Trying to get less density from QTR for gum

[PVia]

Hi all...

How can I get less density from QTR in order to make a gum negative?

I have no problems when printing Pd with my palladium profile which gives me negs about 2.0 - 2.2 DR.

Could I just replace the curve in my Pd profile with a new one, as a starting point since I like everything else about the Pd curve?

IOW, how can I take my QTR profile for Pd and make it DR 1.0 instead of DR 2.0?

Sorry if I'm not too clear...

 

[PVia]

After re-reading Ron Reeder's QTR pdfs, I decided to lower the Default Ink Limit and the Boost by half (from where my Pd profile was set) and also lowered the limits on the lighter inks proportionately.

The negative definitely printed lighter, and with much less contrast. I can still see all the detail though, or at least most of it.

I'll have to try to print with it tomorrow...

 

[sanking]

After re-reading Ron Reeder's QTR pdfs, I decided to lower the Default Ink Limit and the Boost by half (from where my Pd profile was set) and also lowered the limits on the lighter inks proportionately.

The negative definitely printed lighter, and with much less contrast. I can still see all the detail though, or at least most of it.

I'll have to try to print with it tomorrow...

I would just eliminate the boost and lower all of the Default Ink limits by about 50%. That should cause a rather dramatic change in transmission Dmax and at least let you know in which direction you need to go for farther correction.

Sandy

 

[Loris Medici]

Paul, not something about QTR but wanted to mention anyway:

DR >= log 2.0 is certainly strong for gum but IME (contrary to what many expert say) log 0.9 to 1.0 also is not perfect/optimal for gum. I got best results with slightly contrastier (log 1.3 to 1.5) negatives. Somehow, I can get better shadow detail with such negatives. Shadows are somewhat blocked/dull/lifeless with weaker negatives. A nice (not perfect but pretty trouble free) method would be to use negatives calibrated for traditional cyanotype. You'll get nice results with those, plus, calibrating for traditional cyanotype is much more straightforward when compared to gum. (Calibrating gum is a real PITA considering the consistency level the operation expects/requires! Also, to me, seems to limit all the flexibility the process provides...)

It seems that ammonium dichromate is considerably more expensive in the States. (I can get 1kg pure/analytical grade AD for USD 29.00 here in Turkey.) But I'd choose AD everytime instead of PD; just because you're much more free to choose your sensitizer strenght. 13% (saturated or almost saturated) PD is not a good idea to me. I'd always prefer to work with known solution strenghts. You can't be sure that your PD is always 13%; it will change according to the solution's temperature. I prefer to work with 10%, 5% and 2.5% solutions -> they're always the same strength as long as your lab's temperature is reasonable. (That is > 18C) And when I need it (for paper negatives for instance), I can always mix 15% or even 20-25% sensitizer solutions -> that's not something you can do with PD...

My 2c FWIW.

Regards,
Loris.

...

IOW, how can I take my QTR profile for Pd and make it DR 1.0 instead of DR 2.0?

...

 

[PVia]

Thanks Sandy and Loris...

I lowered my ink density limits and the boost, and got a much less contrasty neg that still had good detail, however it really is too thin now...but at least I was able to see what those adjustments were able to do.

The boost really does help those highlights sing, but the general ink density needs to be lower by just a touch. It's really amazing how much the density drops with only a little adjustment!

 

[PVia]

BTW, Sandy...I really enjoyed your article and photographs in View Camera!

 

[sanking]

BTW, Sandy...I really enjoyed your article and photographs in View Camera!

Thanks. Positive feedback always appreciated!!

Sandy

 

[Colin Graham]

I just started messing with this but try raising the LK density. I had problems in the 'softer' processes like gum and cyanotype with the dark inks blocking way too much up into the midtones and even the shadows, and was getting to the point where I couldn't lower the dark inks much more. A substantial bump of the LK density limit from 33 to 75 helped enormously. The adjustment is like a slider for the crossover of the light and dark inksets. Instead of just adding more ink to the light ink set (as it sounds like it does) it actually compresses the dark ink set farther up into the highlights and keeps them from spreading into the midtones and shadows. Check out the ink curve display ('show curve' button) as you adjust it.

 

[jag2x]

Question: I'm confused with "BLACK BOOST"?
Does "BLACK BOOST" apply ONLY to the "Black (K)" ink?

 

[donbga]

Question: I'm confused with "BLACK BOOST"?
Does "BLACK BOOST" apply ONLY to the "Black (K)" ink?

From the QTR User Manual:

"Another variable that can be used to increase black ink in the shadows only is Black Boost. . This puts a steep curve in the Black ink right at the end pushing black all the way to the value set by Black Boost."

So in the passage above the discussion is based on the results observed for making an ink jet print. For digital negatives this would or could be used to alter highlights in the final print. At least that would be my interpretation. But you may need to augment this setting with the GRAY OVERLAP value to provide smoother results in the highlights.

Don Bryant

 

[PVia]

Colin...much thanks and I'll look into this when I have more time.

I have actually been making great inroads with gum and my negatives for it. I've devoted much of my time the last few months to gum exclusively. As you know, there are so many variables that it takes time to work through them, but in the end you really start to get a grip on the process.

Thanks for your curve and QTR insight...!

 

[Colin Graham]

I should mention that Ron Reeder recommends keeping this value as a constant in his QTR manual, and messing around a little more with it I'm starting to see why. While increasing the LK limit does keep the dark inks from climbing up too far into the mids, it also shifts the ink control that is meant to separate the shadows further up into the midtones, which of course leaves little control over the shadows.

Depending on the process, this could create a lot of problems. It worked really well with traditional cyanotype, but with gum it's merely displacing the need for a severe curve from the midtones to the shadows, which is much more difficult to tweak with a curve.

