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Archive 2013 · 70D bounced flash exposure bug (testers needed)

  
 
bobn4burton
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p.1 #1 · p.1 #1 · 70D bounced flash exposure bug (testers needed)


I started a thread on dpreview forums about a problem I was seeing with my new 70D where I'd get serious under-exposure when using a bounced flash. Still early on, and fairly limited testing, but this is starting to appear like a pretty widespread 70D problem. So I'm looking for more people with 70D's to test and post back so that we can get a better idea of how widespread this problem is...and hopefully get Canon to address it in a future firmware update. You can read the whole thread here if you'd like:

http://www.dpreview.com/forums/thread/3584178

But I'll provide a quick/executive summary of what we've found so far:



  1. Most 70D bodies appear to have this problem, although there are 1 or 2 people that it appears don't suffer from this problem
  2. When bouncing the flash relying on ETTL/ETTL-II for flash exposure, resulting pictures are 1-2 stops under-exposed
  3. To see this problem, you really need a fairly dark room...ensuring the flash is the primary source of light
  4. The lens affects the degree of under-exposure. The slower the lens, the worse the under-exposure. (i.e. f1.8 lenses actually do pretty well, f3.5-5.6 lenses result in 1-2 stops under-exposure and f4.0 lenses are in the middle)
  5. We've been testing in all camera modes so far and the problem persists through all modes (even in fully automatic green box mode)
  6. If using FEL before taking the picture, exposures turn out great. So this problem only affects exposure algorithms used for pre-flash exposure metering when using only the shutter button.
  7. I have personally tested 9 total canon dslr bodies. Xsi, T4i(x2), T5i, 70D(x3), 5Dm3, 1Dm3. The three 70D bodies all showed this problem. All 6 of the other bodies gave pretty good to great results.
  8. I have also tested with three different flashes, and it appears the problem is independent of flash so far.
  9. You can fix the exposure by dialing in additional FEC, but this shouldn't be needed for general use and is what ETTL/ETTL-II is supposed to take care of (which is does fairly well on other bodies)


I'm sure I've missed more details which you can find by referencing the above linked thread or just asking here. But I'm hoping I get can some more 70D owners from this forum to test and report back their results. I haven't contacted Canon support yet because I wanted to gather as much data/documentation as possible first.

BTW, I completely love this camera BTW. Video is amazing...and just an all-around great camera. I do tend to take a lot of pictures of my kids indoors with bounced flash...so this is the only problem I have with the camera. I can work around the problem by using FEL or dialing in some FEC, but that just takes extra time and makes it harder to get candid shots of my kids...



Dec 09, 2013 at 12:55 PM
gwaww
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p.1 #2 · p.1 #2 · 70D bounced flash exposure bug (testers needed)


This is very interesting. I just got my 70d today, and I have the opposite problem. It overexposes bounced flash! 580exii, 580ex, Nissin and even my 270exii. I have to FEC -2 stops. I have a 5d mkiii and just came from a 7d before the 70 and never experienced anything like this.


Dec 10, 2013 at 11:10 PM
bobn4burton
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p.1 #3 · p.1 #3 · 70D bounced flash exposure bug (testers needed)


Very interesting...yours is the first case I've heard that over-exposes. Most that have tested report under-exposure. There are a couple of people that report normal exposures. And now yours is over-exposing...

Could you give a little more detail on your test shots, maybe even post a test image? What lens were you using? What mode where you shooting in? What room/ambient conditions where you shooting in? etc...



Dec 11, 2013 at 03:23 PM
gwaww
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p.1 #4 · p.1 #4 · 70D bounced flash exposure bug (testers needed)


Sorry, I am unable to post images. I was using my Sigma 18-35 and also I tried my Sigma 35, so both were used at 35mm. The room was my office which has only a ceiling fixture and I would consider the room a little dark. I am surprised that the 270 could even be that bright. I was shoot























I was using 2 lenses, Sigma 35 and 18-35 both at 35mm. I think I've solved my issue. The room was my office, which is lit only by a ceiling fixture. The camera was on Program mode and auto ISO and chose ISO 1600. I reshot on ISO 200 and it exposed fine now. If I try the same shot with my 5D MKIII the camera choose ISO 800 and the exposure looks better. I don't usually put my cameras on auto ISO and here's more reason not to.










Dec 12, 2013 at 06:57 AM
Paul Mo
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p.1 #5 · p.1 #5 · 70D bounced flash exposure bug (testers needed)


gwaww wrote:
Sorry, I am unable to post images.



Can we help with that?



Dec 12, 2013 at 07:09 AM
bipock
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p.1 #6 · p.1 #6 · 70D bounced flash exposure bug (testers needed)


My 70d underexposes by about stop when bouncing. I just dial in an extra 3/4 stop and move on.



Dec 12, 2013 at 09:26 AM





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