Poor highlight contrast

Discussion in 'Enlarging' started by polyglot, Feb 9, 2010.

  1. polyglot

    polyglot Member

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    Hi all,

    I'm pretty new to this printing thing and I'm having trouble with poor local contrast in the highlights. I have great contrast in the shadows though. I'm doing split-grade printing using a colour head on Ilford MGIV and Kentmere Fineprint VC.

    What I'm doing is this:
    a) find magenta exposure to get max-black somewhere
    b) find yellow exposure (additional to (a)) that gives detail in whites that I care about

    The problem is basically that the shadows are composed mostly of the high-contrast layers of the paper and the highlights are composed mostly of the low-contrast layers. The net effect is all-shoulder and therefore pretty flat-looking because the highlights just don't have that bite. If I combine the two exposures into one (by doing partial settings on the colour head), I get an identical result as expected - it doesn't matter if the blue and green light arrive concurrently or not.

    I find that to get the contrast I want, I'm burning in the highlights with magenta (blue) rather than letting the yellow (green) exposure take care of them. Net result is I can have a flat-looking print that's about the right overall tone, or a more contrasty print that's too dark.

    Is this a fundamental problem with multigrade paper? Do I need to switch to graded paper to solve it? I'm finding that I have (for a given film) a pretty constant ratio of magenta:yellow exposures on the enlarger so I could probably get away with using only a couple of grades.

    Or am I doing something wrong? If I could get better results with my current materials, that would be preferable.
     
  2. Jon Shiu

    Jon Shiu Subscriber

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    Try a weaker yellow filtration.

    Jon
     
  3. JBrunner

    JBrunner Moderator Staff Member Moderator

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    Make the soft evaluation first, then add the blacks. Soft on hard adds more exposure everywhere, so instead get the highlights you want, then add the black you need.
     
  4. polyglot

    polyglot Member

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    Jon: you mean weaker yellow as in a different cutoff wavelength, or yellow with more magenta in it? My enlarger has dichroic filters and turning the knobs just winds the filters in/out. So "less yellow" just means more blue gets in - seems to me it would be the same as extending the magenta exposure. Using actual designed-for-multigrade filters could well be different, I don't know.

    JBrunner: OK, I shall try that.

    thanks guys.
     
  5. Jon Shiu

    Jon Shiu Subscriber

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    Using too high of a yellow filtration can cause a flat tone, ie like trying to print with a grade 00 filter. In cc terms, instead of using, for example 90Y, try 30Y. Does that make sense?

    Jon
     
  6. Marco B

    Marco B Member

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    In my experience, getting highlights to properly print on some fibre based papers is far harder than on RC paper. I recently printed a test print on some AGFA RC that I still had laying around. Good overall tonality from highlights to blacks. I than switched to my Kentmere Fineprint VC and started printing. The first thing I noticed was the lack of highlight detail, compared to the RC.

    This was something I have only subconsiously been aware of before, as I usually don't proof my FB prints with RC.

    However, the solution for me is really to pre-flash my papers. This kicks the highlights into the printable range. With only minimal additional burning in, I was than able to match the RC print.

    I am slowly getting more and more convinced that pre-flashing paper is almost a necessity for all fibre based papers if you want to be able to capture the full density range of a negative... and that means shadows as well, as it will allow shorter exposure times, and a slightly lower overall contrast (although that mainly seems attributable to the lost highlights without pre-flashing)
     
  7. polyglot

    polyglot Member

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    Jon: in terms of discrete filters (00 vs 0 vs 1) it makes sense. In terms of dichroic filters, I'm not convinced it will work due to the mechanics of the filtering but I'll certainly give it a try.

    Marco: indeed, I have a number of Ilford RC prints with lively highlight detail and in comparing them with my Kentmere FB prints thought maybe it was a brand issue. I can check that though because I have plenty of Kentmere RC (ignored up 'til now except to check it's speed against the FB) and a couple sheets of Ilford FB though that's warmtone.

    I'll give the preflashing a shot... do you preflash white? filtered? Seems to me (totally guessing here) it might be useful to preflash magenta to get an upswept curve: high contrast will register immediately in the highlights but the lower contrast won't have any effect until perhaps VI.
     
  8. keithwms

    keithwms Member

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    Polyglot, why don't you post an example.... or link us to one you've already posted...

