Help with Rebel Xti AE Lock and AE Lock/Shutter Custom function

[anjou]

I was trying out a few things mentioned in the book Understanding Exposure and

also wading through the Rebel Xti manual. I could use some clarifications from

the experts here.

 

The author suggested getting the camera close to the subject to meter, lock it

with AE lock, and then move back, recompose, focus and shoot the picture. So at

the time I am close to the subject, the is camera locking focus and exposure.

And when I move back and depress the shutter halfway, it is re-locking focus and

using the AE locked exposure. Did I get this right? When moving back, will

adjusting the focal length throw off the exposure (I have a constant aperture

zoom, so same aperture is available at all focal lengths). I have been trying

this technique with C.Fn-4 set to AF/AE lock, should I be setting it to AE

lock/AF? How often do you use this technique to shoot pictures? On a tangential

question, when do you use center weighted and partial metering?

 

Can somebody explain the C.Fn-4 settings? This is my interpretation (c.f. page 104):

 

0. AF/AE lock = Shutter button depressed half way is AF, AE lock button function

is AE lock

 

1. AE lock / AF = Shutter function is AE lock, AE lock function is AF. So it

inverts the function of the two buttons.

 

2. AF/AF lock, no AE lock = Use in AI servo mode. Shutter function is AF, AE

lock button is to lock AF. Exposure is locked when shutter is fully depressed.

 

3. AE/AF, no AE lock = Use in AI servo mode. Shutter function is AE, AE lock

function is to start and stop AF. Exposure is locked shutter is fully depressed.

 

Thanks.

Umesh.

[steve_parrott]

I am just going to give you the simple ways I approach this. When you move in close to the

subject to take an exposure reading, all you are doing is being sure the camera is

exposing for the SUBJECT, and not being thrown off by other lighting in the scene. Simply

use SPOT metering to do the same thing. Alternatively, if you move in and take a reading,

just take note of the readiing and set your controls MANUALLY to those readings. Then the

exposure is locked in regardless of how you recompose or move back or change focus

without having to deal with AE lock buttons and custom functions and such. I like to keep

things simple. Persoanlly, I have never seen any use for partial or center weighted

metering. I think it is splitting hairs that is of little use in the real world. Others may find

these modes useful, I am just saying that *I* never have. I either use MATRIX or SPOT

metering only, and set exposures manually when I want to be SURE they it not change. I

just cannot deal with all the buttons and custom function stuff.

[matias_orchard]

Reasonable advice, I guess.... but I would LOVE to know what is the actual use of this custom function.

 

Canon has updated its EOS site, and the tutorial is now much more comprehensive, although it does not touch custom functions... ;-(

 

 

Cheers,

[matias_orchard]

Took a small break, and found this:

 

http://creativekarma.com/ee.php/weblog/comments/custom_function_4_on_the_canon_eos_digital_rebel_xt_350d/

 

It explains very well how the CF4 works. I have to believe that it is the same thing for the XT/XTi/30D/40D. Someone please confirm this.

 

 

Cheers,

 

MO

[denny_wells]

I have a friend who uses either setting 1 or 3. Doing that, he gets his exposure information by pressing the shutter button, but gets his focus by pressing the button on the back with his thumb. He likes that because he can easily seperately control the focus and the exposure (which you may not want to set based on the same location).

 

I find those settings rather annoying, and I use the 0 setting. On the rare occasions where I need seperate focus and metering, I can get exposure with the shutter button, then lock that exposure with the button on the back and recompose and re-focus with the shutter button.

 

We are discussing a digital camera here - there's nothing to lose by trying each of the settings for several shots in different situations and see what works best for you.

[anjou]

Hi Matias, Excellent link. Now that I understand CF4 more, I am finding CF4-3 with AI Servo AF pretty versatile. It was easier for me to take pictures for me when AF and AE were separate buttons.