I'm glad to see other people are noticing the difference in brightness, as I thought I was the only one

From what I've seen, the older, striped Pelikans have bright, solidly colored stripes. A few years ago, the material changed, and the stripes became variegated (dark with some bright areas) and pearlescent. Most of the Pelikans I have are of the older variety, but one of my M400s is of the newer variety, and the difference in the material is pronounced. Thus, in my opinion, the differences in photos you've seen online aren't caused so much by differences in the way the photos are taken as by a difference in the actual material of the pen. All the pens posted in the thread so far seem to be of the newer, pearlescent variety, except for the one penmanila posted, which seems to be of the older variety with solid stripes.
I have a strong preference for the older variety, as I feel the newer variety feels cheap in comparison, whereas the older stuff feels more solid... or it could simply be my mind

Additionally (and I've mentioned this in two or three other posts, so I hope I'm not becoming repetitive) the newer variety has pockets of air between the outer, striped sleeve and the inner sleeve, creating large, foggy patches in the pen's translucency.
That being said, if you like pearlescent finishes, you needn't pay attention to me!
I had mentioned in another thread that I would take a few pictures comparing an old pen and a new one, but I've yet to get around it...