Finally got to work out the 'graduation factor' of the pearls in the choker. As well as I could.
For starters, the picture came from
HERE.
Took te picture, got it magnified about 6X, measured and counted the pearls, and the result goes something like this:
The circles give the relative size of the pearls from the section of the choker visible in the picture.
A little experiment concluded that about 60% of a tight choker like that would be visible in the mirror (or in a photo) from that position. The rest remains hidden in the back of the neck.
What that means, is that if you need
15 inches, the graduated section infront has to be 9 inches of pearls ging down from 15mm. The rest of the strand could be going down to seed sizes, or just continue with the smallest size from the graduated section, as you wish.
The series of real life sizes matching the picture would be for half a strand:
15mm - 12,5mm - 11mm - 10mm - 9.5mm - 9mm - 8,5mm - 8mm - 7,5mm - 7mm ->
plus a six inch section of 5 - 7 mm pearls ito complete the back of the strand.
N.B. This little arithmethic considered knots to be ~2mm each.
And there's something else... these numbers are guessed starting with the 15in length of the strand you suggested. The choker in the picture must have been shorter as it sits higher on the neck of a dainty model, which maks the same aritmetic to guess smaller pearls as everything is scaled to the length of a strand - pobably
not the way pearl strands are composed in real life. I would estimate that the strand in the picture had the largest pearl of ~13mm.
The picture is not good enough to show the individual shapes of the peals well, as much as visible, they appear semi-baroque safe for the largest one that is clearly round.
I've recounted the thught process here for you beaders to find the mistakes! In particular, I wasn't sure at all how to account for the length of the knots.
Hope this was fun for you too