I just passed up on a Caltar II N F6.8 because some archives I have read talked about it needing a center filter, and I'm not in a position to buy a filter in a ddition to the lens. I'm wondering if this is true and if 90 F8's are better in this respect. Also, since my needs aren't critical in terms of enlargements over 11x14, would a 100mm Wide Field Ektar be a good compromise for a 90, and save m e a couple of bucks?