Looking for Pt/Pd calibration advice

Last night I made my first Pt/Pd calibration prints and I am hoping to get some advice from the forum. So far you have been very helpful.

This is my first foray into alternative processes - and I havent made a wet print in probably 7 years.

I am using a Pt/Pd mix with medium contrast - my drops for a 6x8 are:

Ferric Oxalate #1: 8 drops
Ferric Oxalate #2: 8 drops
Pd Soln: 12 drops
Pt Soln: 4 drops

Firstly I established my base exposure as 8 minutes on a 3M UV Exposure Unit using a step wedge. Next I printed an RNP HSL chart onto Pictorico Premium OHP using a HP 9180 on "HP Advanced Photo Glossy" & Best quality. Here's the result:

View attachment 189

The X on the left shows the color I picked for my negative base. It turns out to be HSL=(0,95,100) or RGB=255,12,12. There were many choices judging by the result - but I picked this one based on Sandy King's recent recommendation that RGB-(255,0,12) was working well for him on the HP9180 in terms of a smooth transition.

Next I created a ChartThrob Step wedge with the base color, printed and scanned. Here is the result:

View attachment 190

The first three steps are pure white and then it goes to Dmax at around 50%. This is reflected in the curve created by ChartThrob:

View attachment 191

In addition ChartThrob tells me that while this is a valid curve, I might want to consider reducing my exposure to make more optimal use of the paper/emulsion.

So, here are my questions:

1. How does my HSL array look? I notice that other ones posted seem to have a more gradual transtion from light to dark - mine seems more abrupt.
2. Given than my first ChartThrob test shows me achieving Dmax at 50% should I consider reducing the contrast of the emulsion. Wouldn't that be better that using a curve that maps my 256 inputs to only about 128 outputs? Does that matter?
3. I notice quite a bit of dithering on my step wedge. Is that indicative of what large areas of midtone will look like on my final print? I had the impression that diginegs (done well) don't show these artifacts. However, I do see them on other peoples test charts - just not on their final prints. Is that just because the final prints are less magnfied and the dithering is still visible?

Any advice on where to go from here would be very welcome.

Just for fun, and because I had some spare coated paper not needed for testing last night, I printed a neg from my 1956 Rolleiflex - this is using the same 8 min exposure on the same emulsion as my test prints. And this was an average density negative:

View attachment 192

I am happy with the result for a 2 1/4" square print - my first real Pt/Pd print. I am hoping that I will be able to get these types of tones from diginegs when I finally get there. Will I be disappointed?

Thanks again,

Richard

1. The HSL looks good. Lots of areas of potential for density. Different than an Epson but that's fine. I would just keep that curve moving toward the corner though. Don't know why ChartThrob abruptly zigs it into the wall like that.
2. What you could do if posterisation (read: lack on tonality) is a concern is lessen your reliance on contrast agents until your negative colour achieves dMax density equivalent to the colour of say RGB 127,0,0. This is deep enough that the CcMmY are still the only heads producing the blocking colour but not so dark that black ink in taking over in the driver and giving you a drop in resolution. In essence you're matching the capabilities of your printer and inks to your emulsion. Compromising, giving a little on both ends. See what your first print looks like though. At least you'll have a bench mark to show improvement.
3. You'll know once you see the print if artifacts are an issue. All printers are not created equal. You're right they're exaggerated on step wedges a lot of the time because people are printing small to save on materials. They might not be as noticable in the final print.
I'm interested to see your results. That's the image you're going to print? Nice!

~m
p.s. judging by your ChartThrob test print RGB 255,17,17 will "nail" your blocking colour to the corner.

mkochsch said:

1. The HSL looks good. Lots of areas of potential for density. Different than an Epson but that's fine. I would just keep that curve moving toward the corner though. Don't know why ChartThrob abruptly zigs it into the wall like that.
2. What you could do if posterisation (read: lack on tonality) is a concern is lessen your reliance on contrast agents until your negative colour achieves dMax density equivalent to the colour of say RGB 127,0,0. This is deep enough that the CcMmY are still the only heads producing the blocking colour but not so dark that black ink in taking over in the driver and giving you a drop in resolution. In essence you're matching the capabilities of your printer and inks to your emulsion. Compromising, giving a little on both ends. See what your first print looks like though. At least you'll have a bench mark to show improvement.
3. You'll know once you see the print if artifacts are an issue. All printers are not created equal. You're right they're exaggerated on step wedges a lot of the time because people are printing small to save on materials. They might not be as noticable in the final print.
I'm interested to see your results. That's the image you're going to print? Nice!

