For the first question, you probably have two cameras - your gige camera and the built-in webcam. You need to get the adapter you want. Play around with this code snippet to adapt it to your needs:
hardwareInfo = imaqhwinfo % Print what cameras are there.
adaptorNames = hardwareInfo.InstalledAdaptors;
% Might look something like:
% InstalledAdaptors: {'dcam' 'gentl' 'gige' 'lumeneraimaqw64' 'matrox' 'winvideo'}
matches = strfind(adaptorNames, 'lumenera');
% Find out which index is the Lumenera Camera.
LumeneraIndex = find(~cellfun(@isempty, matches));
theLumeneraAdaptor = adaptorNames{LumeneraIndex}
hw2 = imaqhwinfo(theLumeneraAdaptor)
devInfo = hw2.DeviceInfo
devName = devInfo.DeviceName
devID = devInfo.DeviceID
For the next question, don't use set(). Simply do this:
src.exposure = theDesiredExposureValue;
