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Thread started 04 Oct 2013 (Friday) 09:03
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5dmk3 and 580exII Underexposure Issue

 
Aswald
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Oct 05, 2013 11:26 |  #16

Wilt wrote in post #16347900 (external link)
Hmmm...back when the 20D came out, it was routine for folks to have to dial in FEC +1EV routinely, in order to get the right tonal density in a scene shot with flash...regardless of direct flash or bounced flash it was the same. Then, when the 40D came out, that need for 'permanent FEC' disappeared...direct flash and bounced flash seemed accurate without FEC. Not sure what is the issue with your 5DIII, but offer that bit of historical insight.

The fact that you have already bumped up FEC with no better results might be a clue as to the nature of the problem. The shots you posted would not seem to have any corner case content that should fool ETTL metering; the white shirts in the first photo might result in a bit of underexposure, but certainly not the other shots.
The G9 shows you what you should get...my speculation is that the original Canon dSLR flash engineering team left Canon for a while, but have now come back to Canon. :rolleyes:

This is great info and very interesting. Perhaps the engineers at Canon does change the algorithm of the way a camera body reads the E-TTL signals.

I took a few more shots this evening of and decided to use different ISO (as suggested by Tony earlier) and I started to notice something I've never noticed before. The 5Dmk3+580ex2 flash output seems to match the exposure set on the camera, no more, no less. It is as if taking the photo without any flash at all.

It also seems that the flash output commensurate with the camera's metering. If the camera's meter is under then the resultant picture with flash would also be under. At any one time, the background and subject looks as if it had the same exposure level. I.e, dark background, dark subject or bright background, bright subject. As I dialed the ISO up (more sensitive) the subject became brighter as did the background.

I will post some pic a little later to illustrate.




  
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tonyniev
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Oct 05, 2013 11:47 |  #17

Aswald wrote in post #16348010 (external link)
This is great info and very interesting. Perhaps the engineers at Canon does change the algorithm of the way a camera body reads the E-TTL signals.

I took a few more shots this evening of and decided to use different ISO (as suggested by Tony earlier) and I started to notice something I've never noticed before. The 5Dmk3+580ex2 flash output seems to match the exposure set on the camera, no more, no less. It is as if taking the photo without any flash at all.

It also seems that the flash output commensurate with the camera's metering. If the camera's meter is under then the resultant picture with flash would also be under. At any one time, the background and subject looks as if it had the same exposure level. I.e, dark background, dark subject or bright background, bright subject. As I dialed the ISO up (more sensitive) the subject became brighter as did the background.

I will post some pic a little later to illustrate.

correct, here is an ETTL flash shot, this is t iso 3200, F 6.3 for depth of field and 1/100 for no blur from movement...when shooting parties I even set at TV say at 1/80 if the place is really dark , but mostly on AV at near widest and high iso to get around 1/100. This is a dar science museum, aperture for flash and shutter speed for ambient light

IMAGE: http://tonyniev.smugmug.com/photos/i-sDHtD6n/0/L/i-sDHtD6n-L.jpg

Cheers,
Tony
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tonyniev
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Oct 05, 2013 11:57 |  #18

this is manual flash at iso 640 F6.3 1/160, full power distance is about 30 feet on 5D2 and 580EXII, I use manual flash and when subject is near I shoot at 1/4 power for fast recycling with power pack:sorry for the watermarks,

IMAGE: http://tonyniev.smugmug.com/photos/i-zbjZtN6/3/L/i-zbjZtN6-L.jpg


also manual flash at 1/4 power:
IMAGE: http://tonyniev.smugmug.com/photos/i-bMRNPGN/0/L/i-bMRNPGN-L.jpg

Cheers,
Tony
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tonyniev
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Oct 05, 2013 12:02 |  #19

ETTL is easy to use :-) my granddaughter taking my photo iso 3200 F 5.6 1/100

IMAGE: http://tonyniev.smugmug.com/photos/i-chRzBrk/0/L/i-chRzBrk-L.jpg

Cheers,
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Aswald
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Oct 05, 2013 12:08 as a reply to  @ tonyniev's post |  #20

ISO640, 1000, 1250, 1600
Tv 1/100, Av F2.8 Manual Exposure, 580ex2 set on bounce. White ceiling less than 3 meters in height. All others equal.

Notice how the subject is illuminated as per ambient exposure?


