
Size:	8.7 KB 
ID:	53004

    Also, here is a picture of the head on LPL 6700 (not mine, shamelessly copied from Google image search):

    Click image for larger version. 

Name:	2908177012_1526dcc7a5_z.jpg 
Views:	43 
Size:	103.9 KB 
ID:	53005

    I am not cropping the image. The projected image is exactly what I see from the 6x4.5 or 6x6 negative. The stray lines of light are beyond the projected image on baseboard alone (no easel). The lines stay there no matter what aperture I choose on the lens.

  4. #4
    Worker 11811's Avatar
    Join Date
    Jan 2010
    Location
    Pennsylvania, USA
    Shooter
    Multi Format
    Posts
    1,620
    Is the film holder inserted all the way into the gate?

    Does your enlarger have a "beam spread" adjustment used to optimize the lamp position for different film formats? (e.g. You raise it up for 35mm and lower it for 120.)
    Even if your lamp is out of adjustment for the film you are projecting, there still shouldn't be any stray light getting by the film holder. You would just have vignetting or a hot spot/

    There shouldn't be any light getting around the negative. The film holder blocks that from happening unless it's not fitted properly or if the gate isn't closed all the way.

    What if you got a large piece of cardboard, cut a hole in it just big enough for the lens and held it up to the bottom of the enlarger? Would the marks still be there?
    That would prove whether the light is or isn't coming out of the lens.

    I'm a little confused by this... You say that there are four sharply focused rectangles bordering the image? Right? Sharply focused?

    If they are sharply focused, they couldn't be just any old stray light coming from the enlarger.
    I can think of two things would cause a sharply focused edge:
    1) Something AT THE FILM PLANE.
    2) Something ON THE EASEL.

    The blades of the easel, lying flat on the paper, would make any stray light look sharply focused. The only other thing I know that would make sharp edges would be something at the film plane that's letting light through which is being focused by the lens. Even an internal reflection from the lens is likely to be blurry. (Unless the easel blades sharpen it.)

    And, at the risk of sounding like a pain, are you sure you are using the right film holder that has the right sized hole in it which matches the size of the image on the negative?
    If the film holder doesn't match the size of the image on the negative... if the hole in the holder is too large... you will have light leaking around the negative and it could possibly be sharply focused.

    More questions: You are absolutely sure your paper isn't getting fogged by room light or your safelight?
    Are you using a red "safety filter" under the enlarger to focus the image? (Or some setting of the enlarger?)
    I never do that. I always sacrifice a sheet of paper (fix, wash and dry without exposing it so that it's pure white) to put under my enlarger to focus on. I never take my paper out of the box until I'm ready to burn it.

    Are you sure that there is no stray light in the room? No gaps in the safelights? No holes in widow coverings or doors?
    You're not turning on a light in the room or using a flashlight? (Even if it's filtered red.)

    You are using a four-blade easel. Right?
    Randy S.

    In girum imus nocte et consumimur igni.

    -----

    http://www.flickr.com/photos/randystankey/

  5. #5
    Rick A's Avatar
    Join Date
    Mar 2009
    Location
    north central Pa
    Shooter
    Multi Format
    Posts
    5,780
    Images
    31
    I agree with Randy. Looks as though your 4 blade easel is cropped too tight on the size paper you are using. A mask around the easel will alleviate the problem, or make a larger print for that size paper(or smaller paper).
    Rick A
    Argentum aevum
    BTW: the big kid in my avatar is my hero, my son, who proudly serves us in the Navy. "SALUTE"

  6. #6

    Join Date
    Apr 2011
    Location
    Denver, Colorado
    Shooter
    Medium Format
    Posts
    130
    Thanks for all the help again.

    Quote Originally Posted by Worker 11811 View Post
    Is the film holder inserted all the way into the gate?
    Yes

    Quote Originally Posted by Worker 11811 View Post
    Does your enlarger have a "beam spread" adjustment used to optimize the lamp position for different film formats? (e.g. You raise it up for 35mm and lower it for 120.)
    Even if your lamp is out of adjustment for the film you are projecting, there still shouldn't be any stray light getting by the film holder. You would just have vignetting or a hot spot/
    Not that I know of. The lamp position in LPL 6700 is fixed.



    Quote Originally Posted by Worker 11811 View Post
    What if you got a large piece of cardboard, cut a hole in it just big enough for the lens and held it up to the bottom of the enlarger? Would the marks still be there?
    That would prove whether the light is or isn't coming out of the lens.
    I tried that. I still see the stray lines of lights. Thats why I thought that the light is coming out of the lens.

    Quote Originally Posted by Worker 11811 View Post
    I'm a little confused by this... You say that there are four sharply focused rectangles bordering the image? Right? Sharply focused?

    If they are sharply focused, they couldn't be just any old stray light coming from the enlarger.
    I can think of two things would cause a sharply focused edge:
    1) Something AT THE FILM PLANE.
    2) Something ON THE EASEL.

