The ETW web site at http://www.easttexaswoodturners.org has a member’s gallery where you can display pictures of your finished work. To accommodate the club’s limited web site storage space, it is recommended that pictures you wish included in the Member’s Gallery be as small as possible within the constraints of the item being displayed. This document will describe some rudimentary methods to accomplish this goal. It is by no means a comprehensive tutorial on working with digital images. A list of software and educational resources is provided at the end of this document. As with most things in woodturning, the quality of the final product will be directly related to the effort expended in learning how to use the tools available.
Web Site Requirements:
The maximum size picture acceptable is 640 x 480 pixels, at 72 DPI (dots-per-inch), saved in a JPG format, and preferably under 75K in file size. A picture of around 400 x 300 pixels would be ideal and more easily kept within the 75K file size limit. A title/description should be provided to the webmaster for inclusion in the web site display. Though it is possible to add the title/description text to the picture, it is more efficient for storage and display if this information is provided in text format for the webmaster to add to the site separately from the image.
Email pictures as an attachment to the webmaster at firstname.lastname@example.org.
Most digital cameras and scanners can produce pictures at the above size. However, you may wish to capture the picture at a larger resolution if you wish to also be able to print the picture at its full size and at its best resolution. If your picture is larger it should be resized and compressed to meet the above requirements before sending to the webmaster (see below for advice on these processes).
Resizing A Image:
An image for viewing only on the monitor can be set to 72 DPI. While this figure is not necessarily what your monitor displays, it is an industry “standard” that insures the image will display properly on the majority of monitors in use today. Refer to the menus in your photo-editing software for a function similar to "Resize/Resample" or "Image Size". Change the width of the image to the desired number of pixels and the height will automatically be changed in accordance with the software’s built-in aspect ratio. Most photo-editing software use techniques for resizing images that add a considerable amount of “blur” to the image. To compensate for this blurring, it is necessary to sharpen the resized image after each increment of resizing. If you are resizing an image down to less than 50% of its original size, you will get better results if you sharpen it once for every 50% increment of resizing. Most photo-editing software has a “Sharpening” option, usually under an “Image” menu option. Never save the resized image to the same file name as the original image. If you do you will never be able to retrieve the original image. Also, be sure to read the following section on compressing an image before saving the resized image.
Compressing A Image:
The ETW web site will only use images submitted in the JPEG format. JPEG stands for the Joint Photographic Experts Group and uses a file extension of .jpg. JPEG compression uses a sophisticated mathematical technique to produce a sliding scale of graphics compression. You can choose the degree of compression you wish to apply to an image in the JPEG format, but in doing so you also determine the image's quality. The more you squeeze a picture with JPEG compression, the more you degrade its quality. JPEG can achieve incredible compression ratios, squeezing graphics down to as much as one hundred times smaller than the original file. This is possible because the JPEG algorithm discards "unnecessary" data as it compresses the image, and it is thus called a "lossy" compression technique. Save your original uncompressed images! Once an image is compressed using JPEG compression, data is lost and you cannot recover it from that image file. Always save an uncompressed original file of your graphics or photographs as backup.
Most photo-editing software will allow an image to be saved in the JPEG format by choosing the “Save As” menu option and specifying the jpg format. The amount of compression can be specified by selecting the “Options” button on the “Save As” Dialog screen, and then entering the percentage of compression desired. There is no standard compression percentage. Each picture will tolerate a different amount of compression without significant loss of quality. Experimentation is the only course of action. You might start with a 50% compression ratio and compare the resulting picture with the original to decide whether the resulting quality is usable. Also check the resulting file size of the compressed picture to see if it falls within the ETW guidelines. Try to get the smallest file size possible with an acceptable image quality. If further compression is desired, work with the original image and select a greater ratio for the new image. DO NOT further compress the first compressed image. Quality degradation will be less by always starting with the original image.
Resources on the Internet:
A Few Scanning Tips
by Wayne Fulton – http://www.scantips.com
(expensive but loaded with useful information)
Digital Photography – Pocket Guide
By Derrick Story – look for a new or used copy at Amazon.com
(not specific to any camera – handy size for your camera bag)
Sizing Photographs for Web Sites
Preparing Photos for the Web
Web Graphics Basics
JPEG Wizard Online Optimizer
A free service for compressing images. Not the most expedient method to obtain a compressed image, but the ratio of compression to quality that this service provides is excellent.
Note: space in the above addresses are actually the underscore “_” character
IRFANVIEW - http://www.irfanview.com - Freeware
A very fast, small, and compact graphic viewer for Windows 9x/ME/NT/2000/XP capable of the resizing and compression processes mentioned above.
Paint Shop Pro - http://www.jasc.com – Commercial
A reasonably priced full feature graphics editing program. Latest version is 8, but any available version is capable of the resizing and compression processes mentioned above.
Adobe PhotoShop - http://www.adobe.com/products/photoshop/main.html - Commercial
Considered the Cadillac of full feature graphics editing programs. Latest version is 7, but any available version is capable of the resizing and compression processes mentioned above.