The ion exchange filters sold in supermarkets and hardware stores generally produce water that is chemically equivalent to single distilled water - like that you can buy in the supermarket. This is suitable for just about any photographic use. Other filters, such as activated carbon filters, simply remove grit and some organics and odors and may reduce chlorine a bit. These may not solve some photographic problems, so you should either go for distilled water or deionized water, possibly by using one of the deionizing filters. More elaborate deionizing units are available from laboratory supply houses that produce water equivalent to triple distilled or semiconductor grade water. These are overkill. In fact, tap water is fine most of the time.