Looking at my trusty little "the f stops here" lens chart, I see a 210mm on a 5x7 is equivalent to a 150mm on a 4x5. But picking nits, the two formats have slightly different aspect ratios and I wonder how that works. Specifically, assuming the above mentioned lens combinations, will the 5x7 show as much as the 4X5 PLUS a tiny bit on the sides, or nearly exactly the same field of view as the 4x5 with a bit on the top/bottom chopped off? Thanks for any help in this. Believe it or not, I'm contemplating a specific shot for which this slight distinction will matter.