~m
p.s. judging by your ChartThrob test print RGB 255,17,17 will "nail" your blocking colour to the corner.

Click to expand...

Thanks for the quick response. Here are some comments on your answers:

1. I don't think it matters whether the curve goes horizontal or down to the corner - all output values at or below that point will produce dMax any way.
2. So what you are saying is that it isn't that desirable to have values below, say, (127,0,0) in the digineg since the printer will be using more black ink to achieve this density and that this will compromise resolution? That's interesting - I had wondered whether the lower contrast emulsion might reduce the dithering effect since it will cause the different dots that make up the color to be lower contrast too. Sounds like that this might be outweighed by the effects of black ink.
3. I am certainly hoping to get smooth mid tones - that for me is one of the reasons to do all of this.

Actually, that little print was just a negative picked at random so I could maximize the use of my precious emulsion - and to get the satisfaction of seeing something other than test charts! I haven't made the final decision which image will be my first digineg.

I think I'll take your advice and make a print using this curve as a benchmark before I do more tweaking.

One more question - how many shades of gray is Pt/Pd supposed to be able to differentiate? How does that compare with Silver based papers?

Thanks

Richard

You will greatly improve the quality of your prints if you abandon the Ferric Ox No. 2 method of contrast control. Look into the use of Na2 as a contrast agent. Much, MUCH better approach to the craft.

Kerik said:

You will greatly improve the quality of your prints if you abandon the Ferric Ox No. 2 method of contrast control. Look into the use of Na2 as a contrast agent. Much, MUCH better approach to the craft.

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Kerik,

Thanks for the comments. I have seen some of you beautiful platinum work on and off for years - sadly I have only seen it on the web to date.

For Na2 - I had received this advice here a couple of weeks back:

BillSchwab said:

Not to step on Sandy here, but with a digineg properly made you should have no need to control contrast with the Na2. What I like most about the diginegs is the ability to bend my negative to match the ES and use pure palladium. I only use the Na2 when printing in camera negs that need adjustment.

Bill

Click to expand...

Obviously I do need to settle on an emulsion that has a contrast that works best with my paper and inkjet negatives. Are you saying that even if one doesn't intend to control contrast on a negative by negative basis, that Na2 will still make a better print?

Thanks

Richard

Richard,

NA2 is unnecessary, and so is #2 FO, as long as you can produce the requisite contrast in the negative. That is what Bill was saying.

You will find that with a properly calibrated negative system, you will have no need for contrast control in the printing steps. This is the real benefit of diginegs, other than opening the alt processes up to non LF shooters. You won't believe how much more efficient you can be in the darkroom if you've locked your contrast down properly in the digital steps.

If your printer will enable it, you would be best served for a variety of reasons to avoid any restrainer anywhere in the process. It's perfectly viable to do this with the Epson printers out there, but I can't speak for the HP printers. I'll be that if you do a black-only negative, you'll have enough density to do that, though.


---Michael

Poliweb said:

Thanks for the quick response. Here are some comments on your answers:

1. I don't think it matters whether the curve goes horizontal or down to the corner - all output values at or below that point will produce dMax any way.
2. So what you are saying is that it isn't that desirable to have values below, say, (127,0,0) in the digineg since the printer will be using more black ink to achieve this density and that this will compromise resolution? That's interesting - I had wondered whether the lower contrast emulsion might reduce the dithering effect since it will cause the different dots that make up the color to be lower contrast too. Sounds like that this might be outweighed by the effects of black ink.
3. I am certainly hoping to get smooth mid tones - that for me is one of the reasons to do all of this.

Click to expand...

1. 
   
