It is difficult to tell when a space is small enough to be insignificant, because we can't read the VMS. A vertical offset may be significant too as noted by ReneZ. The same is true for larger-than-necessary spaces, as they often look deliberate: have you noticed how the last glyph of a word is sometimes squeezed, horizontally, to make room for a larger-than-necessary space just after it?
So my transliteration distinguishes between quarter-spaces (barely visible or unsure), half-spaces, spaces, spaces and a half, nearly double spaces, double spaces (and more, like suspicious vertical offsets).
So my transliteration distinguishes between quarter-spaces (barely visible or unsure), half-spaces, spaces, spaces and a half, nearly double spaces, double spaces (and more, like suspicious vertical offsets).