Dear All, based on previous discussions on SAED pattern indexing in RG, I have got the idea that the camera constant, C, of a TEM-SAED set up, is the product of lambda and L, where lambda is wavelength of electron and L, the camera focal length. And, the interplanar spacing, d = C/r, where r is the distance between the rings (or spots) from the central spot. Since the numerator has both units in length, I found that the distance between r should also be expressed in terms of length for which I converted the reciprocal spacing (scale bar given as 5 1/nm in my SAED image) to nm, by taking reciprocal. Now, the concern is that lambda was calculated to be 0.0027nm (corresponding to 200kV) and L was told to me by the technician as 300 mm. Using these, the value of C comes to be 0.81*106 (nm)2 while r was obtained to be around 0.2 nm. Thus, using d = C/r gave a very high value which I could understand, is completely erroneous. Kindly advise on where am I wrong and how to correct? Thanking all of you in advance.