Al here from Shatter Safe
I promise not to turn this into a commercial or advertisement
but at least I am honest about who I am.
As you are wanting this film for a shed, and there should not be any activity during the dark hours, your idea would work. However, all a "bad guy" has to to do is cup their hands around their eyes, and they will see in. .. not very well, but they will still see in.
I think that the frosted type film is the best solution for you and it is readily available in small 18" x 5 or 6 foot rolls at either Home Depot, or at Lowes. and look.. I even gave you the links
This film that sells for about 15-20 dollars, will allow about 85% of the daylight in, and will make it impossible for someone to see inside. Simple application, cheap, and will accomplish your task.