To measure frame unsteadiness I adjusted the video camera to include the sprocket holes in the video frame captured. I could then measure the position of the first all white pixel (RGB = 255,255,255) after the sprocket hole leading edge. Initially I did this manually using Xnview on a series of sample-grabbed BMP frames to prove the principle but it was tiresome to use. I then modified an image comparison program to inspect only a small area, 30x5 pixels, about the sprocket hole edge and captured the pixel row number when all 5 pixels became white and stored the data. The pixel row number from the first sprocket hole is used as the reference from which subsequent sprocket hole pixel row numbers are compared and the difference calculated with sign + or – to generate the unsteadiness data for analysis. Fast Fourier analysis of the unsteadiness data is then used to obtain an amplitude/frequency plot of the unsteadiness. I used an Excel spread sheet method to do this as it can readily provide an output plot of the analysis. Figure 7 shows a plot of unsteadiness computed from 128 data samples taken using HD = 1080 pixels and Standard 8 mm film with a picture height of 3.68 mm so a pixel = 3.68/1080 = 3.4 μm. The very low sprocket hole unsteadiness measured confirms the observed image steadiness performance of the film transport mechanism used in METS.
Research papers on the subject show that both the frequency and amplitude of unsteadiness are significant to an audience reaction.
Frame unsteadiness test results
