A few weeks ago I brewed a Vienna lager. I used Diamond lager yeast, which is supposed to drop clear, so I didn't use any gelatin or other fining agent in the fermenter. I cold crashed to below 36 F for 48 hours, transferred to a keg and immediately put that in the fridge. After a week or so I drew a sample and it was quite murky. A couple of days later it was still not clear, and I was very disappointed. The next day I added gelatin to the finished and carbonated beer, which I have never done. After 3 days it is clear. Of course it might have cleared up in that time, anyway, but it didn't seem as if that was going to happen any time soon.