Photographic prints from your digital files

Preparing files in Photoshop: Starting and Finishing

Color balance

Choosing a digital camera

Tradeoffs between using Photoshop (or other editing software) and on-line editing

Stitching images together to increase the pixel count and/or the field of view.

Tradeoffs between high quality ink jet (the kind we use) and traditional photography

Preparing files in Photoshop: Starting and Finishing

Starting.  Let's say your objective is to make a 22" x 28" poster.  When we print this poster, we will expand it (at 300 pixels per inch [PPI]) to 6,600 x 8,400 pixels, or 55.44 Megapixels.  If your poster contains line art (e.g., text), and you want it to look as sharp as possible, then this is the file size you should start with. (In other words, multiply each dimension by 300 pixels per inch, and that is the number of pixels you need for your starting file size.)   However, if you can tolerate a small amount of fuzziness, you might be able to use as few as 150 pixels per inch.

If your poster does not contain line art, (e.g., if it is just a photo), or if the file comes to you with line art already embedded in it (and it's not a Photoshop file),  then there is no good reason to expand the number of pixels.  Let's say, for example, that you are starting with a 1200 x 1800 pixel (2.16 Megapixel) image.  If you import this into Photoshop, do a little cropping, and wind up with 6,600 x 8,400 pixels, there is no detail which will

look any sharper than it was in your original image.  You might just as well have sent the file to us at 1200 x 1800 pixels.  The pixel interpolation that Photoshop would do to fill in the missing pixels is no different than the pixel interpolation we will do for you when we print your photo.  Moreover, the 1200 x 1800 pixel image will take about 1/25 as long to transmit as the larger file would take.  (To some readers, this fact is very obvious.  However, quite a few of our customers have made life unnecessarily difficult for themselves by expanding their files in Photoshop when they gained no benefit by doing so.)

Most posters contain a mixture of photos, text, and other line art.  Following the above example, let's say that your 1200 x 1800 pixel photo is printed within your poster at 14.66" x 22" (82 PPI), and the rest is text and other line art (over and around your photo), printed at 300 PPI.  Why not print the whole poster at 82 PPI (1,800 x 2,300 pixels)?  The world will probably forgive you for the blurriness of your image, at 82 PPI.  But, they will probably not forgive you for the blurriness of your text at that same resolution.  We have come to expect some blurriness in images (even the best professional images).  But we do not expect blurriness in type.  You might be able to get away with, e.g., 150 PPI.  But at less than 100 PPI in a 22 x 28" poster, the result will not look professional.

For posters larger than 22 x 28, there is some leeway in the number of PPI that you need.  A 5 x 7 print is typically viewed at 18" distance.  The same is true for an 8 x 10, or for a 16 x 20.  For

 posters larger than 20 or 30" in the longest dimension, people typically stand back a ways to view it.  Let's say your poster is 40" x 72".  For that, 75 PPI type would probably look professional, even though type at 75 PPI in a smaller poster would not look professional.

The cost of professionalism is a large file size and long upload time.  If you know how to save your photos, you can save yourself a lot of time and pain.

Finishing.  Staying with our example, above, a 22 x 28" poster at 300 PPI, the worst case scenario (in terms of file size and upload time) is that you will choose to save this file uncompressed (e.g., as a TIF file).  Uncompressed, it will occupy 166 Megabytes.  At 250K bits/second (a typical DSL line), in its uncompressed state, it will take 110 minutes to upload.  Obviously, that is an unacceptable upload time.  Fortunately, you can also choose to save it as a JPEG (JPG) file, which will take 1/10 to 1/30 as much space.  Typically, that would take about 5 minutes to upload (again, assuming a DSL line).  If you put a print, made with a good JPG compression, next to a print made from the original TIF file, in nearly all cases no-one will be able to tell which is which.

A "good" JPG compression, in Photoshop, means than when you click "save as" and select JPG compression, you will choose a number in the range of 10 to 12.  This will give you a file compression probably in the range of 10:1 or 20:1, and the quality will be excellent. 

 (When the program asks you for compression type, choose "baseline.")  (Nearly all digital cameras use the same type of JPG compression, giving around 10:1 compression, and no visible loss of quality.)  If you use lower compression numbers, the result will be JPEG artifacts, which appear as halos or waves around objects.  The author has never seen a JPEG artifact in a properly compressed file.

There are other compression algorithms, e.g. BMP or GIF.  On the whole, they do not achieve the quality vs compression advantage that JPG provides.  (An exception is cartoons or posters which do not contain more than 256 colors.  For those, GIF is an excellent choice.)

You might also send files to us as Photoshop (PSD) files.  Although many customers do this, we don't encourage it, inasmuch as many Photoshop files contain color table information and/or font information which our file format converter cannot process properly.  (In nearly all cases, you will be able to tell from the thumbnail image in your on-line directory whether the file format conversion was successful.)

If you plan to do additional editing, later, on your file, it is best to save it in two formats -- the Photoshop format and the JPG format.  You can send the JPG format to us for printing, but if you do additional editing or revising, that is best done starting with the Photoshop PSD file