 Number 239 - April 2003 |
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| A Brief Introduction to Digital Photography Part IV - Publish Your Photographs | |
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by Richard P. Ten Dyke | |
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Perhaps the most
interesting and dynamic topic in digital photography is printing,
because the quality of the printed image has improved dramatically in
just the last few years. Skip to the bottom line - the biggest problem
in printing, until about a year ago, was that colors fade. Color prints,
no matter how good they looked originally looked like a pizza in about a
year. That problem has been solved, and it opens digital photography to
those who take photography seriously, as an art form.
But let's back up and discuss the first problem first - how to make a good looking photographic print. The answer is simple, use a good quality ink-jet printer with ink and paper recommended by the manufacturer. Laser printers work too, but the result always looks like it was printed on a laser printer. It appears that Epson has lapped the field, and is now far ahead in the quality-permanence department. They offer two kinds of inks - dye and pigment. Pigment inks are the longer lasting, but the new dye inks are better than they used to be. (I do not necessarily recommend one brand over another, and I have a three-year old Hewlett-Packard that still works just fine, but I do not use it when I want the best quality.) Publish Your Photographs Printers use the CMYK (Cyan, Magenta, Yellow, Black) method of printing. Recall that when we talked about image capture, we were using RGB (Red, Green, Blue). What is the difference? It depends upon whether we are adding light or subtracting it. On a display we are adding light. We have red, green, and blue phosphors that glow. When all three are glowing at their brightest, their combined output adds up to White, which is the sum of all colors. When we put ink on paper, we are subtracting light. The white light falls on the paper, and some of that light is absorbed by the ink. What is not absorbed is then reflected. If we subtract yellow from white light, we get its complement, blue. So what we call blue ink is a substance that is subtracting yellow from white. If we subtract cyan, magenta, and yellow from white light we should get no light, in other words, black. However, reality and theory are a little off at this point, and what we really get is a dark, muddy brown. So we supplement the system with the addition of a true black ink. Another area of contention is very light colors. For this reason some of the high quality printers now come as CcMmYK printers. The "C" stands for Cyan, and the "c" stands for a light cyan. Same with "M" and "m" for magenta. Yellow is already a light color, so no "y" is needed. These printers offer a better gradation of tones. Interestingly, the problem of light and mid-tones applies to black and white photographs as well. For that reason, some new printers now come with a "Gray" as well as a Black. These are identified seven-color or "CcMmYKk" printers, and the results, as they say, will knock your socks off. I don't have one of these - yet. Paper? It makes a difference. Use the manufacturers' recommendations. The final image is a marriage of ink and paper, and, like any marriage that is expected to last, they should be compatible. Ink-jet papers are coated, and you can get several weights and textures, such as glossy, semi- gloss, matte, and watercolor. You can print on uncoated papers as well, but quality suffers. It should be noted that some printing processes do not yield water resistant prints. The Epson prints, on their best papers, are water-resistant and some others may be, but check to be sure if it is important to you. A few other issues in printing are paper size and printing speed. There are always tradeoffs, of course. Not everyone needs to print on 13 inch paper, and not every one needs 6 pages per minute. Ink-jet printers are slow, so you will be trading speed for quality all the time. Another issue is cost. The ink-jet printer companies make most of their money on supplies, and in particular, on ink cartridges. Yes, you can buy cartridges that have been refilled by third party vendors, but since I never use them I am not the person to recommend for or against them. There are some other printing methods still in use. If you want high speed, low materials cost, and can suffer slightly reduced quality, then a laser printer might be your best choice, particularly if you are in the real estate business or some other area where you want to print 100 or more copies of something. There are also special purpose printers that are limited to 4 x 6 inches, for example. One older printer technology is dye-sublimation which offers high quality, but is slow and expensive and disappearing from the scene. Displaying Photos on a Monitor Another practical use for your photos is to display them on the computer monitor or project them with a digital projector. You can create a slide show that runs continuously, or you can develop a presentation that is under the operator's control. Many software packages will help you do this, but we cannot review them all. Slide shows differ from printing in that a smaller image file is needed to achieve maximum quality. The viewing screen on a computer has only limited capability to render detail, so one can get by with smaller files. For example, a typical monitor with an 800 by 600 pixel screen presents an image containing 480,000 pixels. A 3-megapixel file, desirable for printing, contains six times as much information as can be displayed effectively on the monitor. For developing the presentation, Macintosh owners with OS-X can use iPhoto, which is designed primarily for managing a photo inventory, but has some editing capability and contains a slide show feature. Another well-known package is Microsoft's Power Point presentation software package that runs on either a PC or a Mac. If you save your file on a CD, you will then be able to show your show using any computer that has the program installed. |
