How To: Digital Photo Resizing and Making the Most of Your Gallery Space.
One of the most commonly misunderstood topics on the internet is how to span the gap between taking a digital photograph, and formatting it for use on the web (and forums like backcountrypilot.org.) I have been in this business so long that editing photos and images is like second nature, but I can understand how some people who are maybe more tentative or less inclined to computer experimentation might cringe at the thought of editing digital images. I thought I would post some of my techniques here in hopes that some of you guys who don't currently do your duty of showing the rest of the world what a day in the life of flying with you is like, might start.
Wow, that looks like some hot air down below, <a href="http://www.backcountrypilot.org/forum/topic/how-to-digital-photo-resizing-292#howtostart">just take me to the procedure.</a>
For Microsoft Windows users, there is a super easy alternative. <a href="http://www.backcountrypilot.org/forum/topic/how-to-digital-photo-resizing-292#20620">Try this one</a> for a quick and easy way to resize.
First, a little background on digital imagery: A digital image is a binary file(as opposed to ascii-text like html) full of data that describes pixel locations and their Red-Green-Blue(RGB) values. A pixel is one unit of display measurement on a computer screen, composed of 3 "dots." Each of these dots represents Red,Green, or Blue, with values between 0 and 255. The pixel itself is a variable size, depending on the dots-per-inch, or DPI, or your screen. A standard computer screen uses 96 dpi. This is the basis for representing images with a computer screen. Resolution is the number of pixels available on your computer screen. It can be expressed in width and height dimensions (1024x768) or as the square of those values(1024 x 768 = 786432 pixels.) This is where the term megapixels comes from.
My digital camera is capable of 4.1 megapixels, or 4,100,000 pixels. Take the square root of this and you will get the ballpark dimensions of the maximum resolution my camera is capable of 2024x2024. Since standard 35mm camera images(and their digital descendants) are not actually square, but have a 4:3 ratio, the real numbers are 2272x1704 pixels.
Why is this important?
Digital photography achieves quality through greater image resolution. In the early days of digital photograpy, film was thought to still be superior with its fine, organic grain. But around 5 megapixels, digital photography becomes the superior format. However, unlike a 35mm film negative, you are limited by the pixel. On a computer screen, there can be no representation smaller than 1 pixel, anything smaller is achieved through fuzzy logic and illusions. A digital image that is equal in quality to a 35mm slide or negative, is, in reality, approx 2300 pixels by 2300 pixels square. If your screen runs at 96 dpi, and your resolution is set to 1024x768, that image is approx 24 inches wide. Since my monitor is only 18" diagonally, I can't see the whole digital image at once without zooming out. I would need 4 monitors arranged in a square to view it all at once.
When you transfer your images from your camera to your computer and view them, your viewing software is zooming out, or shrinking them in memory for your viewing convenience. Stored on your hard drive though, is a big old file that is larger than a megabyte(mine are 1.3 MB at 4.1 megapixels. Digital SLR's take Raw format photos whose file is more than 30 MB.) This file is good to keep unchanged as the original, raw, high quality image(especially for printing) but if you want to share on the web, it's simply OVERKILL. That's why we need to resize it and compress it.
Why this is important for the Backcountrypilot.org gallery:
Unless you upload your photos to the general gallery categories, they go into your User Gallery. Each user on this site gets 30-40 MB of photo storage space. If you upload photos that are a gargantuan 975K(max allowable upload is 1024K), you'll fit about 30 photos in your gallery. If you follow this procedure, your photos will be about 100K, and you'll fit about 300 images in your gallery, plus the people downloading the large size will thank you!
<a name="howtostart"></a>The Procedure:
My personal guidelines for the images I upload to the gallery are:
1024x768 pixel resolution(up to 1600 is allowed in the gallery), and 75% compression(I'll explain below.) This is more than enough to give someone a large view or use it for a desktop wallpaper.
1) Locate where you have stored your files on your hard drive. In an effort to make digital photography easier for the everyday guy, some of the software included with cameras makes the file transfer(copying to C: drive in MS Windows) transparent. This makes it tough for somebody to learn where the heck their image files are being stored. I'm not going to teach you how to use your file system browser, but I suggest you learn your hard drive with the same familiarity you give your instrument panel.
2) Make a copy of the file(s) you want to resize and edit, name them something intelligent, like waterlanding2_120505.jpg. I never use spaces, but rather a underscore _ character instead.
3) Open the file with your favorite image editor. For the purpose of this demo, I am going to use The Gimp, which is a free, open source image editing program that rivals Adobe Photoshop in power and features. It runs on Windows, Linux, and Mac OSX. As a linux user, I love open source software. Even if you want to use another program, it should have the same general image editing features.
Now that I have the image opened in The Gimp, it's only a few steps from being web worthy.
4) In the Gimp image window menu, click Image > Scale Image. In the dialog that pops up, specify 1024 as the width(for a standard landscape orientation, specify 1024 for the height if you took the photo sideways.) The other dimension will adjust proportionately automatically to maintain the aspect ratio of your photo(usually 4:3.)
5) For Quality, select "cubic(best)"
6) Click Scale, and it resizes.
7) Click File > Save As, save it as the same name. Click OK to replace existing image.
8) At this point the compression, or quality dialog pops up. Dial it down to 75(on a scale of 1-100, else 7.5 on a scale of 1-10), click OK. Compression is another term for JPG quality. The lower this value, the more interpolation is used to determine pixel values. I have found that 75 is a good compromise between quality and file size. It helps reduce your file size by A LOT.
9) You're done. You've made a copy of the original super high-res image and resized/optimized it for web viewing. Open the next file for resizing.
These steps should be the same in other image editing software, and use terms like Resize, Quality, etc.
Now that you have a optimized image, upload it to the gallery.
I will continue to update this How To with more image editing tricks for enhancing your photographs or saving poorly exposed ones.[/b]
1) Make a copy of your original image, take note of where it's located on your hard drive. i.e. "C:/Users and Settings/zane/My Documents/My Photos/IMG_3984.JPG" Name the copy something fancy and descriptive.
2) Open the copy in Gimp, or your favorite image editor.
3) Resize the image by selecting "Scale" or "Resize" or something synonymous to that. Specify 1024 as the width, height should automatically adjust proportionally if the software is worth a crap.
4) Save the file with 75% compression/quality.
5) Go upload it to BCP.