Martin Aislabie
Subscriber
I was looking through my 5x4 Neg Files then it struck me the Negatives I am looking at are not 5 inches by 4 inches at all 
I got out my engineers steel ruler and measured the exposed size of the negative as 120mm x 96mm with a diagonal of 153mm
This still gives a 5:4 length:width ratio
Even the sheet of film isnt 5x4 inches its 125 x 100mm (4.9 x 3.9 inches)
Can someone shed light on how we got to this size?
Has 5x4 ever actual been 5x4 inches or has it always been a close metric equivalent to 5x4 inches :confused:
Martin

I got out my engineers steel ruler and measured the exposed size of the negative as 120mm x 96mm with a diagonal of 153mm
This still gives a 5:4 length:width ratio
Even the sheet of film isnt 5x4 inches its 125 x 100mm (4.9 x 3.9 inches)
Can someone shed light on how we got to this size?
Has 5x4 ever actual been 5x4 inches or has it always been a close metric equivalent to 5x4 inches :confused:
Martin