Last month you learned how to use your new digital darkroom to print a photo-calendar using Calendar Creator Plus. While the calendar portion of the print looked great, you were probably disappointed with the photo size or quality.

Problems! First, you want the photo to be as big as possible. This will show off detail better. Calendar Creator Plus, like most inexpensive printing programs, does not tell you how big the picture should be.

Next, you want the photo to be printed at the maximum quality level that your system allows. How do you force Calendar Creator Plus to print something you can be proud of? That's the second problem.

The Big Picture

Last month, you printed your photo-calendar with the optional Big Pictures scaling set to "Don't Scale". That simply printed the photo "life size" relative to your printer. If the original was small, the printed photo was also small. If you experimented and scaled your photo, then you got a full-size image. Problem was, that image was either distorted or cropped. Even so, that is the first step to your solution. Now you simply measure the image size. On my system, the image is 184mm wide by 108mm high. Why doesn't Calendar Creator Plus just tell us these numbers? Well, the dimensions change, depending upon the number of titles you include, the size and style of fonts you select, etc. This size is the size you get when you use the exact settings that I gave you last month. Measure your own printed image, which may be slightly different.

If you want your original to fit this size exactly, then it must have the same aspect ratio. You will get maximum quality if the aspect ratio of your scanned image is the same as the aspect ratio of the printed image. The aspect ratio is 184mm divided by 108mm, equals 1.7.

A 35mm frame has an aspect ratio of 35mm divided by 24mm, equals 1.5. You will need to crop a 35mm image slightly when you scan it.

The Secret Formula (Again!)

To maximize quality, use this formula:

Input resolution = output resolution * quality factor * scale

The input resolution is the resolution that you will need to set on your scanner. The output resolution is the resolution that you will use on your printer. The quality factor depends upon your printer's method of screening photos. The scale is the relative size of the final image to the original image.

Relatively Confused? Let's clear things up with an example. Step 1 is to determine the quality factor. Look in your printer manual for screening or screens or half-tones. The industry standard method of screening is half-tone screening, or amplitude-modulation (AM) screening. If your printer uses this, select a quality factor of 1.5 to 2.0.

My Epson Stylus Pro, and many other newer inkjets, support frequency-modulation (FM) screening, usually called error diffusion printing. If your printer supports FM screening, use a quality factor of 0.67 to 0.75.

In either case, the lower value gives a smaller file size, but the higher value gives better results.

Step 2 is to pick a printer resolution. My Epson will print at 180 dpi, 360 dpi and 720 dpi. Let's pick 360 dpi for this exercise. This will keep the file size down for quicker printing.

Step 3 is to select the scan area in your image, adjust the aspect ratio to 1.7, and calculate the scale. Let's scan from a 35mm slide. Load your scanning software and bring up a preview image. Select an area for scanning. Your software should show you the width and height of the selected area. Adjust the selection until the width is 1.7 times larger than the height. For example, you might select an area that is 32mm long. Now, 32mm divided by 1.7 equals 18.8mm. That means your image selection should be 18.8mm high. Adjust it to this value. Divide the output width by the input width to find the scale. We know that the print size will be 184mm wide and the scan size will be 32mm wide, so 184mm divided by 32mm equals 5.75. This is the scale.

At this point, you have finished gathering the numbers to plug into the secret formula. For this example, using a printer with FM screening, you know that the output resolution desired is 360 dpi, the quality factor desired is 0.67, and the scale is 5.75. Let's calculate:
input resolution = 360 dpi * 0.67 * 5.75 or
input resolution = 1387 dpi

Set your scanner software for a scan output resolution of 1387 dpi. That's all you need for high quality output on your printer. If you really want to push your system to the limit, use a quality factor of 0.75 in the above formula and set your scanner for the resulting figure (which you calculated to be 1553 dpi, right?). This last figure reflects the maximum quality your system can print from your original 35mm image. Scanning at any higher dpi simply wastes your time and will not produce a better print.

Blast Off!

Scan and save your image, then load it into Calendar Creator Plus using the same settings that I gave you last month. When you print the calendar, the photo will be "full size" and looking good. Now recalculate for a printer resolution of 720 dpi (if your printer works at this resolution). Create a new scan (that's right, at 3105 dpi). Print another calendar at 720 dpi on glossy paper. The results will be almost as good as doing it the old-fashioned way with Kodalith masks, multiple exposures and smelly chemicals!

Go Forth and Multiply! Practice these techniques until you understand how they work and why they are important. Use the secret formula before you scan anything, to make sure you get the best quality output that your system can produce.

Next month I return to web site design for professional photographers like you. I will focus on commercial web sites this time, not personal web sites. The first article deals with the single most important thing you need to know about when building a commercial web site: How To Control Costs.