why is my focusing off?

Discussion in 'Enlarging' started by jordanstarr, Aug 10, 2011.

  1. jordanstarr

    jordanstarr Member

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    It happened just now and I can't fix it. I focus my print, run it through and it comes out not-in-focus. I readjust, act quickly and it's still out of focus. So, I adjust the tension knob on my 4x5 beseler and still the same problem. What I found out is that when I look through the grain focuser and hit the expose button, it starts out of focus and comes into focus gradually over 15 seconds. Any thoughts on solving this besides waiting with a shhet under the lens 20 srconds before exposure?
     
  2. Dear

    Dear Member

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    I tried something like it once.
    No matter what I did, I just couldn't get it crisp after the enlarger.
    Turned out that I had exposed the whole thing through the back of the paper!
    It was matte paper so it was difficult to see which side the emulsion was on.
    But that doesn't sound like what you're dealing with, since you say it gradually get's to focus? :confused:
     
  3. bdial

    bdial Subscriber

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    Is this a color head with a fan?

    If the lens stage isn't moving and the head assembly isn't moving, you shouldn't see any change. is it possible that your eye is adapting with the grain focuser, and the image is out of focus the whole time?

    What happens without the grain focuser, can you see the same change when you switch on the enlarger?
     
  4. paul ron

    paul ron Member

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    Negative buckling from the heat?

    What size neg are you printing?

    Try a glass neg carrier.

    .
     
  5. jeffreyg

    jeffreyg Subscriber

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    With some grain focusers you can focus its eyepiece. Mine has an etched square on the mirror and the the eye piece can be focused first. Also I put a piece of print paper (previously processed) in the easel with the grain focuser on top of it. If the negative is popping, wait the 20 seconds before focusing.

    http://www.jeffreyglasser.com/
     
  6. bobwysiwyg

    bobwysiwyg Subscriber

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    My thought as well.
     
  7. Ian Grant

    Ian Grant Subscriber

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    Sometimes the head on enlargers slip, they usually have a counterweight or spring system. This happens with Durst's and some other makes because the pressure pads wear, these lock the head assembly and it's very simple adjustments to cure the problem. Ironiocally the head creeps up the column.

    Ian
     
  8. Ian C

    Ian C Member

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    The problem is almost certainly the negative warming from the heat contained in the light passing through it. That makes the part of the negative exposed to the light expand as it warms. The rest of the negative is clamped by the metal carrier and stays cool and doesn’t expand. The expanded film must go somewhere, and it does.

    It warps getting a pregnant belly upward and out of the shallow depth of field projecting a fuzzy image. At the same time, other parts of the negative that stayed within the depth of field project a sharp image.
    To keep the negative cool the enlarger must be equipped with a heat-absorbing glass filter. That’s a special type of glass that contains an iron compound that absorbs the excess heat from the light passing through it. The HA glass actually gets quite warm in the process. Regular glass is worthless in this function, because it is transparent to heat.

    The HA filter is placed below the lamp before passing to the condensers, although some older machines had the HA filter placed between the two condenser lenses. The glass sheet negative carriers are also used to keep negatives flat during projection. They’re expensive and introduce 4 additional dust-catching surfaces.

    Diffusion enlargers, like most dichroic color and VC enlargers, have the filter placed between the lamp and the mixing chamber. Omega dichroic enlargers place the filter on the side of the mixing chamber. Dichroic filtered diffusion enlargers tend to run relatively cool.

    Even so, for really long projections, such as must be the case when making large prints, require glass carriers to keep the negative flat, because such long projections allow the heat to build sufficiently to pop the negative out of the plane of focus.

    Sometimes the center is sharp, but one or more of the edges is fuzzy. This can happen if the lamp is on long enough to pop the negative. The center is bellied up and brought to focus. But the outer regions are below the center and defocused.

    I’ve found that by adjusting the focus so that the grain is sharp through the grain magnifier the moment that I snap on the lamp and watching until the negative begins to defocus due to heating, I can establish the time limit during which the image stays sharp.

    Suppose that a negative that is initially in focus will stay sharp for at least 7 seconds. By dividing the exposure into segments no longer than the safe limit, I can make much longer exposures as needed to make large prints. I do this by making shorter exposures with, say 10-second cool-down periods in between.

