Printing
The final stage of the digital photography process is taking the image that you have created and actually turning it into a printed photograph. This stage can be just as perplexing as getting the image in the first place. On the surface, printing seems like a very straightforward process — all the printer has to do is to take the digital image and print each colored dot on a piece of paper. Unfortunately, this process is considerably more difficult that it appears. Here I will take a look at several aspects of this conversion process and try to shed some light on the subject.
Adjusting the Monitor
Wait a minute! I thought we were talking about printer here. Why am I bringing the monitor into it? Well, the problem is this: Your goal is to take what is on the screen (your monitor) and get a similar result out of your printer. Ideally, what you see on the printed output should match what you see on the screen: the same colors, the same brightness, the same contrast. But what if what appears on your monitor as yellow to you on the screen is actually a light shade of green? What if your monitor is too bright and shows more detail in the dark areas than it ought? If you think about it, the first thing you have to do is to make certain that your monitor is correctly adjusted.
Before you begin, your monitor should have been on for at least one hour so that it has had time to fully settle in. Make sure that your system is configured to display 24-bit or 32-bit color. 16-bit color is not sufficient. Consult your operating system manual to verify and change this if necessary.
Look at this grayscale. If your monitor is correctly calibrated, each of the blocks should appear as distinct shades of gray. If you cannot see any difference in the extreme areas, then you will need to adjust your monitor's brightness and contrast settings so that all of the blocks are visible and distinctly different.
You should also check and adjust your monitor colors using specialized software, such as Adobe Gamma (packaged with Adobe Photoshop and Photoshop Elements) or WiziWYG (available as a free download from Praxisoft (www.praxisoft.com)). Only one of these programs should be run on your system. These programs will guide you through a process that adjusts the red, green, and blue levels on your monitor so that you have a reasonably adjusted monitor that displays a fairly accurate range of colors. If you require more precise color adjustments, you may wish to purchase a monitor adjustment tool, available for $100 - $250 (www.colorvision.com).
Once you have a properly adjusted monitor, you can then start considering the problem of printing.
Choosing a Printer
If you do not already have a printer, or are considering getting a new printer, here are some things to consider.
Printer Colors vs. Monitor Colors
Monitors have three primary colors: Red, Green, and Blue (RGB) that are combined to create all of the colors visible on your monitor. These colors are additive, which is to say that as the colors combine, more light reaches your eye. Thus white is the combination of all three colors at full intensity, and black is the complete lack of any of the colors. Printers also have three primary colors: Cyan, Magenta, and Yellow (CMY) that combine to create all of the colors visible on your printer. These colors are subtractive, which means that as the colors combine, less light is reflected from the page to reach your eye. Thus which is the complete lack of any color, and black is the result of the maximum mixing of all colors. In practice, due to imperfections in ink, a satisfying black color is difficult to achieve using this technique, so an additional black channel is used. This results in the printing colors of Cyan, Magenta, Yellow, and blacK (CMYK).
Printer Type
There are two major type of printer commonly available: Inkjet and Laser. Both of them emit microscopic dots of ink or toner that combine or dither to create all of the colors possible from that printer.
Inkjet printers work by spraying microscopic drops of ink onto the paper. All of them provide the basic four colors (CMYK), although many of the higher-end printers utilize additional lighter shades of CMY to provide more precise colors, and some offer different inks for text and photos. Generally speaking, the more ink cartridges there are, the better the color matching, although the differences may be too subtle for the average person to appreciate, especially if you do not compare identical pictures side-by-side. Still, if you want the best possible color output, you need to look to printers with a wider variety of ink from which to draw. The cost of printing a full 8.5 x 11 photograph may run anywhere from 30 cents up to a dollar or more in ink and special paper.
Name Brand vs. Generic Ink
Inkjets are infamous for their expensive ink. You can often purchase an entry-level printer for little more than the cost of the ink. There are numerous vendors that offer ink cartridges for 50-80% off of the manufacturer's cartridges, but surprisingly they aren't worth it. The ink they provide has a tendency to be slightly off-color, has a tendency to fade or smear, and are inconsistent in their output. The biggest problem is that these inks tend to clog the print head, requiring at least a costly and time-consuming cleaning and, at worst, the replacement of the entire printer. The same holds true with ink refill kits. Apart from being potentially disastrously messy, these ink may be prone to the same problems as off-brand inks, including the tendency to clog the print head. In the long run, you are better off biting the bullet and purchasing the manufacturer's ink rather than trying to save a couple of dollars and struggling with generic suppliers.
