Digital Outback Photo
- Photography using Digital SLRs

Digital or Film

by Les Schofer

 
I have been processing digital camera files from my Canon DCS-1 (Kodak 460 on a EOS-1 body) for 4 years now. Back then I knew I didn't know all I needed to know but I didn't know how much I didn't know. This camera design is now about 6 years old, and some of the features and qualities have been improved on greatly by Kodak's subsequent models. Almost every make of consumer level digital camera will yield better "out of the box" color than mine will. I had to learn "seat of the pants" color correction to be able to deliver accurate or pleasing files. In the past 1 1/2 years I have learned and implemented color management practices into my workflow. Since my and other professional level digital cameras can capture colors outside the printing gamuts of just about every printing device, you have to know what the nature of color is (theory), how the computer interprets and portrays color, and how to get it from here to there, or from device to device. When someone scans a transparency and hands off a digital file, the scanner is already fitting the large analogue portrayal of the subject (the chrome) into a digital space. A file taken by my digital camera and just imported into a particular working space in Photoshop, is like having a bunch of chairs in an appropriate size room, but they are not arranged or spaced properly. Opening a digital camera file into a PS working space is properly done by doing a Profile to Profile from the profile I built for my camera to the RGB workingspace chosen in RGB setup. After you have edited the image to your heart's content there, then a decent P2P can be done to the space of the output device you are going to.
 
Essential information regarding these issues can be obtained from Andrew Rodney's web site.
 
This generation of Kodak camera is noted for producing artifacts sometimes called color confetti or Christmas tree lights, and blue channel noise. Quantum Mechanic was first developed for this, and gets run on virtually every file I process. The newer versions give you the option of sharpening in the same step. The few files I have worked on from more recent digital cameras seem to have a color blurring filter function (that's what Quantum does) built into the camera software. I saw the evidence of blurred away artifacting on some D1 images I examined. The noise that the D1 produces at high ISO's is not effectively dealt with by the original QM, it's inventor, Dennis Walker has developed the Band Aid tool for D1 images. If you have a Kodak DCS camera, you always blur the noise before sharpening. Otherwise you will just be accentuating something you want to minimize. Here is where my first assignment with a D1 gave me some skunky results. The owner set it up to write jpgs in the camera, and from what I understand it performs sharpening right at the camera level that cannot be turned off. this particular assignment was a twilight football game and I had to set the camera at ISO 800. The noise patterned, was sharpened horrendously. The one piece of advice for every digicam shooter is, "Know your device!"
 
The artifact blurring effect of Quantum is the springboard for me to mention the value of other color spaces, such as CIE Lab. Before I knew about Quantum I learned that you can convert to Lab and perform a gaussian blur on the a & b channels (all the color of the image is in these 2 channels. All the detail is contained in the L (lightness) channel. You can blur the color but not affect image sharpness. While there you can sharpen just the L channel, which, on the DCS cameras, contains almost no noise. Dan Margulis has written a book called Professional Photoshop 5. In that book he goes into the nature of the Lab color space and some interesting things you can do there.
 
I believe that once you have tweaked and finessed a file to a spectacular degree, you can wreck it real fast by nonjudicious sharpening. I already mentioned cleaning up before sharpening. It's like bathing before getting dressed for church. My camera is a 6 megapixel device. In terms of rendering fine detail it is a bit better than 35 mm. In terms of grain, it is the equal of 4x5...if you don't wreck it with sharpening. My standard radius of USM is 0.6. My amount is usually 200-280. But my threshold is seldom below 4. If yo follow the recommendations of some books and use a 0 threshold, you can make your photo look like it was shot with 800 speed film. If there is a significant amount of noise in the capture (Quantum minimizes it, but does not eliminate it), and becomes more noticeable because of some severe moves in levels or curves, then dark areas with a lot of blue channel noise will get groady pretty fast if you sharpen with a 0-1 threshold. keep in mind here that I am writing about a camera that employs no sharpening in its acquire. So I am exercising control over all the sharpening. I understand that D1 users who choose the NEF format can exercise this discretion. Again, "Know your device!"
 
I have used my 6 megapixel device to produce 4 billboards and quite a few large format inkjet display photos over 5 feet tall. An image processing indiscretion that is unnoticeable in an 11x14 will blossom into a blunder at these sizes. Some parts of the image may be better left unsharpened. A huge expanse of blue sky may contain a significant amount of noise (and in the red channel...go figure). It is usually pretty easy to select that sky and then inverse the selection, sharpen the rest of the picture, and even apply a heavier dose of Quantum to the sky than to the rest of the picture. believe it or not I use my 6 mp camera, to shoot sports for a university. My maximum ISO is 100, and I base my exposures on a 200, which means I must do some extensive moves in Photoshop, so dark areas are particularly noisy. And if my focus is not totally crisp, I must sharpen at a higher radius (1.8 to 3.0) to rescue it. This extra high sharpening reeks havoc on noisy areas. Most of the time when I prepare one of these shots I will do a slightly rough (not pinpoint accurate) selection around the athletes who are the center of interest, and then inverse the selection and hit the background players and crowd with a gaussian blur. This reduces the effect of the noise, which would appear like film grain, very prominently in out of focus areas. Since the eye gravitates to areas of sharpness, I have focused the viewers interest more on the real subject of the picture.
 
I was involved in a recent discussion group on the topic of whether the photographer should sharpen his file or let the designer or print shop do it. I need to make my picture sharp, because, "I Know My Device!!!!!!!!" The professional preparing the file for the final output might well sharpen for that purpose, but assuming there is a knowledgeable person in that position is a big assumption. Get as much knowledge as you can (there, I snuck it in again) and then take an appropriate amount of responsibility. If your camera processing software sharpens at all before you are staring at it in Photoshop then your strategy would be different from mine In my 22 years of film photography and 4 years of digital, I have found out there are almost unlimited opportunities for others to screw up your work after it leaves your hands. Following are a few questions you should ask to the resident prepress expert at the commercial print firm you are dealing with:
  • What TACO (total ink limit) makes your Heidelberg happy?
  • When you get these files on disk will you resample them during sizing to the layout parameters?
  • What dot gain should I separate for when preparing files for your press/paper combination?
  • Will you utilize a profile that I embed in my file?
  • Will you accept the files in RGB, and if so what working space do you have set up?
  • Can you supply me with an ICC profile for your proofing system?
  • Do you convert colors when opening a CMYK file that does not match your CMYK setup?
 
If the answers to more than 2 of these fall between "Du-u-uhhh!" and "What do you mean?" then you may be dealing with the wrong vendor. Of course, photographers doing jobs for design firms and ad agencies are seldom in the loop when the printing decision is made, and many times it isn't made and the paper hasn't been selected until some weeks after you have shot and delivered your pictures.
 
This has led me into the area of creating ICC profiles for each output device I deliver files for. I have profiled the proofing systems of 7 local print firms, and with my Kodak 8650 dye sub printer (which I've also profiled) I can simulate what the file will look like on company A's 3M Matchprint proofer.
 
Now go out there and be gentle with that sharpening tool! (And "Know they device").
 

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