The Delta Projection Print Calculator Scale, gives perfect exposures every time. It has eight pie wedges of calibrated, graduated density, that help determine the exposure time, by showing the time in seconds. All it takes is one test exposure, its easy to use, and saves time, paper, and chemistry. The scale is 4 x 5" in dimension.
When I work with a really unknown negative I will put this on the easel and get a starting point with a test print. This projection print scale is NOT 4x5 inches as it says it is. The actual measurement is 4 1/2 x 5 3/4 inches and when you utilize a 4x5 inch piece of paper you will not be able to fit the time designations onto the test print. A minor but annoying inconvenience when working with a darkroom newbie.
still have to try this out