Hi Hap,
You wrote in a message to Matthew Kiwala:
 HN> I thought a 127 or 135mm lens was normal for 4X5. Are you sure on
 HN> the 210mm? I've been told that is a short tele for 4X5.
 HN> chat with you soon!
 HN> hap
Well going by the formula Ed put on here recently that standard focal lenght 
is equal to the digonal I get 162mm but as I have not seen a lens of that 
size I would guess the 135mm or 200mm would be the nearest.
4" * 25.4 = 101.6mm
5" * 25.4 = 127mm
Square root of ( 101^2 * 127^2 ) = 162.64mm
Standard angle of view = 53deg =360/PI*ATAN(0.5*Diag / Focal Length)
The reverse of this formula (Diag/2)/TAN(Radian(Angle/2)) 
                                          ^Only needed if you use Spreadsheet
Will give you the focal lenght for any given angle of view eg 50deg Standard, 
25deg Slight telephoto (100mm on 36mm film) Wide angle 90deg (around 22mm)
Regards,
Stan 
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