Fuji X-E2 built-in TTL flash

mcjtom

I just discovered your articles on flash photography and trying to learn from it.  Thanks!

I have a question that may seem primitive, but I can't find any technical answers for it:

Fuji X-E2 has a tiny flash built in.  It uses Fuji TTL system and can be biased by +/- 2 stops.  I'm trying to use it for fill flash in relatively well lit outdoor situation.  I typically leave the flash exposure compensation to -2EV and play with ambient exposure, hoping for the best.

I'm trying to understand it better, and here is where I'm confused.  

Fuji X-E2 doesn't keeps the ambient exposure constant, regardless if the flash is on or off (within allowable shutter speed limit).  The TTL flash exposure is added to the ambient exposure.  There is a preflash, so the camera knows how reflective/distant the subject is, but then I have no idea how the camera uses the AMBIENT exposure to regulate the flash output?

It seems to me that it reduces the flash output if the ambient exposure is about right and increases the flash output when the ambient portion of the exposure is underexposed, but I can't be sure.  

I expected that the TTL flash would be solely based on the preflash and independent of the ambient exposure, but it looks like I was wrong.

Would you know where to find any more info on it, or perhaps how to test it to convince myself what exactly the TTL flash is doing?  Even if you are not familiar with Fuji TTL system, it can't be that different from other systems, I imagine.  Does what I said above make any sense at all?

Cheers and thanks!

Nikonguy

If you have the shutter speed, aperture, and ISO set in a way which would yield a well exposed photo of your subject without the flash, the flash doesn't have much to do. So using TTL in this situation will result in the camera selecting a low flash power. Similarly, if everything would be rather dark without flash, then the flash power will need to be fairly high.

Also, when the flash fires, depending on the situation and camera settings (particularly aperture and ISO), your ambient background exposure will change because the flash got added to it. Imagine shooting in a dark room - the flash is potentially going to light up the room, not only your subject.

I guess it would help to see some examples of the problem you're dealing with because there are a lot of variables beyond the TTL preflash - flash mode being used, camera settings, active focus point, subject distance, etc. When I'm troubleshooting flash photos, a trick I employ sometimes is to shoot with the flash turned off, then turn it on and shoot. This way you can clearly see the impact of the flash. Good luck.

mcjtom

Thanks.  I don't really have a problem with the flash, I'm just trying to understand better what is exactly that it does.

The way I understand it is more or less what you described: i.e. the flash power it already adjusted based on ambient exposure - the flash compensation is in relation to this already adjusted flash.

Which leaves me with a question: if I use this flash as a fill-light, I'm not sure how to adjust the flash, since the camera does its own mysterious (but perhaps helpful) adjustments, and my flash compensation is on top of this.

This is, I understand, different from the TTL flash not automatically compensating for ambient exposure, just deciding on the flash power based on its distance and reflectivity, not the existing ambient light.

I'm just not sure about all that - and I can't find any documentation on it.  I remember looking for similar info for Canon flashes years ago, and finding the explanation.  Canon did some serious hocus-pocus with its flashes, but at least I understood what they did and didn't do, and could gage my adjustments accordingly.  I can't find anything of that sort for Fuji X.  Would anyone know any better?

Cheers!

Nikonguy

You said,
"i.e. the flash power it already adjusted based on ambient exposure - the
flash compensation is in relation to this already adjusted flash."
and
"This is, I understand, different from the TTL flash not automatically compensating for ambient exposure"

Just to clarify with modern TTL a preflash of a known amount will be fired before the exposure and the camera will measure then calculate what strength of flash would give the correct exposure given variables like area being focused on, subject distance, flash mode being used, aperture, ISO, shutter speed, etc. What I meant is that if the ambient exposure is largely correct anyway, the calculation is going to result in a low flash power. Likewise, if the ambient exposure is very dark, the calculation will result in a lot of flash being needed.

For fill flash, I would normally set a basically correct exposure manually (so I'm in control of aperture, shutter, and ISO) and then dial in a negative flash compensation. Neil has a few articles on this. Here's one:

http://neilvn.com/tangents/best-fill-flash-settings/

If you have some samples, it might give some context for what problem are you trying to solve.

Neil vN

The one crucial bit of information missing here - is your camera in Auto / Program mode, or in Manual exposure mode?