You might know that there is a wide range of image file types. The majority of types were pretty much decided upon years ago with many of them made mainstream by both the web as well as software firms such as Adobe. The most popular type is the JPG. Most digital cameras will offer to allow you to use this one to save your photos, plus maybe one or two additional "high quality" ones. JPG also tends to be the type mobile devices and tablets like to shoot and save photos in. Another popular one used to be Bitmap which likely gained its popularity with Windows users since that was the main one Microsoft Paint prompted you to save images. The web also early on introduced other types such as PNG as well as GIF. These handful of ways to save an image only scratch the surface of what out out there. As a result people always want to know when it comes to printing, what is best or at least what type of file we prefer at FinerWorks.
Before we can really tell you what is preferable lets talk about the two different type of images formats: raster and vector. The difference between the two is a how the image data is stored in the file. A raster image is going to be what most people are used to. It is an image file that contains a finite number of pixels across and pixels down. Each pixel represents a color that all together makes up a viewable picture like a massive mosaic. Beside JPGs, other popular these will include but are not limited to TIF, BMPs, Raw, NEF, and even PSD (Photoshop file). Because each pixel is so small, you really don't see these individual pixels unless you are zoomed in really high or the image has been enlarged a whole lot.
A vector based image is going to be a little more difficult to visualize. In many respects a vector image is more like a data file. It contains a series of coordinates and other mathematical information that tells the computer how to render the image on a screen. What makes things more confusing is you can actually embed raster images within the vector file. Vector files tend to be widely used in the graphic design, printing and publishing industry. Popular formats include EPS, AI (Adobe Illustrator), and even PDFs. What makes vector images advantages over raster images are the fact that they can be printed to any size without being pixelation which are those little annoying blocky areas visible in low resolution images where you have defined differences in colors or subject matter within the image.
Before you ask, should you then convert your raster image like a JPG and resave them as a PDF or bring them into Illustrator and save them as an AI file to eliminate potential low resolution issues. The answer is a resounding NO! As I had just said, you can embed raster images but those raster images will not look better than if you printed them as a JPG or other raster type. We sometimes see this when people create PDFs they want us to print. They might include their artwork or photo, print it at a very large size. Any text or shapes they added using their vector based software program looks nice and crisp and sharp but the image they included does not look as sharp or crisp. The vector format is popular within the printing industry and we have been pulled into accepting these with a lot of kicking and screaming, but definitely we prefer raster images and let me tell you why.
While vector images are popular for printing, they are less than ideal for what we do. If we were a commercial printer producing signage, blue prints or other low detailed images, the vector format would be fine. But understand that with the printers we use, we are widely utilizing photo processing software simply because it is the best suited for our customers work. The printers themselves are also engineered primarily for the photo or fine art printing industry. Most of the images sent to us are ether photos or scans of artwork or even regular photography itself which is why it does not make sense to normally send a vector file. And I should also mention that even if you do send a vector file, the software that drives the printers converts every image into a raster format regardless if it is not.
There are also problems associated with vector formats we see. In just about every case in which a print from a vector file did not print correctly, it has been a result of inaccurate readings of the file. This is primarily related to conversion issues or the software which automatically processes the image might not understand some proprietary properties within the file. Since there can be a wide rage of properties and settings that make up a vector file, not all software will read all these settings. For instance, sometimes text won't properly convert if we do not have that font used on our server. Backgrounds might be viewed as transparent which can result in a black background versus a white. Finally the width and height need to be properly configured which is not always clear depending on the file type you save it as. AS an example, we have had customers that have wanted the artwork they created in Adobe Illustrator centered within a specific size with nice margins around it so the artwork does not butt up against the edge of the print. Because they did not properly define the dimensions they wanted the file, the software which we use to process it uses the outermost regions of the artwork as the boundaries.
So obviously rasterized images are preferred over vector but what about file types we prefer. Of the rasterized images, we tend to prefer either JPG over TIF or even PNG. Not that there is anything wrong with a TIF but there is the potential for such things as transparent layers to wreck havoc and not print correctly. If you do submit a TIF, just understand that it needs to be void of any layers (which programs like Photoshop can preserve) and it must be flattened so that any transparency in the background is converted to white. Otherwise it might print black. JPGs do not have this problem. Bitmaps are also fine and might be a good alternative if you do not want to submit a JPG.
