I'm planning to acquire a LF system(possible a Horeseman 45FA) to get better nat ure chromes then with my 35mm. I want to use the 6 x 9 and 6 x 12 rollbacks bec ause the 120/220 film is cheaper and the ease of use. For the 6 x 9 format, I ca lculate a required circle of 108.167 mm. For the 6 x 12 format, I come up with a circle of 134.164 mm. In order to calculate the angle of view for a given le ns, I just form a simple ratio of the image circle required for the given format .
As a example, for the Nikkor W 105/f5.6 LF lens, we have an angle of coverage of 73 degrees at an image circle of 155 mm. Then for the 6 x 9 format we calculat e an AOV(angle of view) of 73*108.167/155 = 50.94 deg. For the 6 x 12 format, th e AOV = 73*134.164/155 = 63.187 degrees. Since the image angle is realy calculat ed from the horizontal distance, the true angle of coverage for these two exampl es will be slightly less then as calculated.
Question. Is this logic correct?
Question. Would a Nikkor SW 90/f8(IC=231mm, AOC=105 deg.) be a better LF lens t o start off with? For this I calculate AOV(6x9) = 105* 108.167/231 = 49.167 deg s and AOV(6x12) = 105*134.164/231 = 61 degs.
Question. Is the F8 lens to slow and does it need a center filter?