How often? every ride.
However, I fail to see the relation between upload limit and the number/type of images captured.
Surly, there needs to be a upload limit. That limit is currently 5, not 20 (one cannot select more than 5 images using the upload screen.) Seems 20 (I don’t really know - I am no longer being presented with any images from which to select…) is the upper limit on the number of images from which the user can select to upload, or the upper limit of the number of images to be presented to the user at end of ride (these two are not identical issues.)
Why link the number of image captures to this functionality is beyond me… (actually, I suspect it is linked to some static memory set aside for image thumbnails - and if that is the case, than that incorrect upper limit assumption has brought us here…) Let the user browse 100 images, if that is the number of images taken. There is really no reason for this “feature” to have existed in the first place.
The reason for taking a large (let’s say >20 is “large”), is, as I stated elsewhere a long time ago is:
Basically, one wants to select the best and most interesting image to use. The more images taken the better one’s chance of finding those “best” (subjectively…) images.
There is also the “small” issue of blank (white rectangle image placeholder) image upload presentation, linked (somehow, maybe) to the number of captures taken: as long as this “feature” exists, it is exceedingly difficult to gauge whether these two issues are linked (my guess: yes.)
This limit, vehemently denied by Zwift support for such a long time, is also one of the most poorly documented Zwift features, which your acknowledgment of finally conforms. However, confirmation is not documentation.
The question (to me…) is not “why drop” bur rather, “why keep”. It was a mistake - fix it. I propose Zwift drops this “feature” altogether, the sooner the better. If you do decide to keep it, document it and make sure to understand the side effects - and document them (like: “No images will be presented to upload if more than 20 are taken during a ride”) as well.
Keeping this mis-feature leads me to consider alternative, external, screen capture solutions. Surely, Zwit does not need a third wheel…