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The material on this page was provided by John Parks.
Enlarging digital photographs: For best quality prints, a 3.0 megabit camera makes excellent 5" x 7" prints. The higher the number of megabits, the greater the quality of print that can be made from the image. An image from an 8mb camera can be used for an enlargement of 13" x 19" or more.
It is not necessary to spend more money for a higher megabit camera in order to make larger prints. Software is available to increase the size of the enlargement that can be made from fewer megabit images. An example is "Smart Scale", made by Extensis, which allows the user to enlarge a picture up to about 1600% in the computer. This is a plug that works with Photoshop and other graphics software. Note that this method does not actually add detail - in order to get a larger, high detail photograph, you must take several overlapping photographs and then merge and trim them in a graphic program such as Photoshop.
The iLife suite that comes with OS-X includes the iPhoto program for sorting photos in the computer and providing some basic editing. Many Epsom printers come with a program called "Film Factory" This will do a lot of the same chores that iPhoto performs but work better for putting different size photos on the same page if you wish to place multiple prints on a page, like placing four 4" x 5" print on 8" x 10" paper.
Image file size will determine the size and quality of any enlargements. You camera should be able to make a 14 to 20 Mbyte for an 8" by 10" enlargement with an uncompressed TIFF format file (that is, it retains all the detail and therefore the highest quality).
Much smaller files can be produced using JPEG compression. This compression is lossy and so the quality of a subsequent print is reduced. The number of images that can be stored on a compact flash card (used to store the images) with the digital camera depends on the compression used when the picture is taken. A 256 Mbyte compact flash card with a 5mb camera can hold the number of pictures shown in the table:
| Mode | Number of Pictures |
Image Size (Mbytes) |
|---|---|---|
| RAW | 24 | 9.50 |
| TIFF | 16 | 14.00 |
| JPEG (fine) | 90 | 2.10 |
| JPEG (standard) | 122 | 1.10 |
| JPEG (economy) | 183 | 0.65 |
When pictures are stored in the computer in JPEG/JFIF format, then it is compressed each time that it is saved and more information is lost each time. This is undesirable if you want to make large prints from the picture or use it repeatedly in graphics applications. The way that I overcome this loss of quality is to convert the image to TIFF (or some other lossless format) before performing any kind of editing or manipulation of the image in graphic applications.
RAW pictures are unprocessed and special software is needed to open the files for work in graphic editors and applications such as Photoshop.
TIFF format files are lossless and can be edited by almost every graphic editor or application.
JPEG format files are lossy but much smaller than RAW or TIFF files. However, they provide surprisingly good results with the smaller files because of the ingenious compression algorithm. This format allows more photos to be stored on CD-ROM, hard drives, compact flash cards, micro drives, and other storage media.
To obtain the sharpest photographs, printing the photos at 240 ppi to 300 ppi gives good results on most home printers.
The terms ppi (pixels per inch) and dpi (dots per inch) are used interchangeably, even by manufacturers of photo and printing equipment. Jet printers often go up to 1440 dpi or even 2880 dpi but this resolution is only effective when photographic paper is used and can only be distinguished with a magnifying glass.
Image data is needed to support the print size required. Prints generally lose detail noticably at less than 240 dpi. Prints will only look noticeably better above 300 dpi if high quality photographic [paper is used. Details are often less important in smaller print sizes such as 3 1/2" x 5 1/2" that are often used in photo albums.
Many of us have collected a lifetime of photos, either as slides, color negatives, or as prints that were made before digital cameras and home computers became available. When scanning slides or prints you need to figure out the dot per inch to scan at in order to obtain acceptable quality prints. For example:
To obtain a 10" print with 300 dpi you will need to scan 3000 dpi
To obtain an 8" print with 300 dpi you will need to scan 2400 dpi
There are accessory programs available to use to maximize the quality of you photos and solve specific problems. I found that many of the old slides that I scanned had dust and scratches. Silverfast is scanner software (often included with the scanner) that removes dust and scratches well and allows the user to save the image at a preferred file size and format.
Many of the simpler photo editing chores such as cropping, naming, rendering in Black and White, and cataloging can be performed in iPhoto (Free with OS-X)
Plug-ins are 3rd party software that work with Photoshop and other graphic editors to add to their functionality, especially with new filters. Some of these make long and complex sequences into simple operations. Special effects can be included in Plug-ins - for example "Flood" adds water to a photograph with adjustable waves, ripples, and reflections so that you can make you relative appear to be standing in a flood!
Photoshop was originally designed for graphic artists. However, many amateurs now use it for fun in a creative way to produce pictures that a camera lens will never take. Photoshop Elements (A reduced but still very powerful version) often is bundled with scanners or can be purchased and will provide all the photo editing tools that most of us will require.
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©Macintosh Appreciation Group of Island County (MAGIC) 2004
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