I'm trying to learn how to use a flash with a Sony system. My camera is a A6600+30/1.4mm. My flash is a small Hahnel 360RT (Godox 350 clone with several improvements) set in TTL mode.
I would like to use TTL and balance ambient vs flash light easily.
I hate to say this, but the easiest way to do this is if your camera is in M mode, not using auto-ISO, because there are so many different factors to juggle.
The more automated modes you use, the less control you have.
So I've set the exposure compensation to correct ambient light only.
Um. According to
this page of the a6600 user manual Sony is similar to Nikon. EC (exposure compensation) affects
both flash and ambient, while FEC (flash exposure compensation) only affects flash exposure.
You cannot "set the exposure compensation to correct ambient light only", because EC also messes with the flash.
Typically, with flash, most folks shoot with the camera in M mode to to explicit control over iso, aperture, and shutter speed to have more precise control over the flash/ambient balance.
If I need to correct, I'll dial directly on the flash.
That only affects the flash. And whether you're changing iso, aperture, shutter speed, or flash power can all be a bit up in the air with the automated modes.
However, it doesn't work a I expect. In A or P modes, the SS doesn't go slower than 1/60 even if I dial a large positive exposure compensation.
Yup. Because the camera is now taking control over the flash/ambient balance, and it's probably nerfing your shutter speed so you can still handhold.
In S mode, the exposure compensation is hard to predict and does often lead to strong shifts in subject (flash) exposure.
Yes. Because of how shutter speed and flash work. This is more complex than you think it is, and you don't quite understand how everything works together because you're still thinking there's only one good exposure combination of iso, aperture, and shutter speed.
With flash photography, you have
two separate exposures in each image, because you have two sources of illumination: ambient (all the light in the scene that isn't the flash) and flash.
Ambient exposure is controlled by iso, aperture, and shutter speed. This you know.
But flash exposure is controlled by iso, aperture, power and flash-to-subject distance.
Shutter speed (at or below sync speed)
does not affect the flash exposure at all, but only the ambient light level in the image.
And because these sets of controls are different, the ambient can be at a different level from the flash. That's what's meant by balancing the flash against the ambient.
But if you're using an automated exposure mode that can also adjust the ISO or the aperture (say, shutter priority mode),
then you're going to be messing with the flash level of exposure as well, because ISO and aperture both affect flash.
Do you know a good resource to learn auto exposure with flash with the Sony system ?
Just me, but an auto exposure mode is a whole helluva lot harder to control flash with than using M. You could possibly use aperture priority mode a little bit more easily than shutter priority. But for full ambient/flash balance control, you need to be able to lock both your ISO and aperture while keeping your shutter speed at or below your camera body's sync speed (1/160s). That generally means using M mode and a fixed ISO setting.
A nice web tutorial, a YT video ? Anything not just advertising gear, but explaining the Sony approach to TTL.
All TTL does (on any brand camera system) is control the flash's power, based on through-the-lens (TTL) metering. The camera sends out a metering "pre-burst", measures it, then, based on the exposure settings you have, adjusts the flash's power to what it thinks is a "good" power level for exposure.
But. Sometimes it can't guarantee a great flash exposure. If you're shooting at macro distances, it's easy for the flash to be too powerful, particularly if you're not in control of your aperture and ISO. If you're already overexposed in the ambient, then the flash is going to blow out, as well, because you're just adding even more light, etc.
With flash, you really can't just let the camera do all the driving in automated modes and have much control. You really need to be able to think your way through the light.
I would recommend starting with mastering ambient-only exposure if you haven't yet. Learn about iso, aperture, and shutter speed; google "the exposure triangle" or read Bryan Peterson's
Understanding Exposure. And be comfortable shooting in M on your camera, first.
Then, hit Neil van Niekerk's Tangents website's
Flash Photography Techniques section. This will give you the basics of on-camera flash, TTL, HSS, flash/ambient balance, and
bouncing with an on-camera flash. You'll learn basics on how to control the intensity, direction, quality, and color of your light. Once you start getting frustrated with the limits of on-camera flash, then you can hit
David Hobby's Strobist Lighting 101 for off-camera flash.
Thanks for your patience and time. I can now experiment again with my close statue head and distant background to sort how the Sony system TTL works in different PASM modes.