U of S | Mailing List Archive | alt-photo-process-l | RE: digital negative possibilities for gum

RE: digital negative possibilities for gum

Hi Katherine, this has been a very thought-provoking thread and I liked the
clarity of this post. It is so easy to unintentionally mislead students!


-----Original Message-----
From: Katharine Thayer [mailto:kthayer@pacifier.com] 
Sent: Saturday, 21 October 2006 5:49 a.m.
To: alt-photo-process-l@usask.ca
Subject: Re: digital negative possibilities for gum

On Oct 20, 2006, at 5:44 AM, stwang@bellsouth.net wrote:
> And each of these affect how the resulting gum print would look
> like. And each will need a different curve and a different way of  
> printing.

I think this last point is especially well taken, and should provide  
a warning against reading too much into comparisons where the  
printing method is held constant across different negative types or  

We think we're making our results more interpretable or generalizable  
by holding everything constant, but in many cases we're doing the  
opposite.  For example, I've been puzzled in the past by  
demonstrations that compare the DMax or contrast for different  
concentrations of dichromate, keeping the exposure time and  
development time constant.  Of course, if you're going to go that,  
you can show anything you want by choosing an exposure time that  
favors the conclusion you want to draw.  But the only reasonable and  
meaningful way to compare the contrast and DMax of different  
concentrations of dichromate, is to print each concentration at its  
natural exposure time, which will be different for each dichromate  
concentration (since speed varies directly with concentration)  and  
compare the contrast and DMax of the resulting prints that are  
properly printed for the dichromate concentration.

By the same token, if you compare different negative types using the  
protocol for one negative type  as a standard protocol applied to all  
the different negatives, then the negative type whose protocol you  
used  will of course come out looking best, because the protocol is  
calibrated for that material.  But it would be misleading to say that  
means that material is better just because it looks better in a side  
by side comparison of this kind.  If you'd calibrated the protocol on  
one of the other types of material, then that's the kind that would  
come out looking best.  The only way to really compare different  
negative types in a meaningful way is to print each using the  
protocol which optimizes its performance, which as Sam says will be  
different for each of them,  and then compare those prints.   These  
*seems* less standardized, but it's actually more standardized.   
You're optimizing the print, rather than standardizing the protocol,  
and optimizing the print after all is what we're after, isn't it, or  
have we got so obsessed with standardization that we've forgotten  
what the goal is? By standardizing the protocol, you're actually  
confounding the results, not clarifying them.

Perhaps an example would help clarify my meaning.  It's like the time  
I printed a small image on a lot of different paper samples, to use  
in a demonstration to show how gum looks on different paper surfaces  
and textures and so forth. I certainly wasn't going to calibrate the  
printing time for 20 different papers (and yes, different papers do  
require different methods too) so I just used the printing time I  
always used for my standard paper, which at the time was Arches  
Aquarelle.   But they drew a completely different conclusion from the  
demonstration than I intended them to.  I just wanted them to see  
that different papers give a different look, in terms of detail and  
texture, to a gum print.  But instead, they concluded that because  
the print on Arches was perfect in tonal scale and contrast and all  
that, that Arches must be the best paper to print gum on.  I'm not  
sure I ever managed to convince them, though I tried very hard, that  
the print on Arches looked best because my whole printing protocol  
was calibrated for Arches, and that if I had calibrated for a  
different paper, any of the other 19, then the print on that paper  
would look best.

Sorry, I'll get off my soapbox now, but this is something that I've  
been thinking about for quite a while around different issues.


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