In this post I'll discuss how to prepare your files for your fine art or photographic printing job. There are some basic rules to follow that will ensure the best possible reproductions. Along with these rules there are a number of steps that you need to be aware of and some terminology that you should be familiar with. Let's start with some terms you should know or learn about.
- RAW vs JPEG vs TIFF
- To scale or not to scale
- Color Space - RGB vs CMYK vs sRGB
- Gamut (huh?)
So these are some terms that all come into place when you are preparing a digital file for printing whether you plan on printing it yourself on your desktop printer or having a professional (me!) do it for you on my super, state of the art Canon printer. Ok...here we go.
RESOLUTION: Everyone knows that 300 DPI (dots per inch) is considered "high resolution" (used for printing) and 72 DPI is considered "low resolution" (used for the web). Most digital cameras will produce images at 72 DPI and it depends on the setting in the camera to determine if the image will be small or large. I would say that if you choose to shoot your artwork or make a photo with a consumer level digital camera you'll want to choose the setting that will produce the largest file size. This way when the image is converted to 300 DPI for printing purposes then the quality of the final output will suffer the least. Rule of thumb is set your camera at the highest quality/resolution that you can get. Resolution also comes into play in Photoshop or when using RAW files and I will discuss that next.
JPEG vs RAW: If your camera does not support the RAW image format then you are shooting in
JPEG. The JPEG image is a fully processed 8-bit image. JPEG is known as a "lossy compression" method meaning that some original image information is lost and cannot be restored, possibly affecting image quality. That usually manifests in less shadow & highlight detail. The RAW image format AKA digital negative (12 or 14 bits) is akin to a film negative . It carries all of the information needed to make an image but defers the processing. In order to use this file you need a RAW processing program such as Adobe Camera RAW or Adobe Lightroom (or a professional like me who does it for you!). The RAW format is best used when post-processing will be used to enhance the image. It is in the post-processing stage where one can bring out the full benefits of shooting RAW. The TIFF format is a "lossless" format and is great for archiving images and if you plan on bringing these images into a program like InDesign. TIFF's can include paths and alpha channels.
SCALING: In all cases, scaling an image whether going larger or smaller will always affect the pixels in the image. Making an image smaller is less problematic than making it larger. That said, it is often unavoidable but when doing so understand that when scaling an image more than 50% larger than its original image size the results may be undesirable. You may see artifacts, pixilation and blurring (softness) in the image. There are a few tricks that we professionals use to optimize the process so I would strongly suggest that if you need an image larger than it's native size, leave it to me to handle that. I will tell you the best size for the enlargement and ensure the best quality.
SHARPENING: Most digital images that come directly from a camera will need some sharpening. Most cameras will have a setting for that but it's best to do it during post processing and at the very end prior to printing. Sharpening JPEG images need to be handled carefully as do images that have been previously scaled up. The pixels have already been altered either during compression or enlargement so careful consideration to sharpening is crucial. Again, it's always best to start with a RAW file. Sharpening can then be done prior to exporting since you are working in a non-destructive environment. That said, there are sharpening techniques that can be utilized in Photoshop to get desirable results.
COLOR SPACE: Most consumer grade cameras default to sRGB color space. It was designed to give pleasing results on monitors and the Internet. It was not necessarily meant to be used for high quality printing. AdobeRGB is a more acceptable color space for printing higher quality images. It has a wider color gamut. What that means is that AdobeRGB represents a given set of colors more accurately. CMYK is only used for offset printing.