D.P.I.? Layered Files? Vector Art?
In the promotional products industry, art requirements sure have changed over the years. “Camera-Ready Art” has become an ancient term, and now we contend with things like “vector” art, or “resolution”, or RGB vs. CMYK, as well as many more. Distributors almost need a graphic art degree to even speak the language!
Hopefully I can take a few posts here to explain some of these things so you can better understand why one supplier might need your client’s logo sent in a different setup than another.
For this first post, I’ll talk about resolution. You get frequent requests for “high-rez” art… and most suppliers will define this as “300 dpi”. “DPI” simply means, “Dots Per Inch”, and it’s an indication of how much visual information is placed within a given physical dimension. In the digital age, we are really referring to “pixels per inch” when we are looking at our computers’ screens, and the “dots” come into play when the image or text gets imprinted onto a piece of paper or a promotional item. Yet we still hang onto the term, “dpi”, and use it interchangeably with “ppi”. I’ll be using “dpi” for this post just to keep things consistent.
A Grid of Tiny Squares
With the exception of vector art (more on that in a separate post), a digital image is divided into a grid of tiny squares. Each of these squares, or “pixels”, is assigned a solid color. Most images found on web sites are set at 72 dpi. Most images intended for print are set to 300 dpi.
Let’s say you have an image that’s three inches wide. It’s saved at 72 dpi. Three inches multiplied by 72 dpi gives us 216 pixels across the width of the image. Now take a different 3-inch-wide image that is set at 150 dpi. This second image will contain 450 pixels across the width. A third 3-inch-wide image at 300 dpi will have 900 pixels of information on the horizontal dimension.
Since each square is assigned a solid color, you can see how an inch of your image being divided into 300 squares can allow for a lot more detail than using only 72 squares in that inch.
But Wait! There’s More! (Or Not…)
So, if your image is divided up into 900 squares (300 dpi), and you tell the computer to make it 72 dpi (while maintaining the 3 inch physical dimension), the computer has to take 900 pieces if information and condense it down to 72 pieces of information. Obviously, doing so is going to involve compromises… and a lot of detail will get lost.
But the inverse is not true. (And this trips up many people — including some who’ve claimed to be “graphic artists”.) If your image is already a low-rez 72 dpi, and you try to increase it to 300 dpi, the computer can only take the information in that image and spread it across a higher number of pixels. Kinda like if you bake a pan of brownies. At first you make 2 cuts in one direction and two cuts in the other to give you nine brownies. But then you realize you have to feed more people , so you go back and make a cut in-between each of the previous cuts — 3 more cuts in each direction giving you 6 brownies across and 6 brownies down. Now you have 36 brownies, but you really don’t have “more”. When you try to go to a higher number in resolution on the computer, it is a very similar issue.
Two cuts in each direction gives us 9 brownies (pixels) per pan
More cuts make more brownies/pixels, but technically there's still the same amount of food.
But in the movies…
Okay, so you see these deals in the spy movies and TV shows where they get a photo that someone took with a regular digital camera from the top of a skyscraper and they keep zooming in and zooming in until they can read the numbers on the credit card held by a customer insude a store window 10 blocks away. I sure hope you know by now you can’t believe everything you see on the screen. There is just as much fantasy involved in a scene like this as there is in superheroes that can fly or reverse the earth’s rotation.
You can only zoom in so far before those squares get so big that they just look like the image shown earlier in this post. The computer can sometimes “guess” to add some pixels to fake things, but obviously not enough to generate numbers or letters or a recognizable human face when that information isn’t there to begin with.
Do the Math
Now, if you have a supplier telling you the imprint area for a given item is 3 inches square, and they need at least a 300 dpi image, you need to make sure your image is at least 900 pixels across. But what if you know your image is 10 inches square, but only 100 dpi. Does that render your file un-usable? Hardly. If you do the math, 10 inches x 100 dpi gives you 1000 pixels — more than enough for the imprint area. When you reduce the physical dimensions of your file, but keep the same pixel count, you are basically making all those pixels smaller, so more of them fit in an inch!
Hopefully this has shed some light on things for you. In my next post, I’ll be discussing the difference between vector art and “raster” art.
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