IMAGE: http://farm6.staticflickr.com/5483/10102494554_3b22235282.jpg
IMAGE LINK: http://www.flickr.com …24280281@N03/10​102494554/  (external link)
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IMAGE LINK: http://www.flickr.com …24280281@N03/10​102529145/  (external link)
IMAGE: http://farm3.staticflickr.com/2860/10102593813_6a6ca2accc.jpg
IMAGE LINK: http://www.flickr.com …24280281@N03/10​102593813/  (external link)
IMAGE: http://farm4.staticflickr.com/3789/10102535255_c433c21180.jpg
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Aswald
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Oct 05, 2013 12:16 as a reply to  @ Aswald's post |  #21

These are the same pics adjusted in DPP for same subject brightness. Adjusted the exposure, WB and sharpness. Cropped.

Sorry the pics aren't too sharp or interesting. I took them for testing and sharing.

Previously, if I wanted the background darker, I just needed to adjust the ISO. Now it would seem I have to do a bit more work. I'd have have to lower the ISO AND push up the flash output.

IMAGE: http://farm8.staticflickr.com/7448/10102652906_5de10600a8.jpg
IMAGE LINK: http://www.flickr.com …24280281@N03/10​102652906/  (external link)
IMAGE: http://farm4.staticflickr.com/3800/10102658236_82ec7dc7a2.jpg
IMAGE LINK: http://www.flickr.com …24280281@N03/10​102658236/  (external link)
IMAGE: http://farm8.staticflickr.com/7405/10102604975_257a471177.jpg
IMAGE LINK: http://www.flickr.com …24280281@N03/10​102604975/  (external link)
IMAGE: http://farm8.staticflickr.com/7300/10102570094_e56a90a304.jpg
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Aswald
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Oct 05, 2013 12:18 |  #22

Interesting shots Tony. Electrifying to say the least. Love the bevy of beauties! Thanks for sharing.




  
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Aswald
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Oct 05, 2013 12:33 |  #23

I'm still unsure if my experience with the 5Dmk3+580ex2 is consistent with Canon's design algorithm for how flash photography should function. Why should a flash system output only enough light so that the subject is only as bright as it's ambient light. If it was a dark room, surely the subject would end up dark as well.

I did some more test and depending on the subject color, the flash outputs different power as well.

For instance, if I took a picture of 2 cards, one white and the other grey 18 (mid grey), the 2 pictures would have different overall brightness due to the different output from the 580ex2 flash. Curious....

Is this how it is supposed to be? If this is how it is supposed to be then the 5Dmk3's E-TTL 2 algorithm is far more sensitive and complex as anything I've come across with the 5Dc.

It does remind me of the 1Dsmk3 + 580ex2 somehow.....




  
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tonyniev
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Oct 05, 2013 13:41 |  #24

Aswald wrote in post #16348131 (external link)
I'm still unsure if my experience with the 5Dmk3+580ex2 is consistent with Canon's design algorithm for how flash photography should function. Why should a flash system output only enough light so that the subject is only as bright as it's ambient light. If it was a dark room, surely the subject would end up dark as well.

I did some more test and depending on the subject color, the flash outputs different power as well.

For instance, if I took a picture of 2 cards, one white and the other grey 18 (mid grey), the 2 pictures would have different overall brightness due to the different output from the 580ex2 flash. Curious....

Is this how it is supposed to be? If this is how it is supposed to be then the 5Dmk3's E-TTL 2 algorithm is far more sensitive and complex as anything I've come across with the 5Dc.

It does remind me of the 1Dsmk3 + 580ex2 somehow.....

from Wikipedea E-TTL (Evaluative-Through The Lens) is a Canon EOS flash exposure system that uses a brief pre-flash before the main flash in order to obtain a more correct exposure. Unlike TTL and A-TTL metering, which use a dedicated flash metering sensor mounted in the base of the mirror box, E-TTL uses the same evaluative metering sensor used for ambient metering. Like TTL (and like the actual flash metering, but not the pre-flash, of A-TTL), the sensor is internal to the camera and takes its exposure via the lens so any filters added to the lens will also affect the E-TTL readings giving more accurate exposure information to the camera.
The pre-flash occurs immediately before the main flash (except when using the camera / flash in 2nd curtain synch mode) and is barely perceptible, although it can be seen if you watch carefully for it. The pre-flash may cause undesirable reactions from animate objects - e.g. humans may blink as a reaction to the pre-flash, and have their eyes closed by the time the main flash occurs. When using flash exposure lock (FEL), the pre-flash is fired when FEL is activated.

