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ExpoDisc Conversation with Diane Wallace

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Please... get a life. There is life beyond a Custom White Balance setting. geees!
pbleic said:
Deception in reporting of results doesn't necessarily mean you have
are biased by money. It means that you are not reporting your
results accurately, on purpose. This can be for many reasons,
including just plain ego, or an unwillingness to consider the
possibility that one is wrong.

When reporting testing results, it is DECPTIVE to report a
"perfect" result alone, without mentioning that every retest failed
to achieve this same result (until you are pushed to say this). And
then to continue to claim that your result was the unreproducible
one. Deceptive; no other word for it.
Mjack1957 said:
By the way... I don't lie or engage in deceptive practices. I'm
not selling Pringles lids on the side. :)
pbleic said:
Mjack1957 said:
pbleic said:
But, your posts suggest that you are still early in your learning
about photography:
http://forums.dpreview.com/forums/read.asp?forum=1031&message=7987867
http://forums.dpreview.com/forums/read.asp?forum=1031&message=7986740
In the learning vein, perhaps you might sit back a bit on this one
and read, reflect and learn a bit more about WB. Auto WB is pretty
mediocre on the DR. Much as I love the camera, this is true. Read
the review here and elsewhere. WB is especially poor with indoor
lighting. Your post, suggesting that AWB is "excellent in all
lighting & light temps that I've tried it in" suggests that you
either haven't really tried it in a lot of different lightings OR
you don't have a particularly critical eye YET about WB. If this
is the case, you surely will develop it as you work with the camera.

The $100 for the ExpoDisc (or so) is a lot for an amateur, and the
delta between it and a Pringles lid may not be so great in your
eyes. But many pros swear by the thing, saying that it has changed
the quality of their pictures and the speed of their workflow.
Don't buy one until you feel you need it. I dismissed it
completely until recently, and am still witholding complete
judgement until I get it and test it. But I read a LOT about it on
almost every pro forum and it seems excellent. And, I am at a point
in MY photography where I feel I can learn a LOT from listening to
pros and more knowledgable people.

Hey, it also might be helpful if you don't base your conclusions on
ONE test that, by your own admission, is NOT reproducible.

http://forums.dpreview.com/forums/read.asp?forum=1031&message=8071656 Any scientist knows that the first tenet of a "publishable" experiment is reproducibility. Anything less ranges from sloppy to fraudulent.
Mjack1957 said:
http://forums.dpreview.com/forums/read.asp?forum=1031&message=8071656
RATPhoto said:
I'm glad it is working for you but showing the tests shots would be
good (in the seperate thread you started).

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Paul

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Paul

------------------------------------------------
Pbase supporter
Photographs at: http://www.pbase.com/pbleic
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Copyright 2003, 2004 All rights reserved.
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Paul

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Photographs at: http://www.pbase.com/pbleic
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Copyright 2003, 2004 All rights reserved.
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Isn't it in this person's interest to promote the Expodisc and only release or report positive feedback about the product manufactured by the company she owns?

Why HAS this expodisc so suddenly turned into a holy grail and custom WB seemingly become the centre of the photographic experience? Some of us like the light just the way it is, thank you very much.

I'm sure for every pro that swears by the Expodisc, there's one who doesn't much care for it. Where are Diane Wallace's recountings of her communication with the latter sort?

regards.
 
phototakeouter said:
Isn't it in this person's interest to promote the Expodisc and only
release or report positive feedback about the product manufactured
by the company she owns?

Why HAS this expodisc so suddenly turned into a holy grail and
custom WB seemingly become the centre of the photographic
experience? Some of us like the light just the way it is, thank you
very much.

I'm sure for every pro that swears by the Expodisc, there's one who
doesn't much care for it. Where are Diane Wallace's recountings of
her communication with the latter sort?

regards.
Click to expand...
--

 
jasonh said:
There appears to be a mis-communicated aspect to using ExpoDiscs,
Pringles lids, grey/gray cards or indeed any other device for
setting WB. This mis-communication may lead to confusion,
inaccurate testing and general mis-understanding of the WB process
and associated tools.

It is often commented by some that they are testing these devices
by comparing the RGB values of the resulting shot taken with the
device in question. E.g. you see references to R 128, G 128 and B
128 and similar.

