Is chromatic metering bias on bodies without RGB meters, like the N70, a relatively constant factor? That is, that while using a colored filter the TTL meter will set exposure a stop off, say, no matter what the light level is. If that's true then why doesn't Nikon publish a TTL exposure compensation table for at least its own filters? Yeah, it's a relatively small degree of bias but it can be a pain to get it dialed in for each filter since the viewfinder readout only displays full-stop increments. What TTL exposure factors are other N70 shooters using with the standard B&W colored filters? Does a deep red filter (I've used both a Nikon R60 and Tiffen #25) throw off the N70 AF sensor due to a similar chromatic bias? A couple of times while shooting my daughter backlit, using an 85mm f1.8 wide open with a red filter, the AF sensor focused on the plane of her hair--specifically, the halo of backlit hairs--instead of on her face. Granted, relying on AF with such a shallow DOF is really risky and I tried to shoot mostly MF, but it's hell trying to get the eyes in focus when you're shooting a backlit subject with dark filter and said subject is squirming her head around. The AF sensor was probably picking up on the wealth of edge definition in the pattern of hairs, but I'm just wondering if a deep red filter gives throws off the focus enough that you need to figure in a definite compensation alá focusing for infrared film. Does any top-end AF body allow you to dial in a focus compensation factor so you can shoot stuff like HIE using AF? Just curious.