You need to go manual flash if you want to shoot with flash fill in, here I metered for th e background, iso 200 1/200 at F14 b3cause it was bright sunlit noon, but there are shadows under the model:

IMAGE: http://tonyniev.smugmug.com/Photography/Outdoor-fashion-shoot/i-vKPngdg/0/L/IMG_0645-L.jpg

also use a 18% grey card to get exposure and white balance:
IMAGE: http://tonyniev.smugmug.com/photos/i-b2KrwRF/0/M/i-b2KrwRF-M.jpg

Cheers,
Tony
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gtrag94
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Oct 05, 2013 21:53 |  #25

E-TTL works the same as the camera's meter. If the subject is bright, the camera lets in less light. If the subject is dark, the camera lets in more light. EVEN THOUGH IT SHOULD LET IN THE SAME AMOUNT OF LIGHT IN BOTH CASES.

The flash works by seeing a high reflectance of the preflash on a bright subject and says to emit less power than it should. Dark subject gets overexposed because it doesn't reflect much light and the camera says to pump up the power. EVEN THOUGH IT SHOULDN'T.

Using FEL wouldn't burn through the batteries because it's just letting you tell it where to preflash. Same power is used as when letting the camera do the preflash itself. FEL is kinda like spot metering.

Try using exposure settings that are a lot farther apart. For example take one shot at 1/100s, f/4, ISO 200 and another at ISO 1600. Compare the amount of light on the subject in both (should be the same as long as ambient isn't messing it up) and compare the amount of light in the background. You can do the same for shutter speed (pick 1/30s and 1/200s while keeping the ISO the same.. maybe 800?).

Also to note, the Speedlite's FEC setting always takes priority over the camera's setting. If you want to use FEC via your ISO button on the camera, make sure the speedlite is set to "0" FEC.

Double check your flash settings in the menu (External Speedlite Control) and make sure they're all default or that your changes make sense.

Finally, with Auto Lighting Optimizer set to "Enable" you'll usually end up with silly results because the camera is processing them for you/correcting your mistakes.

Turn off all helpers and you'll find what you're used to seeing.


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Oct 05, 2013 22:39 |  #26

gtrag94 wrote in post #16349028 (external link)
E-TTL works the same as the camera's meter. If the subject is bright, the camera lets in less light. If the subject is dark, the camera lets in more light. EVEN THOUGH IT SHOULD LET IN THE SAME AMOUNT OF LIGHT IN BOTH CASES.

The flash works by seeing a high reflectance of the preflash on a bright subject and says to emit less power than it should. Dark subject gets overexposed because it doesn't reflect much light and the camera says to pump up the power. EVEN THOUGH IT SHOULDN'T.

Using FEL wouldn't burn through the batteries because it's just letting you tell it where to preflash. Same power is used as when letting the camera do the preflash itself. FEL is kinda like spot metering.

Try using exposure settings that are a lot farther apart. For example take one shot at 1/100s, f/4, ISO 200 and another at ISO 1600. Compare the amount of light on the subject in both (should be the same as long as ambient isn't messing it up) and compare the amount of light in the background. You can do the same for shutter speed (pick 1/30s and 1/200s while keeping the ISO the same.. maybe 800?).

Also to note, the Speedlite's FEC setting always takes priority over the camera's setting. If you want to use FEC via your ISO button on the camera, make sure the speedlite is set to "0" FEC.

Double check your flash settings in the menu (External Speedlite Control) and make sure they're all default or that your changes make sense.

Finally, with Auto Lighting Optimizer set to "Enable" you'll usually end up with silly results because the camera is processing them for you/correcting your mistakes.

Turn off all helpers and you'll find what you're used to seeing.

so what settings do you suggest for the images of his daughter under the condition he shot?


Cheers,
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Aswald
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Oct 05, 2013 23:44 as a reply to  @ tonyniev's post |  #27

Tony, thanks for the heads up from Wiki. What it says corresponds with what I'm experiencing. What it means for me at the end of the day is that with the flash plonked on the 5Dmk3, I now have 2 sets of exposure readings to work with. I'm just deciding which way works better for me.

So far, the quickest method (as you suggested) is to use manual flash which I tried. I dialed the power to 1/16 and that seems to work well generally for 70mm shots with ceiling less than 3meters high. It gives the same exposure as using FEL to meter on a gray card.

