Schneider Componon-S 150/f5.6 Focus Shift

Discussion in 'Darkroom Equipment' started by Martin Aislabie, Jul 6, 2008.

  1. Martin Aislabie

    Martin Aislabie Subscriber

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    I bought a 2nd hand 150/f5.6 Componon-S for 5x4 enlargements a couple of years ago.

    I have always focused the lens wide open then stopped down a couple of stops (normally 2 stops to f11)

    However, last night I checked the focus again when I stopped down to f11 and found the focus which had been fine at f5.6 was very slightly out.

    I then did a couple more checks and found that the focus at f11 was indeed different from the focus at f5.6 – and consistently so.

    I can rule out inadvertent movement to the lese stage during stopping down – as it would return to correct focus when the lens was set to its focusing aperture

    I don’t know how old the lens is or its history but externally it looks fine and has not scuff marks or dents to show any damage

    Has anyone else experience of focus shift on Componons?

    Should I just bin it & buy a new lens?

    Thanks

    Martin
     
  2. richard ide

    richard ide Member

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    Just a thought; but check and make sure a cell is not loose.
     
  3. Ian Grant

    Ian Grant Subscriber

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    Strange, I've been using Componon's and Componon S's for quite a few years in various focal lengths and have never had a focus shift.

    Someone on this forum had a very similar problem 6 months or a year ago, it turned out to be the enlarger head was creeping very slowly down the column. It was Durst enlarger in that case, they have a friction adjuster that wears over the years, you just need to tighten them every so often. I have had this happen myself but it showed up far more apparently.

    Ian
     
  4. Martin Aislabie

    Martin Aislabie Subscriber

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    How do I tell if there is a loose element?

    Martin
     
  5. Martin Aislabie

    Martin Aislabie Subscriber

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    Hi Ian, I thought at first I must have been a bit ham fisted and moved the lens carrier as I adjusted the aperture but when I focused at F5.6 and checked it at f11 it was out and when it was set back to 5.6 it was right again.
    I then did it at f11 > 5.6 (out) > f11 – good again
    I also noticed I had to adjust be the same amount (obviously in opposite directions) between f5.6 & f11
    Therefore I am pretty sure I hadn’t moved the lens

    I checked my other lenses (bought from new and carefully looked after) and no focus shift

    I had considered focus shift of enlarger lenses as a historic phenomena – that modern good quality lenses didn’t (shouldn’t) do

    Martin
     
  6. df cardwell

    df cardwell Subscriber

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    How are you evaluating the focus shift,
    by eye, by magnifier, or by the print ?
     
  7. Dave Miller

    Dave Miller Member

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    Consider converting it to a paperweight.
     
  8. Mick Fagan

    Mick Fagan Subscriber

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    Martin, I read this after dinner, before going to develop some film.

    After the film was developed I put a 4x5 neg in and using my 150 f5.6 Componon S I checked out your situation on my own enlarger.

    Firstly I checked it using my Peak grain focus finder, which is about the best in the business, then I did the same thing with my Paterson (small) grain focus finder.

    There was a noticeable difference between the two, but this is mainly the ability to see slightly more stopped down with the Peak, than the Paterson.

    What I found after careful evaluation was that using FP4+ film, set to enlarge onto a 12x16 sheet of paper, I was able to see grain wide open. I then stopped down in ½ stops, with my eye constantly at the eyepiece. I noted that after 1 stop it looked ever so slightly that the focus had shifted, at 2 stops a poofteenth more looking out of focus, 1 more stop to f16 and my eyes just cannot see well enough to figure out what I'm seeing. This was more or less the same for the Paterson, except f11 was it on that unit.

    The thing though, whilst at first it looked as though it was going out of focus, it wasn't, could your problem be the message your eye is sending to your brain, it certainly at first seemed like that to me.

    Then a few times I clicked the lens open, yes it was in focus, that is, I could see the grain. I did this with both grain focusing units, they both did the same thing.

    I then focused at f11, which is the darkest I can see grain at, I then opened the lens in ½ stops and watched the previous thing happen, but in reverse.

    There is of course a bit of a thing happening with our eyes, they really don't see too well as the light level drops, you do have good eyesight I assume? A 150 lens is usually a reasonable amount harder to focus carefully as the enlargement is usually smaller, therefore the grain is harder to see. The light on the enlarger has to work at it's maximum spread, usually making it ½ a stop darker before you start.

    As you have had the lens for some time, am I right in assuming you weren't happy with what you were producing with it?

    Mick.
     
  9. Martin Aislabie

    Martin Aislabie Subscriber

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    I am using a Peak 2000 ? (the metal one)

    I can see the grain fine at both F11 & at F5.6 - but the focus I need is slightly different

    I think Dave is probably right in his analysis - once upon a time it used to be a fine enlarging lens now it is just a paperweight waiting to happen

    Ho hum !

    Martin
     
  10. df cardwell

    df cardwell Subscriber

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    Martin,

    Re-read Mick's post.

    Are you saying the prints are out of focus,
    or are you judging the image in the magnifier ?


    If you focus the image with the Peak,
    and the prints are out of focus,
    then all you have to do is confirm that you've adjusted the eyepeice properly
    (look at the directions packed with the Peak). This IS important.

    'Focus Shift' is a design flaw, not some sort of entropy
    like a toaster evolving into a lawn mower.


    When you stop down, you're have four problems;
    depth of field, a 3 dimensional subject, and diffraction.

