first of all this is a very easy idea based on the cellphone trick (http://www.hv20.com/showthread.php?t=180) with a slight difference and most probably somebody thought of this idea before me. problem is, it's not practical trying to adjust the aperture while holding a cellphone in front of the lens, especially when working with many impatient actors.
if you know the cell phone trick, just read below the red line at the bottom.
if this was posted before me, moderators please delete the post. anyway, here we go:
This method is based on this idea: in a dark enviroment camcorder first opens the aperture wider to f1.8. When it comes to f1.8, the only way to lighten up the image is to add gain. So in dark enviroments, camcorder adds gain in 1.5db steps. Maximum gain is 27db, so there are 18 steps of gain available. So it goes like this:
But image with gain is noisy and most people prefer a darker image with less noise. So here i am trying to tell how to get rid of the noise.
First of all zoom out till it's at widest angle. adjust your camcorder to shutter priority mode and adjust your shutter (I personally prefer 1/48 shutter in 24p mode). Then lock your exposure (click on the joystick, press down, you'll see EXP on the little menu, then press up, exposure is locked). Then check your aperture by half-pressing the photo button(you should have a mini-sd card inserted). If aperture is at f1.8, probably there is gain. Push the jostick left and slide the exposure one step. check your aperture again by half-pressing the photo button. Repeat it till you find f/2.0. When you find f2.0 you now know where the gain starts and you can control aperture. If you slide exposure one step to the right, you'll get an image at f1.8 without gain.
The problem is, when you are in a very dark enviroment, even if you push the exposure all the way to the left, you may not be able to skip from f1.8 to f2.0, because when adjusting exposure there are 11 steps to the left and 11 steps to the right but in camcorder there are 18 steps of gain available.
So if you push all the 11 steps to the left and still at f1.8 double push up button on the joystick (just like double clicking on a mouse). Do it fast.
So we are fooling the camcorder by setting the exposure to automatic but before the camcorder understands what's going on we lock the exposure again
Now, the exposure slider is centered and we have another 11 steps available to the left again. Slide the exposure to the left until you find f2.0.
Hope that helps.
Please correct me if I made any mistakes.