Calibrating for Canon PRO-100

[zuluz]

Here's a summary of how I calibrated my digital negatives using a Canon PRO-100 printer. If you have a PRO-100 you already know that it's not the best printer to use for digital negatives, mainly because (1) its dye-based ink doesn't block UV as well as pigment ink printers like Epson, (2) the driver doesn't give you any way to control the ink density, dry time, or whatever else Epsonites enjoy. Yet, it's the only printer you have and you want to get the best out of it. So first, set your expectation that you will have limitations. But the good news is that you can still get pretty decent prints.

This calibration was for:

• Canon PRO-100 printer
• Pictorico TPS-100 transparency film
• Simple Cyanotype process
• Bergger COT 320 paper
• DIY 11x14 UV box using verifiedUV™ 365nM UV High Output Light Strips
• Using Peter Mrhar's EDN system

Step 1: Exposure for Dmax and Paper-White

I used a Stouffer 21-step wedge to get the Dmax. Total exposure was 32 minutes and I overlayed Pictorico TPS-100 on the left side of the wedge. The base Stouffer film is reported to have a density of 0.05 or about 1/6th of a stop. TPS-100 seems to have about 3 steps separation compared to Stouffer, so by my estimates it requires 1-1/2 stops more exposure.

Given the Dmax of Stouffer is around 6, we can estimate:

Dmax = 32 * 2^(-(6-1)/2) * 2^(1.5-(1/6)) = 14 min

However, to get a good enough paper-white I couldn't go beyond 11 min. So, this is the main limitation: we lose almost 1/2 stop of Dmax. So,

Optimum exposure = 11 min

As you see from the following scans, even at 11 min I don't get a great paper-white, but I didn't want to go down to 10 min and lose even more Dmax.

Step 2: Media Settings

I did a test to see which media setting (paper profile) gives the best UV blocking, and the winner was "Matte Photo Paper", so that's what I use for all prints.

Step 3: Find the optimal color block

EDN's ColorBlocker is fairly straight forward to use once you figure out the documentation. Here's a scan of my HSB print:

EDN's ColorBlocker likes H=220 as the optimal color with the widest range. I wish the documentation would say what the exact algorithm is, but here's where you may need to try a bunch of prints to see if you can converge on a color. Another limitation of PRO-100 is that most colors don't fade gradually into highlight (row 0), and those that do, don't have the best range. If I were to eye-ball it, I might have picked something like H=130. But I went with what EDN picked, H=220.

Step 4: Find the linearization curve

Using EDN, here's the scan of my chart that I used as input:

And, here's the curve EDN came up with:

Step 5: Testing the calibration

Putting it all together, I printed the chart with the linearization curve and here's the result:

As you see here, the highlights don't fade well into paper-white, but this is a limitation I will live with. Maybe I do need to lower the exposure time further.

and the graph:

which is fairly linear but not quite there. I did try to combine the first and second corrections per the EDN documentation, but the results were pretty bad; I was getting a lot of banding on gradients. I guess it's possible to fine tune this further by hand, but the results are good enough for me, so I stop here.

Hope this is helpful to Canon PRO-100 owners.

 

[koraks]

As you see here, the highlights don't fade well into paper-white, but this is a limitation I will live with

Yeah, that's always a challenge with digital inkjet negatives and alt. process prints. I wouldn't lose any sleep over it; you might drive yourself crazy. Slightly underexpose any print that needs those pure whites; cyanotypes are easy to make anyway, so just 'roll another one, just like the other one' (but with a little less exposure this time) if it's necessary.

If you *really* want to solve the highlight problems and position yourself optimally for linearization, look into halftone screen negatives. But resolution with any inkjet (or laser) printer will be limited.

 

[nmp]

Hope this is helpful to Canon PRO-100 owners.

Not just Canon PRO-100 owners, but anyone wanting to learn making correction curves for digital negatives using the EDN system. Nice, succinct write-up that is easy to follow - thanks for sharing.

As you see here, the highlights don't fade well into paper-white, but this is a limitation I will live with. Maybe I do need to lower the exposure time further.

One thing that I am not sure you have done (if so then, please ignore the following) is to make sure that the non-paperwhite density is not related to less than adequate UV opacity of the negative but rather to due to chemistry (compromised sensitizer, "dark" reaction in the paper before exposure, etc) or what I call "process fog" which can introduce blue density during development (e.g "bleeding.") To eliminate these possibilities a test can be done with a part of the grid covered with a black cardboard or something very opaque like Rubylith and expose, develop normally. If the density underneath the barrier is same as the 255 block, then it is not the UV opacity of the negative, but one or more of these other factors (and lower exposure won't solve the problem.) If not, i.e. it is closer to paperwhite, then it is the negative.

:Niranjan.

 

[zuluz]

One thing that I am not sure you have done (if so then, please ignore the following) is to make sure that the non-paperwhite density is not related to less than adequate UV opacity of the negative but rather to due to chemistry (compromised sensitizer, "dark" reaction in the paper before exposure, etc) or what I call "process fog" which can introduce blue density during development (e.g "bleeding.")

Good point. To be sure, I did an exposure test with a black strip:

Here's an exposure range from 0 to 14m, increments of 2m. As we see, zero is washing out nicely, even up to 6m. Starting at about 8m staining begins.

 

[nmp]

Good point. To be sure, I did an exposure test with a black strip:

View attachment 343025

Here's an exposure range from 0 to 14m, increments of 2m. As we see, zero is washing out nicely, even up to 6m. Starting at about 8m staining begins.

Very nice! They look very clean - no sign of "bleeding" along the edge of the negative strip. May be this is a property of the SImple cy. Classic has a tendency to stain highlights adjacent to a dark area, particularly with acidic development.

This also shows visually what the best exposure is for an optimum combination of Dmax and Dmin. To me right around 8 minutes seems to be the "sweet spot."


:Niranjan.