First I appreciate your effort and time, we got some great responses to yesterday’s entry. Here’s the cut to the chase answers with discussion and analysis to follow.
Primary defect: the armhole of the shirt was too high.
Correction: Lower the armhole.
Secondary defect: Shoulder slope.
If the primary defect was due to the tee shoulder being too high, then the left shoulder would have been better than the right side because the left shoulder of a right handed person is higher than the right. Meaning, the left shoulder was higher so it would have fulled out the too-straight shoulder slope of the tee. However, since the tee fit tighter on the left side of the body, we can know that shoulder slope of the shirt is not the primary problem. Now, the reason why the problem is worse on the left side is because that side is slightly longer because the body is listing or leaning over to favor the right. One side (right) compacts and the other expands. That my right handed model’s left back is ever so slightly larger than his right is more obvious from the back.
In the photo above right, you can see that the left shoulder is higher and with worse constriction. The red lines represent perfectly squared lines. In the photo at right -in which slope and handedness is less obvious- you can still tell owing to neck angle and orientation. Actually, you can tell if someone is right or left handed by looking at their feet. Not always, but nearly so. A person who was born left handed but forced to learn to write with their right hand will still have a left handed body. [Call me crazy, I amuse myself by gauging perfect strangers, calling it before I’ve seen them use their hands. Now even Mr. Fashion-Incubator can do it. A clear pattern forms after awhile. My favorite finds are lefties who’d been forced to become righties. I always have to mention that I can tell and they’re suitably impressed.]
Primary vs secondary defects:
There are several ways to define the difference, the easiest is a matter of comfort vs cosmetic. A primary defect requires correction because it is critically related to comfort. A secondary is mostly cosmetic.
Another way to define primary vs secondary is a matter of triage. If you could only repair one, correcting the primary defect would result in the greatest benefit.
A third difference between primary and secondary is determined by elimination and may not be strictly comfort related. A defect can be said to be to secondary if correcting it will move the problem somewhere else, creating a “new” problem. A secondary defect repair does not solve the root issue.
By the way, nobody taught me any of this. I didn’t read it in a book or anything like that. It came from 30 years of analytical fitting experience so if you see this elsewhere (presumably without attribution), it probably came from here.
Returning to our example, lowering the armhole would solve the primary problem of a tight underarm. The folds are formed from scye to neck-shoulder point because that span is too short and looking for the closest opening -namely a cut edge to spread. The best way to correct it is to increase the length between the two points -resulting in a lower armhole.
One would or could then correct the secondary defect of shoulder slope for the sake of appearance. We know it is secondary because cutting fabric from the shoulder line would have made the constriction worse because whatever extra length that was in the shoulder line (that didn’t need to be there) couldn’t be borrowed by the underarm for movement. There are plenty of square shoulder garments (kimonos etc) that do not tightly constrict the armpit so we know that shoulder line does not govern armpit discomfort.
Summary: Correcting a primary defect will reduce discomfort. Correcting a secondary defect improves the look of it but doesn’t impact wear-ability and may move the problem elsewhere requiring yet another iteration. Secondary defects get the most attention (often on public sewing forums) because they are usually the most obvious.
Again, thanks to everyone, quite a few deserved gold stars. Karen asks that some terminology be defined but I’m not sure which terms she was referring to so I (or you) can elaborate as needed in comments.