IrfanView has a lot of ability of how you want create a Contact Sheet. Perhaps you are only using the default values.
By changing the Sheet Dimensions (values in pixels), the quantity of Columns and Rows to create, you can get quite a few thumbnails on one page.
With just a few changes (W=2400, H=3300, C=6, R=10) I was able to get 60 nice size thumbnails on one page. I am sure I could get over 100, of a usable size, on one page. How many do you need?
The thing I miss most from my 35mm days is the ability to have index pages for my digital photo collection. I can print thumbnails from Paint Shop Pro 7 and from Irfanview but the spacing is so wide between pictures that I can't get anywhere near the number of pictures per page that I would like. I can create an index page with Paint Shop by resizing each shot and manually fitting each shot on the canvas using the print multiple pictures option, but this not practical for many pictures.
I don't need captions since my pictures are organized chronologically. Any help in this area would be appreciated.

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