[alt-photo] Re: Your Approach to Making Negs for Platinum Printing? Ideal Negative Contrast and Dmax?
donsbryant at gmail.com
Sat Oct 8 21:53:35 GMT 2011
I don't know what the link to the old archives is but there are years and
years worth of discussions there. Perhaps Kees will post the link.
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
Sent: Saturday, October 08, 2011 5:34 PM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: Your Approach to Making Negs for Platinum Printing?
Ideal Negative Contrast and Dmax?
I must be looking inthe wrong places. I figured there must have been plenty
of this discussion before. I'll look through the archive link I have. Maybe
I have a weird link or I just want paying attention. I'll look through it
On Sat, Oct 8, 2011 at 2:29 PM, Francesco Fragomeni
<fdfragomeni at gmail.com>wrote:
> Wow! Thanks for all for all of the info. I'm only working with large
> negatives (I shoot 8x10 and larger) in this case so my follow up is in
> regard to what you posted regarding in-camera negatives and not the extra
> digital stuff.
> "Below are some observations I have made in the past (you will find
> others in the list archives, from me and others). For the traditional Pt
> process, you want a negative with a density range ("DR") of 2.0 or higher
> generally aim for 2.4) to get both Dmin and Dmax in the print. Note that
> not all films available today will produce such a DR, no matter how you
> expose and develop them.
> BTW, I encourage everyone to stop speaking of "stops" and "contrast range"
> -- much better to identify clearly what you mean and speak of "exposure
> scale" ("ES") and "density range" ("DR"), to make sure we are always
> the distinction in mind. On this, see my message of 11 Oct 2009, in the
> archive. For example, while the ES of traditional Pt is around 2.1 to 2.4
> (and, therefore, a negative that produces a full-scale Pt print will have
> DR of 2.1 to 2.4), the full-scale DR of the Pt print itself is much lower
> only 1.4 to 1.7 (the latter only with heroic efforts)."
> I definitely agree with what you're saying. I often get confused with all
> of the different terminology. When you say DR do you mean the range
> FB+F and the most dense tone in the negative? I have a X-Rite transmission
> and reflection densitometer at home and I'm unsure of how to read a neg to
> determine is DR or a prints ER. Is it simply reading most dense area and
> least dense area and taking the difference? My processes are always much
> more visual then technical but I'd like to grasp an understanding of how
> make all of these measurements so that I can empirically understand what
> visually seeing and doing.
> I am specifically interested in figuring out how to properly measure the
> density range in a negative so that I can match my visual understanding of
> what these negatives look like to the actual measurement of the negatives
> density range. I hope that makes sense. I suppose I'm just looking for a
> little clarification on the best practices for using a densitometer and
> to relate the measurements to density range and exposure scale.
> Thanks so much for the help!
>> Francesco wrote:
>> Now that I'm
>>> venturing fairly aggressively into platinum, I'm very interested in
>>> how you all approach making your negatives for platinum. I'm speaking
>>> specifically about in-camera negatives (no digital negs or other
>>> here). Achieving the ideal contrast for platinum is what I'm interested
>>> For silver, a negative with a contrast range of around 3.5 stops will
>>> well on a grade 2 filter or paper. There is also a ideal negative dmax
>>> some people use as a standard to shoot for but I'm not sure what that
>>> is. As I understand it, platinum calls for greater contrast to take
>>> advantage of the longer tonal range of the platinum process.
>> Below are some observations I have made in the past (you will find others
>> in the list archives, from me and others). For the traditional Pt
>> you want a negative with a density range ("DR") of 2.0 or higher (I
>> generally aim for 2.4) to get both Dmin and Dmax in the print. Note that
>> not all films available today will produce such a DR, no matter how you
>> expose and develop them.
>> BTW, I encourage everyone to stop speaking of "stops" and "contrast
>> -- much better to identify clearly what you mean and speak of "exposure
>> scale" ("ES") and "density range" ("DR"), to make sure we are always
>> the distinction in mind. On this, see my message of 11 Oct 2009, in the
>> archive. For example, while the ES of traditional Pt is around 2.1 to
>> (and, therefore, a negative that produces a full-scale Pt print will have
>> DR of 2.1 to 2.4), the full-scale DR of the Pt print itself is much lower
>> only 1.4 to 1.7 (the latter only with heroic efforts).
