when challenge results are out, I often see that I had given highest scores to the images that have ranked between 30th to 50th.
Is something wrong with my appraisal? Does it happen to you too?
Happens to me all the time. I am usually able to recognize which images will ribbon or make top 10 (in other words I "uncerstand" the voters fairly well now) but this doesn't always coincide with my own evaluation of the merits of the images. The voters as a whole value WOW factor and sharpness more than I do; many great images are more subtle and do not score especially well.
I wouldn't worry about it if I were you; your personal taste is just that: personal. There's no reason you should be in agreement with the collective voters all the time.
I just gave a partial answer to your common complaint here. My top vote rarely breaks the winning top twenty of thirty, same as you. I like to equate this phenomenom with a collegiate number one draft choice ending up in the NFL Hall of Fame. Many, many more inductees into Canton have come from lower rounds. First, because that is such a larger pool of atheletes accomodating better odds. Second, the "dream" players from the first round might not have the grit, drive and determination that a lower drafted player must harness to achieve comparable financial or respectability status. Some of my "lower round" picks in the Challenge voting are Jerry Rices and Walter Paytons, even though snubbed by knowledgable "scouts with a camera."