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:
But I'll provide a quick/executive summary of what we've found so far:
- Most 70D bodies appear to have this problem, although there are 1 or 2 people that it appears don't suffer from this problem
- When bouncing the flash relying on ETTL/ETTL-II for flash exposure, resulting pictures are 1-2 stops under-exposed
- To see this problem, you really need a fairly dark room...ensuring the flash is the primary source of light
- 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)
- We've been testing in all camera modes so far and the problem persists through all modes (even in fully automatic green box mode)
- 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.
- 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.
- I have also tested with three different flashes, and it appears the problem is independent of flash so far.
- 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)
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...