What EXACTLY does the rectangle on the LCD back measure?

This question is in regards to the Canon 6D EOS.

Obviously, focus and exposure. But what about white balance. (I'm thinking no.)

Thanks in advance,

Richard

 

Any chance of an image to which rectangle that you are referring to?

Gary

 

Hey, Gary,

No need for photo. (I'm talking about the rectangle that you can move around with the arrows in order to pick focus.)
Also, since posting this, I've empirically determined that this rectangle has nothing to do with white balance. It chooses focus and exposure only.

If you're wondering why this could be an important piece of information for photographers to have, read on. But I must warn you, this is a rather specific situation, and it may not have any bearing on the photographs you process. If you're still reading, tuck in:

If you're shooting jpegs, knowing this doesn't matter.
If you're shooting RAW and editing RAW, this doesn't matter.
However, if you're shooting in RAW, and using a plugin that converts the file format to something other than RAW (TIFF, in my case), then this bit of knowledge is all important.
The workflow for one of my freelance jobs involves making HDRs using 5 RAW files. The people I work for think the rectangle is picking white balance, but while training, and watching them process files, I noticed that after processing the RAW files into TIFFs (using a plugin in LR), they were still hunting around picking white balance for every setup!
This is bad for two reasons: 1) it's an obvious waste of time. 2) the time to pick color balance in this type of workflow is BEFORE you convert RAW to TIFF. As I'm sure you know, RAW files, being sensor data dumps, have great processing latitudes. If you need to make a shift in the white balance for a RAW file, you get great results. But once you turn that RAW file into a TIFF, you lose much of that processing latitude (it gets even worse for JPEGs).
Since altering my workflow, I've stopped having to hunt around for the correct white balance on every shot.
I'll give an example.
Say I take 10 setups of the same room. My boss would have me waste time directing the rectangle to a portion of white within the room (thinking the Canon is choosing white balance, as well as focus—the exposure component hasn't dawned on her). As you know, achieving focus on a white wall or ceiling is an exercise in frustration, as the camera hunts to lock focus. Instead, I quickly direct the rectangle to something it'll quickly grab focus on, preferably something with contrast but the bulk of which represents a tonal value closer to 20% gray than white. I then quickly shoot the room. Once the photos are in my darkroom software (I use LR for this job because that's what my boss requires; LR is not my first choice, but it is a highly competent program, and I have learned workarounds for many of its oddities that I perceive as shortcomings), I select the HDRs for the 10 setups (50 photos), choose the correct light balance from one shot, and then sync that white balance to the other 49 shots. I then proceed to all the other rooms using the same technique, picking the white balance from one shot in the room, and then syncing it to to all the other photos in that room. After processing the HDRs I end up with TIFFs with nearly dead on white balance. Do I still end up with areas of a room that need warming (near a window, say) or cooling (overly warm lighting), yes. But now I'm warming a cooling a TIFF photo that isn't already terribly out of white balance. As a result, I end up with more natural colors, and faster workflow.

All the best,

Richard

 

Took me a minute to figure out what rectangle you were talking about, the focus point.

 

Exactly! (well, it measures exposure as well as focus)

 

No your focus point doesn't measure exposure. That is done by the light meter and by what metering mode you are using.

 

Respectfully, I'm not seeing the behavior you describe. Example: I set the camera for aperture priority mode, I then set my camera on a tripod and aim a dark door in a white wall. I adjust the focus/exposure rectangle such that two thirds of the rectangle is on the dark door, and one third is on the white wall.
My shutter time for this example is 0.4 seconds. I then move the focus/exposure rectangle such that two thirds of the rectangle is on the white wall, and one third is on the dark door. My shutter time for this example is 0.3 seconds. If I compare the two resulting photos, side-by-side, one is darker; one is lighter.

If, as you suggest, the rectangle measured only focus, then this would not be the case.

However, as it clearly is the case, both focus and exposure are being measured by the rectangle.

You can watch this effect more simply if you point your camera at a subject with dark and light areas, and then move the rectangle to and from the dark and light areas. As you move the rectangle, the LCD will compensate on the fly—growing lighter and darker—as the camera alters the exposure.

 

the digic 5+ is probably your main point of interest in this, by locking in all settings in manual then freeing them up one at a time to perform various single tests should give you the answers you want.
have you tried blocking the metering assist beam etc to eliminate those.
think of the features of the camera like a room full of engineers being asked a question, unless you gag them all but one, they will all have something to say.
it also depends what functions the non imaging pixels do on the sensor as well, some are just focusers

 

I like your thinking! And thank you for your time and effort. Much appreciated! However, in this case, as the camera is mounted, I don't see how the metering assist beam comes into play. The only thing altered between the two shots is the placement of the focus/exposure rectangle. It's very clear: the rectangle measures and effects both focus and exposure. There's nothing left to figure out. It's a done deal.

 

https://www.imaging-resource.com/PRODS/canon-6d/canon-6dTECH.HTM

from a quick read it looks like the metering and focusing are done through the sensor (i dont know alot about how they work, just from your question and research)

 

You're right, of course. Speaking in literal terms, the sensors do the measuring. However, if you refer back to the tag line for this topic . . .

What EXACTLY does the rectangle on the LCD back measure?

. . . then you'll get straight to the point here at hand. As it turns out, the answer is focus and exposure. The genesis of this question was to find out if the rectangle had something to do with white balance. (One of my free-lance bosses says yes; and, not thinking this was correct, I sought out this forum for clues.) Since that time, however, I've figured it out. Hopefully, this exercise might be of some use to someone other than myself. The answer, BTW, to the question of whether or not the rectangle on the back of the LCD measures white balance is: no, it does not.

 

so what gauges the white balance for auto wb?

 

I don't know. But it's a safe guess that the sensor measuring white balance is using the entire photo, or a portion of the photo significantly larger than the little rectangle on the back of the LCD.

 

As a longtime user of gray cards, I'm in complete agreement with you. But I think bringing up gray cards for this topic is an unnecessary complication. It's real simple: the little white Focus/Exposure rectangle on the back of the LCD doesn't have anything to do with white balance. And it's easy to demonstrate.

Like most camera systems, not everything is in the manual. And as curious photographers, isn't that the fun of it?
(All of my camera manuals contain hand-written corrections and notations.)

 

have you tried blocking the metering assist beam etc to eliminate those.