>> There are two things at work here: (i) matching the negative density
>>> ("DR") to the printing exposure scale ("ES"); and (ii) the character of
>>> exposure scale, however long or short it is. If the DR of your negs is
>>> short to match the printing ES, you'll get low-contrast prints with
>>> (but not very deep) shadows and/or fogged-looking highlights. But even
>>> the negs have the right DR for the process, the characteristic curve of
>>> printing process may be ugly.
>>> The standard long-scale Pt process has a very, very long linear scale
>>> with symmetrical, gently rounded toe and shoulder, typically printing
>>> whole step wedge with some scale left over. Therefore, you need to use
>>> negatives with a very high DR to obtain all of the available print zones
>>> with this process. Photographers have not typically made negatives this
>>> "bulletproof" since the late 19th Century, so folks have tried a number
>>> different methods to shorten the Pt exposure scale (adding dichromates,
>>> hydrogen peroxide, etc., etc.). These tricks shorten the exposure scale
>>> raising the threshold exposure -- not really a very promising way to go
>>> about it. Anybody who has done serious sensitometry with the process
>>> seen the ugly characteristic curves the short-scale versions of the Pt
>>> process produce. I have yet to see prints made using any short-scale Pt
>>> process that came close to the look of "real" (long-scale) Pt prints.
>>> Unfortunately, so many workers are using the short-scale processes now
>>> many people don't even know what a good Pt print is supposed to look
>>> I commend to you an experiment: Make some in-camera negatives with a DR
>>> above 2.1 (try to hit 2.4 for starters), and print them using the
>>> full-scale Pt process. I bet you never go back to digi-neg Pt printing
>>> again, and depending on how big you think prints need to be, that you
>>> acquire one or more LARGE format cameras or learn to make good enlarged
>>> negatives in the darkroom (not so easy now that slow, blue-sensitive
>>> films are long gone). If you have no option besides digital, have a
>>> bureau make some 2.4 DR negatives with an imagesetter using your files.
>> Think of it as mapping. The scene you photograph has a certain range of
>>> luminance values. You want to translate, or "map," these luminance
>>> to useful negative densities, which can in turn be mapped to the
>>> reflection densities of your chosen printing medium.
>>> To do this, we start with the exposure scale ("ES") of the printing
>>> medium. Using calibrated step wedges, we see what range of exposures
>>> the full range of printed tones the medium is capable of producing --
>>> more exposure is indistinguishable from the blackest tone, and any less
>>> exposure is indistinguishable from the lightest tone (paper white, or
>>> to it). Now, if we want the full range of tones the process is capable
>>> producing to be represented in our print [which may not always be the
>>> we know that our negative must have a density range ("DR") equal to the
>>> printing medium's ES. So, we arrange to translate the luminance values
>>> the scene to the particular negative densities that will produce the
>>> tones we want to represent each scene luminance value.
>>> Not so long ago, we did this by adjusting our exposure and film
>>> development, and then perhaps reducing or intensifying the negative or
>>> masking it for printing, and finally by dodging and burning as we
>>> It sometimes took all that, because we have to condense or compress the
>>> 1,000,000:1 luminance range of the scene we photographed (this is about
>>> normal for a sunlit scene) down to the 100:1 (or less) density range
>>> print can reproduce.
>>> These days, people who print digitally can use Photoshop to adjust the
>>> mapping from the as-captured (or as-scanned) image file to the negative
>>> will be used to make the print. This is much easier, and also much more
>>> flexible, than doing it chemically or with masks. However, the goal is
>>> same -- to translate or map certain luminance values in the scene to the
>>> desired print density values, using the negative as an intermediary.