    RE: preflashing, I usually do three stops under (=shorter than) the normal exposure.

    Note also that with split grade technique you can manipulate any part of the tone curve. But... pardon the insult if it is one... maybe the issue is more to do with your negs? Consider where the details are falling on the density/exposure curve of the film. If the highlights that you'd like to see in the print are way up on the knee, then they will clump/posterize unless you work quite hard in the print phase. If you lower your exposure a bit, some of that highlight detail will slide down along the shin of the curve where it has more slope... hence better highlight differentiation. Of course, shadows will also slide more into the toe, but from what you describe, you can afford that.

    RE: Marco's comment about fiber vs. RC, a big issue for any newcomers to FB is the drydown and how much that changes the apparent contrast. I go at it two ways: (1) print a grade or so more contrasty on FB or at least "bracket" the contrast on a test print that I can microwave and quickly see the result; (2) overexpose the FB print and bleach back a bit. Though this method I find that I can get about as much highlight zing as I could ever want.
     
  9. Marco B

    Marco B Member

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    I preflash with a grade 2. To be honest, I haven't tried any other grades, as I simply assumed using the "ideal" grade 2 would give the best results as it would effect both of the VC "layers". But your thinking may have some usage. Try it out with different grades and report the results here for all of us to learn something new if anything interesting comes out of it...

    In terms of exposure time: as required for pre-flashing, I determine the maximum exposure that still leaves my paper white. On my Laborator L1200 with Ilford Multigrade 500H head, that means 0.4 seconds at F16 and enlarger head set at its highest position.
     
  10. ath

    ath Member

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    Maybe I just simply don't understand this - I always had the understanding that preflashing reduces the contrast in the highlights and adds more detail (bringing back blown out highlights by reduced contrast).
     
  11. Marco B

    Marco B Member

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    If your highlights don't print at all, which is the situation I was referring too, there is no "highlight contrast" :wink:, so if the pre-flashing helps in getting highlights in some parts of the print, it actually increases the contrast there...

    I think it is better to say that pre-flashing reduces or influences the overall contrast of the entire print.
     
  12. RH Designs

    RH Designs Advertiser Advertiser

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    If your highlights don't print at all, your overall exposure is too short. That's exactly akin to insufficient negative exposure resulting in irretrievably blank shadows. As you're split-printing I suggest you establish the soft exposure first based only on the highlights, then use the hard exposure to get the midtones and shadows how you want them. Occasionally if I'm having trouble with a negative with soft highlights I find a preflash followed by a grade 5 exposure only works quite well at adding detail to the highlights without the muddiness that can occur by simply increasing exposure. Flashing certainly does influence the overall print contrast and the best way to establish the right balance of flash and image-forming exposures is by a test strip. Well, several test strips probably! Use white light or a soft filter when flashing VC paper, a hard filter will not work - it just adds overall exposure.
     
  13. Marco B

    Marco B Member

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    Richard, I think these two quotes are slightly contradictory. I don't agree the overall exposure is necessarily to short, and your second remark seems to confirm this, as you state a simple increase of exposure can cause overall muddiness.

    In addition, as I stated with my recent RC / FB experience, sometimes the RC prints proper overall including highlights, while the FB has good midtones and shadows, but fails to print the really dense parts of the negative. Please note that I am talking very dense parts, that usually require some additional burning in as well.

    Flashing can help make these highlights more printable, without altering the overall midtone and shadow appearance to much in my experience.
     
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  15. polyglot

    polyglot Member

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    ath: in my theoretical understanding, preflashing reduces the total dynamic range of the print without changing the slope of the characteristic curve. Some people refer to the total DR as "contrast" and as such it is a reduction thereof. The intention though is to increase contrast (slope of the curve) without increasing DR and thereby blowing highlights. The alternative to preflashing is using a softer filter, which reduces print DR by flattening the curve.

    Yes, it could be my negs. Some in particular are probably overexposed by about a stop but most are not and I'm having this issue on all at the moment.
     
  16. CPorter

    CPorter Member

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    What's on the negative in the area in question, can you examine it with a loupe? Is there noticeable density differences in this highlight area so that you should expect it to print with the desired contrast?
     
