ETTL and old habits

[Tom W]

Here's a little demonstration of how my old habits have proven less than desirable when using E-TTL flash.

I have a habit of using the center focus point almost exclusively. I'm not sure of the evolutionary process that caused me to gain this habit, but it is a habit that may need breaking.

My practice is to first focus with the center square on the subject and hold the shutter button halfway down. This locks the focus and allows me to frame the picture without losing my chosen focus point. I then frame my subject and release the shutter.

That works well in non-flash situations. It allows me to choose, without any doubt, what I intend to use as my focus point (pre-focusing in manual might achieve the same result). But, as the following pictures illustrate, it isn't necessarily the best approach for E-TTL flash.

http://home.comcast.net/~trwilk3/Images/CenterETTL.jpg

In this first picture, I set my center focus point on the male figure, then pressed the shutter halfway to lock focus. I then recomposed to include the female in the picture. However, when I did so, I moved the active focus point over the bright window between the two primary subjects.

This doesn't please the E-TTL system. It doesn't lock on the subject upon which I've acheived pre-focus, but instead follows the location of the active focus point at the time of exposure. So, the flash considered the brightness of the window in its interpretation of how much flash it should provide. The result is the dark image you see above.

http://home.comcast.net/~trwilk3/Images/RightETTL.jpg

Now, in the second image, I've changed my tactics. Instead of pre-focusing with the center point and recomposing, I moved the focus point to the farthest-right focus square in the camera (which sits right about on the male's neck). Then I simply composed and shoot. Since E-TTL exposes based on the active focus point, it exposed the flash properly this time and provided enough flash to properly illuminate the subject.

A couple of glaring (pardon the pun) solutions present themselves readily - let the camera choose the focus point. I'm admittedly afraid of this approach, but I don't really have any grounds for such fear. To me, it just introduces another variable into the equation. I'll be experimenting with this approach soon.

Another solution (duh) would be to readjust the blinds so that the brightly-lit outdoors did not have such a strong influence on my pictures. This was a matter of laziness on my part.

My next approach will involve exposure lock. It doesn't appear that exposure and focus lock can share the same button, so I may have to learn a new habit - pressing the "*" button to lock exposure. Perhaps that will be the subject of my next big topic whenever that happens. :)

[Cadwell]

Good examples :)

I may be missing the point here (it happens quite a lot) but I don't get why you are looking for "A couple of glaring (pardon the pun) solutions"... it seems to me the technique you used for the second picture worked very well. If that works, why do you need other solutions? :?

[dtrayers]

I was a center point focus person and used FEL a lot until I started using the 7 focus points again. I just make sure the selected point(s) are on the subject(s). Even without using FEL I get more consistant results.

[PacAce]

Tom,

If you are using a flash, the focus lock and the exposure lock for the flash ARE different buttons right from the get-go. Use the shutter release button pressed halfway for the focus lock and use the "*" button for the flash exposure lock. Press the shutter release halfway first to get the focus lock, then press the "*" to get the flash exposure lock and then recompose and depress the shutter fully.

But moving the focusing point as you stated works well, too. Half a dozen of one and 6 of the other... :)

I usually use the moving AF point but there are times when FEL works better like when the AF point isn't in the frame.

[Tom W]

Good examples :)

I may be missing the point here (it happens quite a lot) but I don't get why you are looking for "A couple of glaring (pardon the pun) solutions"... it seems to me the technique you used for the second picture worked very well. If that works, why do you need other solutions? :?

Actually, my point was more to start a discussion than anything.

However, if there is a problem, then it is that I don't trust the camera to make the right selection of focus points, and I think its a little cumbersome to constantly be adjusting the selected point based on where I want the subject in the picture. In the example I used, manual selection was a good choice because the subjects were essentially sitting still for me. But in an atmosphere where people are constantly milling about (such as parties and receptions), things need to move much faster than that.

[Tom W]

I was a center point focus person and used FEL a lot until I started using the 7 focus points again. I just make sure the selected point(s) are on the subject(s). Even without using FEL I get more consistant results.

Perhaps I need to get over my fear of automatic stuff (I still prefer a manual transmission as well). Has the 7 point auto-focus been reliable for you?

[Scottes]

Good point to remember when I flash in a bright environment. Thanks for the tip and example.

Now I wonder what happens when 2 or 3 sensors confirm focus?

[defordphoto]

Good point to remember when I flash in a bright environment. Thanks for the tip and example.

Now I wonder what happens when 2 or 3 sensors confirm focus?

The camera and flash both explode simultaneously from overload.

[Cadwell]

Actually, my point was more to start a discussion than anything.

However, if there is a problem, then it is that I don't trust the camera to make the right selection of focus points, and I think its a little cumbersome to constantly be adjusting the selected point based on where I want the subject in the picture. In the example I used, manual selection was a good choice because the subjects were essentially sitting still for me. But in an atmosphere where people are constantly milling about (such as parties and receptions), things need to move much faster than that.

