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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 06 Jun 2013 (Thursday) 17:17
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Bounce flash in ettl - unexpected results

 
swoffa
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Jun 06, 2013 17:17 |  #1

Hi All,

I was shooting the kids inside and bouncing the flash but getting extremely underexposed images in ettl mode. So I sat down and took some shots of the couch, it doesn't move as quickly. The histogram for 1 & 3 is sitting just left of centre but the 2nd is way to the left. I don't have any software here at work to grab this to upload but you can see what's going on.

What am I doing wrong here?

edit: Was just looking at the exif in camera and noticed that these were shot in P mode. Not sure what happened there because that would be the first time the dial would have stopped there, ever. I guess it explains the jump from 2.8 to 4.0 though.

1st one is ambient at 1/250 , 2.8, iso 16000

2nd flash bounced off white ceiling 1/60 , 4.0 iso 400. Must have bumped it to 4.0 as I just noticed when I was checking the exif for posting.

3rd Direct flash 1/60 , 4.0 , iso 400.

IMAGE: http://imageshack.us/a/img196/9628/ambient.jpg

IMAGE: http://imageshack.us/a/img23/8196/bouncedu.jpg

IMAGE: http://imageshack.us/a/img842/3659/directj.jpg



  
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Numenorean
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Jun 06, 2013 17:20 |  #2

You stopped down which is cutting your flash down. You drastically cut the ISO....why? Those are both going to cut your flash.


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swoffa
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Jun 06, 2013 19:10 |  #3

I realise the settings changed (and I'll redo this again in manual) But even so, shouldn't ETTL boost the flash power to correct?




  
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Numenorean
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Jun 06, 2013 19:13 |  #4

swoffa wrote in post #16007038 (external link)
I realise the settings changed (and I'll redo this again in manual) But even so, shouldn't ETTL boost the flash power to correct?

Unless there's no more power left to boost. ETTL isn't perfect either and isn't always the best for bouncing.


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swoffa
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Jun 06, 2013 19:55 |  #5

What's the best method, go full manual including the flash?
That will play havoc as I change the aperture quickly depending on the dof required to catch both boys. They're not always on the same plane( in more ways than one).

Would AV and/or auto ISO be better?




  
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mike_d
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Jun 06, 2013 21:41 |  #6

I have a 5D and find that ETTL tends to underexpose consistently when bouncing, especially if there's any white in the scene, like a wall. I set the camera's exposure manually (usually f/2.0-f/4 depending on the lens, ISO 400-800, and 1/160') and set the 580EXII to ETTL with +2/3 of FEC. Works fine most of the time or at least gets me close enough to touch up the exposure in LightRoom.




  
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dmward
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Jun 07, 2013 08:37 |  #7

To use ETTL properly takes practice. Remember, the camera meter is now a reflective flash meter and will respond just as it does with ambient light. i.e. trying to turn everything middle gray. Too much white will mean under exposure, too much black will mean over exposure.

When bouncing the effective flash to subject distance is the distance from the flash tube to the bounce surface and then to the subject.

I love ETTL. I put camera in manual when inside and Av when outside where shutter speed is not at risk. Then ride ISO and FEC outside and FEC inside to fine tune exposure. It takes practice.


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JakAHearts
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Jun 07, 2013 09:01 |  #8

mike_d wrote in post #16007371 (external link)
I have a 5D and find that ETTL tends to underexpose consistently when bouncing, especially if there's any white in the scene, like a wall. I set the camera's exposure manually (usually f/2.0-f/4 depending on the lens, ISO 400-800, and 1/160') and set the 580EXII to ETTL with +2/3 of FEC. Works fine most of the time or at least gets me close enough to touch up the exposure in LightRoom.

ETTL will underexpose if there is white in the scene, regardless of whether you are bouncing or not. :D

Im with David, I LOVE ettl. I set the ambient contribution I want usually through a highish iso and then just dial flash exposure compensation up or down depending on the tones in the scene. Works like a charm most of the time.


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dmward
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Jun 07, 2013 09:20 |  #9

Here's an example. Not because its a great picture but to illustrate how well ETTL works once you've got the hang of its characteristics.

