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

Re: digital negative possibilities for gum

OHHHH totally good point:  I was using Image>Mode>bitmap.
Now I have another thing to try--the diamond thingy, below. 
So many things to test...but thanks for the input,

Marek, yes, you can actually see the minute dots by the eye
with gum!  So those who say gum is not sharp--heck--it sure
is.  But what I mean is that the little dots, the softness
of the image under bitmap is actually kindof...pleasing.  I
dunno--it's weird, but I was very impressed at the feel of
the image with this kind of neg.  I'll try the other stuff
this week and report back.
----- Original Message Follows -----
From: Katharine Thayer <kthayer@pacifier.com>
To: alt-photo-process-l@usask.ca
Subject: Re: digital negative possibilities for gum
Date: Tue, 17 Oct 2006 08:39:59 -0700

>On Oct 16, 2006, at 8:07 PM, Katharine Thayer wrote:
>> Chris, what kind of bitmaps were you using, a halftone
>> screen,   diffusion dither, or some other?
>> Katharine
>The reason I'm asking is that I'm not sure what it is
>you're   comparing when you're comparing a negative made by
>printing the file   as a bitmap file to a negative made by
>printing it as a regular file.
>The assertion I've heard (Mark is the last person I
>remember making   this assertion here) has to do with
>halftone separations  rather than   bitmaps per se, and
>goes something like this:  gum printers "have   found" that
>halftone separations give better clearer colors because  
>the color is laid down next to each other rather than on
>top of each   other.  I said that might be true of opaque
>pigments, but certainly   not of transparent pigments,
>which can be printed directly on top of   each other
>without muddying the color.
>With halftone separations, the screen angle for each of the
>  separations is set so the color is laid down in a rosette
>pattern,   each full dot being made of a rosette containing
>each of the three   colors, like three different-colored
>petals making up a flower. In   that case, the color really
>is laid down next to each other rather   than on top of
>each other, and would give you the comparison you seem   to
>be after.  But if you were using halftone separations of
>this   kind, it seems like you would have said so, rather
>than   characterizing the negative type as a "bitmap."
>So, some clarification would help me understand what it is
>I'm   looking at here, thanks.
>> On Oct 16, 2006, at 6:57 PM, Christina Z. Anderson wrote:
>>> Good evening all,
>>> Over the last week I have been testing four kinds of gum
>>> negs,   with tricolor
>>> gum and gum over cyanotype (cyanogum). My goal was to
>>> see if   bitmapped negs produced clearer, more brilliant
>>> colors as I read   somewhere, or even worked with gum,
>>> and then to find an   acceptable, cheap, low tech
>>>beginner mode of gum printing. 
>>> I made sure to actually attach the negs side by side so
>>> all other   variables
>>> were exactly alike--coating, dry time, development, etc.
>>> So here's the skinny:
>>> 1.  Trigum printed with a negative on cheapy Photo
>>> Warehouse OHP transparency with all inks, no curves
>>> 2.  Trigum printed with a negative on cheapy Photo
>>> Warehouse OHP transparency with all inks, no curves, and
>>> bitmapped 360 ppi input   and
>>> output
>>> 3.  Cyanogum printed with a negative printed on
>>> expensive   Pictorico, all
>>> inks, no curves
>>> 4.  Cyanogum printed with a negative printed on
>>> expensive   Pictorico, curved
>>> correctly for cyanotype, magenta and yellow separately,
>>>colorized neg 
>>> These are my observations (NOT declarations or
>>> assertions); YRMV: 1.  Bitmapping surprised me--it
>>> actually produced a pretty darn   good image!
>>> It was softer, a bit less contrasty, but heck, with what
>>> little ink bitmapping uses and with the fact you can use
>>> cheapy transparency,   it is
>>> definitely a keeper,especially for teaching beginners
>>> low tech gum. 2.  "All inks" was a bit smudgy and
>>> required drying with the PWOHP/  Epson
>>> 2400, not with Pictorico.  Funny, my cyano layer printed
>>> with   minute round
>>> spots of lighter tone--not the dreaded speckles--and
>>> when I louped   the
>>> negative I saw that the printer lays down minute round
>>> spots of   different
>>> color inks that in turn expose cyano differently, like
>>> little mini   filters.
>>> Very interesting. With gum this is no problem--the
>>> spottiness, of   course.
>>> 3.  Cyanotype absolutely requires a curve--by the time
>>> the   highlights are
>>> printed in, the shadows are totally overexposed unless
>>> your image   is short
>>> scale to fit the 4 or 5 stops of that process's range. 
>>> My next   test is to
>>> curve just the cyano and use the two bitmap magenta and
>>> yellow   negs to print
>>> gum over. And then next I will probably curve the
>>> individual negs   and then bitmap.
>>> 4.  If not printing with a cyano underlayer, you can get
>>> an    acceptable
>>> print with no curves, neg just inverted and printed as
>>> is, and   adjust the
>>> layer with exposure, development, pigment load,
>>> brushing. But all   of you
>>> already knew that, I'm sure I'll be told. I prefer the
>>> all inks   unbitmapped
>>> to the bitmapped--I think.
>>> 5. In my eye the better print was produced by a properly
>>> curved neg, but how will your viewer know there is a
>>> "better" rendition unless   all the
>>> images are side by side, you know?
>>> 6.  Bitmapping didn't produce clearer, better colors
>>> because of   "individual
>>> dots laid down side by side and not on top of one
>>> another". 7.  All methods can be capable of producing
>>> fine prints, once the   gum printer can meld his/her
>>> method to whatever workflow is chosen. 8.  Bitmapping
>>> has....possibilities...I'm not sure what yet, but   it
>>>really did surprise me. 
>>> If you want to see the visual, copy and paste this URL
>>> into your   browser:
>>> http://czaphotography.com/show.php?what=learning&which=1
>>> and scroll down to the very bottom of the images; it'll
>>> be there. Bye!
>>> Chris
>>> CZAphotography.com

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