My understanding is that these tests are pretty useless by
themselves (unless they are taken in perfect white light, equally
balanced in all 3 channels, that has been tested with proper
equipment).

Neither an ExpoDisc nor a Pringles lid (which seem to be the most
preferred methods in these forums) - nor even the "holy grail"
gray/grey card - will give you exactly the same RGB values under
each set of shooting conditions.

This is the point of a reference WB device: it shows you (or more
to the point, the camera or the hardware/software tool you use
afterwards to process the shot) in which way the scene's lighting
was off from a 'true' WB. This allows you to correct the colour
cast and develop the shot as it looked to the human eye (which
automatically corrects for WB).

Thus if under tungsten lighting your device shows a perfectly
uniform distribution of RGB (say 112, 112 and 112) this does not
indicate a great WB device. Far from it! A decent WB device would
show the light as having the characteristic orange tint associated
with tungsten lighting (higher in Red channel, lower in Blue),
quantifying it correctly and then allowing you to compensate
correctly for it, giving you a decent true colour rendition.
Click to expand...
In reading these threads, I've been frustrated in a similar manner as you. The reference to Kevin Kubota observing equal RGB values using ExpoDisc to photograph the light from a table lamp was particularly disturbing.

David
 
... the question still arises in my mind as to the basic assumption that lies behind this whole subject. Is it desirable to "correct" the RGB levels of each photo to bring them into parity? Or put another way, does a correctly white-balanced photo necessarily have an average of its RGB values (or those from within 180 degrees of the centre of the photo) in exact balance? Maybe so, but this seems counter-intuitive to me.

--
DB
 
phototakeouter said:
Why HAS this expodisc so suddenly turned into a holy grail and
custom WB seemingly become the centre of the photographic
experience? Some of us like the light just the way it is, thank you
very much.
Click to expand...
I think you're being overly dramatic. I have the Expo/Disc. I use it every day. It works as advertised. That makes it worth its price. What else do you need to say?

As for 'liking the light just the way it is', I can't agree with you there. A camera sensor does not see light the way your brain does. And the normal white balance settings can't always adequately adjust for this.
 
jasonh213584 said:
Thus if under tungsten lighting your device shows a perfectly
uniform distribution of RGB (say 112, 112 and 112) this does not
indicate a great WB device.
Click to expand...
If I understand you correctly, you seem to be saying that people are taking expodisc reference shots and expecting the reference shots themselves to display 128/128/128 RGB values. This would be ridiculous, of course, as the reference shot should bear the "tint" of the ambient light source.

The "test" is to use the expodisc to take a CWB reference shot, then to apply that shot to a known "neutral" subject like a grey card, and verify that the grey card yields equal RGB values (not necessarily all 128, but close to each other).

Of course, if you're using a grey card to verify that the expodisc works properly, then it makes no sense to try to compare your results against use of a grey card (instead of an expodisc) for the CWB reference shot. In these "which works better" comparisons you necessarily have to just compare the end results with what you think looks best. This experiment needs to be performed "blind" for it to work properly, i.e. you should choose the best result without knowing at that moment which device was used to take the shot, otherwise your prejudices will take over (and "I just spent $100 on this thing" can lead to significant prejudice).

Ultimately, the job of the expodisc (or pringles lid) is just to "mush the light together" while assuring that there is no difference in colors passed through to the lens between the "with expodisc" and "without expodisc", i.e. that the expodisc is perfectly neutral in color.
-harry
 
David Barker91965 said:
... Is it desirable to "correct"
the RGB levels of each photo to bring them into parity?
Click to expand...
The purpose of white-balance is to produce an image of a subject that reflects how it would have looked if the subject had been photographed in perfectly "white light". In other words, that the colors in the image are accurate when compared to the reflective properties of the subject. In other other words, we're correcting the colors of the shot to compensate for the non-white ambient light available when the shot was taken.

Note, of course, that photographers often go to great pains to capture subjects in non-white light, particularly the oranges/reds of a sunset. So white-balance is only wanted when you want it, particularly in cases where the ambient light is unflattering (e.g. green flourescent lights in an office building).
David Barker91965 said:
Or put
another way, does a correctly white-balanced photo necessarily have
an average of its RGB values (or those from within 180 degrees of
the centre of the photo) in exact balance?
Click to expand...
There's no notion of "overall RGB balance" for the subjects in a picture. If you take a photo of a purple dinosaur, your image should be mostly purple. Anything that assumes a scene has an "average color" of white (including somebody trying to use an expodisc by pointing it at the subject instead of at the light source) doesn't make much sense to me.
-harry
 
The expodisc pointed at the purple dinosaur seems, perversely, to yield good results.