  17. JBrunner

    JBrunner Moderator Staff Member Moderator

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    About a stop over exposure is where I aim at for a split grade printing negative. I find contras-tier or expanded negs work better for me with the technique.
     
  18. polyglot

    polyglot Member

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    Yep, there is plenty of detail in these highlights: they show up fine in neg scans and if I print at a higher grade and burn them down instead of using a softer filter.

    I should get to the darkroom on Monday (it's 25km away at the camera club) and give the preflashing and yellow-before-magenta a go.
     
  19. RH Designs

    RH Designs Advertiser Advertiser

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    If there's no tone on the paper in an area where you want some, then the exposure is too short - only exposure to light can put tone on paper. However, because highlights generally fall in the toe of the paper curve contrast will be inherently lower than in light mid tones. So they require a greater exposure increase than would be desirable for the remaining areas. Flashing adds overall exposure, whereas image forming light will add relatively more exposure in less dense areas of the negative. That's what causes the muddiness. A flash exposure sensitises the paper so that even highlight areas start to move out of the toe, increasing contrast, and then a high contrast image-forming exposure is used to produce the mid and dark tones.

    In your earlier post you said you are using Agfa RC and Kentmere FB papers. That's not really comparing like with like. They are very different animals, and I personally much preferred the results I got with Agfa FB paper to Kentmere.
     
  20. markbarendt

    markbarendt Subscriber

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    My understanding of pre-flashing is to get the whole material (film or paper) up closer to the threshold of where it will record detail.

    For paper, pre-flash can easily double the total amount of light that the highlight areas receive.

    In the shadows which are heavily exposed the pre-flash may only increase the total exposure 1/2 a percent so the effect is negligible.

    The risk or limit is simply reaching the point where the paper fogs.
     
  21. Marco B

    Marco B Member

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    I wasn't suggesting they were anything alike, and AGFA MCC was my preferred paper too before AGFA went bust... (the RC variant was just some left over stock that I used). But even so, I have used Kentmere VC Select too (RC), and Ilford RC and FB papers. Although I haven't tested this properly, my gut feeling tells me I always have had a bit more trouble printing highlights on the FB variants...

    Looking at your last post though and the further explanation, I think we basically agree about the effect and usage of a pre-flash :wink:

    Lastly, also taking your own and now Polyglots experience with Kentmere Fineprint VC into account, I think that at least for this specific paper, pre-flashing should be considered in case one has difficulty printing (highlights). My experiences are good with it on Fineprint.
     
  22. RH Designs

    RH Designs Advertiser Advertiser

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  23. dancqu

    dancqu Member

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    Another Approach

    Currently I'm working with the SLIMT. Effectively the thin
    areas of the negative are increased in density. That is,
    shadow areas in the print are held back. The print is
    given a post exposure short soak in an extremely
    dilute potassium ferricyanide solution.

    If interested search via Google for, latent image
    bleaching . Dan
     
  24. polyglot

    polyglot Member

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    How dangerous is this ferricyanide bleaching business? Judging by the name it doesn't sound like something I want to splash around in the dark (ok so it might be post-fix except for you saying it's on the latent image but nevertheless I'll need an open tray of it on my already-full wet-side). Local photo stores don't carry it, so my only option to get it would be if it's safe enough to ship.
     
  25. JBrunner

    JBrunner Moderator Staff Member Moderator

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    It isn't so bad. The cyanide is bound up in the salt. Keep it out of acid and you will pull through. You can order it from PF.
     
  26. Marco B

    Marco B Member

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    Like Jason says, ferricyanide is not something to really worry about, except for not mixing it with strong acids, as it might than release toxic and potentially deadly cyanide gas. I remember one APUG member even saying "you could use it as fertilizer in your garden", as cyanide is a potential nitrogen source for plants, to illustrate how relatively harmless it is.

    To put it also in context: the blue color of cyanotypes is actually a pigment called "Prussian blue", which is made from ferricyanide too, and is complex of iron cations - the ferrous part of the ferricyanide - called ferricferrocyanide.

    And the same pigment Prussian blue is also used in artists oil and acrylic paints, and was used for the famous "bleuprint" technic of copying. Actually, Prussian blue was one of the first chemically synthetized color pigments developed and found its way into oil painting sometime in the 19th century. Before that, most color pigments used in paints were more or less "natural" pigments.

    Marco