Triple-layer bw dig-neg


#1

Hi Walker,

 

On the altphoto.org mailing list you mentioned a triple layer bw digital negative method. Would you like to explain it here?

best regards,

Kees

 

"If anyone is interested, I have figured out (at least mathematically in my brain) how to profile triple digital negs using PiezoDN. This would work for both “traditional” double or triple, or combo dark/white methods and would work with both carbon and pt/pd using 129 calibration steps."

#2

Here’s the gist of it.

So, basically I figured out that if you “manually” tune 3 curves to print three negs that make up your image, and that image is a standard 129 step PiezoDN target, you can read that target and literally use just that 1 measurement set to linearize all three curves. Because all three curves combine to make the 1 target, methematically linearizing all three of those curves with the measurements from the 1 target should linearize the final print.

The hard part is manually tuning the three curves in the first place. You use the Piezography Curve Adjustment tool for this. Really you can simply tune the three curves exactly the same way you would tune the original photograph in photoshop to print each negative (shadows first, then mid-tones through shadows, then highlights correct?)

The first neg would have to blow out the HLs and have open shadows (so very light).

The second negs would need to still blow the top HLs and be slightly darker over-all.

The third neg would need to be very light/open in the shadows (while maintaining dMax on the darkest 2% to keep tonal separation) while bringing the highlights in.

Combination of the three should give you no tonal reversals on the 129 steps and allow for linearization.

After linearizing all three curves from the first target you should be able to print a totally linear image.


#3

Thanks Walker, thats a clever concept! I really like the curve adjustment tool already. I’ll give this a try on multi layer carbon soon.

Kees


#4

Apologies in advance if I have misunderstood or misinterpreted what you guys are discussing. Are you talking about using 3 separate negs in register for a 3 part exposure? If so, this is stirring a memory from at least 15 years ago. Kees, you may remember some of this if you were on the alt-process list back then.

There was a woman named Amanda something from the UK who came to an APIS conference in Santa Fe in 2001 or maybe 2003. She showed some very fine Pt/Pd prints made with 3 negs - separated for highs, mids, and lows - and printed in 3 exposures prior to development. I don’t recall anything about how she made the negs. There was also a guy whose name I have forgotten from an outfit called Salto (or something like that) that I think was based in Belgium who was doing something like this. I’m positive that he attended the 2001 APIS conference.

There is also the idea of multi-layer printing such as what David Chow was investigating before his untimely death, but I think that is not what you are talking about.

This sounds very interesting if I am following your line of thought, Walker.


#5

Yes, this is essentially what I was thinking. Specifically though, this can add extra metal to the shadow areas, the idea being to maximize dMax of the printed black. Some rumors out there testify that Irving Pen’s triple-print platinums were in the 1.7 to 1.8 dMax range.

-W


#6

Follow the link in my previous post (and the links within it) for more about Penn. But I think he was achieving that deep black by multi-layer printing with separation negs, rather than multiple exposures on a single layer.

I’ve reached Dmax of 1.7-ish with fumed silica as a base layer before coating, but haven’t yet gotten a streak-free print. If that kind of black was more important to my work I’d pursue this route, but at least for now it’s not.

 


#7

That’s very interesting Keith. Your knowledge in these regards is vast. Thanks!

-W