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How To Make Digital Negatives - ©  David Fokos

Preface

This book is the culmination of a 18 month-long scientific/artistic exploration into the use of digital negatives for printing fine-art quality photographs. I am happy to report that the process works extremely well, and is relatively easy to implement. 

In these chapters, I have tried to cover absolutely everything someone might want to know about the process, and to present these topics in a way that could be easily understood by even the least technical person. After having read the whole book, someone with no experience or technical background in digital imaging should completely understand the process at a level beyond that of most people who work with these systems everyday! For those who do not wish to understand, but just to quickly obtain results, have also included a quick, easy-to-follow, step-by-step procedure. 

Though the process outlined here, with small modifications, may easily be applied to any of the traditional or alternative photographic printing processes, this article will focus specifically on its application to platinum/palladium printing.

For this process it is assumed that you own or have access to a computer with an imageediting program such as Adobe Photoshop. It is also assumed that you will have some way of transporting large computer files (depending on what you are doing, these files may range from 4 MB to 125MB). Iomega's Jaz Drive and SyQuest Disks are the two most common removable drives for this application. 

Introduction

• Chapter 1

Don’t Need To Understand It, Just Tell Me What To Do

So maybe you're wondering, "Why would I want to use a digital negative?" Well, here for your consideration, are a few of the reasons I like working with digital negatives.

1 - Platinum printing is a contact printing process which requires a negative the size of the final print and a strong ultraviolet light source. The strong UV source and long printing times generally preclude extensive, precise dodging and burning. In the past, I have not done any dodging or burning on my prints, due to the danger of exposure to strong ultraviolet light. Now, with digital imaging, I can make a new negative which has all the dodging, burning, etc., included, so all I have to do is make a straight contact print. 

2 - I can conveniently make enlarged negatives (well, I actually have them made for me) so I don't need a darkroom. 

3 - If dodging and burning are done manually, every exposure will be slightly different from the last. Have you ever seen the "recipe" John Sexton or Ansel Adams have written out for one of their prints? Once I’ve made any desired modifications to the negative, I just make a straight print each time. I know I could do this optically to an enlarged negative, but I believe it is much more precise done digitally. 

4 - With digital imaging, I can work on my image as a positive rather than as a negative. Once you scan your negative, you can instantaneously "invert" it so that you see it on the computer monitor as a positive. This is also great for "proofing" your negs without having to print them.

5 - I can undo and redo changes as many times as I like until I get just what I want. You can't do that with negative reducer! 

6 - I can make multiple copies of my image file, alter each one differently, and then compare them side by side on my computer monitor to decide which I like better.  

7 - The ability to work on small areas is remarkable. Imagine, for example, a field of tall blowing grass. After you print the image you notice a slightly dark area, perhaps the shadow of a passing bird. The more you look at it, the more this area of the print distracts you. Normally, you would just dodge that area a bit as you printed. However, there is the problem of dodging exactly that area and none of the area around it, for exactly the right amount of time, every time you print that negative. With digital imaging, it's very easy to do the "dodging" on the computer file. Another example: suppose you have a small scratch, hair or dust speck in the middle of a big blank sky. Seamlessly retouching either the print or the negative is extremely difficult. With digital imaging, it takes about 5 seconds. 

8 - Some things are much more easily accomplished using digital imaging. Making "masks," adjusting the contrast, unsharp masking, "burning" a smooth gradient, all take just seconds on the computer, but are difficult or time-consuming done manually. 

9 - Enlargements often print as sharp as contact prints. 

10 - I can adjust the contrast to print perfectly on my standard paper using my standard developer (no contrast agents) every time. This allows me to use just one standard formula and one standard printing time. The prints come out smoother because I'm not using any contrast agents. Printing time tends to be short -- just long enough for the area under a clear piece of film (base+fog) to reach Dmax. 

11 - Digital imaging gives you the potential to do some manipulations which are just not possible using analog means. For example, you can change the shape of one of your images, compressing or stretching in this direction or that. There are cases where a little of this might help, but now we're venturing into philosophical territory. Personally, I prefer to keep my manipulations to those which could also be accomplished non-digitally, but it doesn't mean you have to. 

My findings and methods are presented here in easily digested steps. 
For those who don't care why the whole business works, but just want to know how to make it, reading the "What to do" section following this introduction will painlessly, albeit blindly, walk them through the process without any of the technical information. 
For those wishing to fully understand the process, I then go on to explore the technical details -- though these have been presented in a way that everyone should be able to understand. 
There's a lot of information here, but if you take your time you'll be able to understand it all. Relax, go slow, re-read sections if you have to -- it'll be worth it! 

