Mechanics of Printing
So different papers do different things. So it is crazy to sit there and think that all your work will always be printed on one stock of paper. At the moment, I'm experimenting with you know, the Japanese sort of rice paper look and feel to certain images. I've got a series of images that I'm working on. There's landscapes which I think will suit that type of paper so you gotta broaden your horizon when it comes to paper and experiment of course. Buy some sample sheets, you know. Print some photos, have a look at the same photos printed on different stocks and how it changes. You'd be surprised at how easy then that makes the decision process of selecting the right paper for your print. So the mechanics of printing, okay? When we look at an image on a screen, how do we translate this information from screen to paper? Every pixel has an individual color with a specific color value so the pixel itself can only have one color, each pixel. And then the pixels around, with different colors ...
will give us the perception of continuous tone, okay? Now when we print, we send that pixel of color with its specific color recipe, and we talked about that in color management earlier in the course, to the printer driver basically which will interpret that recipe into dots of the ink on a page represents a particular color value. Let's address this question here of PPI versus DPI because we look at these printers and you know, we're sending images on the screen at 360 DPIs and then you think 'My printer can do 2880 DPI so I'm getting increased resolution'. Well it's not quite that simple and I'm gonna explain a little bit of the misconception in the terminology. When we talk about PPI, refers to pixels per inch in order to measure pixel resolution. Where do we need pixel resolution? We need pixel resolution on our screens so when we talk about PPI, we're referring to our screen resolution and the image on that screen. In other words, the actual visual image itself. DPI, dots per inch, typically is used to measure printer dots on a page. A digital image is made up of pixels, or colored dots, we talked about that earlier. Millions of dots together give us the impression of a continuous image. So understanding that, how do we go from pixel to printed dot? There is a way. Resolution, when we start to talk about resolution, is simply a measure of how many pixels the image has over a given area. And that's when we have our image on our screen and there's a 300 pixel per square inch, or 360 pixels per square inch and so on and so on. 300 PPI refers to 300 pixels per given unit of measurement. In our case, we're using 300 pixels per inch. 72 pixels per inch is less pixel, it's spread out over a square inch. So in other words, when a camera shoots, it shoots to a fixed pixel count and it's up to us how far spread out we want those pixels to be, whether we spread them out at 72 pixels. We don't lose pixels, the pixel count is still the same. It's 72 pixels per inch, we're spreading the pixels out and making our image larger and at 300 pixels, we're concentrating the pixels more into an area, giving us higher definition, but at the same time smaller image and we look at this a little bit later when we look at resizing and re-sampling and interpolating in Photoshop. So if we increase resolution, we decrease print size and vice versa. So resolution goes down, print size goes up. So, and then if resolution goes up, print size comes down which makes sense. So we have a pixel here on the left hand side. That is a pixel and that pixel has to be interpreted into color onto a printed page. Now that pixel can be made up by lots of hundreds of different dots so when we talk about a printer resolution being 2880 in the case of Epson, it means that it has the capability of 2,880 dots per square inch. In other words, a high resolution to create lots of little dots to make up an individual pixel. So the dots on these things here, on the printers, are much smaller than the pixel itself. So a lot of dots are making up that particular square or that particular pixel. And of course the higher the DPI of the printers, the appearance of this continuous time because at the end of the day, we are printing little squares. We're printing them close together and it's up to the printer then to make it perceive like we are seeing a continuous tone. So that's how we go from pixel to ink itself, or how the information is translated across.