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Canon XL1S / XL1 Watchdog
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Old January 26th, 2002, 11:02 AM   #1
bingalls
 
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More questions on white balance

I have read the threads on white balance but have a few more questions. I have a regular old XL1 and am wondering:

1) Are people actually using the two additional presets other that fully auto (A) & manual (i.e. indoor and outdoor mode)? If so when? What about using the indoor setting in "spotlight mode"? Other uses?

2) What exactly is the baseline setting used by the Auto circuitry? Is it based on an 18% grey bounce standard or what and under what kind of light? Can it be adjusted or does that require a trip to the factory?

3) If you manually set your white balance, lock exposure, shoot a bit; and then go to Auto due to lighting changes that have occurred are your manual settings lost?

4) Finally, am I correct that the only difference in white balance between the XL1 and the XL1s is the ability for the latter to store some additional manual settings (beyond the presets) for easy access? Do they both use the same Auto (A) circuitry?
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Old January 26th, 2002, 11:27 AM   #2
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>> Are people actually using the two additional presets other that fully auto (A) & manual (i.e. indoor and outdoor mode)? If so when? What about using the indoor setting in "spotlight mode"? Other uses?<<

In response to this question, I used the Indoor setting to film a whole production of Romeo and Juliet (set in Shanghi 1930), purely because I had no time to set the manual white balance.

In the end the shots came out pretty good, maybe a little bit red, but it added to the visual style of the production. (short clip can be found on my web site URL: http://www.videoproduction4u.tv, and click on Promotional)

The white balance can be used as a filter, making pictures blue, reddish or natural, by adujusting the different setting.

Hope this helps,

Ed Smith
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Old January 26th, 2002, 02:52 PM   #3
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1) I need to do multiple white balancing in one "swoop," so it is handy, but not always necessary.

2) I don't know, but 18% sounds fairly likely, then again Canon favors red, so I wouldn't doubt they might have a slightly different preference for exposure, too. They do use a type of matrix metering which is better than just a flat, or center-weighted 18% reference.

No need to adjust it. That's where the exposure compensation dial (if in auto) comes in so well. If you like it hot, just dial in an extra click or two, if you like it darker, down....

If you shoot in manual, just keep the meter from being centered (which indicates proper exp. according to the meter).

I generally shoot someone with some white in the frame so I look for zebra stripes to barely (to moderately) appear. I also set the zebra stripes to 90 because I feel that @ 90 (I think your xl1 is set to 100), the image is white with just a touch of definition left. Therefore, for me, I shoot for that, and let everything else fall where it will.

I think the black level setting could also be adjusted on the xl1s, to make an overall shift.

3) Unless the internal battery is dead, your wt. bal settings are saved until reset.

4) I'd assume the "A" circuitry to be similar, but ??? I do like the presets for both wt. bal. and custom presets. It's nice to have some control of sharpness and the like. I guess the new 1S is a bit better in low light. I got a lot of noise, but shot this one scene at +30dB of gain and GOT THE SHOT. People are still amazed (not the hyper critical ones, like we here, but Avg.Joe)!


Are you encountering specific situations that through you off? Could you be more specific to your trouble?

For ex:
I shoot a guy dressed in white/black against a light yellow-colored wall. I know that the meter is going to be thrown off, so I look for things I know to be true... things like white and zebra striping. If he's wearing white, I know I'll have to over expose according to the meter until the zebra starts. Reverse is true for if he's in black... I'll have to dial it down, according to the meter until his face is way out of the zebra.

The Yellow wall, makes the color balance off a bit, hence, manual wt. balance.
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Old January 28th, 2002, 11:47 AM   #4
bingalls
 
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"No need to adjust it (white balance circuitry under auto). That's where the exposure compensation dial (if in auto) comes in so well. If you like it hot, just dial in an extra click or two, if you like it darker, down.... " So from this are you suggesting that the AE shift knob is actually adjusting white balance? This brings up another interesting point. Exactly what is the AE Shift doing. I find I use it quite often to eliminate zebra stripes along with gain and white balance changes. Maybe I'm getting in my own way?

And a related question: If you are in Auto, Tv or Av mode and you push the Exposure Lock button to see your settings, with the AE shift in play are you actually seeing the settings that you are shooting or is there an override in effect?

Thanks
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Old January 29th, 2002, 01:42 AM   #5
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re: "no need to adjust it"
I was thinking that Q #2 was about the meter's calibration, not the Wt. Bal. Perhaps it's my mistake.

The nutty thing about my 1S, is that if you have the gain set to auto and the scene is made up with dark objects, even in "full" manual, the circuitry can still try to boost the gain to make the scene "correct" according to the cam's meter.

AE shift is like tinting. Things are still in auto form, but you are tinting the exposure more to your liking ( and often to keep the image in check, as you just mentioned...meters are not foolproof). It's like shifting the film speed dial on a 35mm camera. The trick is knowing under what circumstance is the meter going to be thrown for a loop where the AE shift comes in handy.

Say you are shooting in a park but there are lots of dark trees that will try to make your cam overexpose a bit. So, you dial in -.5...looks better. But now the sun goes behind a cloud. If you are in auto and using the shift function, your scenes should have about the same density (contrast might be different, but 1st things 1st).

You could shoot in manual. You meter the scene, underexpose by .5 stops. Exactly the same SS and f/stop settings (if you were to read the data code on playback as before). But now if the sun goes away, you must make the adjustment manually. Oops, sun's out again.......So AE shift is a cool feature.

My ASSUMPTION is that once you lock an exposure, it's locked. It shouldn't matter what is dialed in prior to locking it.
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Old January 29th, 2002, 01:29 PM   #6
bingalls
 
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Sorry.....I'm still a bit confused.......

here's an example: Let's say you are in Av mode. Previously you have manually set the white balance, and moved the gain to -3db (I have an XL1 not an XL1s). Finally you moved the AV shift to tweak the scene so it was "just right". You then flip the Exposure lock on and off merely to verify what settings (i.e. shutter & apeture) you are using . Lets say it says 1/60 at F 4.0. So you now believe you are running with your own white balance setting, at a gain of -3db, with a shutter of 1/60 and an apeture of F4.0. Yet the AE shift is in play. So what has it done? Subtly affected all these parameters? Just the gain and white balance? What? Anyone care to comment?

Thanks
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Old January 29th, 2002, 02:55 PM   #7
 
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to the best of my knowledge:
1-ae shift changes the correct exposure setpoint in software. In other words, it resets what it thinks is a correct exposure without affecting white balance.
2-white balance shifts the hue of the colors, very slightly....not an exposure related parameter
3-gain shifts the sensitivity of the detector to light without shifting white balance. this is equivalent to changing the ASA rating of film. with autogain on, the camera will automatically boost gain when it hits max open aperture and minimum shutter speed. gain boost is accomplished by increasing/decreasing the voltage across the detector. The detector works most optimally at the design voltage equivalent to zero gain. as you increase the voltage(gain) the detector becomes more sensitive but you also increase what's called the detector noise. detector noise is what you see as white specks on a black backround, AKA "grain".
4-as luma values decrease(b&w intensity) in the scene, the detector also becomes less sensitive to the chroma(color), therefore, it begins to look like it is losing saturation(actually it is)...there is, however, NO color shift.
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