Q&A - Why is the exposure "off" with my TTL flash

I've received my first couple of questions for Q&A.  I want to thank both writers and will address questions in a timely fashion.  I will also keep writer's contact information and full names confidential.  So here's the first one. "Hi.

I have a Canon Rebel model T2i.  The built in flash makes bad pictures so the guy at the store said to get a bounce flash with TTL.  I bought a Canon 430EX II.  When I use the flash sometimes the pictures are good, but sometimes they are too bright.  I have attached two examples.  Is my camera not working with the flash?  The sales guy said TTL gave perfect pictures.


Well thanks for writing in Jacqueline.  I appreciate you attaching the pictures for me to look at.  I think I can answer your question.

The sales person was correct in recommending a TTL flash as they do make flash very simple.  In the kit you bought you get what Canon calls eTTL.  It's the same idea.

When you take a picture without flash, the camera sets the exposure based on the light reflected from the subject.  When you use any kind of TTL flash, the camera sets the exposure based on the amount of flash reflected from the subject.  It does this by controlling how long the flash lasts, what we call duration.

In both your example pictures, you are correct that they are too bright.  I assume you are shooting in JPEG because that is what you sent me.  Nothing wrong with that, but correct me if I am wrong.  If you look around your subject's in both pictures, the background is pretty far away.  In the picture of the older couple with the cake, it looks like you shot it in a hall or hotel ballroom, a place with very high ceilings and walls some distance away.

The camera and flash combination are looking at the reflected light from the entire scene as the light hits the sensor.  Because your subjects in both cases take up only part of the total image, the camera is adjusting exposure (flash duration in this case) to try to achieve balanced lighting across the entire image.  Since the walls are so far away compared to the couple, the camera and flash are working hard trying to light the back wall and overpowering the couple with the cake.

This doesn't mean that there is a problem with the camera or the flash.  Actually things are working as they should.  There are a couple of ways you can make this a more successful photograph.  Easiest is to fill the frame with the couple, tightening your composition to exclude more of the background.   Because they are standing up, you could have shot this as a vertical image and thereby tightened things easily.  By excluding more of the background, the meter won't see as much of it and won't work so hard to light it.  The other way is a bit more work but is a very useful skill to develop.

Your camera has exposure compensation, so you can tell the camera to add or take away exposure depending on the subject and the creative effect desired.  Similarly you can compensate for flash exposure with flash exposure compensation.  I've attached a link to a Canon site you can review but here is the quick steps to this.  I thank Canon for making this available.


EOS Rebel T2i, T3i, T3 

1. Press the [Q] button on the back of the camera. The Quick Control screen will appear.

2. Use the [Cross key] buttons to navigate to and highlight the feature you want to change.

3. Once the setting is highlighted, use the [Main dial] (immediately behind the shutter button) to change the setting. There is no need to press the [Set] button afterwards to “lock in” the setting. If you do press the [Set] button, the camera will display a contextual submenu that shows the full range of available options. Use either the [Main dial] or the [◄►] buttons to highlight and select a setting on the submenu.

When using the EOS Rebel T2i, T3i, or T3, the Quick Control Menu is the only way to access Flash Exposure Compensation directly, without going deep into the camera setting menus.


Now how do you know which way to dial your compensation?  If the background is a lot darker than your main subject such as when it is farther away for the flash to light, dial in negative compensation.  Start at -1 and adjust to taste.  If the background is close and very white, the camera is going to try to make that white average to grey so add some flash exposure.  Start at +1 and adjust to taste.  Flash exposure compensation is not some black art, but experimentation is going to be involved as is practice.  Repetition is the mother of skill so the more you experiment and try things, the better you'll get .  TTL flash is a really great system and most of the time it's really good, but even when it isn't right the first time, it gives you a really good place to start.  One other tip.  Since you spent money on a flash that has a tilting head, try adding a reflector to it and point the head straight up and not directly at your subjects.  The Rogue Flashbender system is really good and is not specific to a particular flash.  Because the Flashbender is a much larger element than the flash tube, you will get light that is a bit softer and not so many harsh shadows.  If you are home or in a place with "normal" ceiling height, just point the flash head at the white ceiling.  TTL will do a good job in general of giving you really good exposure and the bounced light will be much more pleasing than the head-on flash.

I hope you found this tip helpful.  Here's the link to the Canon document.