Part A

1 - Expose and process your film normally. You can use any negative you have. It does not have to be developed especially for platinum, silver, or any other process. Just develop the negative so you get that textbook "good" negative. 

2 - Take your negative and measure just the image area that you wish to print. 

3 - Figure out what size you would like the final print to be. 

4 - Divide the number from Step 3 above by the number from Step 2 above to get the enlargement factor. In other words, if you are cropping out a 6"x9" area from an 8"x10" negative and you want to make prints that are 12"x18", then your enlargement factor would be 2 (12" divided by 6", and also 18" divided by 9", got it?). 

5 - Multiply the enlargement factor by 450. 

Part B

6 - Read Section 2d. “Dealing With Service Bureaus And Printers,” and then look in your local Yellow Pages for “Desktop Publishing,” and “Printers.” Call around to find someone who has an “imagesetter” capable of outputting a resolution of at least 3600 dpi -- more is o.k., too. Less is not. Find out if they can make a “drum scan” of your negative, and also, if they would be willing to output a “halftone” negative on their imagesetter for you. Be sure to ask for prices and to shop around -- I’ve received quotes ranging from $19 to $100 for the same job! 

7 - Take your negative to the people with the imagesetter (these shops are often referred to as “service bureaus”) and tell them that you want them to give you a drum scan of your negative. They should scan your negative using one of the drum scanner’s “native resolutions.” The resolution should be equal to or greater than _____ dpi, where _____ is the number you got in step 5.

Have the file put onto your SyQuest, Jaz, or other large file disk. Make sure it is in a format that your computer/image-editing program can read.

Part C

8 - Take your scanned negative home, load the scanned image into your computer.     If the image is a negative image, then invert it (so that it is a positive) and save it to your computer’s hard disk. If it’s already a positive, then just save it. Load the file from your hard disk and edit the image so that it looks just the way you would like it to look, and then save the file to a new name (so that your original scan is always preserved). 

9 - Change the image size so that the size is the same as what you would like your final print to be, and then set the resolution to 450 dpi. This is done in Photoshop by going to Image>Image Size. 

10 - Sharpen the image using “Unsharp Masking.” In Photoshop, this can be found by going to Filters>Sharpen>Unsharp Mask. Use these values: Amount = 100%, Radius = 1.5, Threshold = 4. 

11 - For platinum/palladium printing, apply to the image the platinum.acv curve (for PCs) or the platinum curve (for Macs) both are included on the disks that came with this book. In Photoshop you would go to Image>Adjust>Curves, then click on “Load,” and then enter the location of the file called platinum.acv (or just platinum for Macs). This will make the image on your computer monitor look terrible! Don’t worry, your negative will print great. If you don’t do this, then your printed image will look awful. 

12 - Add some extra room above your image for a step tablet. Do this, in Photoshop, by going to Image>Canvas Size. A small picture of a square divided into nine little squares will pop up. Click on the little white square just below the black square. This should make the square you clicked become the black square. In the box which says “Height,” add 2 inches to whatever number is there and click OK. You have just added two inches of blank space above your image. Save your file to yet a different name (so you can go back and edit the other files). 

13 - Open the file called steptab.tif (also included on the disk that came with this book -- the file in Mac format is called step tablet and is found on the included Mac disk). Select the whole image (in Photoshop: Select>All), copy it, and then paste it into your image file (the one with the 2 inches of extra room at the top). Using your mouse, move the step tablet up into the 2 inches of black space above your image, and then deselect it by clicking outside the dotted line. Save this file to the same name as in the last step.

14 - Copy the file from the last step to your portable storage media (SyQuest, Jaz, etc.) 

Part D

15 - Take the disk back to your service bureau and tell them that you would like them to make a halftone negative for you from the file on the disk. Tell them to use a “45 degree, elliptical-dot linescreen,” and an imagesetter resolution of 3600 dpi. Also tell them that you need the 1% step of the step tablet (at the top of the negative) to have an “optical density” of between 2.8 and 3.4 (after subtracting film base + fog). This is so your negative will have the correct density range for your paper. Later, depending on the density of the negative, you may have to adjust your paper a bit. But for now, make sure they measure “optical density” and not “percentage dot.” They may look at you oddly, but insist on it and assure them that you know what you’re doing. 

Part E

16 - When the film is ready, take it home to print. Expose until the 100% step of the step tablet just prints as Dmax (i.e., as black as possible). This is your standard printing time. From here you can vary the time +/- 20% to fine tune your print. 

• Chapter 2

Yes, I Want To Understand The Process - The Technical Explanation​

Section - 1. Your In-Camera Negative 

You can use any negative you have. It does not have to be developed especially for platinum, silver, or any other process. Just develop to get that textbook "good" negative.

