Digital Photo Printing Tips

Many photo printing services offer various means of uploading your digital photo files. Some also offer online tools to edit your photo before submitting it for printing.
Some services require you to download software to your own computer to facilitate file uploads. Others use a web based file browser. Still others only accept digital files mailed on disks or sent as email attachments.

If you are only interested in snap shots or smaller novelties you probably will not need to worry too much about file sizes. However, if you are looking for large prints, file size will become much more important. The methods available to send these larger files to your print service may become a deciding factor, especially if you have one of the slower internet connections.

While many of those specializing in larger photo prints will go the extra mile to make your lower resolution image files look their best one shouldn't count on this being the case. Or even being possible, depending on how large a print you are considering.
It is always best to do some preliminary work in a photo editing program yourself. If nothing else but to get a feeling for what your image file is capable of. If that gorgeous sunset.jpg gets ripped apart when viewed at 16x20 in your photo editor, don't even think about sending it out to make a 22x28 enlargement.

Digital image files are measured in pixels per inch in digital cameras and most graphics software. If you simply increase the dimensions of a digital image without resampling the resolution falls. If resolution falls below what is needed for printing, image quality suffers.You can easily find the pixel dimensions of an image stored on your computer by right clicking the file name and choosing properties.
Dividing the print size you want in inches into the pixel dimensions will give you the resolution available in your file. For instance, a file 2400 x 3000 will produce an 8x10 at 300ppi. or a 16x20 at 150ppi.

You're going to need at least 150 pixels per inch and preferably 300 ppi at your desired print size to produce photographic quality on paper. Shortfalls can be made up to some extent using resampling (interpolation), where pixels are created by software to fill in the gaps. This technique however, should always be used as a last resort and then used very sparingly.
Resampling adds pixels by "guessing" the appropriate information after analyzing the adjacent pixels. Errors are inevitable and excessive use results in blurring and artifacts being introduced. Whenever possible you will want to get the bulk of those pixels from your original. If the pixels simply are not there to begin with, you will be limited to smaller print sizes.

Many online photo print services offer tables showing the minimum pixel dimensions your file should provide for a given print size using their service. Files with larger pixel dimensions than required are generally fine, although overkill may not provide any better image quality depending on the system in use.

Another pixel dimension issue which frequently comes up is the aspect ratio. Photographs cannot simply be stretched to fit a different aspect. At least not if one doesn't want it to look like it was made in a funhouse mirror. Images can only be cropped to fit a different aspect. If your photo is a rectangle as most are, and you choose to print it square, you'll need to cut off the long ends as with a pair of scissors. This is known as cropping.
For most photo prints it is best to try to closely match the aspect of the image you have to avoid surprises. Automated services may simply lop off what is needed from one dimension to fit your chosen aspect regardless of what is being cut.
A custom service may offer other choices such as centering the uncropped image on the print size you order creating uneven borders. Custom services are also more likely to take into account what will be lost in cropping, adjusting it accordingly or they may suggest alternative print sizes.

Getting a high quality print depends a great deal on it's source.
If you are scanning a photograph, an 8x10 glossy will produce a more useful file for printing than a 4x6. Scanned photo prints should probably not be considered as a source for substantially larger prints. Photo prints on paper simply do not contain enough quality information to begin with. If scanned at too high of a resolution the image will become very noisy.

If you are scanning film negatives or slides, you may want to look to a scanning service to get the most from your original. This is not at all the same as getting a picture disk made at the local 1hr photo lab. These disks are designed for online sharing and relatively small prints made on a desktop printer.
Dedicated film scanners are designed to pull out every bit of information your film has to offer. If you want a really huge enlargement made from your film you'll want to locate a service that offers drum scanning.

If you are shooting with a digital camera you will only be limited by your camera's sensor as long as you remember to always store .jpg images in best quality mode/lowest compression/largest file size. If you never plan to print your pictures, and you are satisfied viewing them on the low resolution requirements of a computer monitor this won't make much difference.
If you may ever want to print your photos though, and who knows for sure until the shot has been taken, you'll want to forget the memory saving settings and stock up on extra memory sticks for your camera instead. When that real keeper comes along, you'll be very glad you did.

Overly compressed .jpg files are useless for printing and enlargement.
If you are one who likes to edit your image files it is always best to convert your file format to a lossless one such as an uncompressed .tif before you start manipulating it.
Many digital cameras offer the ability to save your photos in the uncompressed .tif format.

Lossy compression formats such as .jpg lose information each time they are compressed. Making changes and re-saving the file
re-compresses it with each save causing image quality to deteriorate.
Once you are satisfied with your edits you can save a copy as a high quality .jpg for easier transmission of your file to a print service while reserving the lossless format for future manipulation.
You could just send the uncompressed .tif to many print services, but these tend to be very large files and some services will not accept them particularly when uploaded online.

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