[alt-photo] Re: Your Approach to Making Negs for Platinum Printing? Ideal Negative Contrast and Dmax?

Sat Oct 8 21:33:58 GMT 2011

Don,

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
all again.

-Francesco
On Sat, Oct 8, 2011 at 2:29 PM, Francesco Fragomeni
<fdfragomeni at gmail.com>wrote:

> Etienne,
>
> Wow! Thanks for all for all of the info. I'm only working with large format
> 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 (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 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 keeping
> 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 a
> 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 between
> 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 the
> 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 to
> make all of these measurements so that I can empirically understand what I'm
> 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 how
> to relate the measurements to density range and exposure scale.
>
> Thanks so much for the help!
>
> -Francesco
>
>
>> Francesco wrote:
>>
>>   Now that I'm
>>> venturing fairly aggressively into platinum, I'm very interested in
>>> hearing
>>> how you all approach making your negatives for platinum. I'm speaking
>>> specifically about in-camera negatives (no digital negs or other
>>> processes
>>> here). Achieving the ideal contrast for platinum is what I'm interested
>>> in.
>>> For silver, a negative with a contrast range of around 3.5 stops will
>>> print
>>> well on a grade 2 filter or paper. There is also a ideal negative dmax
>>> that
>>> some people use as a standard to shoot for but I'm not sure what that
>>> number
>>> 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 process,
>> 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 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 keeping
>> 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 a
>> 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 range
>>> ("DR") to the printing exposure scale ("ES"); and (ii) the character of the
>>> exposure scale, however long or short it is.  If the DR of your negs is too
>>> short to match the printing ES, you'll get low-contrast prints with murky
>>> (but not very deep) shadows and/or fogged-looking highlights.  But even if
>>> the negs have the right DR for the process, the characteristic curve of the
>>> 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 the
>>> 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 of
>>> different methods to shorten the Pt exposure scale (adding dichromates,
>>> hydrogen peroxide, etc., etc.).  These tricks shorten the exposure scale by
>>> raising the threshold exposure -- not really a very promising way to go
>>> about it.  Anybody who has done serious sensitometry with the process has
>>> 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 that
>>> many people don't even know what a good Pt print is supposed to look like.
>>>
>>> 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 standard
>>> 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 copy
>>> films are long gone).  If you have no option besides digital, have a service
>>> 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 values
>>> to useful negative densities, which can in turn be mapped to the available
>>> 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 gives
>>> the full range of printed tones the medium is capable of producing -- any
>>> more exposure is indistinguishable from the blackest tone, and any less
>>> exposure is indistinguishable from the lightest tone (paper white, or close
>>> to it).  Now, if we want the full range of tones the process is capable of
>>> producing to be represented in our print [which may not always be the case],
>>> 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 in
>>> the scene to the particular negative densities that will produce the print
>>> 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 printed.
>>>  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 that a
>>> 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 that
>>> 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 the
>>> 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 using
>>> the Photoshop tonal controls (levels, brightness/contrast, whatever) to
>>> adjust a digital capture for the desired print values (i.e., if you are just
>>> printing digital images on paper), with two added wrinkles: (i) you have to
>>> understand how the characteristic curve of the printing process responds to
>>> the negative values, and (ii) you have to be able to imagine how to "do it
>>> in reverse" since you are working on a negative -- if you want the shadows
>>> to have more contrast in the print, you have to increase the contrast in the
>>> 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 (with
>>> the caveat that the curve should be monotonic -- never reversing slope --
>>> unless you are after special effects reminiscent of the Sabattier effect).
>>>  In my view, there is no substitute for learning enough
>>> sensitometry/densitometry to really understand how the mapping works, and
>>> then to test your processes to see how they distort the mapping so you can
>>> correct for it.  It's not very difficult, and once it is mastered you will
>>> 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 on
>>> 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 in
>>> grade school, cartographers have come up with hundreds of different ways to
>>> do it, each one good for some particular task.  If you want to be able to
>>> visualize comparative land areas, you use a different projection than if you
>>> want to determine bearings from one place to another.  The same is true for
>>> mapping tonal values in photography.  So, the "right" curve is the one that
>>> produces the results you want -- i.e., the one that maps the scene luminance
>>> 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 using
>>> the same process."  No two people ever use the "same" alt process, because
>>> there are way too many variables to control.  And no two monitors are the
>>> same, or scanners, or printers, or Pt "emulsions," or coating techniques, or
>>> 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
>>> yourself.
>>>
>>> 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 the
>>> monitor (as a positive), then let the computer figure out what negative
>>> densities are required to map the monitor view to the final print (though
>>> once again, the monitor has a considerably greater luminance range than a
>>> print has density range, so it will be a "rendition" of the monitor image,
>>> not a literal copy).  Only you can build such a curve, after doing the
>>> sensitometry/densitometry on your equipment and printing processes.  There
>>> are aids available, but IMO one is much better off gaining an understanding
>>> of the fundamentals and just doing it -- just as people who really
>>> understood what they were doing always got better results than people who
>>> "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 anything,
>>> 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 rather
>>> than by figuring.  But if your curve doesn't produce prints that are
>>> pleasingly rendered based on the screen image, you need to change something.
>>>  You can futz around with the process to try to match it to the curve you
>>> have, but that's the hard way (and you may well not ever find a variation
>>> that works as you'd like).  Better to adjust your printing process until you
>>> get the most linear scale you can (for reasons I won't go into here, having
>>> 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 this,
>>> if you work at it, and thereby get correct overall tonal rendering by using
>>> a curve that compensates for the nonlinearity.  However, you still won't get
>>> 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 the
>>> cost of the Pt process, I just can't see why one wouldn't use it to its full
>>> advantage -- which IMO requires using the long-scale process.
>>>
>>
>>
>> Best regards,
>>
>> etienne
>>
>>
>>
>>
>>
>>
>>
>>
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