Somebody please explain! Why X-E1 JPEGS are darker?

Well everyone has given you the answer. I don't think it is they who do not understand the question but you who does not understand their answer.

I will add something else - Flourescent light levels fluctuate and they do so at a speed we usually do not see (sometimes though we can see a flicker). BTW, during this cycle the WB also changes.

However, I assume you took more than 1 picture with each camera so the light fluctuation should have shown on both cameras.

Of all the cameras I have owned and still own, the Fuji (XP1), has metering which gives me what I consider nearest to the perfect exposure.

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The sky is full of holes that let the rain get in, the holes are very small - that's why the rain is thin.
Spike Milligan