Many, many thanks to Patrick for his video tutorial http://hv20.info/yopu/hv20aperturecontrol.mov, and to Jason for his article http://dvxuser.com/jason/hv20/.
Iím sorry, but I just couldnít follow the UK accent in the video tutorial on my non-amplified speakers. The article was very helpful, but left out the preliminary steps and gave two ways to not do it first. I figured we needed a step by step guide for people in the same boat as me.
CONTROLLING EXPOSURE ON THE HV20:
[Cell phone trick and SD Card trick included.]
First, make sure you install a medium sized mini-SD memory card by opening your LCD screen, then opening the little door at the bottom. This step gives you a way to check your settings, later on, that you wonít have without the card.
Push in the dummy card and it should pop part way out. With the camera turned OFF, pull the dummy card out and replace it with a real SD card. It goes in with the SD logo on top. Push in until it clicks and stays in. Close the door.
INITIALIZE THE CARD per page 65 of the manual. (Slider to card, rotary switch to Player, press function, select menu, select initialize.) Wait for it to finish formating the card.
Second, make sure the slide switches on the right side are then set as follows: Top switch to P and bottom switch to tape (not to card) even though you just installed an SD card.
CHECKING THE F-STOP AND SHUTTER SPEED:
Next you have to enable the photo mode so you can check the f-stop and shutter speed while in tape mode. (Do not do it with the sliding switch on the right side that switches it from Tape to Card.) Instead:
Down Joystick to Still Image rec off (the one above menu)
Joystick right to LW (1920x1080)
Push FUNC to close the menu.
Now when you push of the PHOTO button on the top of the camera half way in it will display the f-stop and shutter speed in bottom right corner of the LCD.
SETTING THE SHUTTER SPEED:
Fully zoom out.
Press FUNC and at the top left of the menu it will say what mode the camera is in. When the top icon on the menu is highlighted, move the joystick left or right to select a mode.
There are two main modes to control what we want to control.
1) Tv mode (shutter priority), which allows you to manually control the shutter speed, but doesnít allow you to directly control the gain or f-stop. Once the mode is selected you and joystick down.
2) Cine mode. Cine mode tries to be fully automatic but has a gamma curve that tries not to blow out highlights or crush blacks, overall it seems darker though. CINE mode will Ďtryí to go to 1/48 at 24p. Once the mode is selected you and joystick down.
Why chose one or the other? Personal preference. Some people swear by one or the other. Others say use Tv mode outdoors and Cine mode indoors.
NOTE: This menu system is less intuitive that it could be. Even though you can manually control the shutter speed there is no menu item marked shutter or speed. Itís marked Tv. [How did they get Tv for shutter? Tv mode = Time value = fraction of a second.] In the manual they talk about Shutter prio. Maybe in the menu the limited space stops them from saying Shutter priority or shutter control, but thereís no reason to not say it in the manual.
SETTING THE F-STOP with ZERO GAIN:
What you do have control of is the Exposure control, which is really the camera balancing the shutter, f-stop and gain, but it can be locked when you get it where you want it.
Point the camera at a mild light source. No gain will be on when it is pointed at a light source. (Gain turns on when it's too dark.) Your LCD computer screen or LCD cell phone screen work fine. (Donít worry that it looks bluish on the camera screen.)
One suggestion is loading a white picture in your cell phone. Another option is note pad in your cell phone. Make a document with only one period on it, then save it. Either way a fairly blank area to point the camera at is what you want.
Hold it pointed at the screen and press the joystick in. The joystick menu will pop up. If itís not in EXP, move your joystick down until EXP is shown. Keeping it pointing at the screen, Press up ONE TIME and the exposure adjustment bar will appear in the upper left corner. (If you press up a second time the exposure lock will turn off.)
Note the adjustment bar is set to zero db, and was done when pointing at a light source. No gain is on and as long as the adjustment bar is on the gain is locked off!
Now you can aim the camera at what youíre really going to shoot and adjust the EXP left or right until you get the right light level you want. If you have the 70% zebra turned on make sure there are no zebra stripes.
You can now check the f-stop and shutter speed by partially depressing the photo button, even when the EXP menu is visible.
When you have it where you want it press the joystick in ONE TIME. The exposure bar will stay at the top left, but the joystick will no longer move it left or right. It is locked.
If the light changes or you move locations slightly you can press the joystick ONE TIME and make adjustments left or right. DONíT MOVE IT UP or you will release the lock and have to do it over again.
You can't check gain on the HV20, but if you record to tape you can put the tape in a more epensive camera like the FX-1 that can sense the gain on the tape.
SETTING EXPOSURE WITH A DOF ADAPTOR (Thanks to Anx and Dennis at Cinevate / Brevis.)
1. All the basic steps are the same, with the exception that you turn on 70% zebra in the settings section
2. Set to TV mode, 1/48 shutter speed, fully zoomed out
3. Frame something that is basically 50% zebra'd, 50% normal. The trick is finding something fairly brightly lit.
4. Lock exposure - if you do this you'll end up with the full range of -11 to +11, at 1.8F
5. Change the exposure to +9.
Hope that helps.