Originally posted by Digitalis It is important to note in autoexposure modes (such as aperture priority) the shutter speed is limited to 30 seconds - this is most likely why your initial exposures were severely underexposed.
Originally posted by Megapixelmk Perhaps the available light was such that a six stop filter was just too dark to make a correct exposure with the 30 seconds available in manual mode.
Remember to use bulb mode for exposures longer than 30 seconds.
I find that an ND calculator is invaluable in calculating correct exposure according to filter stops. I find the Nisi ND calculator (free) app nice and simple to use.
What those two guys said is right.
You have to use BULB mode and calculate your exposure. First you note the values the camera is metering or take one regular shot and note shutter speed and f-stop, then use App to determine the correct time for exposure. Set the f-stop and then use your cellphone timer to expose for correct time from the app. They are many apps available and feel free to experiment with.
Also make sure that you pre-focus prior mounting ND filter and switch to MF (manual focus) prior taking the exposure to avoid camera attempt to focus again. You can use 2-sec delayed shutter or cable release or whatever release you are using.
Have fun!
EDIT: It is also helpful to set that camera is opening the shutter with one click on the remote and closes the shutter with second click on IR remote.
Last edited by RAART; 09-11-2018 at 08:52 PM.