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  1. #21

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    Quote Originally Posted by pentaxuser
    Ed. Only veering away slightly from your statement, I hope, but is there any truth in the statement in the F Schultz article on the Colourstar 3000 that when choosing an aperture for exposure it is important to aim for between 5-10 secs. Frances says: shorter exposures may be "hot" (colour balance affected? Unfortunately Frances doesn't elaborate) because of the warming and cooling of the lamp; longer exposures may run into problems with reciprocity failure"
    Dear Pentaxuser,

    As Frances Schultz's husband, perhaps I may step in here.

    The heating and cooling of the lamp is indeed the factor that is relevant. Yes, there is a risk of a shift towards red: sorry she didn't say any more about it, but there are always word-count constraints. The shift varies from enlarger to enlarger depending on wattage, voltage, bulb design and (as usual) intangible variables such as the phase of the moon. By 5 sec minimum this should be negligible with all designs; with some, it may be OK at 3 or so.

    As for the 'is there any truth in it', well, yes, we try to make most of what we write reasonably true. We are among the ever-fewer journalists and authors who do this because we love it. It sure as hell isn't for the money!

    Cheers,

    Roger (www.rogerandfrances.com)

  2. #22

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    Quote Originally Posted by srs5694
    I've not done this over the whole range, and I didn't pay much attention to reciprocity effects, but I have done it over a few f-stops. There are definite and visible differences with my 4-element 50mm lenses (Nikon el-Nikkor f/4, Durst Neotaron f/2.8, and Industar-96U f/3.5), with f/8 seeming best of the apertures I tested with all of them. My 6-element Nikon el-Nikkor f/2.8 shows much less in the way of differences across apertures. Testing across the entire range, I don't know how noticeable those differences would be.
    I'd agree. Most enlarger lenses I've tried, good or bad, regardless of the number of glasses (3, 4 5 and 6 in the ones I've used), have a 'sweet spot' which may be limited to a single aperture (such as f/5.6-and-a-half = f/6.8) or may extend across a couple of stops or more. In this 'sweet spot' results are visibly better than at larger or smaller apertures.

    I'd also agree with Ed that manufacturers ain't stupid, but add to his observations that sometimes the maximum and minimum aperture are there to be used only in desperation: wide open and f/16 (or f/22 if available) are unlikely to be the optimum.

    Cheers,

    Roger (www.rogerandfrances.com)

  3. #23

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    Quote Originally Posted by Roger Hicks
    Dear Pentaxuser,

    As Frances Schultz's husband, perhaps I may step in here.

    The heating and cooling of the lamp is indeed the factor that is relevant. Yes, there is a risk of a shift towards red: sorry she didn't say any more about it, but there are always word-count constraints. The shift varies from enlarger to enlarger depending on wattage, voltage, bulb design and (as usual) intangible variables such as the phase of the moon. By 5 sec minimum this should be negligible with all designs; with some, it may be OK at 3 or so.

    As for the 'is there any truth in it', well, yes, we try to make most of what we write reasonably true. We are among the ever-fewer journalists and authors who do this because we love it. It sure as hell isn't for the money!

    Cheers,

    Roger (www.rogerandfrances.com)
    Roger. Thanks for the reply. I should have read my post more carefully before sending. An unfortunate phrase that I used unthinkingly does give the impression that by implication I was calling your wife's truthfulness into question. This of course wasn't my intention and I apologise for this. Please convey this apology to her.

    I should simply have asked the question in a neutral manner what effects short exposures have on colour printing and what factors play a part in such effects.

    You and several others have been good enough to answer. I had received a copy of your wife's article with my secondhand Colourstar and found it a useful read, especially as it was written from the point of view of someone getting acquainted with the Colourstar as I was.

    I had found the actual manual quite hard going. Like most user manuals they are written by people who are too familiar with the equipment to recognise the difficulties a newcomer might have. Her step by step approach written in an easy to understand manner was very helpful.

    It's a pity that Frances wasn't given the space to expand. I might have learned to recognise when fully intergrated measurement was most and least appropriate and how to tackle other printing difficulties.

    I previously used a Paterson analyser which only had a fully intergrated measurement system and lacked the sophistication of the Colourstar. However I have to say that in a comparison of prints produced with both analysers I cannot honestly say that the Colourstar prints have been better.

    I have yet to find a good "How to" colour neg printing book( any suggestions welcome) which comes close to the books that exist on B&W and courses on the subject seem to have gone the way of the airship as a means of flying.

    Maybe Frances and other practioners could be persuaded to pen some articles but that's another issue.

    pentaxuser

  4. #24

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    Quote Originally Posted by eumenius
    Dan, that's so strange to hear that about Meopta -
    I always considered their quality to be quite good,
    at least their older stuff is made very well. Cheers,
    Zhenya
    It is a Opemus 6 with Color 3 head. I bought my
    first 6 in 1961. I liked it so bought again in 1999.
    VC papers are what I had in mind but have gone
    back to Graded.

    I've a new Beseler 23CIII in mind. If Meopta had
    a US distributer I'd consider the Magnifax, condenser.
    They do a fine job of metal work. Their castings are
    very well done. Dan

  5. #25

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    Dear Pentaxuser,

    Your apology is more than accepted. I didn't mean to sound quite as pettish when I replied, so I apologize too. Frances is perfectly happy.