 
It can be difficult to achieve negatives of high enough density range for printing on platinum/palladium based papers. My paper, for example, requires a negative with a density range of 3.00! This has led to the use of contrast agents such as chlorates (in the sensitizer) and dichromates (in the developer) to increase the contrast of the process to accommodate negatives of shorter range. Unfortunately, these additives, in addition to being hazardous, often increase the grain in the final print. And lastly, either the paper or the developer needs to be adjusted for each negative. Negatives with extreme density range become difficult to print on traditional gelatin-silver paper, should you choose to do so later. 

By means of the digital negative process, in-camera negatives may be processed to a normal density range, allowing them to be used easily for all processes. Digital negatives also eliminate the need for contrast agents in printing. This results in a simpler process -.the developer and sensitizer are always the same formula -- and produces smoother prints with higher printing speed. Finally, you have total control of the density range of the digital negative. 

In the next step you will be scanning your negative to produce a computer file of your image. Once it becomes a computer file you will have complete control over contrast, lightness, and darkness (as well as many other aspects of the image); this is done using an image-editing program such as Adobe Photoshop. You will also have complete and independent control of the density range of the final digital negative. For these reasons all that is necessary is that your negative is good, and that you get a good scan. 

The next section contains more information than any other, so just relax and take it slow; you'll be fine. I will be talking a lot about "dots-per-inch" ("dpi" for short), pixels-per-inch (ppi), and lines-per-inch (lpi). Everything done digitally comes down to using a lot of dots, dots in your computer file, dots on your monitor screen (take a look at your monitor with a loupe sometime), dots used to make the image on your digital negative, etc. 

Let’s start off by getting some terminology straight. Many people confuse dpi (dots-per.inch) and ppi (pixels-per-inch) and will even use them interchangeably, although they are really very different things. Ppi, pixels-per-inch, refers to something which appears on your computer. 

Ppi = pixels-per-inch. All computer images are displayed in pixels. If you enlarge a Photoshop file enough (on your computer monitor) the image begins to look “pixelated” .
-like it was put together with all these squares of gray construction paper (many different shades of gray, of course). Each of those squares represents one pixel, and in Photoshop, each pixel is defined by an 8-bit binary number which indicates which of 256 possible shades of gray that particular pixel should be painted. You may have seen a similar effect on television when someone whose identity must be kept secret is being interviewed, and to conceal the person’s identity they use a video trick which makes their face look like a bunch of little squares. This “computer look” is called pixelation. 

To recap -- pixels are squares that are one of 256 possible shades of gray, and are displayed on your computer monitor. 

Dpi = dots-per-inch. Dots are things you get when you print on paper or expose film. Dots are not square, and they only come in black (i.e., they don’t have shades of gray); however, they do come in different shapes and sizes.

 
To recap -- dots only come in black, but they can be different shapes and sizes. You get dots when you print or make film. 

Dots = printing (printed seen on paper or film). Pixels = computers (pictures seen on your monitor).

 
The little chart on the next page may help you keep this information straight. You don't have to understand it now, just refer back to it while you read the text. 

Dave's Lots-O-Dots Comparison Table

Scanners

Resolution in dpi -- range: 450 dpi to 5000 dpi 

A scanner is the machine which changes your in-camera (gelatine-silver) negative into a computer file, and even though it is connected to your computer, its resolution is expressed in dpi. This is because the rating really tells you how many dots-per-inch the scanner will be able to resolve, on whatever it is you are scanning (paper or film).

Computer Image File

Resolution in ppi -- range: 450 ppi to 5000 ppi 

When you scan your negative, the resulting information is the Computer Image File, which is, of course, stored on your computer. When you view your image on the computer, you are viewing the computer image file. When you "dodge" and "burn," etc., on the computer, you are manipulating the computer image file.

Linescreen

Resolution in "lines per inch" (lpi). This is just like dpi, except it refers to lines of dots rather than one individual dot, so it's really the number of lines (rows or columns) of dots per inch -- range: 225 lpi to 300 lpi. 

To make a digital negative, your computer image file is converted into a pattern made up of thousands of tiny dots. The linescreen is the grid pattern of these dots -- so 300 lpi would mean that there are 300 rows (lines) of dots every inch, and 300 columns (lines) of dots every inch, forming a grid.

Imagesetter

Resolution in dpi -- range: 3600 dpi to 4800+ dpi, there are also imagesetters which can only output 2400 dpi or less, but these are not suitable for this process -- 3600 dpi is the minimum acceptable resolution. 
The imagesetter is the machine which, exposes  the film by means of a laser to make your digital negative. The image which the imagesetter is "drawing" onto the film is your computer image file after having been converted into a linescreen pattern.