I see there is a forums spot for posts about PR in relation to our own sites. But although my site is mentioned, this post's concern is more about PR in relation to total image content, which is applicable to any website. Since last February, I'd been waiting for the page in my signature - the redwood grove on - to register a Pagerank with Google. Images from the page, even other folks images linked to, displayed on Google image searches - yet no Pagerank. Right now, the photos you see on the page, were twice as tall and twice as wide, which really makes for great content, since photos of the grove are few and far between. But a few days ago, I was wondering if the abundance of photos might be working against Pagerank. In other words, too many Kilobytes of images when all tallied together. So I reduced most photos from near 60 KB apiece, to more like 20 KB apiece. Now, just 2 days later, the Pagerank bar has gone from a GREYBAR to a Pagerank 3. So it's been about 5 months with not even a "0" Pagerank, and about 48 hours from the image size change, it jumps. Would you say this is coincidence? Or comparable to how you've seen Google analyze pages? This would be new to me, that Google would allow images as good, but lots of somewhat bigger images as bad. Personally, I'd prefer to see larger images on a page next to what I'm reading. But Google may feel differently. Maybe it boils down to the overall total size of the page files - period. Maybe Google wants pages broken down into separate enlargements that can be viewed, or some of the content on separate smaller pages. Like bite size pieces.
Image sizes is NOT an issue and it dosen't matter for google and other search engines at all, the search engines only read the ALT tag of the images it self in the final HTML code... However i do agree that Google have a huge team of people who are doing a human reviews online all the time, After all the reason you've got a PR 3 is just because Google just exported the PR value to the Toolbar !!!
you are just observing a coincidence that is due to the overall page rank update by google.... the changes you made to the images had nothing to do with it