A little introduction of this flash, the HVL F36am. It is a flash that was "carried over" from Minolta's flash, the 3600HS(D). Sony basically didn't change anything at all of this flash when it "migrate" from Minolta to Sony. The only thing that is obvious between these two is: the branding.
A little bit intro about HVL F36am
This flash is compatible with Sony HSS system and it listen to Sony WL flash language.
We can have certain control over this flash's output power by adjusting in-camera flash compensation level. If you do notice at your camera, there are two set of exposure compensation: one is for normal exposure compensation and the other one, which is shown under the exposure compensation scale, is the flash output compensation. Depending on the camera model, the flash compensation, similar to the exposure one, can be adjusted from -3 to +3. By adjusting the flash compensation, we could manage to control the flash output.
How does it work ?
Assuming the Sony's ADI system work flawlessly. First, we measure the exposure of the scene we wish to photograph and got a reading about it, say 1/60s, f/3.5, ISO200. Took the shot, and everything look ok. Then a F36am in WL mode, zoomed at 85mm, placed about 2 feet away from the subject, about 2 feet higher, on a flash stand, is added to the scene so to create a key light onto a model. I wished that the face of the subject would about 1/3 stop brighter than the ambient. What I do is simply set the flash compensation to +1/3.
This is what been done in the camera: first, a preflash will be fired to calculate the exact flash output amount. Due to the command from in-camera flash compensation is set to +1/3, hence the flash output power would add another 1/3 stop. As simple as that, everything is calculated and done within the system.
Let's talk about flash ratio with a F42am
A Sony flash HVL F42am does offer a manual setting for the flash. Couple with F36am, flash ratio can be done with in-camera adjustment as I described above. I can show you the result of flash ratio done similarly as above.
Let me welcome my model of the day. She is the Goddess of Venus, if I am not mistaken. Well, let's call her Ms V then.
This shot was taken with ambient exposure with no flash. Flashes will be added next. The ambient exposure was recoded at 1/8s, f/2.0, ISO200. And the colour was a terrible tungsten yellowish colour !
Then a flash F42am was added into the scene. The flash was set at power level 1/8, zoomed at 105mm, placed about 3 feet away from the model, at camera left.
A control shot with flash fired from camera left, set at power 1/8, 105mm zoom.
The second flash, which is the HVL F36am was placed at camera right, about 2 feet high from the model, zoom at 85mm, pointed at the model's left face.
Control pic with HVL F36am from camera right, high up.
(Flash F42am from camera left was turned off.)
So, how do we play ratio with these two flashes ?
Assuming the F42am from camera left is the "right flash exposure" under this condition. What if I set my in-camera flash compensation to -3 ? Would the output of flash F36am would deducted to -3 stop from the F42am ?
Looking at the right side of the face of the model, the face is constantly illuminated by the flash F42am by comparing to the control photo as shown above. But on the left side of the face, however, is about 3 stop lower than the recommended (TTL flash output) flash exposure by comparing to the 2nd control photo as shown above.
So, does the F36am flash output is -3 stops lower than the F42am's 1/8 level? I couldn't confirm as I don't have a flash meter to measure it, and flash meter can't do the measurement because of the pre-flashing of Sony WL system. However, by eyeballing between the illumination between both sides of the faces, it's a different ratio about 1:2.5 or something like that. Nonetheless, there is a ratio between both sides of the face.
Next, I set my in-camera flash compensation to -2, -1 and 1 respectively and the results are shown as follows:
F42am (level 1/8) Camera left, F36am (in-camera flash compensation -2) camera right.
F42am (level 1/8) Camera left, F36am (in-camera flash compensation -1) camera right.
F42am (level 1/8) Camera left, F36am (in-camera flash compensation 0) camera right.
I stopped my "experiment" at in-camera flash compensation at 0 since the effect of flash compensation +1, +2 and +3 is not easily distinguished under my in-door condition.
One may say, when he/she wishes to play wireless flash photography, he/she may have to set the flash power manually as TTL system isn't trustworthy. I beg to differ though, because sometime, a TTL system may free us from technical aspect of photography, and we could concentrate on composition, and light direction of the subject we are photographing. Of course, this is only my own personal thought; I am just a lazy man to do the setting, and would trust the technology in giving me the best result. :p