View Full Version : Pyrocat-HD & Jobo to scan negs, how to calibrate?

Ralf-Finn Hestoft
21-Mar-2006, 09:12
This is my first post, so please be gentle

I have looked over a lot of Pyrocat-HD posts here and elsewhere and they seem to be very printing-oriented. No problem, except I am trying to scan my negs on an Epson 4990 scanner with Silverfast.

(A bit of background, I am an editorial shooter with a totally digital workflow but have lately had good luck shooting Polaroid Type 55 on my Linhof and scanning the negs and including the digital files along with regular digital files in what I send my clients. However, Type 55 is very expensive and I have a dusty Job CPP2 sitting around so I thought I would try using it to process 4x5 and or 8x10 negs for scanning)

So, here is my plan, any hints or corrections would be appreciated. I plan on testing FP4+, HP5+ and TMY using various times and temps I have found on the net for Pyrocat-HD and my Jobo. I plan on shooting a MacBeth color checker and a Kodak Calibration Target (20 shades of grey, from white to black) plus our trusty mannequin to get a set of "calibration negatives."

Then I plan on scanning them as RGB files on the Epson 4990 using SilverFast and placing the white and black points on the appropiate places on the Kodak target.

My question is: Then what?? How do I evaluate if the negative is "good" or "bad", properly exposed or not? I understand that I can vary exposure to control density of the negs and vary development time to "expand" or "compact" the tonal range of the film, but I am not sure how to evaluate the scanned results nor how to decide which adjustments to make.

I would really appreciate some help to walk me through the film calibration process, essentially using the scanner and its results as my densitometer and the final file as my print.

Also, am I choosing the right films to test, since my objective is scanning and are there any other hints people have on the whole process?

I thank you all in advance!

Ralf-Finn Hestoft

Michael Mutmansky
21-Mar-2006, 09:57

There is a lot of flexibility in the digital workflow for scanning negatives, so there is really no 'right' answer to what you are asking in terms of getting a good scan out of the film, however, there are a few things that need to be done to ensure you are getting the information on the film that you desire in the first place.

I would start with the negatve and for a moment disregard the scanning step. The most important part of the negative is the toe; the place where the shadows become compressed and then eventually disappear into nothingness. This region determines your film speed, and there are many, many methods to determine a 'proper' film speed for your shooting methods. Some people use the Zone System, others use the BTZS method, and there are also hybrid approaches, and finally, there is the iterative approach, which is the least computationally intensive, and with a little thought can be done by anyone without a densitometer.

To test iteratively, I would shoot a scene, metering it in your normal manner (there's a lot of ways to do this as well, so it's important that you remain somewhat consistant in you metering methods). Make a few exposures of the scene, rating the film at the rated ISO, and then go down, as almost all films tend to be a bit lower speed than the actual rated speed. I'd probably go down in 2/3 stop increments for three sheets.

Develop the film in the Jobo and then look at the shadow detail. You should probably scan the film and look at the shadow detail in the computer since that is the method you are planning to use, rather than looking directly on the negative. You will see differences in how much detail there is, and also in the seperation of tones in the shadows. Obviously, the more exposure you give, the more shadow detail you get, but you have to trade off film speed to get that. It seems that many people are about 2/3 of a stop down from rated ISO for their shooting. If I were going to shoot without doing any testing, that's probably what I'd do.

The second step is to determine how much development you need. If you start with recommended times in a Jobo, you may be in good shape. Some people no longer do the N+, N- and N development approach of the Zone System because multigrade paper and also scanning workflows permit some flexibility in the negative density range without too much difficulty. I recommend that people who develop for scanning actually aim for an ideal silver negative because it will then be possible to use the negative for traditional printing as well. If you know that you never will be printing traditionally, then a slightly lower contrast negative will produce very slightly better results, but the difference will only be apparent at very high scanning resolutions. Conversely, I develop my larger negatives for platinum printing, which requires a very high contrast negative, and I am still able to get good scans from them, it just takes a bit of care to do that.

You may be interested in a LF scanning workshop that will be held early in June in Columbus, Ohio at Midwest Photo. It's run by Ted Harris and me, and it deals with these issues and more, and will get you going in a hurry. At the moment, there's a few spaces still available. Email me if you'd like more information.


steve simmons
21-Mar-2006, 09:57
I use the same neg contrast density for printing and scanning. I test according to the Minimum Time for Max Black that I described in the Jan issue of View Camera. This way I can use my negs for any and all purposes.

steve simmons

John Berry ( Roadkill )
21-Mar-2006, 10:26
I think if I was going to expose for scan only, I would make them a little less contrasty than I would for printing normal. Then again most of my negs are keyed to Azo and carbon, which might tax the limits of the scanner.

Bruce Watson
21-Mar-2006, 11:58
I would really appreciate some help to walk me through the film calibration process, essentially using the scanner and its results as my densitometer and the final file as my print.

There are undoubtedly workshops that can walk you through the entire process. It takes most of us a while to learn what we need and iron out the kinks. This isn't something you're going to master in a couple of days, workshop or not.

The basic steps are to figure out your EI and your normal developement time. Fred Picker wrote a book about doing this called Zone VI Workshop. It's out of print but you can find used copies all over. And of course there are numerous other texts out there that describe the process, including the Adams book The Negative.

Once you get that nailed down, and everything you find will help you nail it down for darkroom printing on gelatin silver paper, you are basically set. Any negative optimized for gelatin silver paper will scan beatifully on just about any scanner.

