How to meter when using ND filter?

[kamek]

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Hi all, I'm wondering how you're supposed to use the in-camera meter (I'm shooting on an MP) when using an ND filter.

For example, if I'm using Portra 400 with a 0.9 ND filter, do I:

1. Leave the meter at 400 ISO and let the TTL meter read as usual

2. Adjust the meter to 160 ISO since the ND filter is 3-stops?

Thanks in advance!

[a.noctilux]

1.

😉 miracle of TTL metering ( you already know that ! )

[250swb]

Use the camera's meter, the only consideration is that the MP can only meter to 1 second so anything longer and you'd need a hand held meter set to 50 ISO. Any exposures longer than 1 second you then have to take into account the reciprocity of the film and increase exposure.

[Anakronox]

Just an alternative if you happen to be carrying your smartphone and not a handheld meter.  You can meter without the ND and then use an exposure calculator such as Photopills.  The advantage to that is it has a timer coupled with the calculator so when setting your shutter speed to bulb, you know exactly when to let off the cable release.

As 250swb mentioned be aware of reciprocity failure and account for that.