Quote Originally Posted by E. von Hoegh View Post
Wait a minute. Are you metering with the camera's meter or the handheld meter?? Changing the ISO setting on the camera and then metering with the handheld set to 160 will compensate for nothing. If the camera has TTL metering, it will (as has been pointed out) automatically compensate for the filter factor
Some of the lenses I have do not have 1/3 stops on the aperture ring. Some of them have a mixture of 1/2 and full stop increments on the same ring. So I was just looking for an easy way to open 1/3 stop, no matter what lens I'm using. I'm not going to be using TTL.

What I've been doing is metering at 160 (film speed) and then opening the aperture by 1/3 or 1/2, depending on the lens.
My thought was to meter at 160 and then open 1/3 stop, via ISO dial.
This should give me the same exposure as opening aperture, but be easier since I could just apply the meter reading, and not worry about the filter factor. The filter compensation would already be dialed in. That's my thought anyway.

As Bill mentioned, setting "ISO B" to 125 might be the way to go.

1/3 of a stop may not matter that much, but I have other filters with larger filter factors.