    For example, if my test strips indicate 34 seconds, then I can make 5 exposures of 6.8 seconds. For 23 seconds 4(5.8seconds) = 23.2 seconds. The extra 0.2 seconds is meaninglessly small.

    Pre-heating the negative is a poor solution. If you focus the center of the image, then the edges are still held at or close to the original plane and cannot move upward due to heating. Focusing a “popped” negative gives a sharp center that tapers into fuzziness as you move out radially.
     
  9. pentaxuser

    pentaxuser Subscriber

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    IanC The way the OP describes his problem it sounds as if the heat warping actually brings the neg into focus - admittedly the exact opposite of what you'd expect.

    Beat me.

    pentaxuser
     
  10. Bob Carnie

    Bob Carnie Subscriber

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    Jordan If you are not using glass carriers this will be a constant PIA.
    If you are using glass carriers then something needs fixing on your setup.

     
  11. Ian C

    Ian C Member

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    It can happen that way if the negative is first allowed to heat sufficiently to “pop” it, the central area of the negative is focused in the popped condition, and then the lamp is switched off.

    The negative is thin and cools quickly allowing it flatten back into the original plane while the paper is positioned on the easel.

    Then the moment the lamp is switched on the image is fuzzy because the central part of the negative has cooled and dropped below the plane of focus. But when the timer is tripped, the negative heats and the central area slowly bellies back upward to where it was focused when hot, the image goes from fuzzy to sharp—at least in the central area—during the heating period until the negative is once again fullypopped. But during the transition the sharpness of the projection varies. The result is an unsatisfying print that lacks the full sharpness the negative and lens can deliver.

    The cure is to install heat absorbing glass. This costs about 0.3 stops per sheet. The HA glass supplied with US enlargers is 1/8” in thickness.

    I found that the flatness of my heated negatives was greatly improved in my Beseler 23C II condenser enlarger by installing a single sheet of HA glass, but dense negatives requiring long exposures still got slightly fuzzy over long exposures of, say, 30 seconds or longer. This enlarger is equipped with a 75-watt opal enlarger bulb (horizontal burn PH-111 or vertical burn PH-140, depending on when it was made).

    I removed the sheet aluminum filter drawer from the lower filter slot so that I could install a SECOND sheet of HA glass. With 2 sheets of HA glass the negatives apparently don’t move at all even during exposures of up to 60 seconds or more. The 2 sheets of HA cost me 0.6 stops, but that’s a small price to pay for negatives that stay flat and well focused throughout the exposure.

    Since I’ve used up both filter slots with HA glass I’m forced to use the Ilford below-the-lens Multigrade filters. They work great and don’t degrade the image a bit.

    Some folks use expensive glass carriers, but the excess heat really should be eliminated first before going to a glass carrier. It might be that exceptionally long exposures, such as making a horizontal projection on mural paper (I think Ilford supplies this up to 56” wide) might require a glass carrier in addition to HA glass.
     
  12. Monito

    Monito Member

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    Actually, that's what you would expect.

    While you are focusing, the heat warps the negative. By time you chase the changing focal plane and get it into focus, the negative has reached equilibrium. Then you turn off the lamp and go to get the paper. The negative now has time to cool and warp back down into the cold equilibrium position.

    By time you get the paper, put it in the easel, position it, close the easel and reach for the timer, the negative is out of focus. Then when the timer comes on, the heat starts warping the negative back into the position it was finally focused at. It might never have time to get there and even if it does, the percentage of time spent at that state may be a small part of the timer exposure.

    These are the symptoms the OP describes.
     
  13. jnanian

    jnanian Advertiser

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    sounds like the head might be slipping down the column too ...
     
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  15. Ian Grant

    Ian Grant Subscriber

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    Usually they move up the column because the couter weight spring has to be stronger than the gravvitational effects of the mass of the head. :D

    Ian
     
  16. Bob Carnie

    Bob Carnie Subscriber

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    On my Omegas I have seen the bellows drop if not well maintained.
    This requires some tightening , this usually happens with 35mm position on my systems.
    Once a year I have a tech look at this issue on the Omegas, the durst and deveere never have this slippage.



