Have you ever sent a file to print, just for it to get rejected and returned?
They ask for vector files and you don't know the first thing about vector files, but have to figure out a solution quickly. We've experienced the frustration, first hand, and hope to help clear up the confusion with a little knowledge bomb.
The (Basic) Difference
There are advantages and disadvantage between raster and vector art. We've attempted to simplify the most significant ones in this chart below:
One of the most important points to understand is that raster image files are limited by the files original quality. If you snap a photo right now, that is the highest resolution (number of pixels) that image will ever achieve. You can decrease its quality, but you cannot increase its quality.
It's like buying a set of poor quality sheets with a low thread count. You can't expect to improve the quality of the sheets by magically increasing their thread count. Poor quality sheets are, unfortunately, poor quality sheets. Best reserved for lessor tasks. The best version of these low quality sheets is in their original, brand new condition. When the thread count is pristine, before they've been damaged or made lessor in any way.
Similar to sheets, if the original raster image is of poor quality with low resolution (like thread count), you can't expect to improve the image quality by magically increasing its resolution. Poor quality images are, unfortunately, poor quality images. Best reserved for lessor or smaller tasks. The best version of this low quality image is in its original, brand new condition. When the resolution is pristine, before its been damaged or made lessor in any way.
If you've followed along with the example, you understand that if you began with low quality or a limited number of pixels from the start, there is no way to improve upon its quality.
Just Add Pixels
You cannot simply 'add pixels' to increase resolution to an raster image, any more than you can 'add thread count' to increase the quality of your sheet set.
In the bed sheet example, imagine stretching a sheet far beyond its original size. The further you stretch it, the more apparent each individual thread becomes and if you push it far enough... it'll break apart, becoming nearly unrecognizable.
Similar to the bed sheet, raster images can only stretch so far beyond their original size. The further its stretched, the more apparent each individual pixel becomes and if you push it far enough... it'll break apart, becoming nearly unrecognizable.
The shift in quality can be subtle or severe, dependent upon how far beyond the limits the image (or sheet) is being stretched. We've all seen images that have been pushed far beyond their original size they look a bit like a lego filter, gone horribly wrong.
This doesn't mean that raster files are useless outside of the web (their most popular use), it simply means each file will have its limitations. If you are handling a quality raster file, it's likely to get the job done just fine, provided you aren't trying to plaster it all over your living room wall.
General Raster Speak
- High Resolution Raster Graphics (like high thread count):
Contain more dots or pixels and will produce smoother or more seamless images resulting in a clean, quality output.
- Low Resolution Raster Graphics (like low thread count):
Contain fewer dots or pixels and will produce more jagged and distorted images resulting in a distorted, pixelated nightmare.
Now that we know how absurd it is to try and improve the quality of a low resolution raster image, let's explore alternative options. First, do you happen to have the original image?
If yes, then check it's resolution and hope for higher quality.
If no, you may be stuck using the raster file within its limited capabilities. Or a better alternative, would be to replace the image with a similar, high quality raster image.
Creative Alternative Solutions
Suppose you are trying to use a low resolution raster artwork on a large banner... no bueno.
If this graphic file is your only choice and it must be used, opt for a creative work around. Reduce the size of your raster image on your banner. Making it smaller will improve its quality, since its not being stretched as far.
Then fill in any empty space with creative effects (swirls, bubbles, lines, shapes, etc.) anything that will complement your overall theme. So instead of your banner being just an image, maybe there's text or a repetitive design filling in the empty space.
Vector to the Rescue
There's a reason that vector file types are widely preferred for quality applications, it's as if they are immune to distortions and poor quality. Unlimited in capability, vector images always appear crystal clear regardless of how large/small they are stretched or how much they've been edited. Vector graphics have the unique ability to proportionately recalibrate when their size is adjusted, like magical genius voodoo!
Whenever you have the choice between vector and raster, its usually best to choose vector file formats.