This is a bonus post, because the last one was kind of short. I promise this will be the last post that involves math.
The distance to the soldier in Negative 37 has been bugging me, and as I explained in the second post (Method), I couldn’t use my equation to figure out how far he was from Capa because the rebate was missing. Tristan Da Cunha had created an imagined rebate, but we don’t know how much of the image was cropped. But, now I think both questions have been answered… kind of…
After thinking about how to solve this problem for way too long, I realized I could try to match the grain in Negative 37 and any other negative from that roll, because the rest of them had their rebates (a rebate is the dark border around the image). So, I chose Negative 35, because I had a clear image of it, then put Negative 37 on top as a separate layer, then I started changing the size of Neg 37 until the grain matched Neg 35.
Now, I realize this is very subjective – not at all scientific – and the images were downloaded from the internet (as jpeg’s, not screen shots), but I think it’s a good approximation, and I mainly wanted to see if this matched my other calculations, and make sure it fit into the map of Capa’s activity that day. Short answer, it does.
The M1 helmet used by soldiers in World War II was 7 inches tall. Once I matched the grain, I went through my standard formula tan𝜭 = O/A, with A this time being the height of the helmet, of 7 inches (91 pixels in this picture). This time, 27 degrees was 1686 pixels. It worked out (after about 4 hours of scratching my head) to 22 feet, or 7.5 yards. And that looks about right. My earlier calculation was somewhere greater than 13 feet, so it all matches pretty well.
So, the other question this answers is how much of this negative was cropped. If my opinion of the relative grain sizes is correct, and based on a pixel height of 841 in my captures, the vertical angle of view of the crop is 13.5 degrees, which is roughly equivalent to a 100mm lens.
The Zeiss Book from 1932 lists a 85mm lens and a 135mm lens as the closest to 100mm. They made two 85mm lenses, one f/2 and the other f/4. The 135mm lens was f/4. This above analysis assumes Capa used his 50mm lens, and that’s probably a safe assumption since I doubt if he would want to change lenses while standing in the ocean with lead flying around him.
I’m sure Henri Cartier-Bresson would have made a comment about the cropping…
Magnified view on Negative 37 (left) on Negative 35. I think the grain size matches, you may disagree. If so, let me know in the comments. I realize that these are pixelated versions of a print and a negative snatched from the internet, but it’s all I had to work with.