danielyamseng wrote in post #6067995
I guess I'd rephrase the sentence " I used manual flash output and ETTL average flash but with no promising result"
I've tried to use manual flash output and the ETTL flash set to average mode, but with no satifactory result.
OK. I understand now. You tried both ways.
danielyamseng wrote in post #6067995
for ISO 250, f5.6,1/125
while at ISO800, f5.6,1/15
Well, fooey! I can't read. I see now that you changed the shutter speed. That should have made an even more dramatic change in the ambient light and would have changed the light ratio. The flash, however, would have the same exposure if you used ETTL or didn't change the manual setting.
danielyamseng wrote in post #6067995
Yes, otherwise I can't guess the ration unless I'm using the 1D series body.
OK. To be honest, I'm never in a situation where I can be deliberate enough to take flash meter readings in mixed light.
danielyamseng wrote in post #6067995
They looked washed out, just like a direct flash. I've even tried to reduced flash output using FEC -1 (direct flash) but either I get an underexpose image or the image lost details.
We may be using different meanings for the term "washed out." To me it implies a loss of color like you would get with overexposure. I'm thinking you are using it to mean a flat, front-lighting look. Which diffuser are you using? If it is a small one, it will look a lot like direct flash depending on how much bounce light is contributed. If the flash with the diffuser is actually pointed at the subject, it will look almost exactly like a direct flash because that is pretty much what it is. What are you bouncing off and how far away is it. Also, one whole f/stop of change may be too much change.
danielyamseng wrote in post #6067995
Thus is that a correct expose should be shift towards yellowish color? Is there a way to capture a correct skin tone without using flash gel?
If you are using one color of light on the subject and another color of light on the background, you will have to chose to render one or the other correctly. You can't pick both. Most people pick the skin tones lit by flash as the normal and let the background fall where it may. If the ambient is having an influence on the subject, you'd better gel the flash. Otherwise, the highlights will be one color and the shadows will be another.
danielyamseng wrote in post #6067995
Then how would you know the image is properly exposed? Neither the Histogram nor lcd preview is accurate in this case.
Use a meter? You said you were measuring with an external meter. Trust it. Or put the image on a computer screen or even print it out. Study the histograms of the best looking images. Different looking images will produce different histograms. Learn to recognize what a particular kind of image's histogram should look like.
danielyamseng wrote in post #6067995
As for ambient metering, usually how much EV different from the main subject? For me I'd usually set 1 stop difference.
Sounds good to me, but it really depends on what you want it to look like.
danielyamseng wrote in post #6067995
As for me the easiest would be using the fastest len to shoot without flash but it's not realistic for group photoshoot.
If you are talking about a large group in a dark room, I wouldn't even worry about ambient unless it was pretty bright.
It would be very helpful to see some actual examples of what you're telling us about.