     
  17. DREW WILEY

    DREW WILEY Member

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    Whenever I need to use a 50mm lens for 35mm work, I also use a recessed board for either the Omega
    or the Durst enlargers. Generally I prefer a longer lens, but there is the risk on the Omega of the bellows
    slipping if overcompressed. The idea of not using a glass carrier in an enlarger seems utterly barbaric;
    holding precise focus would seem impossible.
     
  18. jordanstarr

    jordanstarr Member

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    Thanks guys...

    I was also thinking it could be heat warping the negative, but the problem is that it hasn't done this before and then suddenly after 40 perfect prints with my new enlarger, they all start doing this? I have a glass carrier I will try and customize to fit the beseler.

    I can literally watch the negative come into focus, which supports the heat/warping theory, but could it be something else? A power supply maybe? I know intensity of light doesn't effect the focus, it's the negative plane. But any other theories before I dive back down there?
     
  19. Bob Carnie

    Bob Carnie Subscriber

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    Can't agree more strongly.
     
  20. mwdake

    mwdake Member

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    I have a D5 that does exactly that, the head does not move but the bellows lock is a bit loose and I have seen it creep down and watched the focus change.
     
  21. Monito

    Monito Member

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    The idea of using a glass carrier seems barbaric. I've enlarged glassful and glassless and I prefer the latter for cleaner results. Less spotting.

    However, that is for 35mm negatives. I haven't enlarged 8x10, but it seems that people like Clyde Butcher use glass for 8x10 negatives.
     
    Last edited by a moderator: Aug 10, 2011
  22. Monito

    Monito Member

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    The timer does not control bellows creep or column slip. Any relationship would be only coincidental; though absent more info from the OP, creep/slip is an outside possibility.
     
  23. 2F/2F

    2F/2F Member

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    The negative could be moving, or the focusing gears could be slipping. The latter used to happen all the time on my Beseler B22 until I did a "CLA" on it. It's a cheesy enlarger, but the plus side is that it is extremely easy to take apart and adjust. So, I would check both possibilities, though I cannot say I have had the buckling issue with anything but an open 4x5 film carrier. Do you use tape to hold your film down flat?
     
  24. Monito

    Monito Member

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    Jordan, you stated the enlarger is 4x5, but what size negatives is this occurring with? 35mm, 120, 4x5?
     
  25. paul ron

    paul ron Member

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    The negative probably was focused with the heat build up during focusing of an already popped neg. So as the negative cooled again it is out of focus on the start exposure n returns in focus as it warms up again.

    3 solutions.....
    1--Heat absorbing glass is what you need or maybe an extra like I did. I put another HAG in my 4x5 Besseler right in the filter drawer as well as using the standard one in the head. That huge bulb get things pretty hot in there.

    2--Glass neg carrier

    3--- Best solution of all.... Cold light, unless you are doing color work. I converted a long time ago and will never go back to tungstin again.

    .
     
  26. jordanstarr

    jordanstarr Member

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    It couldn't be the column slipping. I tightened it so much that I could barely focus.

    I'm using 35mm negatives. I never had a problem before. I've used glass negative holders before with the exact same results, so I went glassless for the last 2 years and never had an issue with unsharp corners or uneven focusing problems.

    I've had the beseler 4x5 enlarger for 2 months and have been printing medium and 35mm negatives up to 20x24 with amazing results. This only happened last night on all 3 negatives I went in to print. I ended up just focusing, then starting the time 20 seconds before the exposure and all my prints were great after that. It made burning and dodging a huge pain, but I just rolled with the punches. My glass carrier won't fit my beseler, so I'll have to hunt for a new one or make my own. I'm not huge on the idea of spotting more than I need to, but I'm pretty good at it and I guess I'll just have to go that route. I've lowered the top bellows further from the light source so I'll see if I can go that route for a while.

    The only reason I can imagine this issue occurring now is that I had a huge flood in my darkroom last night as well, spent 3 hours cleaning it up, but noticed it was extra humid. I'm wondering if the combination of the heat from the lamp and the humidity in the air had something to do with the negatives buckling? Maybe someone could elaborate on that theory?