Photo Primer

By Mike DuBose, United Methodist Communications
Updated July 10, 2002

This information is intended to help users of United Methodist News Service (UMNS) photos via the Internet and/or those who are new to digital imaging.

Photographs are provided on this page primarily to serve publications using UMNS stories, typically conference newspapers. You may also find them useful in other outlets like newsletters or simply to view with your web browser.

UMNS stories that are accompanied by photographs are shown on the news story page with the tag line "Photo(s) are available with this story."

When the page for a story with a photograph is loaded, the text of the story is displayed along with a thumbnail (small) image of the photograph and a caption. Click on the photo to be directed to the high resolution (full size) version of the photo.

The thumbnail views displayed with stories and on the "Photo Gallery" pages are not suitable for printing. Please be sure you have loaded the full-sized version in your browser before saving the file to print.

A word about pixels

How many pixels do you need?

So, how many pixels are in these pictures?

Getting these pictures from our computer to yours

A word about file formats

FREE caption included!

Permission for use

A word about pixels

Digital photographs are made up of pixels (short for picture elements). You don't really need to know a lot about pixels in order to use these photographs, but you do need to make sure you have enough pixels for the intended final use of each image.

The term "resolution" is often used to refer to how many pixels a digital photo contains. The resolution of a digital image is most accurately expressed as being so many pixels wide by so many pixels high, for example, 640 x 480 pixels.

The terms "pixels per inch" (ppi) and "dots per inch" (dpi) are also often used to describe resolution. A term like "200 ppi" tells you nothing about resolution when used by itself, however. Because pixels have no physical dimensions until they are output somewhere (i.e., computer monitor, laser printer), resolution expressed as "pixels per inch" needs to be accompanied by how many inches wide or high the physical output will be, for example, 200 pixels per inch at 10 inches wide.

An image can be 200 ppi by one inch wide for 200 pixels, or 200 ppi by 10 inches wide for 2000 pixels. As you can see, there are 10 times more pixels across the width of the larger image, yet both are "200 ppi."

How many pixels do you need?

Pictures that will be used only for computer monitor display, such as those on a web page, and not intended for print publication, are typically displayed at 72 or 96 pixels per inch. So a photograph that will be two inches wide on a monitor screen needs to be 144 or 192 pixels wide.

Pictures that will be reproduced on a printed page use a process called halftoning to simulate shades of gray or colors with spots of single-color inks. Halftoned pictures have what is known as a screen frequency that tells how close together the spots of ink will be, measured in lines per inch (lpi).

Different printed outputs require different halftone screen frequencies.

Newsletters intended for photocopying typically use 53 lpi, newspapers 85 lpi and magazines or brochures printed on coated paper 133 lpi or greater. This screen frequency is important because it helps determine how many pixels you need in your image.

A generally accepted rule of thumb is that you need 1.5 - 2 pixels per halftone dot. So a picture that will be printed 10 inches wide in a newspaper needs to be about 1280 - 1700 pixels wide (85 lpi x 2 pixels per halftone dot x 10" wide = 1700 pixels wide).

A picture that will be used four inches wide in a photocopied newsletter needs to be about 318 - 424 pixels wide (53 lpi x 2 pixels per halftone dot x 4" wide = 424 pixels wide).

In dealing with digital photos, it's always better to have too many pixels than too few. You can throw away pixels from an image that has too many virtually without penalty. Adding pixels just increases file size and doesn't add detail.

A sure sign that a picture has been reproduced without enough pixels is the appearance of stair-stepped edges or "jaggies," especially along straight line areas where two different colors or tones meet.

So, how many pixels are in these pictures?

The full-size pictures on our page are typically 1700 - 2000 pixels in the long dimension of the photo (2000 pixels wide for a horizontal, 2000 pixels high for a vertical). Click on a thumbnail photo to obtain a full-size photo.

Getting the pictures from our computer to yours.

Click on the thumbnail photo that you want to download. When it finishes loading, a larger picture will appear on your screen. It will be much larger than the screen itself, forcing you to use the scroll bars on your browser if you want to see it all. (Remember, you need a lot more pixels to print a picture than to simply view it.)

Select "Save as..." from the file menu. Select a destination on your hard drive for the photo. Select "Source" from the "Format" sub-menu, if applicable. You may choose to rename the photo or let it default to our file name. Make sure the file extension ".jpg" is appended to the end of the file name (more on this below). So your new file name might be something like "photo1.jpg."

A word about file formats

Our photos are provided in the JPEG file format, which uses the file extension ".jpg." This is a compressed format that allows much quicker transfer of images via modem than an uncompressed format. Our 2000 pixel wide photos contain 7 - 9 megabytes (MB) of information before compression. When saved in the JPEG format, they take up 350 - 750 kilobytes (k) of space. Each of the JPEG files is small enough to fit on a single floppy disk.

This compression does not come without price, however. JPEG uses what's called a "lossy" compression scheme. This means that some information is lost when the file is reopened after compression. Most of the loss occurs in areas that are not visible, especially when the final output is to be on newsprint. Most of the photos you see in daily newspapers around the country have been saved in the JPEG format.

We recommend you convert the downloaded JPEG file to an uncompressed format before doing any further work with the image. Repeated opening, editing and saving of an image in JPEG format will cause image degradation.

Many newspapers and other publications are put together using page layout software such as QuarkXPress or Adobe PageMaker. These programs work best with photographs in the TIFF format (extension .tif). TIFF in an uncompressed file format that is supported by almost every application that uses image files.

You'll need some kind of image editing software (like Adobe Photoshop) to change between formats. Simply open the photo in JPEG format, choose "Save as..." and select TIFF format. You'll need to change the extension from ".jpg" to ".tif," as well, if your software doesn't do it for you.

FREE caption included!

A caption for each photo is displayed on the page with the thumbnail image. The caption is also embedded in the JPEG image file and is accessible via the "File Info" command in Photoshop. The caption can be cut and pasted directly into your word processing or page layout document.

We hope this information has been helpful to you. If you have any further questions, please contact us by e-mail newsdesk@umcom.org.

Permission for use

This text was created by Mike Dubose, Photojournalist with United Methodist News Service. This information may be reused for church use as long as credit is given to United Methodist News Service.