Hey there, following problem exists with export function and setting limit file size to" on Lightroom 4.0.
Description to reproduce: Trying to export the sample file as jpg with max. width of 600px and limit file size to 150k.
Current behavior: Export will not be done. The error message "Could not create a JPEG that met your limit of 150k bytes" is shown.
Expected behavior: JPEG quality should be automatically be adjusted to create a file with size of 150k or lower.
Manual export setting: Doing manually the export without using "limit file size to" and setting quality to 80, the result is an file of 142k bytes. So reaching a file with correct size is absolutely possible.
This problem can be also reproduced on LR 4.1 RC1 and 2. Seams that only files with hight high white content are affected.
Please tryout the problem yourself with the sample file and promote for this bug.