RESOLUTION EXPLAINED

What is Resolution?

A digital image is a rectangle made up of many small squares of color called pixels. The number of pixels across the width and height of the image is called the resolution. An image with 640 pixels across the width and 480 pixels high has a resolution of 640x480. The more pixels in the image file, the higher the resolution.

Many cameras offer a choice of resolutions from 640x480 up to 5000x3500 or higher. The larger the file resolution, the fewer images that will fit on your camera memory card. Commonly the size of a pocket digital camera image is proportionate to a 4x5.3 print (a 3:4 ratio), and a larger SLR 35mm camera is proportionate to a 4x6 (a 2:3 ratio).

Images viewed on a computer monitor are displayed at 72 dots per inch or dpi. Each pixel is converted into a dot of color. An image with 640x480 resolution will be displayed on a monitor as 640/72=8.9 inches by 480/72=6.7 inches, or 8.9 x 6.7 inches in size. Therefore an image with 640x480 resolution is a good size image to view on a monitor, email to a friend or use on a website. Unfortunately, this resolution is too small to make a quality photographic print.

Resolution matters when printing

At Fromex, we use the most technically advanced equipment available today to produce beautiful photographs from your digital files. In order to produce a photo quality print, we print at 300 ppi (pixels per inch); have at least 300 pixels for every inch of the print. In order to produce a photo quality 4"x6" print we need a file resolution of 6"x 300ppi=1800 pixels across the width and 4"x 300ppi=1200 pixels in height. Therefore we prefer a file resolution of about 1800x1200 or higher for optimum 4x6 prints.   A quality 8x10 print would need an image file with a resolution of 3000x2400 or higher. Smaller resolution files can be printed, but the results will be less than optimum.

When you order prints online from Fromex using our Xwire software, your images are automatically transmitted to us electronically. You will be able to pick up your prints the next day at Fromex or have them mailed to you..

If you are bringing us a CD or USB drive of your image files, please read our Digital File Setup Guide.

Order color prints online HERE.

How to find the file resolution

You can find this information in:

·        Windows: Right click the image file → Properties → Details

·        Mac: Right click the image file → Get Info

·        Photoshop / Lightroom: Go to Image → ImageSize

How many Pixels Per Inch (PPI) is best?

What PPi  is need for each print size? This is not an exact science since there are many variables, including camera lens sharpness, focus, the media being printed and the image itself. Quality photo labs usually recommend about these sizes.

300 ppi: Small prints up to 8x10 that will be viewed in hand or up close ideally should be 300ppi. The ideal resolution since human eyes cannot see anything finer than 300ppi without additional magnification.

240ppi: Fine for images up to 12x18 that will be viewed from 2-3 feet away

180-200ppi: Acceptable for larger prints up to 24x36 and viewed from  4-6 feet.

 150ppi: Acceptable for larger prints 30x and bigger and viewed 8-10 feet away.

 Any lower than 150ppi becomes noticeable and should be avoided if possible.

How to calculate the largest size that I can print my Digital File?

How to determine the maximum “acceptable” print size? Much of this is in the eye of the beholder; everyone  sees things slightly different and personal preferences can vary widely.  Take the pixel resolution and divide it by the desired ppi to see the resulting size.

Example: Your image resolution  is 3000 x 2000, therefore 3000 pixels wide and 2000 pixels high. If you want a 200ppi print for viewing 4 feet away:

3000px width / 200ppi = 15 inches    OK

2000px height/200ppi = 10 inches    OK

OR

Take the resolution and divide it by the print size you want, to see if the resulting PPI  is acceptable. Example: You want a 24” x 36” print.

3000px width / 36” = 83ppi so a 24x36” print is probably too big for this file

2000px high / 24” = 83ppi 

Ideally you would need a larger resolution file:

36” print x 200ppi = 7200 pixels in width.

Conclusion

Every image is different, so do the math;  there are no hard fast rules.  But now that you understand the concept, here are some “general guidelines”:

Pixels Long Side                 Quality Print Size         Acceptable Larger Print

1600 Pixels                                      4” x 6”                                        5” x 7”

2400 Pixels                                      8” 10”                                      11” x 14”

3600 Pixels                                      12” x 18”                                16” x 24”

4800 Pixels                                      16” x 24”                                20” x 30”

6000 Pixels                                      20” x 30”                                24” x 36”