Rodagon Light Leak

Discussion in 'Enlarging' started by Derek m, Feb 25, 2018.

  1. Derek m

    Derek m Member

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    This is an older 50mm 2.8. Where I'm pointing at with the pencil is where the light is coming from. As I adjust the aperture, the darker circle widens. This is not normal with this lens correct? This will be the second defective lens purchase from ebay in a row, which is a shame because the glass is in near perfect condition.

    Also, the glass plate that protects the negative from heat..for b&w printing, is the light blue color an issue or should it be clear?

    Thank you

    *Edit - Sorry..this should have went in the equipment section.
     

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    Last edited: Feb 25, 2018
  2. naaldvoerder

    naaldvoerder Member
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    I use a 50mm Apo-Rodagon N and seem to have a similar "problem", a circular patch of eroneous light. It doesn't affect my ability to primt, as far as I can tell, but it is annoying.
     
  3. OP
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    Derek m

    Derek m Member

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    Really? I printed with it last night and it seemed fine, but yeah, ideally I'd rather have no issues.
     
  4. MattKing

    MattKing Subscriber
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    I would check your light source and your negative holder. This may be from off axis light that is not forming an image from the negative, but still is transmitted through the lens.
     
  5. AgX

    AgX Member

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    The Rodagon has a light-guide illuminator for its aperture scale. That stray light leaking between barrel parts should come from this region. Maybe that guiding illuminator is missing.
     
  6. locutus

    locutus Member
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    cut a thin strip of tape and cover the ring?
     
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    Derek m

    Derek m Member

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    Thanks Matt. I used a pencil to block the area where I'm pointing at and it blocks the light in that area, but I will play around with it some more.

    AgX - The illuminator is there, but that whole section which is part of the aperture ring has wiggle room. So light does seem to be making its way between the barrels.

    locutus - That'd be one fix.
     
  8. locutus

    locutus Member
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    The wiggling might be from the aperture declick mechanism , try playing with that and see what the light leak does
     
  9. sepiareverb

    sepiareverb Subscriber
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    Some liquid electrical tape might be a fix?
     
  10. AgX

    AgX Member

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    Such either will block the light from entering the scale or lock the aperture ring, depending where you apply it.
     
  11. OP
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    Derek m

    Derek m Member

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    So it sounds like it is not normal. Nice to know so I can contact the ebay seller.

    Anyone have thoughts on the color of the glass? Is the blue tint ok or should it normally be clear?
     
  12. AgX

    AgX Member

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    Heat absorbing glass always is coloured.
     
  13. OP
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    Derek m

    Derek m Member

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    Great to know..thanks a lot!
     
  14. Patrick Robert James

    Patrick Robert James Subscriber
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    The first thing to do is to trace the source of the ring of light. Take a pencil and use the tip to throw a shadow in that area. Move the tip of the pencil towards the lens. You should be able to see where the ring is coming from. But...

    That might be coming from something reflecting light between the neg and the lens. I've seen that more than a few times on different enlargers with different lenses. I'd bet anything it isn't your lens.
     
  15. ic-racer

    ic-racer Member

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    Although that light is leaking from the aperture illumination mechanism, many other lenses have off-axis 'leaks' from internal reflections. Many Componon-S lenses have a bright band that one can see by peeking in the lens off-axis. Are you making prints with very white borders wider than the easel blades? If so, you would need to mask the area beyond the blades. If the easel blades cover the off-axis light, you are OK.
     
  16. Hilo

    Hilo Subscriber
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    Just a couple of days ago I had a similar problem with a Computar 50mm and the Valoy II. Not as bright as yours, but a "light ring" for sure. I took out the Computar and with a Focotar the problem was gone. I then noticed the Computar actually came with an extra ring attached to it's rear. When that was removed, the problem was gone.

    So, depending on your enlarger and the yes/no use of an extension ring, the lens may not be fixed well into the screw thread . . .
     
    Last edited: Feb 26, 2018
  17. OP
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    Derek m

    Derek m Member

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    I do see a bright band in the lens. I'm unable to find any problems suggested other than my earlier test with the pencil. When I put the lens cap on, it covers the area where I think the leak is coming from and all of the projected light goes away.
     
  18. Hilo

    Hilo Subscriber
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    In that case someone with an analog repair background should look at the lens. It sounds like inside the lens something is not correctly fixed
     
  19. BMbikerider

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    I have both a 'new' version of the 50.2-8 APO Rodagon and an older 80mmF5.6 Rodagon and neither have that problem. Both have an aperture illuminator. After covering the glass with card and looking at the barrel of the lens with the bulb switched on there was no light coming from the inside of the enlarger head. It could be that an internal light baffle has been displaced and it may benefit from a check by an optical engineer.

    Have you tried getting touch with Rodenstock themselves to get their take on your problem. Don't worry about any language problems, you can use Google translate, but most German firms have people with a good command of English.
     
  20. AgX

    AgX Member

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    The easiest provisional fix would be to cut out the lens cap respectively, put in place, if needed with some sticky interlayer, and use it as aperture ring.
     
  21. OP
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    Derek m

    Derek m Member

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    I am just going to get a refund from the ebay seller at this point. It's the second lens I've ordered that has had problems (the other had fungus). Thanks everyone.
     
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