Number of matches for an Elo Rating system

I'm creating a system that will allow people to rate images.

My idea is to use an Elo Rating system (http://en.wikipedia.org/wiki/Elo_rating_system) for each image and then use crowdsourcing to have people say if an individual image is be开发者_运维百科tter than another i.e

Is A better than B

This will be used to updated the Elo rating of A and B, eventually I would end up ranking all the images from supposedly the best to worse.

For this I have two questions

1. Is this the correct use of Elo or should I be looking at another rating scheme.

2. If the Elo rating is correct and I have 100 images how many "matches" do I need before I can confidently look at the ranking ?

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1 - Elo is pretty simple and efficient solution for this problem, you just have to use other one if you have other requirement. I definitely would choose Elo.

2 - Look, you can trust Elo, but if you don't run the "Matching" you won't get accurate response. "confidently look at the ranking" means to me "as per xx matched times the top winner( or whatever you could call it ) is XYZ so far"