a. When you do the custom setup for the FL-50 (instructions in the FL-50 manual) make sure that the following settings are:
ILL = A
CLP = ON
Light intensity adjustment=ON
b. Camera setup (per instructions in the English language E-1 PDF manual) should be:
Set flash mode to Slow 2nd Curtain (P.103)
Set metering to ESP mode (P.68)
Set exposure mode to Aperture (P.59)
Set White Balance to Auto (P.87-88)
Set ISO to Auto (P.83)
No exposure compensation should be set on the camera (P.65)
c. Mount FL-50 on camera hot shoe.
d. Mount camera on tripod.
e. Turn on camera, then turn on flash. Set flash to TTL Auto flash control mode by pressing the Mode button on the flash until that appears in the display. No exposure compensation should be set on the flash.
f. Adjust your aperture by turning the camera dial (P. 59 again) to accomplish two things; select desired depth of field and secondly, set the operating distance of the flash. This is shown on the bottom line of the flash LCD display. Changing the aperture will change this operating distance and any subject within the near/far distances shown will be exposed properly. The primary subject distance, not the background, should be the primary factor in selecting the aperture setting to control the operating distance of the flash.
g. The camera will select a proper shutter speed and the shutter speed will be slow enough to allow for a time exposure of your background which is why you need to have the camera tripod mounted. Check what shutter speed the camera proposes to use (half depress the shutter button) and, if the speed is slow enough on your camera to require that you set Noise Reduction to ON, be sure to do so.
h. Position your camera so the subject is in the center 1/3 of the viewfinder to ensure a proper flash measurement and exposure. Caution your subject that they will see two flashes separated by as much as a minute and that they should not move until after the second flash. Press the shutter button. The flash unit now emits the TTL preflash which allows it to compute the necessary flash power to use. After the preflash, the camera will take a time exposure which will properly expose the lighted background which you wanted to include in your night image. After the time exposure, the flash will flash the second time to illuminate your primary subject to include it in the image and then the camera shutter will close and your subject can be allowed to move.
i. After looking at some of your images you may notice in the EXIF data that the ISO used for the exposure was not 100. That is because when the ISO is set to Auto and the camera is using a flash it will change the ISO to anywhere between 100 and 400 in increments of 20 to help obtain a good exposure. There is no need to recheck or reset the ISO after flash exposures. It will still be set at Auto. The only way you can tell that the camera used other than an ISO of 100 for any given exposure is to check the image EXIF data.
j. The FL-50 provides excellent results with direct flash without any diffuser except for close-ups of people with short focal length lenses. It is possible to use a Stofen or other diffuser on your flash head with the above setup without having to alter any camera or flash settings (the flash compensates automatically) in those situations, but a third party diffuser should not be needed for routine use. You can also adjust the exposure compensation on the flash.
1. keep an eye on the effective flash distances shown on the bottom line of the flash LCD display when using direct (versus bounce) flash. To avoid subject under/over exposure your subject must be between those limits. You can adjust those limits to be closer to you or farther away by adjusting the aperture the camera uses.
2. The flash will illuminate wide angle shots quite well, but if you are shooting with a lens that allows focal lengths shorter than 12mm the flash will signal a need to apply the diffuser lens by a blinking warning in the top left corner of the flash LCD display when you zoom to wider than 12mm focal length. Keep an eye out for this, otherwise the flash lighting on the right and left sides of the image will fall off.
If your subject is particularly reflective or dull, you may care to adjust some exposure compensation (I rarely do). If so, do it on the flash with the large dial near the bottom back of the flash.