professional bad example

so at some point in the last few months, i realised that there's actually two different kinds of fitted one-piece sleeves with darts.

one can be constructed from scratch like this: start with what i like to call a "historic two-piece sleeve" (follows the natural bend of the arm as closely as possible, top sleeve and undersleeve are the same width). take the portion below the cap. mark the position where an underarm seam would fall, then "unfold" the pattern by mirroring each portion along the front and back lines. this results in a very large dart and a front edge that's markedly shorter than the back even after the dart is sewn. it's actually possible to sew this in some fabrics, but it's better to rotate some of the dart into the front edge to make the difference smaller or nonexistant. then add the sleeve cap.

the second one can be constructed from scratch like this: start with a tapered sleeve (seam narrows as much as possible from bicep to elbow, then continues the same line down to the wrist level). draw a wrist dart to bring the wrist down to the same amount of ease as the bicep and elbow. rotate it into the elbow, if desired.

and i assumed that the second way was just entirely wrong because it results in an inferior fit, and that the authors who show it just didn't know what they were doing. that maybe they didn't really understand the purpose of sleeve darts at all and just put in some ridiculous little token dartlet because they knew it "should" be there. but now i just found that one of my french patternmaking books actually shows both, and gives some reasons why you may want to use the second. it looks better on striped fabrics, for instance. there really is a book for everything...