![]() ![]() For others, they can be vastly different. The result, when I calculate Bv, is 3.51 the EXIF data have -2.30.įor some images, the calculated and reported values are fairly close. I am just now looking at a shot taken with A=6.50 T=0.06250s Sx=200 N=0.297 ![]() I found that it seems to be approximately correct, i.e. I do not know anything about this formula, but I was intrigued by it and so checked it on a few of my images. I found that it seems to be approximately correct, i.e.īv = log2(A^2/(T * Sx)) + log2(1/0.297) =>Ĭan you tell us an example where this is not approximately good?īTW, I expect that the formula holds approximately because the ISO and/or speed are not reported accurately but as approximations to well known values. I do not know anything about this formula, but I was intrigued by it and so checked it on a few of my images. I'd appreciate it very much if anyone could show me the light. When I use the values in the EXIF data for f-number, exposure time, ISO, as well as N, the result is not equal to the brightness value in the EXIF data. I'd appreciate it very much if anyone could show me the light. When I use the values in the EXIF data for f-number, exposure time, ISO, as well as N, the result is not equal to the brightness value in the EXIF data. I am using the standard formula Bv = log2 (A²/T/Sx/N)īv: brightness value A: f-number T: exposure time Sx: ISO N: constant that establishes the relationship between the ASA arithmetic film speed Sx and the ASA speed value Sv, which is 2^(-7/4) = 0.297. There is some inconsistency in the EXIF information, a hidden assumption (hidden to me, anyway), a hardware-related constant that eludes me and that needs to be included in the calculation, or something else I am missing. I would like to calculate this value from other information in the EXIF data, according to APEX definitions. The EXIF data include the "Brightness Value" that the camera recorded for the given image. I am trying to make sense of exposure-related entries in the EXIF data for my X-E1. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |