Process for using Lee Filter's 100mm system Question

[S. Schmidt]

In reading Lee Filter's on-line magazine called Exposure, it describes the process for determining which ND grad filter to use by recommending that one set the camera to manual mode. Because the assessment process described leads to a determination of the difference in shutter speeds for the sky compared to the foreground at a given aperture and ISO speed, I am wondering if this assessment can be made using Aperture Priority mode while setting the ISO from Auto to the desired ISO for the final photograph? Once this assessment/determination is made, then I assume using Manual mode would be required in order to set the shutter speed metered for the foreground.

Being new to the Lee Filter system, I know that I have to get some hands on practice, but I am wondering if I am thinking about the initial part of the process correctly?

[NancyP]

Meter the sky, meter the ground, note how many stops difference there is between the two, and then set your camera on manual at the "ground" exposure and add the appropriate GND (if 2 to 3 stop difference, use the 2 stop GND, if 3 to 4 stop difference, use the 3 stop GND). I do it all on manual, including the initial metering x 2, because I am lazy, and being an old-timer I still think in manual not in auto-exposure compensation.

[robdickinson]

You can use AV mode easily enough but it will always cause you problems when re-framing the shot.

Typically you are working on tripod with lee filters (though not always, and anyhow even if not) manual mode is well worth using.

Just stick it on live view with exposure simulation , pick your aperture and mess with the shuter speed till the ground is exposed right, count the change till the sky is ok. Job done.