I've been looking for a sort of universal profile for gum over cyanotype so I can print all separations at once, so I'll keep playing around with it.

 

[JOHNjohn]

Polaroid Pro Palette 8000

Please can any one help.
I have a Polaroid Pro Palette 8000 which worked fine in the last time I used it a few months ago. Now when I try and print the film, each slide takes a minute or so to run through (in the past it took 5) and it seems to flash through the various red green and blue colors very quickly. Now each color reaches 800 before the next color begins (Im sure in the past it went up to thousands). Does any one there please have an explanation??
Thank you for your help

 

[Colin Graham]

I took another approach to this and have had good luck not using the dark ink set at all, just using the light inkset. There seems to be plenty of blocking in the light inks for low dr processes, and there's no crossover issues because only one inkset is used for the entire range. You might want to mess around with it if you are having difficulty getting your negatives thin enough in QTR.

Here's is a profile I've been using for gum/cyanotypes. Pay no attention to the values in the Boost K and limit k/c/m/y fields, they are turned off in the interface so the values are meaningless. I'll also post a screenshot of the gui as well as it's a little clearer there.

 

[PVia]

Colin...I'll check that profile out.

Basically what I ended up doing is to use my pt/pd negs for tricolor (and other) gum, at about 60% of the exposure. Beautiful clean results...take a look at the first 3 photographs here:

http://www.flickr.com/photos/viapiano/sets/72157624234247830/

 

[Colin Graham]

Yeah, it won't work for everyone, but it does work surprisingly well for certain more 'limited' processes like cyanotype. I was mainly having issues with the initial cyanotype layer blocking up and so I started wondering why I was using all this extra ink for the negs when it was making the exposures drag on forever and forcing me to use tricks like vinegar or citric acid developer. Once I got the profile right for my cyanotype procedure it was an easy matter to tailor the gum emulsion to the same profile.

The great thing about proceses like carbon and gum is there's no much adjustment available with the pigment, sensitizer and exposure you can make almost any negative work. I think I had more trouble with the 'lowly' cyanotype than 3 color gum, carbon and kallitypes put together.

 

[Luciano Teghillo]

This thread is quite old but just to keep the same information in the same place. I have just started with gum printing, first with laser negatives without much success, and now with an Epson R2880, QTR and Pictorico OHP Pro. I have printed Ron Reeder step tablet after reading his book and new PDF with a Pt/Pd profile but it seems that the Dmax of the negative is really high. Could you give me some pointers on how to try and get a profile more suitable to gum printing? I have read many posts here and on the QTR Yahoo group but it seems there is very little information about digital negative and gum. I forgot to mention that I do not have a densitometer but could use a flat bed scanner. Thanks for the help.

BTW, this is the profile I used:
PRINTER=QuadR2880
CALIBRATION=NO
GRAPH_CURVE=YES

N_OF_INKS=8
DEFAULT_INK_LIMIT=100

LIMIT_K=10
BOOST_K=35
LIMIT_C=18
LIMIT_M=18
LIMIT_Y=18
LIMIT_LC=30
LIMIT_LM=0
LIMIT_LK=30
LIMIT_LLK=30

N_OF_GRAY_PARTS=2
GRAY_INK_1=K
GRAY_VAL_1=100

GRAY_INK_2=LK
GRAY_VAL_2=30

GRAY_HIGHLIGHT=0
GRAY_SHADOW=0
GRAY_GAMMA=1

GRAY_CURVE=

COPY_CURVE_Y=K
COPY_CURVE_C=K
COPY_CURVE_M=K

COPY_CURVE_LC=LK
COPY_CURVE_LLK=LK

 

[Herzeleid]

This thread is quite old but just to keep the same information in the same place. I have just started with gum printing, first with laser negatives without much success, and now with an Epson R2880, QTR and Pictorico OHP Pro. I have printed Ron Reeder step tablet after reading his book and new PDF with a Pt/Pd profile but it seems that the Dmax of the negative is really high. Could you give me some pointers on how to try and get a profile more suitable to gum printing? I have read many posts here and on the QTR Yahoo group but it seems there is very little information about digital negative and gum. I forgot to mention that I do not have a densitometer but could use a flat bed scanner. Thanks for the help.

BTW, this is the profile I used:
PRINTER=QuadR2880
CALIBRATION=NO
GRAPH_CURVE=YES

N_OF_INKS=8
DEFAULT_INK_LIMIT=100

LIMIT_K=10
BOOST_K=35
LIMIT_C=18
LIMIT_M=18
LIMIT_Y=18
LIMIT_LC=30
LIMIT_LM=0
LIMIT_LK=30
LIMIT_LLK=30

N_OF_GRAY_PARTS=2
GRAY_INK_1=K
GRAY_VAL_1=100

GRAY_INK_2=LK
GRAY_VAL_2=30

GRAY_HIGHLIGHT=0
GRAY_SHADOW=0
GRAY_GAMMA=1

GRAY_CURVE=

COPY_CURVE_Y=K
COPY_CURVE_C=K
COPY_CURVE_M=K

COPY_CURVE_LC=LK
COPY_CURVE_LLK=LK

I have no experience with the inks you are using, and very very little experience with gum.
But that is quite a lot of ink, I use claria inks (very weak UV blocking) and with that ink load I can print a VanDykeBrown negative.
You should, may be look for a cyanotype profile for your printer and work your way from there.

If you can't find any user made profiles.For starters IMHO you should try half the amount of inks, limit K boost to 20, and make a test.
Then, try step by step increments or decrements, for example 3 value decrease or increase from each ink.

 

[Luciano Teghillo]

Thanks. I had the feeling that I was using quite a lot of ink. I will give your suggestion a try. It would be great if I could see the profile of another gum printer using digital negatives with the K3 inkset. Let's see if someone else chimes in