>>> Applying curves is how we do this. It's fundamentally the same as
>>> the Photoshop tonal controls (levels, brightness/contrast, whatever) to
>>> adjust a digital capture for the desired print values (i.e., if you are
>>> printing digital images on paper), with two added wrinkles: (i) you have
>>> understand how the characteristic curve of the printing process responds
>>> the negative values, and (ii) you have to be able to imagine how to "do
>>> in reverse" since you are working on a negative -- if you want the
>>> to have more contrast in the print, you have to increase the contrast in
>>> lightest parts of the negative.
>>> In theory, you can map any scene luminance value (or digital
>>> representation of a scene luminance value) to any available print tone
>>> the caveat that the curve should be monotonic -- never reversing slope
>>> unless you are after special effects reminiscent of the Sabattier
>>> In my view, there is no substitute for learning enough
>>> sensitometry/densitometry to really understand how the mapping works,
>>> then to test your processes to see how they distort the mapping so you
>>> correct for it. It's not very difficult, and once it is mastered you
>>> truly have the chops to get what you want out of your photographs.
>>> So, all that said, back to curves destroying negative content. Mapping
>>> is mapping -- the person who wants to represent the surface of the earth
>>> a flat surface has choices to make, because there is no way to linearly
>>> reproduce the surface of a sphere on a flat surface. And as we learned
>>> grade school, cartographers have come up with hundreds of different ways
>>> do it, each one good for some particular task. If you want to be able
>>> visualize comparative land areas, you use a different projection than if
>>> want to determine bearings from one place to another. The same is true
>>> mapping tonal values in photography. So, the "right" curve is the one
>>> produces the results you want -- i.e., the one that maps the scene
>>> values to the print densities you want. In general, one way I'd advise
>>> folks NOT to do this is to copy someone else's curve "because you're
>>> the same process." No two people ever use the "same" alt process,
>>> there are way too many variables to control. And no two monitors are
>>> same, or scanners, or printers, or Pt "emulsions," or coating
>>> anything else you use to make prints. So, the only way to end up with a
>>> useful curve for your process flow is to test and figure it out for
>>> Generally, one would like to calibrate one's monitor, then build a curve
>>> for each printing process one uses so one can just adjust the image on
>>> monitor (as a positive), then let the computer figure out what negative
>>> densities are required to map the monitor view to the final print
>>> once again, the monitor has a considerably greater luminance range than
>>> print has density range, so it will be a "rendition" of the monitor
>>> not a literal copy). Only you can build such a curve, after doing the
>>> sensitometry/densitometry on your equipment and printing processes.
>>> are aids available, but IMO one is much better off gaining an
>>> of the fundamentals and just doing it -- just as people who really
>>> understood what they were doing always got better results than people
>>> "learned" the "zone" system by rote.
>>> So, if you have a curve that really does translate (transliterate ??)
>>> from your monitor to your prints, great -- it is not destroying
>>> but rather helping you to map values from your digital image file to the
>>> final print, thereby allowing you to do your image adjustment by eye
>>> than by figuring. But if your curve doesn't produce prints that are
>>> pleasingly rendered based on the screen image, you need to change
>>> You can futz around with the process to try to match it to the curve
>>> have, but that's the hard way (and you may well not ever find a
>>> that works as you'd like). Better to adjust your printing process until
>>> get the most linear scale you can (for reasons I won't go into here,
>>> to do with producing the smoothest tonal range), then developing a curve
>>> that translates from your monitor to your prints.
>>> The problem with the "short-scale" versions of Pt is that they have much
>>> less linear tonal ranges than long-scale Pt. You can successfully map
>>> if you work at it, and thereby get correct overall tonal rendering by
>>> a curve that compensates for the nonlinearity. However, you still won't
>>> the smooth transitions that long-scale Pt can produce. And since the
>>> gorgeous tonal rendering is the real draw of Pt in the first place, why
>>> settle for something less just because one would prefer to avoid dealing
>>> with how to make digital negatives of sufficient DR? Particularly given
>>> cost of the Pt process, I just can't see why one wouldn't use it to its
>>> advantage -- which IMO requires using the long-scale process.
>> Best regards,
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