I ended up creating a simple Excel calculator yesterday, for bellows extension exposure compensation with my forthcoming additional focal length. Before you reply, "But there are 39 gazillion phone apps already," please understand that I do not use a smartphone and like it that way. Thank you. If similar Excel sheets are already available, at least I have had the satisfaction of solving a problem myself.
The calculator is simple, because my Excel and math skills are elementary. One simply enters the focal length; calculations for extension and exposure factor are automatically calculated for a supplied range of distances (which, of course, can be changed for different lenses or preferred distances). It's fine for the work I do.
However, although I created a column for exposure factor, I don't know how to create a formula for a final column rendering that increase in f/ stops based on that factor, which would be formatted as a fraction (that, I can do.)
For example, with a 5.31-inch (135mm) lens entered in one cell, the following calculations are done, but I had to enter values in the last column manually.
Distance, feet Bellows extension Exposure factor Exposure increase in stops
0.84* 11.24 " 4.47 2 1/2
1 9.54 " 3.22 1 1/2
1.5 7.54 " 2.01 1
* Excel sheet has an inches column as well
Can someone provide me an Excel formula for the "Exposure increase in stops" column?
I don't know if anyone else would find this handy. I have written our site owner to ask if he would be interested in posting a link on the home page, once I finish it. Otherwise, since I don't have a website, I may post the file to a Dropbox link for anyone who happens to see it or would like to host it on his or hers.
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