How to convert single images into a video with blending transition?

I would like to convert a series of webcam images into an animation/film/movie/video. Because there is a lot of motion between images, I want a fading/blending transition between images. Many Windows applications for image/photo viewing/managing have a slide show / presentation mode with transition filters and some of them allow to export as a video. For instance, XnView almost does what I want, but it does not allow fine-tuning the transition, i.e. it only has one parameter for transition speed, but it does not allow to adjust the time the image is displayed. Since I want to achieve smooth animation this needs to be adjustable as well.

Now I am looking for a tool that can do what I want. I thought about using ImageMagick's blend option to generate the intermediate frames and combining them into a video using ffmpeg, but I'm not sure how to manipulate the duration of the actual image other than by creating a number of copies. But there may be a better way to do it.