the 'Red-Headed' stepchild of photography

[Paul Fitzgerald]

Good morning,

JohnArs, here are the numbers for 8x10 for an 18" head shot:

[pre]
1.5 Field ft. Lens mm:
10in 8in
Distance ft. Distortion %
0.5 80.28 84.7 67.7
0.75 41.42 127.0 101.6
1 25.00 169.3 135.5
1.25 16.62 211.7 169.3
1.5 11.80 254.0 203.2
1.75 8.80 296.3 237.1
2 6.80 338.7 270.9
2.25 5.41 381.0 304.8
2.5 4.40 423.3 338.7
2.75 3.65 465.7 372.5
3 3.08 508.0 406.4
3.25 2.63 550.3 440.3
3.5 2.27 592.7 474.1
3.75 1.98 635.0 508.0
4 1.74 677.3 541.9
4.25 1.55 719.7 575.7
4.5 1.38 762.0 609.6
4.75 1.24 804.3 643.5
5 1.12 846.7 677.3
5.25 1.02 889.0 711.2
5.5 0.93 931.3 745.1
5.75 0.85 973.7 778.9
6 0.78 1,016.0 812.8
[/pre]

The z-axis distortion makes the picture appear to bow towards the camera in the center. For a head shot you want some of this distortion for depth BUT not too little or too much.The lens distances are to the optical center, not the marked focal length. Like I said, inches make a difference, see how fast the distortion changes.

Have fun with it

[Paul Fitzgerald]

Hi there,

Just to be obsessive, compulsive, anal retentive and relentless, I just set this up with a 305mm B&L tessar on 8x10. Focused to get both ends of an 18 inch SS. ruler, the waterhouse slot is 33 in.(2.75ft.) and 440mm from GG.. Yes, the spreadsheet numbers do work out in the real world but I guess this waterhouse slot is not at the optical center of the lens.

Have fun with it.