Photo Enlargement Basics for Digital Photosby Mike Kruske
Every year digital cameras are becoming better and better at producing higher quality photographs. This is evident by the fact that just recently, Nikon announced it will be phasing out film cameras from it's product line. With the ever increasing digital resolution of today's digital cameras, true film quality photo prints are a reality.
Whether you are printing smaller size digital photo prints, or want to produce the largest photo enlargement possible from your digital camera, the digital resolution in pixels, or the camera's megapixel rating is the main element relative to printing quality.
Digital cameras usually have the feature of setting lower pixel resolution captures to save space on the camera's storage card. If you ever think you will print the photos you are taking, you should always take your digital photographs on the camera's highest quality setting. This setting will provide the largest amount of image data in the photo. The photo's color, contrast and image dynamics will always be much higher in quality, even when printed at smaller sizes.
If you think there is the possibility of photo enlargement of your pictures, it is highly recommended you always have your camera set on the highest quality possible. Photo enlargement options for digital photographs are directly related to the density of image pixels. The higher the original image pixel density, the larger the image can be printed and still maintain original image quality. Original image quality means the actual photo pixels have not been altered in visual appearance at all.
The physical print size of any digital photo is determined by the resolution DPI (dots per inch) assigned to the photo file relative to the original files pixel dimensions. With pre-print image files, the resolution is actually stated in PPI, or pixels per inch. The higher PPI you assign to an image file, the smaller the print size will be.
An example of setting PPI for a digital photos: The example is a Canon 6.3mp digital photo/highest resolution setting. Image dimension settings performed in Adobe Photoshop CS: image > image size - with resample box unchecked. Resampling the image (resample box checked) will alter original image quality.
Original pixel dimensions: 2048x3072
Assigned PPI of 72 - image print size = 28.444 x 42.667
Assigned PPI of 90 - image print size = 22.756 x 34.133
Assigned PPI of 120 - image print size = 17.067 x 25.600
Assigned PPI of 150 - image print size = 13.653 x 20.48
Assigned PPI of 200 - image print size = 10.24 x 15.36
Assigned PPI of 300 - image print size = 6.827 x 10.24
As you can see by the example above, photo enlargement of any digital photo can be accomplished simply by reducing the assigned PPI of the image. This will work only to a certain extent for most printing applications. As the image input resolution (PPI) decreases, the image will become decompressed when printed. The result will be very low quality prints that are pixelated or very grainy or blurred.
A general rule of thumb for image input PPI is 300 for quality photo prints. This would apply to most standard print systems that do not employ advanced raster image processing software. Using the bicubic resampling feature in Photoshop can create an image input file of about any size you want, but resampling the original file will always degrade image quality. The greater the degree of resampling, the greater the degree of image degradation. Degraded digital photos will appear pixelated, or have a very sharp and edgy appearance.
Advanced photo enlargement techniques for digital photos are much more complicated. These techniques utilize proper PPI settings, advanced fractal technology software and sophisticated raster image processing software. Proper file management and the use of these highly advanced software packages, can create image input files with no adverse resampling effects. Photo enlargements with absolute original image quality are possible.
About the Author
Mike Kruske established PhotoArt Imaging Digital Arts Center in 1997 specializing in Photo Enlargement, Digital Photo Enlargement and Wide Format Digital Photo Printing of Digital Images. This targeted experience provides a unique insight into digital photo processing for large format print output. More info here:
PhotoArt Photo Enlargement and Digital Photo Printing