Pixel Counting Biometric Comparison of Oswald photos

[Drew Phipps]

Here is a drawing illustrating the problem of pixel measurements. Since I am making linear ratio comparisons (x1/x2), it's more akin to an area problem than a linear measurement problem:


The yellow circle has an area of less than 1 square; however, it would probably show up after pixilation as 1 square unit. The red circle has an actual area of more than 1 square unit (1.57); after pixilation it could show up as anything from 1 square unit to 5 square units. The blue circle has an actual area of 4.9, after pixelation, it might be anything from 1 to 9 units (but most likely around 5). The more pixels that are present in a picture, the less significant the error becomes.

Recent government studies on pixelation (in ultrasound images for medical purposes) seem to suggest the proper error factor is 1.5 pixels for a linear measurement. Since what I am comparing here is ratios, an expected error factor is (1.5)^2 = 2.25 sq. pixels. Any variations of ratio between photos that is less than 2.25 sq. pixels, I'm going to call insignificant, and any variation greater than 2.25 sq. pixels, I'm going to call significant. ( There's probably a more specific and scientific way to determining the significance of differing ratios, but I don't know it. )

In addition, in comparing ratios of whole numbers whose values are less than 100 (in most cases), the data may be "too lumpy," (to borrow a phrase) and therefore produce apparently significant results where none really exist. (I.E. the difference between 3/5 and (3+1)/5 is far greater than the difference between 300/500 and (300+1)/500). Unfortunately the low-resolution aspect of these photos forces me to work with low numbers.