But why not a JPG. The obvious answer with some of our more experienced might be due to the fact that it is a compressed file. But some of these more experienced customers don't realize that a JPG can print just as well as a higher quality TIF. That may sound like sacrilege to some but lets take a look at this in some detail surrounding why this might be so.
First, to explain what a compressed file is, it simply means the image file's information has been structured in such a format that the amount of space on your computer it used is less than other uncompressed formats such as a TIF, BMP, or PSD file. JPG files can also be compressed at different levels when it is saved with different image editring programs. Your digital camera setting might also give you the option to choose to save it at different levels. One thing to not get confused with is this does not mean the dimensions or resolution of the file is modified, only that the amount of space it takes on your computer is less.
Where you can get into trouble or loose visible quality is with resaving your JPG image over and over again. For that reason if you have had your artwork scanned or photographed and you find it necessary to keep saving the editing you did on that image over and over again, a JPG is not a recommended type to use. That is because each time you save it you have the potential of loosing quality and that image will begin to show visible artifacts within the file.
Let's try to visualize what this might look like. Lets suppose you have a blue sky with a slight gradient as it gets close to the horizon. You may start to notice squarish block-like discolorations in the blue. It might be a little faint but if it is visible it will likely show up in your print just as well. My favorite analogy of a JPG that is being saved over and over again is to use a piece of paper and fold it in half then fold that half in half and again until you make that piece of paper appear small. Or better, lets assume you have a print you ordered from FinerWorks on your favorite fine art paper. After each time you take it out to show someone, you place it back in a box to store it. The box has limited space so you choose to fold it in half when you place it back in the box. For the purpose of this analogy we will pretend this first fold is not really visible when you open it up. But each time you place it back in the box, you choose to fold it over again to make it smaller. Subsequent folds begin to become more visible until eventually when you open it up to show someone you realize all these folds are starting to detract from the prints appearance. While you have saved space in your box by folding it over and over again, eventually the print becomes unusable. If you had only folded it once or maybe even a second time over itself, it would not have been a problem but after that it does become more of a problem.
Does that mean that you should not use JPGs to print? The answer is do not use JPGs if the file has the potential to need to be edited later on. We have had customers not do this an constantly work on the same file. An example is a lady that was trying to get certain colors just right. She would order herself a small print as a proof, see what colors she wanted to adjust and resave the image. She kept doing this over and over again both printing at home and through us. When she was ready to order her set of large prints in volume, an alert member of our staff who had recalled printing some of her proofs noticed that the area around her signature in the painting had started to look a little blocky. After we contacted her, she realized that she should have saved her work in a different format like a TIF but saved a copy as a JPG at it's highest quality settings when ready to print. I can tell you from years of experience that a high quality JPG that has not been resaved over and over again will print just as well any uncompressed format. Over the years I have seen dozens of examples in which customers have printed the same image in both formats and no visible difference was detected. One customer even became a little irate because the two test prints looked identical so she had no way to differentiate which was which.
Going back to my original premise as to which format is better, raster files are obviously going to be more reliable than vector files in terms of the file being read properly and the less likelihood mistakes are made by the processing software. When it comes to file types, our recommended favorite is going to always be JPG in terms of file size, especially if you have a lot of images to upload and you are on a slightly slower connection. For purist who no matter what I say, still think an uncompressed format is the way to go such as TIF or even a PSD, just make sure that you do not save the file in layers or with transparent backgrounds. Usually those transparent areas will convert into white but as a precaution, flatten any layers. In Photoshop this means make it so all of them become the background image. And slso make sure that you do not compress the file when saving it. Photoshop and some other programs will allow you to compress TIF files as well. I have not seen this be a problem but we have in the past had instances in which this has interfered with the ability to open the TIF. We do not currently accept RAW or NEF but other formats like a BMP are PNG will be okay as well. Regardless of the format, make sure you inspect your file before you submit it for printing. Inspect, inspect, inspect.