You can of course optimize farther -- for your particular scanner. That typically means a thinner negative - less density range. Basically (very basically) it's easier to scan a less dense negative well because less density means less silver which means less light scatter. Since you are using one of the staining developers, this may in fact not be the case. The reason is that some of the density of the negative comes from the stain, and decreasing the density is not a one-to-one with decreasing silver for a Pyro negative.

So you come full circle. Optimize your negative for darkroom printing on silver gelatin papers, and you'll be fine.

Craig Schroeder
22-Mar-2006, 15:35
Others are giving better calibration thoughts than I will attempt but I would add that most of my scanning struggles were greatly minimized when using PyroCat HD and similar developers (vs non-staining). My scanner struggles much less with digging out detail in the shadows and the natural highlight control helps too...

Ralf-Finn Hestoft
23-Mar-2006, 13:11
Thanks for all the replies. Let me try to summarize, to see if I get it:

1) Shoot at normal ISO plus two additional sheets, opening up 2/3 stop and 1 1/3 stop.

2) Process normally in Jobo and judge the shadow detail of the step wedge.

3) Pick the best negative of the three and set my ISO based on that neg.

The question is how to judge proper shadow detail. Is there any way to use the RGB dropper function of the scanner software to approximate a densitometer or does anyone have any idea what the values SHOULD be for deepest black 255, 255 255 or what?

After that, so far so good, but what about zeroing in on the proper development time? It is my understanding that, with Pyrocat, shorter development times "expand" the range of tones and longer development times "compress" the range. Otherwise, I suppose I could just scan and print each neg the best I can and see how the step wedges look and lower development time if there is not enough separation in the darkest or lightest wedges. Does that make sense?

Thanks again for everyone's help on this!

Michael Mutmansky
23-Mar-2006, 15:46

Well, that's the problem with scanning, you don't have a true test for development time, and the flexibility of the scanner will accommodate a wide range of negative contrast (and hence development times), but in general most scanners perform best in the range of contrast from a normal silver contrast negative down a little. That's the reason I suggested simply starting with the basic silver recommended development times.

As I said, many people shooot B&W films down from their purported speed by a bit, some go down a lot, because under normal circumstances, the negative will simply be more dense, and there will be more detail in the shadows, but it is a tradeoff on the film speed side to do that more than the amount necessary to obtain good shadow detail for your negative to produce the proper final print result. There's not much reason to have more shadow detail than you will be printing, as it will be lost into the blackness anyway.

That said, wars have been started over how to rate and what the 'proper' film speed is for various films, so you may get many differing opinons on this. In my experience, it is safe to shoot most films at about 2/3 stop down from their rated speed and then develop for 'normal' silver times to produce a good negative for scanning. Some film and developer combinations may be only 1/3 down, but 2/3 down is then a safe position to be in in this case.

Pyrocat is no different than any other normal developer in that the longer you develop, the more contrast is built into the negative. Be careful what terminology you are using when discussiong expansion or contraction. I'm not sure from your last paragraph whether you have the concept backwards or not, but I think you might.

When you develop for a specific process (silver, an alternative process, or even the scanner) you typically are aiming for a target contrast range on the film. That means that your typical shadow will have a certain density, and the typical highlight will have another density, and the difference between them is the range that is important. For silver, the range is normally anywhere from about .9D to 1.10D, depending on the paper used, and other factors. I would suggest that the same target will work well form most people for scanning as well, especially with a staining developer like Pyrocat.

However, there is no good way to actually test density with the scanner, unless you have a transmission step wedge with known density values. You can compare the density of the stepwedge and the negative, and judge the densities that way. I understand that some scanner software have a 'densitometer' built into them, but I would be suspect of the resultant values that you get back until you have done a few comparisons with known densities to ensure it is giving you good results.

If you really overdevelop, you may find that the scanner has trouble with highlight seperation. That would be a good indication that you need to back off on the development a bit, but I doubt that will occur if you follow the basic recommendations for development. One thing about scanning is that once it is in the computer, you have the ability to make fine-tuned adjustment to both shadow and highlight contrast through curves adjustments and other mechanisms in Photoshop, so in my mind the most important thing is to ensure you are getting enough detail on the negative in the shadow zone for what you want in the print.

The purpose for expansion and contraction is related to the actual luminance (brightness) of the subject in relation to the desired result you want to have on the film and further onto the print. When you are shooting under 'normal' conditions; when a scene has the typical 7 stop range from highlight to darkness, the 'normal' development times will produce a negative that has a specific range from bright to dark in the negative, which will match the desired contrast needed to print on silver or scan with a scanner.

If the lighting is very contrasty, the contrast will be translated through the development into a condition where the negative overshoots the contrast range desired, unless the development is reduced a bit to help lower it back into the desired range. Conversely for very flat lighting; the development can be increased to increase the contrast in the negative up to the desired amount.

However, you are now talking about a level of control that probably needs some systematic method of testing to do in a consistant manner, but it would be possible to make some SWAG's at the results and move on to actually making images if you wanted to skip that step. However, I would first start with a single development time for all conditions and then as you shoot and become more experienced, you can start to adjust the time for high contrast and low contrast conditions.

If you want to do thorough testing on this, I would recommend going to the library or ggod bookstore and getting a Zone System book, or Beyond The Zone System, by Phil Davis, or any number of other sources for systematic testing. If you don't feel like going into that level of effort, then I would just do what we discussed; establish the personal ASA for the film, and use the basic 'normal' development times and go from there.

Let me also say that photography is an iterative process; you will start, set some parameters, and then go out and make some images. But as you work through the images, you need to be evaluating what you have done to identify problems and correct them the next time. It shouldn't take too much time to get to the point where you have your system working in pretty good synchronization with what you are looking for.