   It's a matter of deciding between "nothing" and "virtually nothing" in the case of the curve flowing upward. There's not much going on in this particular curve in at area so in practicality it probably won't be noticed. On some curves however the curve is much gentler/subtle and this would have to be taken into account.
   What happens when the colour approaches black is tantamount to "grain" blocked up in the highlights. Not many people have satisfactory results using Epson's "Black Ink Only" option. The other colours one should avoid in making digital negs are "pure" Yellow, Cyan, Magenta. From my tests when you make a negative on purpose or by accident using single ink carts you lose density as well as resolution. On many HSL tests I've examined you can often see these blips on the 60, 180 and 300 degree columns. It may not always be a factor but it's something worth noting. Using dark red (RGB 127,0,0) is probably a safe bet on most colour printers. If you're bored, and I mean really bored, and want to find out for sure, load an empty black cart with Gloss Optimizer (Glop) and print the HSL again and note where the lack of black ink occurs.
   As for shades of grey on pt/pd. I couldn't tell you. Hopefully someone else can chime in with an answer. A some point you're in "dog whistle" territory but I could tell you where that is.
   
   ~m

Richard,

Thanks for your kind words. My point is, if you want to make any adjustments to the contrast of your print, use Na2 rather than FO #2. I agree that you should be able to calibrate your diginegs such that contrast adjustments at the printing stage are minimized, but you'll likely have enough variation from image to image that you may find yourself wanting to boost the contrast a bit at times. When those happen, Na2 is a much better tool than FO #2.

Kerik said:

Richard,

I agree that you should be able to calibrate your diginegs such that contrast adjustments at the printing stage are minimized, but you'll likely have enough variation from image to image that you may find yourself wanting to boost the contrast a bit at times. When those happen, Na2 is a much better tool than FO #2.

Click to expand...

Kerik is right. Even in world of digital negatives there will be some variation from image to image that may require contrast control. The only exception to this if you happen to also live in the very most perfect world where temperature and relative humidity is always exactly the same. The difference in contrast and density in pt/pd between working at 40% RH, 50% RH, and 60% RH is significant. Digital negatives balanced for the lower RH will not give optimum results at the higher RH. And can you always count on the same RH in your working environment?

Na2 is a good method fo contrast control, and I certainly recommend it over the split FO method. However, for the small differences we are likely to encounter with digital negatives, even with RH differences, dichromate control has some advantages.

Sandy King

Plus, unless you always print on the same paper, you will find variations in the contrast needs for a given neg depending on the paper (as well as the environmental variables as Sandy suggests). Finally, it seems appropriate to me that someone learn the variables and flexibility of their process of choice instead of being completely dialed in to ONE WAY. How boring!!!!! I am an animal, not a machine!

Thanks for all the great replies - they have been very helpful. Based on the feedback here's what I plan to do next:

1. Print a digineg based on my current colour & curve. This will serve as a great reference point for me - and I have already taken all the steps to get me to this point.
2. Recalibrate on an emulsion with no restrainer - i.e. just use Ferric Oxalate #1 solution. If I the emulsion is too low a contrast to work then I'll start to increase contrast with FO #2 since that's what I have right now.
3. Next time I order I will get Na2 solutions and use that for contrast control if I need it.

I'll post my results as I go.

Thanks again for the help,

Richard

Here is my second ever Pt/Pd print (the first being the little one earlier in the thread) and my first made from a digineg (based on the colour and curve I created):

View attachment 193

The print is 7x8 inches from a scanned 6x7 cm transparency that I mixed down to a black and white for this test.

I think it's a good start. Perhaps the contrast is a bit low overall. I must say that the negative didn't look very promising - I couldn't make out much detail at all - it's amazing it prints at all!

I can see some mottling with the naked eye, especially in the mid tones. I think that it's at a level that will bother me - so I will have to work to improve it. Here is a blown up section from the print to show the mottling - it's a section that is around 1.5 inches square on the original print:

View attachment 194

It's quite visible here of course - but you are looking at an elargement from the print. Still, I want to improve it.

I think the next step is to recalibrate with an emulsion without any restrainer. And then look for a color that exhibits less "grain". I hear green is in fashion for the B9180 these days

Richard

Great image Richard. Looks like you're off and running.