OK... I see. I'm with you in terms of not trusting the cameras choice of AF point. Maybe that's because I've worked in IT for years and just don't trust computers :lol: However, when I first got the 10D I "let it do it's own thing" for a few shots and was not stunned by the results. I was getting maybe 50% in focus. Switching to the center focus point has given me much better results. I have had some decent results using exposure lock... that seems to work as long as you don't faff about too much after locking the exposure. I think it times out?

[Tapeman]

What kind of transmission does your 10D have? :?:

What if you use custom function 4 (as I do)? When you press the shutter release exposure is set but it does not alter focus which you have set using the * button.

I don't know if the 10D has that function available. If it does try it you might like it. I find it very usefull especially in AI servo.

[rodbunn]

I disagree with moving the "active" point to fit over the "right" place
in the photo for exposure (and flash exposure)... How can you get
that active point in the right spot every time? I feel the ONLY way to
shoot is with the exposure lock. Place the center spot over the EXACT
place you want to use for exposure, then put put the center spot over
the focus place (push the shutter halfway to focus), then recompose.
This is MUCH easier then trying to make a "point" fall right over the
exact place to meter off of..... AND much more consistent..... for multiple
shots, just keep the lock pushed and fire away... very consistant that way.

Rod

[Tom W]

I disagree with moving the "active" point to fit over the "right" place
in the photo for exposure (and flash exposure)... How can you get
that active point in the right spot every time? I feel the ONLY way to
shoot is with the exposure lock. Place the center spot over the EXACT
place you want to use for exposure, then put put the center spot over
the focus place (push the shutter halfway to focus), then recompose.
This is MUCH easier then trying to make a "point" fall right over the
exact place to meter off of..... AND much more consistent..... for multiple
shots, just keep the lock pushed and fire away... very consistant that way.

Rod

Keep in mind that non-flash exposure is not tied to the focus point. That said, I agree - it isn't always practical to move the focus point around for each picture. If the subject is going to stay in one place for a while, it makes sense. But moving around, that becomes cumbersome quickly.

One question about flash exposure lock - when you set it with the "*" button, does it let out a pre-flash at that time? I would think that would be annoying to the subjects.

[Cadwell]

One question about flash exposure lock - when you set it with the "*" button, does it let out a pre-flash at that time? I would think that would be annoying to the subjects.

Yes, it does.

[nosquare2003]

I learnt from Rob Galbraith forum:

http://www.robgalbraith.com/ubbthreads/showflat.php?Cat=&Number=137317&page=&view=&sb=5&o =&fpart=1&vc=1


It's worth reading.

[drisley]

When using manual mode, does the exposure meter always use the center focus point, or the active focus point on the Rebel?

[dtrayers]

In manual mode it's always center-weighted.

[drisley]

Doh, I knew that too.

Never had my coffee today.

Thanks dtrayers.

Doesn't it switch to partial metering when you use exposure lock, even in manual?
If so, does the partial metering use the focus point?

I read the manual, but cant remember that exactly. And I have my manual stored neatly in my Rebel box, packed away. :)

[nosquare2003]

Hi drisley and dtrayers

It doesn't work like that. Please read my above link while I cannot explain better than that. Anyhow, I'll try:

1. The flash metering is biased on active focus point.
2. When no focus point is selected, like manual focus or setting CF4, the metering is evenly weighted by the 35 zones
3. FEL - metering is based on partial metering in centre
(Another thread in Rob Galbraith forum:
http://www.robgalbraith.com/ubbthreads/showflat.php?Cat=&Board=UBB8&Number=192346&Forum=A ll_Forums&Words=metering%20fel&Searchpage=0&Limit= 25&Main=191872&Search=true&where=bodysub&Name=210& daterange=0&newerval=&newertype=&olderval=&olderty pe=&bodyprev=#Post192346

I'm sorry if it is odd to quote from another forum.

[GonzoMan]

Hey Tom - great post!

I'm new to the 10D (been shooting Nikon for 15 years). This camera is quite a different animal than any of those Nikons that I've used for years.

What part of Tenn are you in? I'm from Memphis but live in San Diego now! Would never think of leaving this place - the weather is incredible 8)

Dean*

[dtrayers]

Hi drisley and dtrayers

It doesn't work like that.

Yes, your quite right, in when using the flash the camera will always bias the active focus point(s). I was referring to non-flash mode. Sorry, I forgot the thread topic...

At any rate, earilier in this tread it was mentioned that in non flash mode the exposure is not tied to the focus points. That isn't the case, at least in evaluative metering mode.

Check out the "Getting a Good Exposure" lesson at this link:

http://www.photoworkshop.com/canon/lessons_16-20.html

I've tested it and the article is correct. In evaluative metering mode, exposure is biased towards the active focus point(s).