    Diffraction reduces the resolution of the lens (as magnified by the Peak).

    AS you stop down, you are now looking at an image with depth,
    as the increased depth of field makes it harder to discern the exact plane of focus.

    Finally, the image is darker, harder to see.

    If the pictures focussed at f/5.6 are not good, and the Peak's reticle is adjusted,
    then the lens might be suspect. But there isn't much that ever goes wrong with an enlarging lens.
     
  11. Martin Aislabie

    Martin Aislabie Subscriber

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    Guys, I have re-read the posts and tried this again

    On every enlarging lense I own (4 off Rodenstock Rodagons of various focal lengths) except the Schneider when I stop down the grain in the Peak stay in focus

    With the Schneider the grain goes a little mushy when closed down 2 stops & comes back sharp when opened up again

    The view on the baseboard stays looking sharp in both cases - to my eyes

    I have not yet tried printing the image at both apatures - but I guess this is the next step and then examining the image with a lupe.

    I don't know what has happened to the lens but I doubt it was designed to do this.

    It is also easy to work around - I just focus when stopped down

    However, if I need to produce top quality prints I will be using a different lens to the Schneider

    Thanks for the help/sugestions & input

    Martin
     
  12. Mick Fagan

    Mick Fagan Subscriber

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    Martin, it does appear that it could become a paper weight, as per Dave's suggestion.

    With the cost, generally, of these lenses still quite cheap and reasonably plentiful, get another one, or something better.

    Once on a photographic hike, were quite cold and wished to make a hot drink, the person with the stove was kilometres away, so we made a fire using winter sunlight and a 50mm lens focusing sunlight on some loose cotton fibres to get a flame, works a treat, perhaps you could use it for something similar?

    Mick.
     
  13. df cardwell

    df cardwell Subscriber

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    Martin,

    Please print with the lens and see if it works.
     
  14. Fred Aspen

    Fred Aspen Member

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    When using a 25X grain focuser, I can see the grain getting mushy around 2-2.5 stops down with all my enlarging lenses and I have a few.

    I believe what you are seeing and what Ctein pointed out in Post Exposure is that the lens is becoming diffraction limited at that point and is an indication that perhaps the Schneider is indeed a better lens than the others you are testing. Ctein's chart shows that most lenses of 2.8 peak at about 2 stops down and lenses of 5.6 aperture are quite often peaking wide open to about 1 stop down.

    I would think DF's advice of making a print is well taken and I would think there is nothing wrong with your lenses other than I would be wondering why the other lenses are sharp beyond their peak apertures.

    -Fred
     
  15. Sparky

    Sparky Member

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    I doubt it's diffraction limitation so much as your eyes not being able to see the grain as clearly. I'm not convinced the human eye is equipped to clearly see that. And it may SEEM as though you're getting a focus shift... but I'd be willing to bet that as you stop down and your DOF increases, the point of optimal focus becomes less and less clear. Especially considering the loss of sensitivity to the eye.

    But if you DO decide to dump the lens... well... I could really USE a paperweight...!!! I'd be happy to cover your shipping...!!
     
  16. Martin Aislabie

    Martin Aislabie Subscriber

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    Sparky - I will continue to use it - I want to try checking the focus in print sharpness

    Also I will try focusing with it stopped down

    But if I do dump the lens I will think of you first

    PM me with your details if you want

    Be warned - the lens is firmly attached to a DeVere Mounting Flange

    Martin
     
  17. Sparky

    Sparky Member

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    I was just kidding martin - trying to suggest that it's actually (probably) a really good lens and you shouldn't even think about getting rid of it unless your prints are definitely lacking relative to other lenses you've used. The other thing we never looked at is the enlarger... if you're using something like a beseler - I could easily see the focus shifting just from turning the diaphragm...

    oh - but i guess it's a devere - so NO chance of lens board movement... I have a 504 too...!
     
  18. Critt VanCranendonck

    Critt VanCranendonck Member

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    The shift is most likely caused by a change in distance between the front and the rear element of the lens. Might be caused by opening the lens to clean the inside and reassembling it a little different as it was before. As long as you are aware of this it is no big issue. You will get sharp prints as long as you focus a second time after stopping down.
    Maybe the shift can be corrected by rearranging the elements. But if you are not experienced in this it might be better to leave it as it is.
     
    Last edited by a moderator: Feb 12, 2013
  19. Andrew4x5

    Andrew4x5 Member

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    Perhaps the issue is caused by the change in depth of field and the thickness of the image layer. At f5.6, you might be focusing on the (for example) surface of the image layer, whereas at f11, you might be focusing on the whole image layer. The following article emphazises that instead of focusing on 'grain', you should focus to maximize image contrast - to quote from page 3 of the article:
    "Good focus is achieved by finding the highest degree of contrast difference between light and dark, in a bit of blurry detail, while avoiding the use of film grain."


    http://cool.conservation-us.org/coo...itale/2007-04-vitale-filmgrain_resolution.pdf
     
  20. DREW WILEY

    DREW WILEY Member

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    I've run into focus shift with a few older as well as second-string enlarging lenses, not with any of my
    apo ones. If this only transpires wide open, you can still get close wise open, then stop down one stop for the final critical focus. No big deal. There some superb camera lenses out there which also have
    focus shift with the first stop. They could have easily corrected such designs, but then the max aperture would be smaller. The lens is likely to still be perfectly usable. But if the focus shift is progressive the further you go, you've got a lemon.