Today’s Question: When preparing photos for a PowerPoint show where the quality of the images is important (for showing off the photos to their best) and around 150 photos or more, what would you recommend for file size?
Tim’s Quick Answer: The key for a digital presentation such as a slideshow is to make sure the images are sized based on the pixel dimensions of the display you will be using. You can then save the images as either PNG (Portable Network Graphics) files, or as JPEG images with the Quality set at or near the maximum value.
More Detail: The actual file size for images that will be presented on a digital display (such as in a slideshow presentation) doesn’t tend to be a critical concern, in large part because by definition those files won’t be extremely large.
The first thing you’ll want to do is confirm the resolution of the display you’ll be using for the presentation. In many cases you’ll still find projectors in use with a relatively low resolution of around 1024×768 pixels, or perhaps full HD resolution of 1920×1080 pixels. Of course, you might also have the opportunity to present on higher-resolution displays, such as a 4K display that will have a resolution of around 4,000 pixels wide.
Based on the display, you can then resize the copies of images to be used in the presentation to a size that is at or slightly above the expected resolution. I then prefer to save in the PNG file format if that is supported by the software you’ll use for your presentation. PNG files will generally offer at least slightly improved quality over JPEG images, because the PNG format uses lossless compression. The file sizes will be larger than a JPEG image in most cases, but for a digital slideshow that isn’t a significant concern.
If the software you are using for the presentation doesn’t support PNG files, you can save the images as JPEG files with the Quality setting at (or near) the maximum value. This will still provide good image quality, with a file size that is generally smaller than the PNG file would have been.