The other option (closer to how I used to shoot) would be to up the power (FEC) on the flash and be MINDFUL to check flash exposure for white areas. This will work only if there are some whites. I have to mentally compensate the flash power output as I would for camera metering of a subject. I.e. up power if subject is fairer and down power when it is darker.

I used FEL on a black and white card separately. As expected, the white card came out underexposed and the black card was blown out.

Btw, nice models. You lucky fella...




  
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gtrag94
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Oct 05, 2013 23:46 |  #28

not sure what settings you mean Tony, exposure or camera's menu settings? i.e. ALO, External Speedlite Control, etc...

Tv mode, in my opinion, has no place here. Manual would be much better since you're wanting to stick with a certain shutter speed, aperture and ISO. For that matter, Manual mode on the flash makes more sense from a shooting perspective since nothing's changing. BUT, this is a discussion about E-TTL so shoot as you may.

In this situation, I'd set manual mode on camera, shutter speed to about 1/60s, f/2.8, ISO to make background look like you want and then set the manual flash accordingly. E-TTL would work mostly, but then you get problems like this. I don't like adjusting photos after the fact... wastes time. Plus, you can't show people the back of your camera because "I'll have to fix that one later so it'll look right."


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Oct 05, 2013 23:52 |  #29

Aswald, E-TTL has been the same for a long time. 5D is the same as 5D3. You've always had two exposures to deal with.


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Oct 05, 2013 23:58 |  #30

gtrag94 wrote in post #16349028 (external link)
E-TTL works the same as the camera's meter. If the subject is bright, the camera lets in less light. If the subject is dark, the camera lets in more light. EVEN THOUGH IT SHOULD LET IN THE SAME AMOUNT OF LIGHT IN BOTH CASES.

The flash works by seeing a high reflectance of the preflash on a bright subject and says to emit less power than it should. Dark subject gets overexposed because it doesn't reflect much light and the camera says to pump up the power. EVEN THOUGH IT SHOULDN'T.

Using FEL wouldn't burn through the batteries because it's just letting you tell it where to preflash. Same power is used as when letting the camera do the preflash itself. FEL is kinda like spot metering.

Try using exposure settings that are a lot farther apart. For example take one shot at 1/100s, f/4, ISO 200 and another at ISO 1600. Compare the amount of light on the subject in both (should be the same as long as ambient isn't messing it up) and compare the amount of light in the background. You can do the same for shutter speed (pick 1/30s and 1/200s while keeping the ISO the same.. maybe 800?).

Also to note, the Speedlite's FEC setting always takes priority over the camera's setting. If you want to use FEC via your ISO button on the camera, make sure the speedlite is set to "0" FEC.

Double check your flash settings in the menu (External Speedlite Control) and make sure they're all default or that your changes make sense.

Finally, with Auto Lighting Optimizer set to "Enable" you'll usually end up with silly results because the camera is processing them for you/correcting your mistakes.

Turn off all helpers and you'll find what you're used to seeing.

Thanks for the tips gtrag94! Much appreciated.

I normally shoot in M mode. I've double checked the settings and on M mode both Highlight Priority and ALO are switched off. I agree, they sometimes give unexpected results.

I will try to do more shots to compare based on your suggestions. For the sake of a quick compare, I looked at my initial pic of ISO640 and 1600 and realized that the flash was just outputting the amount equivalent for ambient lighting. I wondered why E-TTL doesn't recognize my subject even though I was using the 24-70 which does provide distance information back to the camera. Due to my lack of understanding of how it actually works, I ended up with a batch of grossly underexposed pictures. Thankfully I was able to process them in raw DPP and still managed to get quite a few usable shots. Thank goodness for the nice dynamic range of the 5Dmk3!

Based on what you suggested, I decided to shoot a subject in almost pitch black last night. Guess what? A very healthy flash output from the 580ex2! And that with a reassuring "pop" from the flash.

It would seem that the E-TTL algorithm on the 5Dmk3 has it's own parameters which dictates when it will stop following ambient exposure for the 580ex2. There must be a cut off somewhere based on what it meters. In a dim but not dark room, the 580ex2 doesn't give that "pop" flash output....and sadly, under exposes the shot or, exposes it to compliment the ambient lighting.

All these are new to me as I never worried about flash outputs with the 5Dc.




  
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5dmk3 and 580exII Underexposure Issue
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