March 22, 2015

What Is the Difference Between DPI and PPI?

DPI and PPI are abbreviations used to describe resolution in digital photography. Resolution means different things in different situations. And there is no standard way to describe it. Most commonly, people refer to PPI and DPI as the same thing, though technically this is not accurate. Let me explain.


PPI stands for pixels per inch and refers to image resolution. This setting determines how crisp the details will appear in a printed photo. DPI stands for dots per inch and refers to printer resolution. This setting describes how many dots of ink are put on the paper by the printer. 

Some people use PPI and others use DPI to refer to image resolution, hence the reason we get confused! When you are preparing images to submit to magazines or contests, the organization may require pictures to be a specific image resolution. Even if they specify DPI (dots of ink per inch), they actually mean PPI (pixels per inch in the file).

Digital camera pictures often are saved at a different resolution than what a magazine or contest may want, anything from 72 PPI to 300 PPI. You can convert the picture to a different resolution using Photoshop Elements or any photo editing program that allows you to adjust image resolution.

Resolution out of the camera at 180 PPI

In Photoshop Elements, follow these steps to change the image resolution from the camera's default to 300 PPI:

1) Open the image you want to change.
2) Choose Image > Resize > Image Size
3) IMPORTANT: Turn OFF Resample Image
4) In the Resolution box type 300.
5) Click OK.

Resolution changed to 300 PPI
Resample Image turned OFF

Your image should NOT change size on screen. If it does, then you did not turn off the Resample Image check box. Choose Edit > Undo and try again.

There is no way to change the default resolution your camera uses to create JPEG photos. If you are shooting raw files, then you can usually set the resolution in the raw converter software, such as Adobe Camera Raw that comes with Photoshop. Click on the Workflow Options link below the image to specify the resolution ACR will use when you open the picture in Photoshop. (This is only available in full Photoshop, not Elements.)
Photoshop Camera Raw Workflow Options with Resolution set to 300 PPI

Some contest and magazine guidelines specify not only an image resolution but also picture dimensions in either inches or pixels. If your image's dimensions do not meet the requirements after you have changed the resolution, then use the Crop tool in Photoshop Elements to meet the size requirements.

1) Choose the Crop tool (type C).
2) In the Crop Tool Options, type the desired width and height in the boxes. Use "in" after the number for inches or "px" after the number for pixels.
3) Set the Resolution to 300 (or whatever the contest or magazine requires).
4) Drag the cropping box around your image.
5) Click the green check mark to apply the crop.

Elements Crop Tool Options set for 4x6 inches at a Resolution of 300 PPI

It is possible the size required may not exactly match how you have captured or cropped your photo. You may have to crop off some of the image to meet the requirements.