Question with flash light 270EX

[ypurcaro]

I love the flash light I got for my canon T1i. But, the problem is I don't know how to control the exposure. Everytime I hooked the flash light on, the exposure meter will not work as without the flish light on. I use "manual" and I have to keep adjusting the F stop or the shutter speed to avoid the "too bright" outcome. I also noticed that when i have my flash light on, the shutter speed some times will not allow me to go lower than 1/200.

Can someone tell me what to do in order to get the right exposure with my speed light? Thank you for your help.

[inkista]

Originally Posted by ypurcaro

I love the flash light I got for my canon T1i.

Tiny terminology note: call it a flash or a speedlight. A flashlight is something else.

But, the problem is I don't know how to control the exposure. Everytime I hooked the flash light on, the exposure meter will not work as without the flish light on.

Your meter is only telling you about the ambient light. You have to think your way through adding the flash illumination to the exposure. The metering can't do this because the flash contribution to the scene isn't there to be measured until you take the picture.

What the camera does is called "eTTL II" or "electronic through-the-lens" metering. The camera tells the 270EX to give out a "preflash" burst of light of a known brightness, meters it, and then adjust the power on the 270EX to compensate. But it may not be completely accurate, given the scene you're shooting. So, flash exposure compensation is typically used to adjust, just like you'd use exposure compensation in the camera without the flash if you were in Av or P mode. Whether or not you can use FEC depends on the camera body you have. The T1i should be able to do this through the "flash control" menu.

I use "manual" and I have to keep adjusting the F stop or the shutter speed to avoid the "too bright" outcome.

How close are you working to your subject?

I also noticed that when i have my flash light on, the shutter speed some times will not allow me to go lower than 1/200.

1/200s is the max. sync speed of your T1i. If your shutter speed is set faster than this, the gap between the shutter curtains isn't going to be wide enough to uncover your sensor all at the same time. You'll end up with dark bars on the top and/or bottom of the image. You have to set the flash into FP/high-speed sync mode so that it can time flash pulses as the gap travels across the sensor so that the entire sensor is "lit" for the exposure. This will, however, drastically reduce your flash's power output.

[ypurcaro]

[QUOTE=inkista;1175886]
How close are you working to your subject?QUOTE]

About 60mm I think. I have attached it in here.

Thank you so much for yor detailed information and thank you so much to correct me with the terminology.

So, what you mean is when I use the speedlite, I have to guess what I need to set for the f, iso, and shutter speed?

Thanks again!

[inkista]

Ok, here's one main way to think of it.

Whenever you take a flash photo, you're combining two exposures: the ambient exposure (that you create with iso, aperture, and shutter speed, just as without a flash), and the flash illumination.

The flash illumination is determined by four factors: your iso, your aperture, the flash's power output, and the flash-to-subject distance.

The higher the iso, the more flash you get.
The larger the aperture (smaller the f-number), the more flash you get.
The higher the flash's power output is set, the more flash you get.
The closer to the subject you are, the more flash you get.

And distance is a huge factor. Light falls off by what's known as the 'inverse square rule'. That means if you double the distance but leave the flash power output the same, you'll get 1/4th of the light. If you triple the distance, you get 1/9th of the light. If you quadruple the distance, you get 1/16th of the light.

That also means, if you halve the distance, you'll quadruple the light. At one third the distance, you'll have nine times the light, etc. etc.

I'd say the reason your flash is blowing out is because you're working so close. You may be working at the minimum limit of the power output.