And more about color:
The first rule in printing images is: "what you get is not what you see." The colors that you see on the monitor, represented in the RGB system, definitely will not appear equivalent on paper, represented in the CMYK system, even though they are theoretically equivalent. Professional printers deal with this issue on a regular basis, which sets them apart from the rest of us non-professionals. Think of printing as firing a gun at a distant target. You aim carefully, but the bullet hits somewhere off the mark. You then adjust your aim, to fire at a point which is now, away from the bulls-eye, in order to compensate. It is similar with printing. When you see your print, you will want to adjust your image on the screen to be different from what you want to see in the print, in order to compensate for the amount by which you missed your target. This is true when printing either color or black and white. I believe that getting a good black and white print is the more difficult, because the viewer is sub-consciously very discerning of subtle warm and cold tones in black and white prints. When you use your editing software, you may want to change the color of a whole image, or perhaps a section of an image. Your image-editing system will have a way of telling you what color exists at any point on the screen. But you may have a problem in interpreting what it says, because it uses an obscure way of representing color. If you have the patience, read the following. We said that the color of a pixel is represented by some amount of Red, Green and Blue. Therefore, a numerical representation of a color would give you a value for each of these values. We allocate one byte of information for each of these colors, so each value can range from a level of 0 to 255. If you open up the color window on Photoshop Elements you might find a color listed as something like: Red 23 Green 208 Blue 255 You will also see this same information expressed in hexadecimal form. The hexadecimal system uses sixteen symbols to represent the sixteen values from 0 to 15. The six additional symbols are A, B, C, D, E and F. The symbol for nine is '9', the symbol for ten is 'A,' eleven 'B,' up to 'F' for the value of fifteen. The decimal value 23, above, becomes 1 x 16 plus 7, or '17' in hexadecimal. The value 208 becomes 'D0'and the value 255 become 'FF' So the same color, above, represented in hexadecimal form becomes: "17D0FF" Note that there is no delimiter between the values for red, green, and blue. The color represented above has a lot of green and blue, and a relative absence of Red, so it would appear as a near-Cyan color. A light Gray would have equal values for Red, Green and Blue, for example: 'EEEEEE' A dark gray could be '363636' A 'warm' gray, with a little less green (more magenta) might be '363336.' We have mentioned two of the basic methods for representing color, called RGB and CMYK. Another is HSL (Hue, Saturation and Lightness), but that is an advanced topic, not to be covered here. And, in summary ... In the four sections of this article we have covered how to capture, store, edit, and publish your photographs. I have mentioned the following products which represents my current investment in a digital processing system. These are only representative of what I, personally, have found useful for my own purposes, and they by no means represent a complete list of all options that are available. Camera: Olympus E-10 Scanners: (1) Film Scanner: Nikon CoolScan IV High Quality Printer: Epson 2000P Computer: Macintosh iBook Image Management Software: iPhoto (included with the operating system) Image Editing Software: Photoshop Elements Total investment: $5,320. Your needs will not be the same as mine. My goal is to be able to print and display high quality archival photographs that are 11 x 14 inches and larger. If you are primarily interested in preserving family and vacation photos, or if your work is primarily for presentation on a computer monitor, digital photography is still your best choice, but you will be able to get your system up and running for less money. Have fun. Richard Ten Dyke is a member of Danbury Area Computer Society who has had a long interest in both photography and computers. He started his photography career with a Leica IIIC in 1952, and his computer career working with an ERA 1103 in 1956. He currently is retired from IBM and resides in Bedford, New York. You can reach him at tendyke@bedfordny.com Copyright (c) 2002 Richard P. Ten Dyke |
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Number 239 - April 2003
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