wonky flash power?

Wilt wrote in post #15370060
-3EV compensation should be equivalent to 1/8 power...1/1 (0EV), 1/2 (-1EV), 1/4 (-2EV), 1/8 (-3EV)

The problem is that with ETTL, when you use 0EV compensation, the flash is still likely NOT to be having to output true full power but is outputting at a lower level...it might be starting with 1/8 power because that is all that the ETTL is commanding of the flash, so that when we dial in -3EV compensation that is 1/64 power...1/8 (0EV), 1/16 (-1EV), 1/32 (-2EV), 1/64 (-3EV)

Flash compensation merely tells the flash metering what to output relative to what it considers to the 'proper exposure' for a given aperture and ISO.

Think of my question another way. Why is it possible to achieve lower power output through FEC than manual?

LostArk wrote in post #15370655
Think of my question another way. Why is it possible to achieve lower power output through FEC than manual?

Only thing I can think of is that flash goes into an HSS type of output 'cause ETTL output is about 1.33 stops lower compared to manual with my 580EXII set on 1/128

LostArk wrote in post #15370655
Think of my question another way. Why is it possible to achieve lower power output through FEC than manual?

In some cases, the flash Manual power setting only goes down to a certain minimum, while ETTL control (and FEC) permit it to go to an even lower setting. For example, the 580EX manual power setting goes as low as 1/128 while some claim that ETTL permits it to get to 1/256.

Wilt wrote in post #15371073
In some cases, the flash Manual power setting only goes down to a certain minimum, while ETTL control (and FEC) permit it to go to an even lower setting. For example, the 580EX manual power setting goes as low as 1/128 while some claim that ETTL permits it to get to 1/256.

Very interesting. I wonder if there's a way to reliably "trick" ETTL metering into triggering these lower power outputs.

LostArk wrote in post #15371131
Very interesting. I wonder if there's a way to reliably "trick" ETTL metering into triggering these lower power outputs.

Hold a white reflector in frame and use FEL with as much negative FEC as your camera is able to do.

It'd be a lot easier to simple throw a 1 stop ND gel in front of the flash and use manual.

Wilt wrote in post #15370060
-3EV compensation should be equivalent to 1/8 power...1/1 (0EV), 1/2 (-1EV), 1/4 (-2EV), 1/8 (-3EV)

I find this statement to be highly confusing (and wrong).

Wilt wrote in post #15370060
Flash compensation merely tells the flash metering what to output relative to what it considers to the 'proper exposure' for a given aperture and ISO.

This is correct.

ETTL can go lower then the lowest manual flash setting. At least a few stops.
That's why the FEC-3 shot can come out darker then the 1/64 power shot.

In another setting, it might well be that it's the other way around.
If the OP would stop down a few stops for instance, or use a lower ISO: The ETTL exposure would remain identical, while the shot at 1/64 power would become darker.

But why not have the lowest manual setting be THE lowest output.?

"Because".
It's always been this way. Nikon as well as Canon. (At least, my SB-24 and 540EZ worked the same)

Who knows. Maybe it's a leftover from the time when flashes only had something like 5 manual power settings (1-1/2-1/4-1/8-1/16)?

windpig wrote in post #15372518
But why not have the lowest manual setting be THE lowest output.?

I found a site that says that the ETTL pre-flash is what makes it possible for the lowest flash setting in ETTL to be lower than the lowest setting in manul. Coversly, it says that highest setting in ETTL will also be lower than the highest manual setting. This was my original hypotheses, so I'm naturally inclined to believe this is the answer. What are your thoughts?

Quote from his site:

When you need to squeeze every very bit of power from your Speedlite, switch it to Manual mode and set it to 1/1. In E-TTL, the Speedlite uses a bit of its power for the pre-flash. By switching to Manual, you eliminate the pre-flash and send all the juice straight out in one big burst.
Conversely, if you are shooting in Manual at the lowest power setting and still have too much light, switch over to E-TTL. The pre-flash will suck up a bit of power and thereby reduce the intensity of the flash. The change will be small, but it might be just enough.

and link:

http://pixsylated.com …ettl-manual-flash-part-1/

Well that makes sense. Per my earlier comment questioning whether the speedlight went into HSS mode. Although not HSS mode, a form of depleted power issue none the less.

doidinho wrote in post #15372600
I found a site that says that the ETTL pre-flash is what makes it possible for the lowest flash setting in ETTL to be lower than the lowest setting in manul. Coversly, it says that highest setting in ETTL will also be lower than the highest manual setting. This was my original hypotheses, so I'm naturally inclined to believe this is the answer. What are your thoughts?

It's from Syl so you can pretty much except it as gospel!

gremlin75 wrote in post #15372736
It's from Syl so you can pretty much except it as gospel!

The name sounded familiar to me, but then again so does Ken Rocklwell. Good to know he is a credible source.

René Damkot wrote in post #15372439
I find this statement to be highly confusing (and wrong).

It is not 'wrong' in the context of FULL power being the starting point (0EV FEC), just as the later statement is equally correct, in the context of 1/8 power being the starting point (0EV FEC). Not stated in context, I agree the original statement could lead to misunderstanding by a reader.

Wilt wrote in post #15373052
It is not 'wrong' in the context of FULL power being the starting point (0EV FEC), just as the later statement is equally correct, in the context of 1/8 power being the starting point (0EV FEC). Not stated in context, I agree the original statement could lead to misunderstanding by a reader.

How about changing your post from "1/8 power" to "1/8 of the 0EV output" if that is what you mean and people are interpretating your statement incorrectly?

I do think the rest of your post provides an eloquent explanation once you get past that first sentance.

doidinho wrote in post #15373076
How about changing your post from "1/8 power" to "1/8 of the 0EV output" if that is what you mean and people are interpretating your statement incorrectly?

I do think the rest of your post provides an eloquent explanation once you get past that first sentance.

I amended the earlier post (with added text in blue), to end the bickering!