This was shot on a cruise boat, low ceiling, lots of really ugly accent lighting, daylight outside, darker interior. Camera was in manual mode, ISO, Shutter speed and F stop to get ambient within about a stop of "normal" One 600EX-RT on camera, second on a light stand camera right. Both in ETTL mode. Speedlite on camera was probably -1 FEC, speedlite on stand was 0 FEC. That's my default. One advantage here is that the bride's white dress and groom's black tux help average out the exposure.


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swoffa
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Jun 07, 2013 09:33 |  #10

Thanks for the reply's. I've had another play with settings, which can be seen in the images.

This first one is at 0EV and no flash.
https://www.evernote.c​om …%208%20;%2012:2​9%20AM.jpg (external link)

Second is with the flash pointed directly at the subject. +1 on the flash.
https://www.evernote.c​om …%208%20;%2012:3​0%20AM.jpg (external link)


Third is with flash head pointed to ceiling, still +1 on the flash.
https://www.evernote.c​om …%208%20;%2012:2​5%20AM.jpg (external link)

Lastly, This is with pressing the M-Fn button to fire pre-flash exposure, flash still at +1.
https://www.evernote.c​om …%208%20;%2012:2​6%20AM.jpg (external link)

This last one gives the better exposure, but surely I don't have to keep pre-flashing before taking the shot. How are you guys working this?


Thanks




  
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digital ­ paradise
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Jun 07, 2013 12:56 |  #11

Although ETTL is a very good tool it is a hit and miss. Bouncing even changes it more. Although flash has nothing to do with with your cameras light meter is uses the same exposure system. You are aware the camera meter will underexpose pure white snow and overexpose black tar.

ETTL is the same. Evaluative flash metering. First there is a pre flash. The system compares the ambient reading to the flash and via all the metering zones, finds the closest object which is typically your subject and meters based on the reflected light from the pre flash. For example a bride in a white dress, a groom in a black tux and the bride and groom together will all meter differently. You can apply the white snow, black tar explanation to that.

You can change your flash to average but this can only be done via camera menus if your camera has that option. Older ones don't. Average metering meters the entire scene, not just the isolated subject. Some say it is better for indoor, smaller places. Large venues and outdoors Evaluative is better.

Some people like to use spot metering with flash. They only way to achieve this is using the FEL. It fires the flash and only meters within the spot metering circle. The when you press the shutter the flash fires with the pre determined exposure. People meter off skin tones and then establish a formula for how much FEC is required. I tried but I don't like using it.

I see your camera is on Center-weighted average. Remember that is metering ambient only and has nothing to do with flash exposures.

So welcome to the world of ETTL. FEC is something you need to get used to using regularly. Bouncing complicates it even more as it has no idea how far you subject is from the camera. Eventually gets much easier once you get used to it. You just need to accept it for what it is and then just have fun shooting.

That is why many people prefer manual flash if the conditions are not changing. Once you establish an exposure it stays the same.


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Left ­ Handed ­ Brisket
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Jun 07, 2013 13:12 as a reply to  @ digital paradise's post |  #12

i don't see where you've listed what kind of flash you are using.

also, noticed there is just 16 seconds between the direct flash and first bounced flash.

should be enough, but just thought i'd mention it if your batteries are not fresh.

seems like odd behavior to me.


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mike_d
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Jun 07, 2013 22:46 |  #13

JakAHearts wrote in post #16008482 (external link)
ETTL will underexpose if there is white in the scene, regardless of whether you are bouncing or not. :D

I realize this, but it underexposes much more when bouncing, even when there's plenty of headroom on the flash power. I just know to add some FEC.




  
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swoffa
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Jun 08, 2013 01:11 |  #14

hes gone wrote in post #16009239 (external link)
=he's gone;16009239]i don't see where you've listed what kind of flash you are using.

also, noticed there is just 16 seconds between the direct flash and first bounced flash.

should be enough, but just thought i'd mention it if your batteries are not fresh.

seems like odd behavior to me.

I get the same results if I'm using the 580exII or the YN568ex.

Brand new alkalines in the unit for the cereal box shots.
I'll try some more shots tonight when I have some time. ETTL just doesn't seem to get me anywhere unless I use the pre-flash exposure.




  
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spur
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Jun 08, 2013 13:02 |  #15

Take a look here and you will learn how to bounce flash easily for what you are trying to do.
http://neilvn.com …h-photography-techniques/ (external link)




  
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Bounce flash in ettl - unexpected results
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