Maybe it's just me, but that makes me wonder "why?"

Answering my own question, I suppose it must be because the overall colour balance of an expodisc reference image is disproportionately more influenced by the brighter parts of a scene than the less bright parts of it, and these brighter areas in turn contribute most to the illumination and colour balance of the scene itself. I haven't worded this very well, but perhaps my meaning will be clear enough?

DB
hm said:
[snip]... If you take a photo of a purple dinosaur, your image
should be mostly purple. Anything that assumes a scene has an
"average color" of white (including somebody trying to use an
expodisc by pointing it at the subject instead of at the light
source) doesn't make much sense to me.
Click to expand...
--
DB
 
The point is that when you correct for "grey" you correct all of the other colors as well. It does not mean you get a grey color balance.

That's the problem with AWB, which assumes "middle grey" is what the average of the scene will be. Thus if you shoot a snowy scene, it comes out greyish.

By shooting a known grey card in the light situation, then the transformations to make the result match the known grey, is the same transformations that need to be applied to all colors.

The ExpoDisc is just a convenient tool to get such a reading.

Lee
David Barker said:
... the question still arises in my mind as to the basic assumption
that lies behind this whole subject. Is it desirable to "correct"
the RGB levels of each photo to bring them into parity? Or put
another way, does a correctly white-balanced photo necessarily have
an average of its RGB values (or those from within 180 degrees of
the centre of the photo) in exact balance? Maybe so, but this seems
counter-intuitive to me.

--
DB
Click to expand...
 
I think you've misunderstood my point.

The snow/grey problem is nothing to do with WB, by the way, it's simply an exposure and metering challenge. The camera wants to render near white as mid-grey unless you compensate.

Back to my question. When you shoot a scene with a grey card you have a known target to which you adjust. When you shoot with an expodisc you are in effect treating the 180 degree scene in front of the camera as a grey card. My question is, how do you know it is a balanced "grey card"? Actually, why would it be, except by coincidence?

DB
LeeBase said:
That's the problem with AWB, which assumes "middle grey" is what
the average of the scene will be. Thus if you shoot a snowy scene,
it comes out greyish.

By shooting a known grey card in the light situation, then the
transformations to make the result match the known grey, is the
same transformations that need to be applied to all colors.

The ExpoDisc is just a convenient tool to get such a reading.

Lee
David Barker said:
... the question still arises in my mind as to the basic assumption
that lies behind this whole subject. Is it desirable to "correct"
the RGB levels of each photo to bring them into parity? Or put
another way, does a correctly white-balanced photo necessarily have
an average of its RGB values (or those from within 180 degrees of
the centre of the photo) in exact balance? Maybe so, but this seems
counter-intuitive to me.

--
DB
Click to expand...
Click to expand...
--
DB
 
Yes, sure, but why? Why doesn't it lead to a reduction in "purpleness" in the final image? Or does it?

I'm asking about reflected light only. The sound theory and practice of incident light sampling are undisputed, at least here.

DB
LeeBase said:
LeeBase said:
The expodisc pointed at the purple dinosaur seems, perversely, to
yield good results.
Click to expand...
It does yield good results, and their website supports using the
disc in either way.

Only if you are using the ExpoDisc to set exposure will you need to
point it at the light source.

Lee
Click to expand...
--
DB
 
LeeBase said:
It does yield good results...
Click to expand...
The only problem with this theory (that pointing the expodisc at the subject is a proper and reliable technique) is that it makes absolutely no sense whatsoever.

