I don't think anyone would argue with the statement that Lightroom's Slideshow Module is not very powerful or flexible. The Slideshow Module is great for a quick slideshow. But if you want a professional looking product you will do much more work than you need to using Lightroom alone.
If you are a full Creative Cloud member then I have good news! You have access to After Effects. After Effects is an industry-leading animation and motion graphics application. It is certainly capable of creating any slideshow you can dream of.
You may be wondering if Lightroom works with After Effects. Since they are both part of one big happy Creative Cloud family they do play well together.
There are three ways to get your images from Lightroom into After Effects. The first is to set up After Effects as an external editor in Lightroom. While this will work via the Edit In feature you may be left with duplicate images in your Catalog. Also, After Effects will not return anything to Lightroom since it will be producing a very different creature. One that Lightroom is not designed to manage. However, it is an expedient workflow from an After Effects perspective.
Another method is to create an export preset to send your images to a folder that After Effects can access. This has the advantage of not creating copies in your Catalog (unless you opt to have them imported after they are created). This is a good way to get images from Lightroom and keep the image sources separate. Note: This method will include any adjustments made in Lightroom.
The third method is to simply drag and drop your images from Lightroom into After Effects. This is the workflow we'll look at here. It's simple and doesn't create unnecessary copies of image files. Note: This method uses the original images without Lightroom adjustments.
To start open Lightroom and After Effects. Resize Lightroom so you can see both applications. Select the images you want to include and drag them to the project panel in After Effects.
Once you drop the images After Effects will become the frontmost application and your images will be in the project panel and already selected.
Next, grab the already selected images and drag them down to the new composition icon at the bottom of the project panel.
When you let go After Effects will present you with the New Composition from Selection dialog box. You are a few choices away from a basic slideshow.
Select Single Composition so that all your images are in one composition (1). You have two choices to make in the Options section. Choose which image will be used as the size of the composition (2) and then decide how long you want each image to be displayed (3). In this case we have chosen 3 seconds. Make sure that you check the Sequence Layers option to have After Effects line up your images so they appear one after another. Choose overlap, set a duration for the transition, and select Dissolve Front Layer (4). This will create a cross fade from one image to the next. When you're done click OK (5).
Looking at After Effects we can see how the images overlap (1). With the playhead in one of the overlapping areas you can see how the fade is underway (2). If you select a layer and then press T to see the opacity values you will notice how After Effects has set up keyframes to handle the gradual change in the opacity of the front layer.
The keyframes appear as small diamonds. With the playhead between them you can see that the current opacity is at 66%. The left keyframe is 100% and the right keyframe is 0%. Simple.
So what have you gained over using the Slideshow Module? Isn't this all possible in Lightroom? The short answers are "nothing" and "yes." However, now that you are in After Effects you can add special effects. Title and text can appear, wander around the screen, and disappear again.
Now you have the ability to match slide durations to music. You can create several compositions and combine them. The possibilities are endless. Have a little fun and give After Effects a try. You will be pleasantly surprised!