    The blades of the easel, lying flat on the paper, would make any stray light look sharply focused. The only other thing I know that would make sharp edges would be something at the film plane that's letting light through which is being focused by the lens. Even an internal reflection from the lens is likely to be blurry. (Unless the easel blades sharpen it.)

    And, at the risk of sounding like a pain, are you sure you are using the right film holder that has the right sized hole in it which matches the size of the image on the negative?
    If the film holder doesn't match the size of the image on the negative... if the hole in the holder is too large... you will have light leaking around the negative and it could possibly be sharply focused.

    More questions: You are absolutely sure your paper isn't getting fogged by room light or your safelight?
    Are you using a red "safety filter" under the enlarger to focus the image? (Or some setting of the enlarger?)
    I never do that. I always sacrifice a sheet of paper (fix, wash and dry without exposing it so that it's pure white) to put under my enlarger to focus on. I never take my paper out of the box until I'm ready to burn it.

    Are you sure that there is no stray light in the room? No gaps in the safelights? No holes in widow coverings or doors?
    You're not turning on a light in the room or using a flashlight? (Even if it's filtered red.)

    You are using a four-blade easel. Right?
    Let me clarify a few things.

    The picture I posted with stray lights is just for illustration purpose only. This is how I roughly see the enlarged image together with the stray light when I am in the dark room with the enlarger light on. The stray lines of light are being seen on the baseboard (without any easel). They are not sharply focused. The image from the negative is sharply focused but not the stray lines of light.

    I am yet to test a paper after exposing and developing.

  7. #7
    Overkill-F2's Avatar
    Join Date
    May 2009
    Shooter
    Multi Format
    Posts
    10
    Try this, place a negative in the carrier, and lay a strip of black paper on top of the carrier, along one edge of the carrier so it just covers a tiny portion of the negative along it's edge.
    Does the stray light leaks change at all?
    ...Terry

  8. #8
    Worker 11811's Avatar
    Join Date
    Jan 2010
    Location
    Pennsylvania, USA
    Shooter
    Multi Format
    Posts
    1,620
    Well, I'm flummoxed...

    If the film holder is inserted correctly and it is properly locked into the gate, no light should be able to get around the image aperture. (of the film holder.)

    Vignetting from a misaligned lamp is eliminated. The lamp holder is fixed.

    If you have blocked the light from coming out of the enlarger except for what comes out of the lens (using cardboard) then there should be no stray light coming out of the enlarger, itself. All the light hitting the paper must be coming through the lens and, by extension, through the film.

    If you had internal reflections from the lens, hitting the paper where it shouldn't, it isn't very likely that they would form rectangular bars. Most likely, they would be oblong blobs. Neither would they be likely to be evenly spaced on all four edges of the image proper.

    If the bars are blurry along the edges, that tends to rule out gaps between the easel blades but it doesn't completely eliminate the possibility.
    If the blades were down, tight against the paper, they would form sharp-edged shapes. But not all easels hold their outboard edges perfectly flat to the paper, either. Even if they are a millimeter above the paper surface, they'd form "mostly sharp" lines but they might be a hair bit blurry. Regardless, blurry-edged lines score a point against this theory.

    So, what's left? Stray light from the enlarger is eliminated. A misaligned film holder is eliminated. Enlarger blades are partially eliminated. There's not a whole lot left that I can think of.

    Does the size and shape of the rectangular aperture in the negative carrier exactly match the size and shape of the negative? It can be a millimeter or so larger but that's it. Otherwise rectangular bars of light might escape around the edges of the image and they might, very well, have blurry edges.

    I assume that this is what Terry is getting at. No?

    A scan or a digi-photo of an actual print that exhibits this problem would be very helpful at this stage of the game.
    Randy S.

    In girum imus nocte et consumimur igni.

    -----

    http://www.flickr.com/photos/randystankey/

  9. #9
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    3,104
    Images
    46
    If you follow the stray light with a stick does it take you into the lens?

    If you put black paper in the negative carrier and completely cover the opening for film. Do the lines go away as the negative carrier opening is blocked out?

    If so, what happens if you show just a sliver of one edge of the negative carrier? Does one line come back?

    I was thinking it might be reflections off the opening edges of the negative carrier. If the carrier is a full-frame carrier (like a filed carrier would be), then around the negative will be four (or eight) bright lines that can reflect around.

  10. #10
    Overkill-F2's Avatar
    Join Date
    May 2009
    Shooter
    Multi Format
    Posts
    10
    Click image for larger version. 

Name:	Negative Carrier.JPG 
Views:	39 
Size:	9.5 KB 
ID:	53016
    I agree with Bill about the neg carrier edges reflections.
    I have filed the edges of my carriers to an angle around 45 degrees and painted them black to stop this very thing. See the image above.
    ...Terry

Page 1 of 4 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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