I've recently acquired a 350mm CF Tele-Tessar lens for my Hasselblad and I'm wondering which filters to use for B&W landscapes. According to Freytag, "With nearly all long-distance shots a red filter is advisable." Is this true? And what about yellow or orange filters? Will one or the other produce the sharpest results? I did shoot my 120mm CFi lens at infinity last month using an orange filter and I was very pleasantly surprised at how sharp those pictures were, even though that lens is optomized for closer distances.