Eyepieces - uneven field illumination?

[Mr Spock]

After many years absence, I'm about to start up variable star observing again. My standard of equipment has moved on since my last observations. I used an ST80 with various Plössls.
I intend using my 80ED with a 42mm LVW and 22mmT4 Nagler, giving x14 and 5°, x27 and 3° respectively.

This leads me to a question: with eyepieces like the Nagler, which to some degree suffer from spherical aberration of the exit pupil, can they provide the necessary even field illumination required?
With variable star observing you compare the variable with one or more comparison stars. In my prime I was able to detect the secondary minima of RZ Cass - 0.1mag.

With such small differences and, depending on placement of the variable and comparison within the field of view, I was wondering what effect an uneven field of illumination would have on estimated brightness of a star.

I'd be interested to hear if anyone has experience of this.

[YKSE]

I don't have experience of Spherical aberration of the exit pupil (SAEP), but my understanding is

SAEP introduces ONLY "kidney bean" effect when the eye is not positioned corespondingly for viewing the center and the edge, it doen't affect filed illumnation, or anything else.

[michael.h.f.wilkinson]

There is always a slight variation of illumination over a wide FOV. I tended to circumvent this by placing the variable and comparison at equal distances from the centre of the FOV, as any variation is expected to be radially symmetrical