MF & Metering

[aam1234]

From what I understand, the focus point selected is used for metering (more weight in Evaluative). But what if you are using manual focus. Where the more metering weight will be. And what about using AE lock in that situation.

Hope I didn't confuse you much. Thanks.


Edit to clarify: these are the things one faces when doing macro.

[PacAce]

Based on my observations with the 10D and the 1DmkII (your mileage may vary depending on your camera), when the camera is set to Evaluative and the lens is switched to MF, the camera will use the Center-weighted Average metering.

What surprised me was the behavior of my cameras when using AE lock. With the 10D, using AE lock did not alter the metering mode selected. For example, if I had Evaluative selected, the camera used the same metering mode when using AE lock. However, with the 1DmkII, whenever I used the AE lock, the camera used the CW Average mode, regardless of the metering mode the camera was actually set to. So, even though the 1DmkII was set to Evaluative, for example, when I pressed the "*" button for AE lock, the metering switched to CW Average metering mode.

You should just try it out for yourself to see how your camera behaves. :)

Note: I set my C.Fn-04 to 0 for this test since it's usually set to 3

[aam1234]

"Based on my observations with the 10D and the 1DmkII (your mileage may vary depending on your camera), when the camera is set to Evaluative and the lens is switched to MF, the camera will use the Center-weighted Average metering."

That's good news. But just to clarify, which focus point does it use for CWA do you think. Is it the center point.

"What surprised me was the behavior of my cameras when using AE lock. With the 10D, using AE lock did not alter the metering mode selected. For example, if I had Evaluative selected, the camera used the same metering mode when using AE lock."

Wow, that's very strange. What's the point of AE lock then.

"However, with the 1DmkII, whenever I used the AE lock, the camera used the CW Average mode, regardless of the metering mode the camera was actually set to. So, even though the 1DmkII was set to Evaluative, for example, when I pressed the "*" button for AE lock, the metering switched to CW Average metering mode."

This is how I understand how it's supposed to work.

Note: I set my C.Fn-04 to 0 for this test since it's usually set to 3

[PacAce]

"Based on my observations with the 10D and the 1DmkII (your mileage may vary depending on your camera), when the camera is set to Evaluative and the lens is switched to MF, the camera will use the Center-weighted Average metering."

That's good news. But just to clarify, which focus point does it use for CWA do you think. Is it the center point.

In CWA mode there is no AF point that is used. The metering is read over the entire viewfinder (except for along the edges) with emphasis on the central part of the viewfinder and hence the name for this mode.


"What surprised me was the behavior of my cameras when using AE lock. With the 10D, using AE lock did not alter the metering mode selected. For example, if I had Evaluative selected, the camera used the same metering mode when using AE lock."

Wow, that's very strange. What's the point of AE lock then.

Actually, this is how I would expect AE lock to work. It should maintain the same metering mode that you have selected on the camera. The purpose of AE lock is so that you can position the camera to get an exposure reading and lock it, and then reposition to focus and take the picture.


"However, with the 1DmkII, whenever I used the AE lock, the camera used the CW Average mode, regardless of the metering mode the camera was actually set to. So, even though the 1DmkII was set to Evaluative, for example, when I pressed the "*" button for AE lock, the metering switched to CW Average metering mode."

This is how I understand how it's supposed to work.

With the DRebel, I think, instead of using CWA, it uses partial metering when using AE lock. I guess this is because with the DRebel, there is no way to select the meterming mode you want to use.

[aam1234]

In CWA mode there is no AF point that is used. The metering is read over the entire viewfinder (except for along the edges) with emphasis on the central part of the viewfinder and hence the name for this mode.

Opps, confused the CWA with the more weight the center point has relative to the other points.


Actually, this is how I would expect AE lock to work. It should maintain the same metering mode that you have selected on the camera. The purpose of AE lock is so that you can position the camera to get an exposure reading and lock it, and then reposition to focus and take the picture.

Of course, and one only has 4 secs to do so, otherwise it goes back to the original mode that the cam was on. Maybe I'm missing something.

The original question was about how the "*" works on MF, since there is no focus point active.

With the DRebel, I think, instead of using CWA, it uses partial metering when using AE lock. I guess this is because with the DRebel, there is no way to select the meterming mode you want to use.

Haven't used the Drebel for a long time, so I don't know how it works.

[PacAce]

The original question was about how the "*" works on MF, since there is no focus point active.

In MF mode, at least for the 10D, using the "*" button for AE lock switches the metering to CWA and no AF point is used to weight the metering.

I guess an easier way to say this is that whenever the focusing is switched to MF, metering used becomes CWA, even when using AE lock.

[aam1234]

Got it! Thanks Leo.

[Titus213]

Hmmm, very interesting indeed. My manual for the Drebel explains that holding the DOF preview button enables AE lock. It doesn't say which metering mode is used or if I can shoot while holding the DOF preview. I can't even think of how I would go about determining this. Any suggestions?

