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  1. #1

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    Grade 0 on VC and graded paper: quality and contrast

    Hello, gentlemen and lady,

    Correct me if i'm wrong. On every VC paper there are two emulsions: low and high contrast. Low contrast emulsion has better tonality, but lacks in contrast. Is it correct that low contrast emulsion is better because the curve is more straight? If that so, what should be the value of contrast of a negative to successfully print on only low contrast emulsion?

    I'm using Pyrocat HD and Fomapan 200, Ilford HP5+, Fortepan 200. May be you've faced similar questions and already know the answers - I'm eager to listen to your words of wisdom.

    Thanks a lot.

  2. #2
    JBrunner's Avatar
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    The more contrast in a negative the "better" it will print with soft filtration, however the exact same print could be obtained with a "normal" negative printed correctly, and still have room for adjustment, rather than trying to match a neg to one end of the printing process. There is nothing "better" about the soft emulsion. The tonality lives in it precisely because it is low contrast. Making a hard negative to print soft, subverts what you hope to gain. It's a zero gain, with some unprintable negs thrown in.

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    JBrunner, thanks for the answer.

    Is my next statement have any sense?

    Using pyrocat we make a negative that prints normally with Azo and Pt/Pd process. Such a negative has a lot of information and still high contrast. Will it be similar effect if we print it on soft end of VC paper?

    Best regards.

  4. #4
    Mike Wilde's Avatar
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    From Memory, CI above 1.8?

    The contrast index, as I recall the term, is used to measure how much light is needed to cause the paper to go from all white to no longer discernable levels of black. Most paper manufacturers discolse this in thier literature, as well as the sensitivity of the emulsion, in an ISO format, which ends up multipluing the contrast range nmumber by 100. So if a paper says at , say for grade 3, .8 to go from white to black it will have arating of 80.

    I am up on this because I was recently gifted a huge whack of old paper. It is still all usable, but not necessarily as originally labelled.

    To test it I project a step wedge on the easel, and use an old verison of what is in essence an exposure meter (melico timer for those who remember that far back) to pick of the time for a lightest grey tone. If a paper says it was say grade 3, and my memory is right that it coresponds to 0.8, and I am using a 0.15 increment step wedge, then I measure the recommended exposure time at 5 steps up from the first not fully clear step. I expose, then develop for a standard two minutes in MG 1+9 developer.

    Once the test strip is dry, I look at it and count the number of steps that can be discerned between all white and full black. If I can still count only 5 steps, then CI if 5x.17 or .75, close enough to 8 for me.

    If the lightest grey is not occuring on the strip where I metered it to be, I go back to the unchanged enlarger projected step wedge, and meter where the actual lightest grey happened. I can then do a bit of math to figure out how relatively sensitive to some arbitrary reference the newly tested paper is.

    I find that old paper that was graded and developer incorporated ( like old agfa 'speed' lines) tends to a) fog a bit, and b) tends to soften with age. If it started out as grade 4, at twenty years ago, it is likely the equivalent to a 2. If it started out as a 2, it might now be a 1.5.

    If it was FB, and not developer incorporated, it is likely still viable. I recently bought 25 8x10 E3SW Kodabromide, expired in '73. for a couple of bucks on a lark, and mostly to puit the envelope it cam in on display with my old products shlef in the rec room, and low and behold it is still as good as new.

    For tanning developers, Sandy King warns that don't develop to thin if you want to print on VC papers, as the green stain tends to counteract the VC filters. Go the other way and developing too long to get higher CI's also will build grain, although the stain of a tanning developer will tend to hide that.

    There is also the issue of unsharp masking to consider in the balance. If you want to unsharp mask, then the resulting sandwich with mask will reduce the effective overall contrast, and then you will need to make sure that you still fit within the 0-3.5 grade window if using VC paper.

  5. #5
    Ole
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    Generally speaking, the density curve for low contrast on VC papers is less straight than for higher contrast.

    Our amazing Norwegian retailer www.fotoimport.no has made this diagram for Ilford MG IV FB, and this one for Varycon KG. He doesn't have curves for the whole range of graded papers, but here are the Emaks papers.

    Even after I've "tuned" the exposure and filtration to give the same tonal range on MG IV FB as on Galerie G1, the graded Galerie still looks contrastier. It isn't; but the straighter density curve gives a better tonal separation where it counts (IMO).
    -- Ole Tjugen, Luddite Elitist
    Norway

  6. #6
    JBrunner's Avatar
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    Quote Originally Posted by SadChild View Post
    JBrunner, thanks for the answer.

    Is my next statement have any sense?

    Using pyrocat we make a negative that prints normally with Azo and Pt/Pd process. Such a negative has a lot of information and still high contrast. Will it be similar effect if we print it on soft end of VC paper?

    Best regards.
    Depending on the particular stain, one of the advantages of pyro negatives is the ability to print happily on both silver, and pt/pd. The stain will have a different density in regard to UV than it will for green/blue or yellow/magenta, so it is quite possible to have negatives that print equally well with both processes.

  7. #7

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    Mike, Ole, Jason, thanks.

    Let me ask another bunch of question.

    Tone separation is a matter of straight part of the curve?
    Amount of tones is the matter of the length of the straight part of the curve?


    So the overall quality is good tone separation plus the amount of tone,is it correct?

  8. #8
    Mike Wilde's Avatar
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    a technical explanation - there may be a simpler way

    tone separation - in a graphical format.


    Almost all of us have at least heard of a film density curve. There is a way to see how it works.

    I have sketched a hypothetical H/D curve for a silver gelatin paper that I recall should come close to a grade 2 or so - it is liner in response to about a CI of about 1.5. (I am winging this from work,; all my references are at home and I am too lazy to look up the info from a vendors web site. )

    I then mimic'ed a dense negative by showing density of a uniform 0.15 increment step wedge running from about 0.07 (typical for the film base plus emulsion fog) to 1.8 - the blackest part of a negative that you would want to try to print (without wanting to resort to dodging or burning in) on silver gelating enlarging paper.

    In my example the steps of different tonality are not uniform in the thinnest are of the negative - which translates to the darkest are of the print. Pre or post exposure flashing could move these tones up the curve to a more linear region, but then all the other levels move as well, and we would be heading into non linearity at the lightest part of the print sooner too.

    As we get above 1.5 in my hypothetical H/D curve the paper reponse begins to saturate, so the curve begins to flatten out. Here the densest parts of the negative do not result in uniform steps of tone change in the print. In this example this could be dealt with by dodging the thinnest areas, or by burning in the densest ares, but either of these are deliberately manipulating the tonal relationships relative to other tones in the original scene.

    One way in this hypotehical case of keeping the tonal scale uniform, while still using this examples #2 grade of paper would be to create an unsharp mask of density range of about 0.35.

    Once the positive mask is sandwiched in register with the negative that here goes to 1.8 the resulting density would be about 1.4 (remenber we now have 2 film bases plus fog). The sandwich would print on this paper uniformly, perhaps with the thinnest part of the negative not even needing the flash with the extra bump in density that the original plus mask base counted in.
    Attached Files

  9. #9

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    Mike, thanks for so informative answer. Now, after all of these answer i have a lot of food for thought.

  10. #10
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    From a design perspective, the gradient of most all negative films is 0.6 and the grade of a normal grade 2 paper is about 2.5. These are taken from the mid scale.

    Since the resultant print is usually 1.5, you can see that the print gamma = film gamma X paper gamma.

    Dickinson and Zawadsky have given the characteristic curves of several makes of VC papers, and Ctein has shown the way it works in his book Post Exposure.

    PE

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