Here are some examples of image corrections of 35mm slides.
Often in old slides from the 60's there is a red shift especially in ANSCO film.
However, many images can benifit from black level adjustment and gamma adjustment which may have been less than optimal on the original slides. Unless the photographer was using an SLR it would be hard to judge lens flare while the photo was being taken.

While correcting the folowing steps are usually followed.
1) Black level reference/saturation and adjust.
2) choose fixed of image based white level.
3) Correct overall gamma, or level enhance.
4) Correct gamma by colour if required.

While correcting the overall gamma we try and guess the main subject of the image, such as a face or object and correct the gamma to bring it out.
In the case of landscapes the choise may be the richest image, and for building one maty select for detail.

In all cases when we colour correct slides the original capture files are not altered so that corrected and un-corrected output files may be produced at all times.