[PacAce]

Hmmm, very interesting indeed. My manual for the Drebel explains that holding the DOF preview button enables AE lock. It doesn't say which metering mode is used or if I can shoot while holding the DOF preview. I can't even think of how I would go about determining this. Any suggestions?
Just taking an educated guess, since I don't have a DRebel to play with, I think that when you use the DOF preview, it'll be just like pressing the shutter button halfway, and will maintain the same metering mode and AF point, if used. You can tell by keeping your eyes on the shutter and aperture settings. The values shouldn't change between half pressing the shutter button and pressing the DOF preview button if what I said is true (there may be a slight fluctuating of the readings due the reading being just borderline of two settings). If the metering does change when using the DOF preview button, then you'll see a larger change in the shutter and/or aperture settings.

BTW, when doing the above test, the test should be set up so that the exposure determined by using Evaluative mode is different from that of using CW-A or Partial mode. A good subject for this is a blank white wall with a blank lens cap tape to the wall. The lens cap in the viewfinder should be large enough to just fill the center partial metering circlie in the viewfinder.

[Titus213]

What do you want me to do, actually get up and check something? OK, OK - but first I did try the preview button and it not only worked (mechanically) as the AE lock but also let me maintain the settings with a half pressed shutter button after releasing the DOF preview. I went from a black screen TV (off) to my PC monitor (on) with metering/DOF preview instituted on the TV. The reported exposure setting and focus did not change. Now to get up and finish the test...

[Titus213]

Turns out I didn't have to get up after all. It was all within reach. The switch to partial metering with the AE lock does NOT happen with the DOF preview button. If I put the lens cap in the center of the viewfinder, covering the central focus points, press the shutter button half way I get a reading that changes dramatically when I press the AE lock button. This shift does not occur with the DOF preview button. It sounded almost too good to be true since I find the DOF preview button to be more convenient than the AE lock button. Must be the size of my hand or something.

[PacAce]

Turns out I didn't have to get up after all. It was all within reach. The switch to partial metering with the AE lock does NOT happen with the DOF preview button. If I put the lens cap in the center of the viewfinder, covering the central focus points, press the shutter button half way I get a reading that changes dramatically when I press the AE lock button. This shift does not occur with the DOF preview button. It sounded almost too good to be true since I find the DOF preview button to be more convenient than the AE lock button. Must be the size of my hand or something.
Don't forget, though, that the two (DOF preview and AE lock) serve two different functions on the DRebel. The DOF preview allows you to lock the exposure using whatever metering mode you have set but it's primary purpose is to get an idea of what the DOF is going to look like with the aperture selected. The AE lock is to make it easier to just get a reading from the center part of the viewfinder for really difficult lighting situations. For example, a brightly backlit situation would call for locking exposure from the subject using partial metering or the AE lock. If you tried that using DOF preview, you would end up with a dark subject unless you pointed the camera somewhere without the strong back lighting when you press the DOF preview button.

[Titus213]

Don't forget, though, that the two (DOF preview and AE lock) serve two different functions on the DRebel. The DOF preview allows you to lock the exposure using whatever metering mode you have set but it's primary purpose is to get an idea of what the DOF is going to look like with the aperture selected. The AE lock is to make it easier to just get a reading from the center part of the viewfinder for really difficult lighting situations. For example, a brightly backlit situation would call for locking exposure from the subject using partial metering or the AE lock. If you tried that using DOF preview, you would end up with a dark subject unless you pointed the camera somewhere without the strong back lighting when you press the DOF preview button.

Understood. The manual indicated that DOF preview was AE lock. After 3 months I'm still getting used to the controls on the camera and find it a bit difficult to 'get it all together'. It will come. Thanks for the help. I will undoubtedly be back for more.

[PacAce]

Understood. The manual indicated that DOF preview was AE lock. After 3 months I'm still getting used to the controls on the camera and find it a bit difficult to 'get it all together'. It will come. Thanks for the help. I will undoubtedly be back for more.
Sorry for being so confusing. I should have said "using the AE Lock button" insead of just plain "AE lock" because, yes, the DOF preview button also locks the AE.

[Bodog]

Since the lens is stopped down when the DOF preview button is pressed, it would seem to follow that the exposure is "locked". Also the manual specifies that the shutter button is pressed halfway at the same time, which normally also locks exposure.

[Titus213]

Since the lens is stopped down when the DOF preview button is pressed, it would seem to follow that the exposure is "locked". Also the manual specifies that the shutter button is pressed halfway at the same time, which normally also locks exposure.

Ah, yes, but the AE Lock button also switches the metering to Partial. DOF preview doesn't do that. A major difference proven (I think) by the test PacAce came up with and that I ran...