Urgent bounce flash question 760D owners

WilbaW wrote:

walkaround wrote:

WilbaW wrote:

walkaround wrote:

See my response in the 70D forum. You have done zero research to understand what you are doing wrong (yes, it is user error). The 70D works exactly the same for bounce flash metering as all the other advanced Canon cameras, which 2 minutes on Google would have shown you.

How do you explain this? - "If I flash exposure lock on the subject before snapping the bounce flash picture with the 70D, all the photos are exposed perfectly. If I don't FEL before snapping the photo, they are all very underexposed."

Because FEL uses an entirely different method of metering the subject.

70D manual

It's metering the subject off the center zone, I hope everyone realizes that.

Which words say that, and what else do I need to know to interpret them that way?

"Aim the viewfinder center over the subject where you want to lock the flash exposure, then press the <*> button."

And when not using FEL, Evaluative E-TTL is metering the whole scene:

When you press the shutter button, the ambient light is metered by each sensor. Then a pre-flash fires and this is also metered by all the sensors. The ambient and flash readings for each sensor are then compared. The area of the scene that shows a significant difference between the readings is the area where the subject is most likely to be. This is because the main subject is likely to be closer to the camera than the rest of the scene and will reflect more of the flash. However, if the difference between the two readings is significantly high, the camera will ignore this area on the basis that the flash is being reflected back to the camera by a very shiny surface, such as a mirror. The pre-flash meter readings from accepted areas is weighted and averaged. It is then compared with the ambient light reading before the main flash output is calculated and stored in memory for the exposure. If the lens is able to provide distance information, this is used to determine the closeness of the subject and any highly reflective areas relative to the background. This information is used to refine the flash exposure. The result is better flash exposure for difficult subjects, such as white wedding dresses.

I'm not seeing what you're claiming is said there. How do you know that FEL doesn't use evaluative metering?

The requirement to point the center zone at the subject.

More details here:

http://cpn.canon-europe.com/content/education/infobank/flash/flash_exposure_lock_and_compensation.do

"To make an FEL reading you bring a mid-tone subject area to the centre of the viewfinder and press either the exposure lock or flash exposure lock button (varies with camera). The flash fires and a reading is taken without an exposure being made. This reading is held for 16 seconds while you recompose the image and take a picture."

And if we look at the Troubleshooting section of the 430EX II manual, we see the very first point about underexposure mentions reflective objects. (also warns about HSS and range decrease)

Err... you think that the problems reported with the 70D are because they have a mirror in the shot?

Err... I'm explaining why using FEL gives a different result than not using it. There are no "problems" reported that are unique to the 70D. The same "problems" were reported by 5D2 and 5D3 owners as well (among other models, as noted). You don't find that to have any bearing on this discussion?

I can't explain (yet) why it seems to work differently in Rebels. They use E-TTL II also, and should behave the same, although they could be using a different algorithm and we would never know. It's entirely possible that, as an entry-level camera, it is making assumptions about flash output that are not deemed appropriate for the enthusiast and pro models.

Sure, but what evidence do we have that they do behave differently? What differences are observed?

Every thread has a common theme: "my Rebel took perfectly exposed bounce photos... my 5D2, 5D3, 6D, 1D2, 1D3, 50D, 60D, 70D shots are always underexposed, when using bounce flash (with a sto-fen... lightsphere... etc)."

There are a lot of variables, which of course can be further disrupted by modifiers, room color, room size... it's a complex dance. It's kind of absurd to expect to never use FEL or FEC, and receive perfect exposures in all use cases.

Sure, but I don't hear anyone saying they are expecting that in reports about the behaviour of the 70D.

Then you're not reading the posts/rants/Nikon commercials in these threads (and on dozens of other sites, over the last decade).

I haven't specifically tested this lately, but in my experience you get similar brightness with or without FEL, in evaluative or CWA, with the flash is direct or bounced. Not "very underexposed" without FEL as reported for some 70Ds. That's not normal.

Do you see a single example photo in this thread, or any other on this topic? Neither do I. Do you see detailed steps to reproduce? Why assume that your shooting conditions are representative of all use cases? I don't see this "problem" either, but I'm bouncing in a normal sized white room, without modifiers, in Manual exposure mode, with a subject only a few feet away (usually).