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- This Week's Free Computer Tip -

172 - Concepts of Shooting Digital Pictures and Scanning Old Photos

Many of you own either a digital camera, a flatbed scanner, or a multi-purpose printer/scanner device, and the rest of you have probably thought you would like to buy one soon. They always look easy to use in the advertisements, and in truth, they are. The only thing is, it helps to understand some concepts about digital information and how it's handled by your computer. This tip will get you started.

What do scanning and taking digital pictures have in common?
When using either a digital camera or a flatbed scanner, you get to say how much "detail" you want to store in the resulting digital file. Scanners let you say how many dpi (dots per inch) to scan. The higher the scan rate, the more detail you capture. Digital cameras offer similar settings, either saving the actual image with no pixel loss or electing to save the image after it is compressed with one of the standard compression technologies (which lose detail).

The big misconception -
Most people have the misconception that capturing more detail results in sharper pictures or better colors. I say misconception because that is only true in certain particular cases relating to the printing of photos. For typical day-to-day uses, less detail produces results which are indistinguishable from "higher quality" images. What higher detail does result in however, is dramatically larger storage requirements AND annoyingly longer download times when you email the picture to Aunt Sally. Where taking a picture (or scanning a picture) at a lower detail may result in a file size of 40k (40 thousand bytes), capturing a higher quality image produces a file that can easily reach 4MB (4 megabytes - a 100 times larger file) in size. Now I know we are all Americans and Americans all believe that bigger is better, right? Well, when it comes to digital photography, the answer is often "No. Bigger is not better."

I'm going to go on to explain all this in layman's terms and some of it may be more than you want to know. If you get bored in the details, skip down to the recommendations part.

With digital images, you want to think about how the picture will be used -
In scanning a picture or taking a picture, first decide how you plan to use it. These days, the most likely use will be to save it and view it on your computer. Later, you might decide you like the picture well enough to email it to Aunt Sally or the bridge club members! What is being done less and less is printing pictures. Printing turns out to be very expensive (trust me) and if you do decide to make copies, your local photo store will do that from your computer files for less than you can do it yourself!

Shooting pictures at 5 mega pixels (or scanning pictures at 1200 dots per inch) as your default setting is a total waste of disk storage space. Worse than that, it will not produce an image of any better quality when looking at it on your computer! It gobbles up your disk storage space in big chunks and reduces the number of pictures your camera can take and hold by a factor of 100. Are you getting the picture here? (no pun intended)

If you are going to print copies of your pictures, the same principles hold true, but with one difference. I will discuss that difference further down in this write-up.

Some basic concepts -
What are "pixels"?
Everything you see on a computer screen is drawn by combining tiny dots of red, green, and blue. Even the colors black and white are created by manipulating combinations of those three colors. There are 256 shades of each of those three colors available and the computer calculates just how to blend them to fool your eye into seeing the color it wants to render.

About your monitor's "screen resolution" -
Whether you realized it or not, you became involved with pixels when you first set up your monitor. Some of you turned on your computer on your first day of ownership and never touched the way the screen looked. You left it set to its default screen resolution. Others decided you didn't like the default screen resolution, and set it to something different. "Screen resolution" could really be called "pixels per inch". The two most common screen resolutions used on computers today are 800x600 and 1024x768. A setting of 800x600 uses 800 pixels to cover the full width of your screen and 600 pixels to cover the full height of the screen. Since the physical size of your screen never changes, switching the resolution to 1024x768 causes text and images to be smaller on the screen. You are squeezing more pixels into a fixed width, so the images have to shrink to fit them all on there. "Higher resolution" = smaller images.

Now, if you are paying close attention, you will realize that the computer screen has other physical limitations. Not only are the width and height dimensions fixed, but so are the number of dots the screen is capable of drawing. While the computer itself is capable of storing an unlimited number of digital "dots" of color information, the screen has a fixed limit of how many dots it can draw. That limit is always the same, no matter whether you have a 15" screen or a 17" screen. The current limit of display technology is 96 dots per inch. (You techies out there - don't write me a letter about that number. It's close enough for government work!) You're going to care about that number (96) when you take or scan pictures.

The important thing to know is that when the computer stores digital pictures, it can, and often does, store many more pixels than can be displayed on a computer screen. If you never print the photo, that is just wasted space.

When you go to view that image on the screen, the viewing program goes through a process of combining all those excess pixels into a smaller number of dots, until it gets down to the number of dots the screen can draw. In the end, it can only draw 96 of those dots per inch. Anything more than that is beyond the capacity of the screen.

It turns out that our eyes think that's just fine. All of us have seen pictures on our computer screens that are very sharp and have perfect color rendition. I can show you the same photo, drawn from a 40k file and then drawn from a 4MB file, and you will not be able to identify which is which. No matter how many excess mega pixels of data are stored, the screen can only display 96dpi (dots per inch), so why store more than that?

Why is screen resolution a consideration?
Screen resolution is a consideration only from one point of view. If you set your camera or your scanner to capture only the number of pixels needed to fill a screen set at 800x600, and your Aunt Sally runs her computer at 1024x768, then your picture will display a little smaller on her computer as compared with yours. In the grand scheme of things, that's a small consideration. Still, I wanted to mention it.

The difference between computer viewing and the printing of photos -
The printing of photos is a different matter in the sense that many newer printers have the ability to print at high resolution and to get "photo quality" prints, you need to do just that. If the photos are printed at 4"x6", less detail may still be fine. If you intend to blow the photos up in size, then more detail will be needed. Try a few to see what settings work best on your printer.

Recommendations -
Alternative #1 - Try taking a few test pictures (or test scans) to determine what the lowest setting is that produces acceptable viewing quality. Also test to see what resolution produces the best printed photos. Then, use those settings when you take pictures or scan pictures. Be sure the test pictures are of the same subject so that you get a fair comparison.

Alternative #2 - Take the pictures at a reasonably large detail but then edit the resulting files down to a reasonable size by using image processing software. This is extra work, but if you just can't decide about the final end use for your pictures, this will be a compromise. Photoshop can be used for this, as can Photoshop Elements (MUCH less complex). Many of the photo processing software packages which come with cameras and scanners will do the job as well. ACDSee is another brand which allows you to edit and resize images.

Digital photography is where everything is going. No more buying film or paying for processing. Instant discovery about which pictures came out and which didn't. Just delete the bad ones. The quality is there and the convenience is soooo much better! Jump in and enjoy!

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