Laser printers work by tracing paper with a laser that imparts a slight static charge to the areas the laser touches. Toner is then exposed to the paper, but only clings to those areas with a static charge. A heating element (the fuser) is then applied which melts the toner onto the paper. Laser toner comes in the standard CMYK colors. Laser printers come in two configurations: One laser, or four lasers. A single-laser printer will use the same laser to put down each layer of toner, passing the page four times past the same laser. These printers are easily recognized by looking at their Page Per Minute (PPM) rating for black and white or color — their black and white rating is much higher, usually by a factor of 4. Another difficulty these printers may have is that of registration — the alignment of each color on the page. Because the paper has to cycle four times through the system, the alignment of the paper can become slightly off, resulting in blurry or fuzzy images. A four-pass printer devotes one laser to each of the four colors. Although more expensive, this system is just as fast in color as black and white, and is less prone to alignment issues. At this time, color laser printers do not generate as clear an image, and offer fewer color tones than inkjet printers, although their cost per page is significantly lower — in the 7 to 12 cent per page range for toner, compared with 25 cents to a dollar per page for inkjet printers.
The cost of color laser printers has dropped dramatically, while their image quality has improved to the point that you can now get a color laser printer for less than $1,000 that will be quite satisfactory for printing of color brochures. You may even find the photo quality to be approaching that of a sub-$100 inkjet printer. As this trend continues, although I am for the moment using an inkjet for printing photographs, I will give serious consideration to a color laser as my next printer.
Printer Resolution
So you've got a printer that boasts 4800 x 1200 dpi resolution with 4 ink cartridges. What does that mean? Is 5760 x 1440 resolution with 8 ink cartridges a lot better? What does that mean in terms of the printout? Why is the horizontal resolution so much better than the vertical resolution? What would be the best image resolution for my printer?
The answer to all these questions is hidden in the arcane terminology and technology used in printing. An inkjet printer has an array of nozzles from which the ink is ejected. Each nozzle is dedicated to a specific ink color. This means that a printer with 4800 Dots Per Inch (dpi) of horizontal resolution with 4 ink cartridges will lay down 1200 pixels per inch (ppi) — 4800 dpi divided by 4 inks. This is the true resolution of the printer. Some printers will match the vertical resolution with the horizontal resolution by making two passes of the print head over the same area, with the second pass offset by ½ a printer dot's worth. So now, let's compare the two printers mentioned above.
- 4800 x 1200 dpi with 4 inks: This yields 1200 (4800 dpi / 4 inks) horizontal resolution and 1200 dpi vertical resolution. The printer probably lays down the ink in a single pass of the print head.
- 5760 x 1440 resolution with 8 inks: This yields 720 (5760 dpi / 8 inks) horizontal resolution and 1440 dpi vertical resolution. The printer probably lays down the ink in two passes of the print head each offset by ½ a dot both vertically and horizontally, since it is unlikely that the print nozzles are the same size vertically as horizontally.
Which printer is better? Probably the one with 8 inks. As we have seen, beyond 300 ppi there is very little extra benefit in higher resolution. The benefit of a wider range of ink colors probably outweighs the apparently higher resolution of the 4-ink printer.
Picking a Printing Resolution
Now that you know how to determine your printer's true resolution, the best results will be obtained by providing your printer with a resolution that allows the printer to print a consistent number of dots per pixel. This means that if your printer can print 1200 ppi (as in the first case), you would do well to print at 200 or 300 ppi rather than at something in between, such as 240 ppi. In the second case, you would probably do better printing at 360 ppi (exactly ½ of the 720 printer head resolution) than 300 ppi.
The built-in printer software will do a good job of simulating odd resolutions (from the printer's standpoint), but to have the most control you should either reduce or increase the resolution of your image to match the printer's optimum. If you need to increase or decrease the resolution of your image in a way that requires resampling your image, it is best to do it in small (10% or less) increments. This tends to blend adjacent pixels and results in a more accurate representation of your image.
You should also refer to this table to provide the appropriate picture resolution to your printer.
Calibrating Your Printer
Assuming that you use an image-processing program, such as Adobe Photoshop, you can create a process to obtain the very best results from your printer compared to your monitor.
- Create a representative picture or, better yet, a collection of a variety of pictures — some with color, others black and white; some with a wide range of tones; some with fewer. Save this image for later reference.
- Print this sample on the kind of printer paper you expect to use.
- Let the page dry for at least 48 hours. Some printer inks will change color slightly over this period of time.
- Reload your sample image into your image processing software and compare it to your printed output.
- Adjust the sample image so that it matches the printed image as exactly as possible.
- Now add adjustment layers as necessary to bring the image back as close to the original screen image as possible.
- Save the settings for these adjustments, either in a macro or action in the software or just by writing down the necessary steps.
Once you have done this process, you should then be able to obtain the same results from your printer (subject to your printer's capabilities) as appears on your monitor:
- Load and edit your image until it appears as you would like to see it.
- Upscale or downscale by 10% or less until your image's resolution matches your printer's target resolution of 300-360 ppi.
- Apply the corrections you deemed appropriate from the previous method.
