• What Does Mushing Magazine Want?
• DPI and Image Size
• My image is 13" wide: is that big enough?
• What about reducing images?
• Naming Your Images
• Choosing the Right Resolution

• What about adding pixels?
• How should I send digital image files?
• Choosing Your Images
• What Format Should I Use?
• Creating a Contact Sheet
• Can I make the picture bigger with Photoshop?

The term resolution refers to how well an image is resolved; that is, how "real" or smooth the image appears to our eyes. The computer displays an image as a series of dots. The higher the "dots per inch" (DPI), the higher the resolution, and the better the image appears to us. When you get enough DPI (~300) then our eyes can't distingish the individual dots at all. This is termed photographic resolution- it looks as smooth to us as a photograph.

The resolution on a monitor is entirely different from the resolution on a printed page. On a monitor the resolution is dependent not on DPI, but on how many colors the monitor can display. For instance, a 24-bit photograph (capable of displaying 16.7 million colors) on an 8-bit monitor (that can only display 256 colors) will appear to have low resolution because the monitor is not capable of displaying all the information in the image. The same image on a 24-bit monitor will look great. A monitor doesn't care about DPI, it's affected by how much color it can display.

Resolution becomes very important when printing. A 24-bit photograph with 72 DPI will look pretty bad when printed (think impressionist painting vs. photography). On the monitor, however, it will look great. That same image at 300 DPI will print much better (photographic quality), but the images on the screen will look exactly the same.

Just because an image looks good on screen does not mean it will look good printed. Images need to have a resolution high enough to look good on paper.

Digital cameras set at default image size and DPI often produce files that seem to be pretty large, look great on screen and seem to be big enough to send to us for publication, but oftentimes the image size is deceiving. For example, we are sent an image that is 13 x 11 inches at 50 DPI. As explained before, we need to have a resolution of 350 DPI for best print quality. If we resize the image without stretching or adding pixels, the image drops in size to less than 2 x 1.5 inches at 350 DPI. If we end up using the image and printing it larger, say 4 inches wide, then we have only half the resolution we desire; the picture will end up fuzzy in the publication.

Luckily the problems with enlarging an image do not affect decreasing dimensions when done in an image editing program. We can always make a big image smaller, but we can't make a little image bigger.

Once you choose the images you want to send, give the files meaningful names. The long file extensions straight from the camera are confusing and offer no insight into the file they represent. A CD sent to us filled with images RA100956­01 through RA100956­165 is not useful. It takes us hours to open and review each image and even longer to go back and find the images we like again. If sending a CD or disk with large numbers of images it is helpful to organize them into meaningful categories and folders such as equipment, feeding, health, races, vaccinations, etc., so we can select from a collection of images for the topics we are illustrating without spending an undue amount of time searching for usable images.

Most consumer-grade digital cameras do not take pictures at a high enough resolution suitable for printing at magazine quality. If your camera takes a picture with the resolution of 1280 x 960 (1.3 megapixels) it can make a print up to 4 x 6 inches with good resolution, i.e., without noticeable pixels. A 2.1 megapixel camera can produce a good quality image up to 8 x 10 inches. For maximum versatility a 3.3 megapixel camera is desirable.

Read the camera's instruction booklet carefully to determine the highest quality (i.e., largest) picture your camera can produce. You will discover that not very many high-resolution photos will fit on your memory card, and it may be necessary to purchase additional memory in order to photograph an event at reproducible resolution. By comparison, an image taken with 35mm film has a resolution of 6 to 20 megapixels, depending on film speed. A slide scanner has no problem producing a 16 x 20 photo at 350 DPI from a slide or negative. Currently there are no digital cameras able to reproduce those results.

Changing resolution and image size is probably the most misunderstood part of working with digital images. Imagine a picture printed on a thin piece of rubber. When the rubber is at its normal size the picture looks fine. If you stretch the rubber to twice its normal size the photo also doubles in size, but it doesn't look as good; it loses detail.

When a digital image file is created it is given a set number of pixels, or "picture information pieces." If you later change the physical dimensions of the file (like stretching the rubber) the pixels stretch and become jagged.

Stretching pixels doesn't work, but it is possible to add more pixels instead of stretching them as you upscale an image. In Photoshop the term for changing the number of pixels as you change the size of an image is resampling. Unfortunately, resampling up doesn't work. The program must guess at what detail to insert as it creates the new pixels. The result is a fuzzy image. Sorry, pixels can't be added from thin air. A large, detailed image is required from the beginning to have it at the end.

The nice part of the difference between screen and print resolution is that it is possible to send lower DPI images for review without sacrificing how they look on screen. If you wish to e-mail an image for review this can be done with a fairly small file at a low resolution such as 4 x 6 inches at 72 DPI. We can look at it on screen and print out a low resolution version for our files. But understand that we can not use such a file in our publication- we need a copy of the image that is at the right size and printing resolution for final output. If you don't have a larger copy of the file please don't send a review copy. It confuses the production process and requires finding alternate images at the last minute. Know the limitations of digital images.

One of the nice aspects of digital photography is how easy it is to transfer images from your digital camera to your computer, printer and CD burner. Just because it is easy to transfer files does not mean that the files are best for printing. Look carefully at your files before sending them. Are they in focus? Do you have a copy at a high enough resolution to print? Is the subject clear? Would I choose this image if I were a magazine editor?

The TIFF format is a raster file format, meaning it is made up of pixels. (As opposed to a vector file which is composed of mathematical elements.) Almost any imaging program can save, open or import TIFFs. The files are very flexible, they can be CMYK, RGB, grayscale, index or bitmap format and can be any bit depth and resolution. It is the best file format for going between Windows and Macintosh computers.

Compression means that the information in a file is squished so the file takes up less disk space. There are two general kinds of compression, lossy and lossless. Lossy means some of the data is lost when it is compressed. Lossless compression loses no data. You can save TIFF images with LZW compression which is completely lossless.

The JPEG file format is a compression format that makes images into much smaller files. The JPEG format is a lossy compression. When you save a file as a JPEG a certain amount of information is thrown away and cannot be retrieved. When you save a JPEG you have an option of file sizes. The larger the file, the less the compression, and the less data is lost. Never save a file with JPEG compression if you are going to print it.

When we receive JPEG files we open them and resave them as TIFFs, but we can't recover the information lost in the origonal compression of the file. Use JPEG files for previews, e-mail, and computer presentations, but not for high quality reproduction or printing.

EPS raster images are significantly larger than their TIFF counterparts. EPS is pure PostScript code designed to work with PostScript printers. An EPS file will not print out properly on a non-PostScript printer such as an office ink jet, but these files are useful when special printing effects are added to a file because an EPS can save those effects and give the proper instructions to the PostScript printer.

GIF and JIF files are primarily Web/computer display files. They are compressed files (lossy) and have limited color display. There is no use for them in professional printing. PICT files are a primitive image format designed by Apple for its programs. They too have limited color display options and often have problems printing on PostScript printers. Please do not send images in any of these three formats.