............Part II continues
SubjectDistance: This is the focus distance. Under the XMP format of Adobe it is found as <exif: SubjectDistance>
FocalLength: Focal length of our optics. In XMP it is given by the tag <exif: FocalLength>
In the same way, we can also help us with angular approaches:
The Wide Angle covers between 100º and 60º, the stardard between 50 and 25º, telephoto (which isolates the objects better) between 10º and 15º .... And by the frontality, contrapicado or verticality of the shot in scene (apart from, as I said, metadata and excluding, by the easy to determine, the "fisheye")
With this data, unless we are using extension tubes for macro photography, where we must also know the length of the tube or set of tubes, we can perform almost all calculations.
Then we divide the sensor width by the magnification factor, for example for a focusing distance of 0.45m and a 50mm optics, the magnification factor is 0.15.
And, how to know the lens with which the image was taken? For comparison, the human eye has a viewing angle of about 140 ° by 80 °. The usual is 36 mm × 24 mm (ie 135mm film or 35mm full-frame digital cameras using 36mm width, 24mm height, and diagonal 43.3mm d in the above formula) Compact digital cameras Declare the focal lengths of their equivalent 35mm lenses. We make the mathematical calculation of measurements between diagonal, horizontal, vertical and focal length and we will have the lens used, which will eliminate later, knowing the alteration that presents said lens on projected objects, twists, distances, perspectives and volumes, locating all The elements of photography in parallel, two-dimensional.
All this long process (it is easier to have the right software) eliminates the margins of error in photogrammetry leaving it to a maximum of 0.09, so our measurement will be very correct.
For example, this system serves to find out even the complicated measurements of a marine bubble of a photo in reality, being a round and three-dimensional element, decentering and tilting. Well, this method applied to porn videos and photos, which are susceptible to the same analysis, is the one I use in most cases. For that I review several photos and videos, not just one, and I do the calculations on all of them. Then, to finish, there are even clear signs and "less scientific", such as the navel / pubis distance. All you have to do is add up all, do the average and give the result. With these applications I found out that in some videos and photos, Mandingo reaches 23.9776 cm (9.44 inches), being now its general measurement 23,1902cm (9,13 inches). Criss Strokes in many videos / photos, applying all the steps and software, results in the majority between 7.5 / 7.65 inches. Lex Steele, when you get more, 8.57 inches, Chris Diamond 7.42 '' and so on ... If in some posts I expose photos "without applying" my method is because it is so evident that, serve as an example, Mandingo is More than 1 inch larger than Wesley Pipes, does not need much discussion, even in spite of those "hands" that are valued so much and of the lenses (whatever) that are used.
I add a FIELD OF VISION table below internationally used:
Longitud focal (mm) 13 15 18 21 24 28 35 50 85 105 135 180 210 300 400 500 600 830 1200
Diagonal (°) 118 111 100 91,7 84,1 75,4 63,4 46,8 28,6 23,3 18,2 13,7 11,8 8,25 6,19 4,96 4,13 2,99 2,07
Vertical (°) 85,4 77,3 67,4 59,5 53,1 46,4 37,8 27 16,1 13 10,2 7,63 6,54 4,58 3,44 2,75 2,29 1,66 1,15
Horizontal (°) 108 100,4 90 81,2 73,7 65,5 54,4 39,6 23,9 19,5 15,2 11,4 9,80 6,87 5,15 4,12 3,44 2,48 1,72