Much of what we do as Technology Education teachers involves a variety of content outside of our core subject (primarily science and math). I try to incorporate a lot of math into my classroom activities whether it’s in the form of measurement, RPM calculations for machinery, dimensioning in my CAD classes, and of course laying out print designs in desktop publishing. The latter is an activity we are currently wrapping up.

Our first graphic design project of the year didn’t really involve much in the way of layout or understanding image/print resolution. However, their last project required that they develop an accurate full size print layout of their project so that they are able to send the job to our color printer. Their project was to design and create a mock credit card (both front and back). All elements of the card were to be created by them (the shape of the card, the lettering, the card type logo, the swipe bar, etc). Before the project began, we discussed how images vary in their resolution (expressed in PPI, or pixels per inch) depending on their use.

First we calculated how to figure out how many pixels are in an image given it’s pixel dimensions (simply take the width x the height). I told them that this is ALL the more pixels a particular image has, and there can be no more than that. This is where camera’s mega pixel ratings come from (1500px x 2000px would be a 3mp camera).

I stressed that most images on the web are low resolution (most commonly 72ppi), and are not suitable for printing. We created a mock high resolution document within Photoshop (ideally not the best page layout program, but it’s what we have). We then took sample images off the internet and placed them into the project window (set at 250ppi). The students observed what happens to the pixels at various resolutions (the image appears to shrink drastically because the number of pixels in an image is constant, the resolution dictates how many of them are in a given inch). We basically broke it down into steps, like this:

Take a 400px x 400px image. That image has 1600 pixels TOTAL (multiply the dimensions). At 72PPI, there are 72 of those 1600 pixels in every inch. At 250PPI, there are 250 of those 1600 pixels in every image. In the latter example, there are more of the 1600 used in every inch, thus the image appears smaller (on screen) than it’s 72ppi counterpart.

I then set up a scenario to calculate appropriate image sizes given a specific resolution as well as a physical print dimension (in inches). We ran through a scenario like this:

You set up project to be printed at 5″x3″ and 250PPI. You need to find an image that will fit that appropriate space at that resolution, and you need this dimension in pixels. So, what they need to do is some basic math:

250 Pixels Per Inch, and the image needs to fit 5″ x 3″. Students must multiply their resolution (250) by each physical dimension (5 and 3) to get the appropriate pixel dimensions which turns out to be
1250px X 750px.

Desktop publishing is both visual based as well as mathematically based. Students need to understand concepts of image resolution, display resolution vs. print resolution, margins, kerning, leading, etc to fully have all the tools to be a successful designer.

This is simply one example of how I try to keep my instruction interdisciplinary, but in reality it’s almost a daily occurrence . From the wood shop to the graphics lab, I’m always incorporating some cross-curriculum content within my lessons. It’s key not only for my subject area’s survival within school districts (as districts begin cutting “elective” classes), but to also help our students see their education as not subject based, but rather content based.

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