If you are new to Lightroom (or not so new, as this took me a while to figure out), you may be a bit confused as to how you can resize images in Lightroom. For the longest time, I searched high and low for the resize option, but came up empty-handed! I was actually using Photoshop to resize, but once I figure out how to resize in Lightroom, I realized just how easy it is. It's a piece of cake!
You will find the resize option in your Export dialogue. So, go to your top toolbar, select File, Export, and you will see this box:
Once you see the above box, use the arrow on the right to scroll down until you see Image Sizing, then check the “Resize to Fit” box.
At this point, you will have several options for resizing, so let’s look at how they work:
Width and Height
With all of the resizing options, you can choose your dimensions in either pixels, inches, or centimeters, as well as select your resolution. In this example, I am using pixels, and a measurement of 3500 X 4500. This is the quick, easy and custom way to set your pixels and resolution.
As you can see above, I changed my dimensions to inches, and entered 8X10. Something to keep in mind is that Lightroom will generally not resize the image to exactly 8X10, but instead, will size the image as close as it can to the dimensions you entered. After I exported this image, the exact dimensions were 8X9.71 inches.
Another important factor to keep in mind is resolution. If you are editing for the web, a resolution of 72 pixels per inch is more than enough for screen display, however, if you are going to make a large print, you will want a high resolution of 240-300 ppi.
Long Edge and Short Edge
With this feature, you can choose to edit either the long or short edge of your image, and Lightroom will automatically adjust the rest of the dimensions for you. This is extremely handy if you are editing a photo for online sharing, as websites and blogs often require a specific pixel measurement on one edge of the image.
If actual file size is a factor in your editing, you can set your megapixels. This is a great option if you are not bound by specific dimensions, but rather, file size. If you are emailing your photos this will come in handy, or, if you simply do not want to use too much space on your blog or website.
Another useful trick in your Export dialogue is that you can create presets for your commonly used dimensions. To create a preset, in your Export dialogue, select Add (lower-left side of box, under Plug-in Manager).
Once you have named your preset, click Create, and in the future, you will be able to quickly apply the same measurements to an image.
As you probably know, one of the greatest benefits of Lightroom is its non-destructive editing. So, you can resize your images in Lightroom, without having to worry about accidentally overwriting your original image with a smaller version. Many times I have accidentally overwritten my original edit with a smaller version in Photoshop, destroying the original forever. Lightroom does not overwrite the original when you resize, though. It is possible to do, but you really have to go out of your way to tell it to overwrite a file! If a file is about to be overwritten, Lightroom will ask you if you want to overwrite the original file, or use unique names. Always select “Use Unique Names” just to be on the safe side.