Join Taz Tally for an in-depth discussion in this video Understanding pixels, part of Scanning Techniques for Business and Home.
Here, let's dive in and take a look at the basic building blocks of a scanned image. The reason why we want to do this is if you understand the basic building blocks of your images and your scanned documents, that is, what the scanner actually captures when it scans an image or a document, you're going to make better decisions when it comes to setting up and controlling your scanner. Earlier, we distinguished between the different types of graphics and documents that we would work with. It's simple line art, detailed line art, continuous tone, grayscale images or photographs, continuous tone color photographs and then documents.
Looking at the building blocks of these four different types of images, and documents, you think, ooh! My Gosh, there is a lot of difference here. Uh-uh. That's the good news, is the building blocks are the same in all of them and I am going to prove it to you. We are going to start with this image here, which is a simple line art image, and I am just going to zoom in until we see the building blocks. And there they are! These are pixel-based images. When you scan something, that scanner converts your images into pixels. In this case, it's just black-and- white pixels. That's all it is.
Just black-and-white pixels. This is called a 1 bit black-and-white image, and these pixels are, if you think of them as being like pixel brick, if you will, this image is all constructed out of these black-and-white pixel bricks. So you get black, black, black, black, white, white, white, white, and along this edge, which is where the image is defined, you are alternating black and white pixels. So that's the simplest kind of image that we actually capture and work with and if we have a very simple graphic like this one, then we are best to scan this as is and convert our simple image into a simple black-and-white image with a nice sharp edge like you see here.
So that's the simple line art image. Let's take a look at the moose, which looks a lot more complicated, and it is. But when we zoom all the way in, look at that. It's still nothing but pixels, and our edge is defined by pixels. But you notice a little difference here. These pixels have not just pure black and pure white, but they have grayscale value to them. That's a really important difference between these two images. That simple line art image was all about defining the edge, so we used simple black-and-white pixels, so we scanned in black-and-white mode.
But when we have detail in our image, like in this case where we have very detailed line art, instead of just scanning in black-and-white mode, we would scan in grayscale mode. We would treat this as a grayscale photograph because it has so much detail and this detail is really developed and rendered at least partially by the grayscale value that's in the image. Then let's move over to what would you normally consider is a conventional grayscale image. This is my buddy Zip, my Cardigan Welsh Corgi, my hiking buddy, so cute.
As we zoom in on Zip, we see again the building blocks or pixels and we create the detail in this image by creating various shades of gray. When you zoom it back out, they all blend together and they look like a continuous tone. But in fact, these are pixel bricks just like in the 1 bit black-and-white image but we have more complexity in terms of a much wider variety of shades of gray. In fact, in this image like in most continuous tone grayscale images we have up to 256 shades of gray.
Then in the color image, the color continuous tone image, we zoom in, and lo-and-behold, oh my gosh, look it. We've got pixels. When we get on an edge, like here let's go to the edge of the Santa Claus hat. It's nothing but pixels. Now, point in fact, this image is really built out of grayscale values just like the continuous tone grayscale images and the color is actually being created on screen by the monitor. If you're interested in learning more about the details of really how color images are put together, then I'd strongly recommend the Scanning for Art Photography and Design or my class on Color Correction with Photoshop.
But for now what you need to understand is this image, this color image, is made up of pixels just like the other images. The color values you see on screen are actually being generated by the monitor. But in order to create this image, we have pixels to which we assign grayscale values and then color by our output devices. You see, it's all the same. It's all about the pixels. I know what you are thinking, what about that document in the lower right-hand corner here? What's that all about? Well, when we scan a document, it looks something like this.
It's text, it's graphics, it's different? It's not! When we zoom in on the scanned version of this document, it's all about pixels just as well. That's like looking at a piece of line art. We've got grayscale value on there to help define the edges, but it's kind of like halfway between the 1 bit black- and-white image, the simple line art, and the more detailed one. We have this very light gradation that you see along here. It's called anti-aliasing. You may have heard that term before. It's just the slight smoothing of an edge and it makes it easier to view the type when we are looking at it with the human eye.
But all of this document is converted into pixels. There is Zip in the Yukon, yay! And here is Zip and me in front of our house on Kachemak Bay in Alaska. We love it there. It's all about the hiking, biking, kayaking, skiing. There we go! See it's all pixels. everything is converted into pixels when you scanned your image with a scanner. Our challenge is to choose the best kind of pixels that we are going to use when we capture our image with the scanner and to set up the scanner to populate those pixels with the best grayscale or color or just black-and-white line art data.
So there are the basic building blocks of your images and we are going to move on and talk about resolution next.
- Caring for a scanner
- Understanding pixels and resolution
- Choosing scanning software
- Scanning logos and line art
- Scanning grayscale vs. color
- Scanning for print
- Converting documents to editable text with graphics
- Scanning images for use on websites
- Converting images and documents to PDFs
- Emailing and faxing scanned images
- Creating PDFs for OCR
- Automating the scan process