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, Katharine. 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. Chris ----- 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. > >Katharine > > > >> >> 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 >>> >>> >>> >>> >>> >>> >> >> > Assistant Professor of Photography Photography Option Coordinator Montana State University College of Arts and Architecture Department of Media and Theatre Arts, Room 220 P.O. Box 173350 Bozeman, MT 59717-3350 Tel (406) 994 6219 CZAphotography.com
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