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Why "300DPI or Greater" is
Not an Image Size
How to Ask for Digital Images without being Confusing
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| How many times have you seen, "send your digital
images, 300DPI or greater. The higher the resolution, the better to see
your artwork." That seems to be the most commonly asked for image
specifications by art shows that are trying to make the transition from
35mm slides. And it's totally untrue and confusing. Throughout this
article I'll be reinforcing a few points to help you
understand.
I've been trying to communicate with art shows for years about how to ask
for digital jury images. |
| Digital Images Defined |
| Digital images are made up of pixels, which are single
data points of an image. The size of an image is determined by the number
of pixels in height and width. If you look at the specifications in any
digital camera manual and you will see a list of the various sizes the
camera can capture, listed in horizontal and vertical pixel dimensions.
Nowhere in the camera manual is the mention of resolution or pixels per
inch (PPI) because digital cameras do not capture pixels per inch, only
actual pixels. Asking for an image in DPI or PPI (see definitions below)
is irrelevant because you’re only asking for the density of the pixels
within the image without asking for the actual image, which needs height
and width to exist. So if you want to stop reading here, please make
sure to ask for digital images by long pixel dimension based on how the
jurors will be shown the images. And if you want to understand more about
digital images, read on. |
| Pixels per Inch |
| Pixels per inch (PPI) and often erroneously stated as DPI
(dots per inch) is the density of pixels within an image. Even more
erroneously is stating DPI (or PPI) as an image size because stating the
resolution is meaningless and once image specifications are understood,
you realize that an image doesn’t exist unless it has height and width.
PPI is strictly a number that relates to printing in that for good looking
prints, the pixels need to be closer together. The most common resolution
usually asked for is 300PPI. But the pixel dimensions (or actual pixels)
needs to support the resolution at the size the image is to be printed. |
| For example; for a print to look good at 8x10 inches, the
pixel dimensions should be 2400x3000 because when you divide the 300PPI
into 2400x3000, the result is 8x10. For a print to look good at 4x6, it
needs to be 1200x1800 pixels because when you divide 1200x1800 by 300PPI
you get 4x6. An image that has been prepared for ZAPP at 1920x1920 pixels
will make a high quality print at approximately 6.4 inches square which is
close to what you get when you divide 1920 by 300PPI. Art shows have had
no trouble making those 1920x1920 ZAPP images into beautiful ads to
promote their shows or for use in their programs. |
| Monitor or Projector for Viewing |
| Monitors and digital projectors do not see resolution
(PPI). They only see actual pixels of an image in height and width. When a
digital image is projected, the program on the computer that sends the
image to the projector fits larger images to screen. That means no matter
how large the image is in pixel dimensions, you can still see the entire
image when projected. Conversely, images smaller than the projector (or
monitor) resolution will not fill the screen. Monitors and digital
projectors are basically the same. The projector connects to the computer
through the same input that a monitor does. |
| 72PPI vs. 300PPI |
| Resolution (pixels per inch) of an image is the density
of pixels within the image. When an image exists in a fixed height and
width in pixels, the resolution (4) can be changed nondestructively by
unchecking Resample (5) in the image size dialogue of your image editing
program and changing it to whatever resolution is desired. Unchecking
Resample keeps the number of pixels (2) and the file size (1) exactly the
same, and nondestructively means it’s still the exact same image, as seen
in the example below. Only the document, or print size (3), changes. |
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| Scanning Resolution |
| Since it's recommended that 300PPI is the magic number
for high quality prints, there are some places that erroneously state that
300PPI should be the scanning resolution. But if you consider the math,
scanning a 35mm slide, which is only an inch by an inch and a half, at
300PPI, will only give you a high quality print at an inch by inch and a
half. That's why the best desktop film scanners scan at 4,000PPI or
higher. If I were having a lab scan my slides, I wouldn't settle for scans
under 3,000PPI. |
| For scanning prints, the resolution should be 300PPI
minimum. And if you're scanning 4x6 prints for jurying, they should be
scanned at 600PPI because a 300PPI scan is only 1800 pixels long dimension
(300PPI times 6 inches = 1800 pixels), too small for ZAPP. A 600PPI scan
of a 4x6 print is 3600 pixels long dimension. Large enough for jurying
(leaving you room to straighten and crop) or to make an 8x10 print,
depending on the quality of the original. |
| ZAPP and JAS online Application Systems |
| When asking for digital images, height and width need to
be specified. Just asking for resolution isn’t asking for an image because
the image needs to have height and width to exist. ZAPP asks for images
between 1400 and 1920 pixels and Juried Art Services has changed the image
long pixel dimensions and now asks for images between 1800 and 4000
pixels. |
| For the best presentation, images uploaded to ZAPP should
be 1920x1920 squared with black borders masking rectangular images. Though
ZAPP allows smaller images to be uploaded, they project proportionately
smaller when you apply to the top shows that project the images. |
| Though Juried Art Services also gives you a range in
pixel dimensions of images to upload, the JAS system only uses monitors
for jurying so all the uploaded images are reduced to the same (700) pixel
size for the jurors to see. The fact that JAS asks for images with a PPI
of 300 is to allow the shows to have images large enough to print, not
realizing the resolution of an image can be changed without changing the
image itself, as can be seen in the above Photoshop Image Size menu. |
| Shows not using ZAPP or JAS |
| This is where the problems occur and the reason for this
article. There is no standard image format and few art shows understand how
to ask for digital images. Basically, shows should be asking for images
based on how they are to be presented to the jurors, making sure that
horizontals and verticals display the exact same size to be fair for all
the artists applying. The original ZAPP 1920x1920 image size is the
perfect way to ask for and view images. The black borders on rectangular
images act just like the slide mount on 35mm slides, displaying both
horizontal and vertical jury images exactly the same size. |
| Art Shows Giving Away Full Size Jury Images |
| Artists need to be aware that recently a jeweler was
caught using other jewelers jury images to apply to shows. There have been
many cases of art shows exposing the artists to possible loss of
copyright, design and loss of sales by posting the full size images to
their web site, or even Flickr. The worst I've seen is on the Paradise
City web site where, in 2011, they posted the full size jury images with instructions under each image
how to save the full size images back to your computer. On the Paradise City web
site screen capture below, I removed all artist identification and I'm not
going to post the link to any of the full size image pages either because that will contribute to the problem. |
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| To obtain this image at it's full size, right click on
the image and select "Save Picture As.. (Internet Explorer) or Save Image
As.. (Firefox, Netscape) from the pop-up menu if you are using Windows.
When using a MAC, right click on the image and select Download Image.
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| If you have any additional questions or comments, feel free to
contact me
by e-mail or call
412-401-8100 |
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