Turning the camera inputs down is the better way, assuming that you're not overdriving the mic transmitter to begin with. You don't want to set your levels too low on the transmitter because you will open up a whole set of possible issues including interference, drop-outs and noise-up, etc.
Set your transmitter gain as high as possible without overdriving (distorting) the signal.
Thanks for the advise... the signal is very hot coming direct into the camera so have to turn levels way down on the camera... but works ok. Wondered if putting say -6db attenuation into the transmitter would help... this is with ordinary talking levels in interviews.
So your advise is to stick with putting the camera levels down..
A few points for clarification. There's the input sensitivity of the transmitter, the output level of the receiver and the input level of the camera. All three need to be set right to get the best results.
The transmitter input sensitivity ONLY has to do with the mic sensitivity and how loud the sound source is. Read the directions for your transmitter so that you get a high enough reading on the TRANSMITTER. You want to make that as high as possible without clipping.
The output of the RECEIVER is frequently adjustable; sometimes from mic level to line level. You give us no specifics, so helping you is difficult.
You said setting the camera to line level made the incoming audio too weak. That probably means your receiver has a mic level output. If that's the case. Keep your camera input set to mic level input and readjust the receiver output.
The traditional wisdom is to run the previous stage (the receiver in this case) with a healthy level so you don't have to crank up the inputs on the camera to the fullest extreme. In general, operating any audio gain stage at its maximum results in more circuit noise.