The only observation I can provide to help explain why this appears to work is to remember that the expodisc pulls in light from a greater angle of view than the lens does, so while the lens may be framing a purple dinosaur, the expodisc is actually pulling in light from a far wider angle, maybe even a 180 degree hemisphere.
LeeBase said:
and their website supports using the disc in either way.
Click to expand...
I got the impression that the directions on the web site were written by people who had no clue what they were talking about. The last time I read them, the directions on the web site actually referred people to this web site if they needed any help, which was probably the best advice they had to offer.
-harry
 
hm said:
The only problem with this theory (that pointing the expodisc at
the subject is a proper and reliable technique) is that it makes
absolutely no sense whatsoever.
Click to expand...
I still don't understand your objection. The ExpoDisc produces an image that, for a given light source, tells the camera what "grey" should look like.

Then you tell the camera, use this picture for grey, and the camera does, which pulls all the colors into balance.

The color of the source light does not make a difference. It works with the sun, with all the various indoor light sources, with mixed light.

It's what the expodisc does to take WHATEER the source of light and come up with a "grey correcting" image.

But -- hey, I'm no Ansel Adams protoge'. If something works, and it shouldn't by your theory, and the fact that it works again and again, means there is something wrong with your theory (or your understanding of the theory).

Now, I wouldn't dare suggest that I could go toe to toe with anyone on light theory. But I can say that I and others have demonstrated that you can get good results with reflected light use.

What sort of test would you propose one of us try to prove your point?

Lee
 
David Barker91965 said:
The snow/grey problem is nothing to do with WB, by the way, it's
simply an exposure and metering challenge. The camera wants to
render near white as mid-grey unless you compensate.
Click to expand...
Use an expodisc and watch white become white again. The problem with snow is the same problem, the assumption that the camera makes that scenes are "middle grey".

Sure, you can compensate by increasing exposure.

And you can use the handy expodisc tool as well.
David Barker91965 said:
Back to my question. When you shoot a scene with a grey card you
have a known target to which you adjust. When you shoot with an
expodisc you are in effect treating the 180 degree scene in front
of the camera as a grey card. My question is, how do you know it is
a balanced "grey card"? Actually, why would it be, except by
coincidence?
Click to expand...
The expodisc diffuses the light to give you an image that is just as good (or better than) a grey card.

From their website:

ExpoDiscs work in conjunction with built-in sensors and software to instantly create an accurate white balance reference regardless of the light source (incident or reflective light, including all mixed light and flash) or the color of the subject (including close-ups, and subjects lacking very light objects or having one dominant color). The multiple facets of the prismatic lens (more efficient than a dome) collect multiple samples of light from 180 degrees, scrambling it to create an accurate average (in the correct proportion) of all light that contributes to subject illumination. A white diffusion disc provides even illumination across the full frame, and the appropriate color-correcting filters are sandwiched in-between during assembly to create units which are individually color-corrected to within 3% of being perfectly neutral. Each unit is provided with a card noting it’s precise color rating and density. No other commercially available product can provide this level of accuracy.

Lee
 
Well of course she's not going to publish negative reports, but that doesn't mean she's hiding anything. The thing does EXACTLY what it is advertised to do, so it's hard to imagine complaints from anyone who took the time to learn how to use it, unless it's a "good, but not worth the incremental improvement over a coffee filter" argument.

In case you're interested in a negative review, here's one:
http://www.the-digital-picture.com/Reviews/Wallace-ExpoDisc-Review.aspx

You will note the rigorous methodology that went into the review.
Mjack1957 said:
phototakeouter said:
Isn't it in this person's interest to promote the Expodisc and only
release or report positive feedback about the product manufactured
by the company she owns?

Why HAS this expodisc so suddenly turned into a holy grail and
custom WB seemingly become the centre of the photographic
experience? Some of us like the light just the way it is, thank you
very much.

I'm sure for every pro that swears by the Expodisc, there's one who
doesn't much care for it. Where are Diane Wallace's recountings of
her communication with the latter sort?

regards.
Click to expand...
--

Click to expand...
 
On the CompuServe PhotoForum back in early to mid '90s there was a never ending argument/feud between George Wallace and a well respected photographer, author who went by the name Ctein. George was defending his ExpoDisc which was built to the 18% gray 'standard' and constantly debating Ctein's claim that modern cameras and light meters were factory calibrated in the 12-13% range, not 18%.

All I'll say is George did not fare as well in the argument. Note, back then the ExpoDisc was only marketed as an film exposure tool, not as a color temperature tool. As one of the SysOps there George even sent me two in the 58mm size. I never tried them since my lenses at the time required 67-82mm sizes.
 
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