    Cheers,

    Roger

  6. #26

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    Quote Originally Posted by Roger Hicks
    Dear Pentaxuser,

    Your apology is more than accepted. I didn't mean to sound quite as pettish when I replied, so I apologize too. Frances is perfectly happy.

    Cheers,

    Roger
    Thanks. You didn't.

    pentaxuser

  7. #27
    Ed Sukach's Avatar
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    Of course there is a "best" - optimum aperture - in ALL lenses. That is NOT restricted to enlarging lenses alone. In the design specifications, every parameter is given as a center "target", with acceptable limits either way.

    What continually amazes me is the brittleness of some who use those lenses. There is something of a "perfectionist cult" out there that does propagate the idea that "Only the OPTIMUM MUST be used!!" Unfortunately, this philosophy necessarily LIMITS the flexibility of use. Most photographers will not hesitate to use a camera lens over a wide range of apertures; yet some of the same photographers will use only ONE stop in enlarging.

    One useful flexibility is the depth of focus (remember this is a projection lens). A wide (? "deep"? "extensive"? - a whole lot) is a definite disadvantage in focusing the enlarger. The use of the maximum aperture results in the most "snapping" into place when focusing, and stopping down from there adds a cushion, minimizing errors. Additionally, if one has ever employed "The Brick Trick" (note 1) - tilting the easel to correct perspective issues, the value of using the smallest available aperture for its great depth of focus becomes apparent.

    Here I write about "acceptable" limits. There are those who will cry, "There are NO acceptable limits! Everything MUST be PERFECT!" Good luck to them! It is certainly noble to try to do the "best we can", but after the twentieth or thirtieth print (don't laugh, it has happened to me!) there is a time to stop - and consider the realities involved: No work, in photography, or art, or any other human endeavor, will ever be perfect. All we can hope for is producing an "acceptable" print (and I think my standards of acceptability are pretty damned high - certainly higher than I've seen in some exhibition printing) in the most efficient manner possible.

    Personally, I have never found my "standards" compromised by the use of ANY aperture of any enlarger lens. Certainly there is a DIFFERENCE - but , paraphrasing Isaac Asimov, there are a whole lot of factors other than enlarging lens apertures that are far more significant in enlarging.

    All that above must be protected: My Opinions - Your Mileage May Vary.


    Note 1: From a Camera and Darkroom article of the same title. I miss that magazine!
    Carpe erratum!!

    Ed Sukach, FFP.

  8. #28

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    Ed,

    your words seem to be very true - I really can't see much difference in my Fujinon EX 50/2.8 and 105/5.6, and Rodagon 80/5.6 lenses behaviour on their maximum aperture and, say, f/max+2 stops. I made the normal-sized prints (8x10'') and a maximum magnification possible prints, and the grain pattern is as crisp as it could be from this negative. Some stopping down doesn't alter the picture significantly, or that's just my eyes that lie There's indeed some very slight subtle change - but it doesn't change the picture, really Looks like the optical designers really know their stuff, don't they?

    Cheers,
    Zhenya

  9. #29

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    [QUOTE=Ed Sukach] There is something of a "perfectionist cult" out there that does propagate the idea that "Only the OPTIMUM MUST be used!!" Unfortunately, this philosophy necessarily LIMITS the flexibility of use. Most photographers will not hesitate to use a camera lens over a wide range of apertures; yet some of the same photographers will use only ONE stop in enlarging.

    Here I write about "acceptable" limits. There are those who will cry, "There are NO acceptable limits! Everything MUST be PERFECT!" Good luck to them! It is certainly noble to try to do the "best we can", but after the twentieth or thirtieth print (don't laugh, it has happened to me!) there is a time to stop - and consider the realities involved: No work, in photography, or art, or any other human endeavor, will ever be perfect. All we can hope for is producing an "acceptable" print (and I think my standards of acceptability are pretty damned high - certainly higher than I've seen in some exhibition printing) in the most efficient manner possible.
    QUOTE]

    I couldn't agree more. My only caveat would be, "Work as close to the optimum as makes sense. After that -- the picture is the thing, not theoretical perfection"

    In other words, if you can work at the optimum aperture, do. If not -- well, as you say, that's why the other apertures are there!

    Betcha, though, that there are tech-nuts who would criticize your prints on purely theoretical grounds, even if (a) they're superb pics and (b) the tech-nut couldn't begin to come close, even technically.

    Cheers,

    Roger (www.rogerandfrances.com)

  10. #30
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    Observing a projected B&W image through a grain magnifier while varying the aperture is illuminationg (groan. It's the best pun I can manage in the mornings). With a good lens, fine grain can start to get slightly mushy below f/5.6. That's a problem? If a client persists in examining my prints with a 10X loupe, I'll not stop down below f/8. Nor will I use the maximum opening. There is some vignetting with my EL-Nikkor 50mm f/2.8 wide open. My biggest objection to limiting the small apertures on an enlarging lens is the small depth of field when used as a camera macro lens. Life is too short to waste time enlarging at f/32.

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