Slideshows in a Digital Age

Kodak carousel trays

Life used to be simpler. In the old days, when I wanted to put on a slide show, I just gathered up my 35mm slides, arranged them in a Kodak Carousel tray (or two), and headed off to do the show. Everyone had carousel projectors and screens. There were some worries, but they seem minor:

  • you could forget to screw the closing ring in tight on the slide tray; invariably, you would then proceed to dump your slides all over the floor; or
  • the bulb on the projector could burn out (this can happen today, too, but not so frequently).

Now that we are deep into the digital media revolution, the choices of how to put your images up in front of an audience are myriad:

  • Where do I want to put the images? Onto a screen? Or onto a big monitor or TV?
  • Do I have to do anything special to my images? What resolution or size do I need to use?
  • How do I want to run the show? Manually advance the pictures or make the show into a movie?
  • Do I want to add audio? Motion (a la Ken Burns)? Video? Fancy fades and dissolves?

I have been looking into these questions recently and will address the first two points in the rest of this article, while I will post an article on the last two shortly.

Where Are You Displaying the Images?

The grayer-haired of us automatically think of projectors and screens, but the arrival of large-screened monitors and TVs have made them a real possibility for smaller audiences.

On the projector front, you have a range of choices in resolution (SGA, XGA, etc.), brightness (the lumen level) and contrast ration (the ratio of brightness of brightest points to the darkest).

Most offices or small auditorium projectors offer either SGA (800×600 pixel) or XGA (1024×768 pixel) resolutions. Other resolutions are available, all the way up to the best presently available of HD 1080p (1920×1080 pixels). This link will open up a chart in wikipedia that summarizes the present alphabet soup of resolutions.

What is really interesting is the overlap of home theater with what had been the relatively simple domain of slide projectors. This opens up all sorts of high definition, high fidelity options. I have added a number of links at the bottom of this article on projectors and home theater devices.

If you have a big, high resolution monitor, this can make a terrific display for a small group. Better yet, a wide-screened, HD TV can expand your group to your whole family or a room full of guests. You may have to investigate cabling requirements to ensure getting the most from your computer to your HD TV. To my mind, if your computer and your HDTV both have HDMI, then things are great. Otherwise, it gets more complicated. Here’s a link to forum thread at c-net that can be a starting point for this area.

If you are using someone else’s projector or monitor, of course, all these decisions have been made for you, so how does that choice matter? The basic idea is that as we move the image from our cameraa or scanner, through our computer and software to the screen, the resolution of the projector or monitor becomes the limiting factor at how much information gets to the screen.

Today’s cameras can easily generate 5 or 10 megapixel images (or 10 or 20 megapixel images for high-end digital slrs) and your computer can handle many times that. An XGA projector, on the other hand, can handle only 1024 times 768 pixels, or 768,000 pixels! So what happens to all those “excess” pixels? Somewhere in the chain from the computer to the projector all the images are downsized and the excess pixels are dropped.

Even if you are lucky enough to be sending your slide show to an HD 1080 TV or monitor, that device can handle just 1920 times 1080 pixels, or a little over 2 megapixels. Still not as much as your camera can record, but a lot more than the XGA projector!

Knowing about this disparity between camera resolution and projector resolution, you realize that when you produce your slideshow, you have two choices regarding how to handle the excess:

  • you can ignore the projector constraints and fill your slideshow with full-sized images. Your hardware will take care of downsizing the images to fit the projector’s size limits; or
  • you can downsize the images yourself that you use before putting them into your slideshow program. Just as an aside, this will have no impact whatsoever on the quality of the image that finally shows up on the screen.

Although it is more work to shrink the images yourself, the benefits are many:

  • smaller images mean smaller slideshow files.
  • smaller slideshow files mean quicker load times, quicker save times, easier backups, less strain on aging computers, etc.
  • these add up to quicker production time, especially if you are dealing with lots of pictures.

Here’s an example. Assume you are using an XGA projector. As the last step in your picture processing (find the images, crop them, adjust their color, brightness, contrast, etc.) and before dragging them into Powerpoint (or whatever program you are using), downsize the images to fit inside the 1024×768 pixel window that the projector allows. If your camera recorded at 3 megapixels, this is a 4:1 reduction in file size for a full frame image. All modern photoediting programs (Photoshop, Photoshop Elements, Lightroom, Aperture, to name a few) can do this, as do a number of online services. Better yet, if you are doing all this on a Mac, you can do it all using Finder and Preview, two Mac apps that come with every Mac. See my article, Resize Images for Digital Slideshows, for more details.

The point is to tailor the image to the particulars of your slideshow.


Here are a series of guides and review articles:

Here are a few manufacturers’ sites: