Expo Disc Review

Al Pacheco · Nov 23, 2002

It doesn't alter the colors at all.

And a neutral density filter would work just fine except you'd need to couple it to a diffuser of sorts and select the right ND factor...maybe a 0.9. But all that said, the Expodisc is very handy in certain situations where you need to take an INCIDENT light reading. And it must be treated as such.

I actually don't use it for white-balance. However, it is probably better than nothing in a pinch and is certainly more durable than a grey/white card.

The web site doesn't provide enough proper information as to how the thingy works. Too bad.

gary ng said:
My understanding of the custom white balance from the description
of using a white/gray card is that, the camera expect to see the
color cast from the surrounding light and only by measuring this
cast based on the assumption that the object(white card) that it is
shooting at is color neutral, it can detect the color cast and make
subsequent adjustment to photo taking in the same lighting
environment.

DavidP said:

The expo-disc is supposed to turn all colors into 18% gray.

gary ng said:

I confused you. My understanding of the Expo Disc and custom white
balance is that it is basically a very 'thick' filter of a 18%
gray. So say if the scene has a light source that end up with an
overall yellow bias, what the camera sensor see would be a uniform
yellow. If this picture is used to for white balance
correction(custom white balance), the camera just subtract this
amount of yellow from the actual picture taken.

So in theory, I can use a very dark ND filter(may be multiple of
it) to simulate the 18% gray.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

Don Schultz43010 · Nov 23, 2002

Hi Jan:

I read the review of the expo disc and on page two it said on a bright sunny day with the expo disc in place, pointed at the sun, your camera should meter f16 at 1/125. A piece of 20 lb. IBM multi purpose white paper will do the same thing. So does that mean that the expo disc is no better than a two cent piece of paper?
Don.

jan sanders said:
For perfect color on my D60 and D-30 I use an Expo Disc, end of story.
Much discussed here as well as WB issues. Now there is a review of
the Expo Disc available, you can find it here:

http://www.digitalfocus.net/sections/reviews/ColorManagement/Expodisc/Expodisc_1.htm

at the Digital Focus site.
Enjoy!

Jan Sanders
Los Angeles

gary ng · Nov 23, 2002

That is my thought too. The problem is that it is hard to find a piece of white paper that is true white(for measuring white balance) and expo disc is more durable.

However, at 50 dollars plus shipping(I lived oversea so it is 15), it is quite expensive for me.

Don Schultz said:
jan sanders said:

For perfect color on my D60 and D-30 I use an Expo Disc, end of story.
Much discussed here as well as WB issues. Now there is a review of
the Expo Disc available, you can find it here:

http://www.digitalfocus.net/sections/reviews/ColorManagement/Expodisc/Expodisc_1.htm

at the Digital Focus site.
Enjoy!

Jan Sanders
Los Angeles

Click to expand...

WalterK · Nov 23, 2002

gary ng said:
That is my thought too. The problem is that it is hard to find a
piece of white paper that is true white(for measuring white
balance) and expo disc is more durable.

Would we be just as well off with a Kodak 18% Gray card, which is white on the back? I carry the small one (4x5, I think) in the camera bag for setting the WB. What would be the advantage of the Expo-disk over this?

--
Walter K

Al Pacheco · Nov 23, 2002

I replied in another thread about my results with this method. I think it is worth trying. The Expodisc MUST be used properly or you might as well leave home without it.

http://www.dpreview.com/forums/read.asp?forum=1019&message=3829941

WalterK said:
gary ng said:

That is my thought too. The problem is that it is hard to find a
piece of white paper that is true white(for measuring white
balance) and expo disc is more durable.

Click to expand...

Would we be just as well off with a Kodak 18% Gray card, which is
white on the back? I carry the small one (4x5, I think) in the
camera bag for setting the WB. What would be the advantage of the
Expo-disk over this?

--
Walter K

gary ng · Nov 23, 2002

I would say convenience. With a white card, I need to have someone holding it. Other than that, a gray/white card should serve the job well.

WalterK said:
gary ng said:

That is my thought too. The problem is that it is hard to find a
piece of white paper that is true white(for measuring white
balance) and expo disc is more durable.

Click to expand...

Would we be just as well off with a Kodak 18% Gray card, which is
white on the back? I carry the small one (4x5, I think) in the
camera bag for setting the WB. What would be the advantage of the
Expo-disk over this?

--
Walter K

jan sanders77139 · Nov 24, 2002

gary ng said:
WalterK said:

gary ng said:

That is my thought too. The problem is that it is hard to find a
piece of white paper that is true white(for measuring white
balance) and expo disc is more durable.

Click to expand...

Would we be just as well off with a Kodak 18% Gray card, which is
white on the back? I carry the small one (4x5, I think) in the
camera bag for setting the WB. What would be the advantage of the
Expo-disk over this?

Click to expand...

No variations are possible with the EP, such as shadows, angle of card, reflections. Also as noted, white is not always white when you try and use paper or other things such as a wall etc. The EP is calibrated to exact standards and noted on every case. I don't know about everyone else but the reduction in work flow is priceless! The bet $50 I ever spent on camera equipment!

Jan Sanders

Joo · Nov 24, 2002

And... lets not forget, the grey/white card will fade over time. I just replaced my grey card about a month ago because it had faded. The custom white balance off of the faded grey card caused the photos to be too warm.

Joo

jan sanders said:
gary ng said:

WalterK said:

gary ng said:

That is my thought too. The problem is that it is hard to find a
piece of white paper that is true white(for measuring white
balance) and expo disc is more durable.

Click to expand...

Would we be just as well off with a Kodak 18% Gray card, which is
white on the back? I carry the small one (4x5, I think) in the
camera bag for setting the WB. What would be the advantage of the
Expo-disk over this?

Click to expand...

Click to expand...

No variations are possible with the EP, such as shadows, angle of
card, reflections. Also as noted, white is not always white when
you try and use paper or other things such as a wall etc. The EP is
calibrated to exact standards and noted on every case. I don't know
about everyone else but the reduction in work flow is priceless!
The bet $50 I ever spent on camera equipment!

Jan Sanders

--

Maybe one day I'll take a decent picture. In the meantime, I'll blame the equipment.
http://www.pbase.com/jchung/portfolio

Taz61703 · Nov 24, 2002

JohnM said:
I hold it in front of the lens & shoot an image pointed straight at
the light source(IE: straight in to the sun).

This is not really what the directions say, but it usually works
great.

If indeed the best results are obtained when the Expo Disc is used as an incident reading device, then this would seem to make it not very useful for on board (or on bracket) flash. (And btw, I agree that it seems to make sense to point it toward the light source.)

However, Jan's pictures that he's posted here previously and on the Expo Disc website seem to indicate that flash is where the Expo Disc excels. I guess that's part of the reason he keeps on insisting that the disc is best used as a reflective measuring device.

But personally, in my use of the Expo Disc I've never been able to replicate the same excellent WB when using flash that Jan demonstates...at least not on a consistant basis. And when the Expo Disc causes the shots to be off...I've found they are WAY off.

So that, coupled with the same lack of consistancy in non-flash shooting situations, keeps the Expo Disc in the bottom of my camera bag...which is too bad. I so wanted to like this little device and the convenience it provides. But I guess I should realize that there's no "free lunch" when it comes to a proper WB.

MikeA · Nov 24, 2002

JohnM said:
I hold it in front of the lens & shoot an image pointed straight at
the light source(IE: straight in to the sun).
This is not really what the directions say, but it usually works
great.

How could the Expo/Disc be effective unless it's used incident-meter-style? In a situation in which the photographer can't be in the subject position, how can he guarantee himself he's "measuring" the color temperature of the light falling on the scene -- as opposed to the lighting conditions at the camera position? I can't imagine how he could. Maybe I'm just missing something obvious about how this product is used...

Peter Sills · Nov 24, 2002

If you want to METER the scene then you want to use the ExpoDisc to turn your camera into an incident light meter by metering while aiming at the light.

However, if you want to use the ExpoDisc to determine proper WHITE BALANCE, then you would aim it at the subject, as the subject is being hit with not only direct light, but reflected light, and potentially more than a single light source.

Does this clear it up? It is invaluable for the D30 or D50 user. It is less important, though still quite helpful for the 1D/1Ds user as there is essentially a small ExpoDisc built into the camera (the reflected White Balance sensor on the outside of the camera).

Peter

Taz said:
JohnM said:

I hold it in front of the lens & shoot an image pointed straight at
the light source(IE: straight in to the sun).

This is not really what the directions say, but it usually works
great.

Click to expand...

If indeed the best results are obtained when the Expo Disc is used
as an incident reading device, then this would seem to make it not
very useful for on board (or on bracket) flash. (And btw, I agree
that it seems to make sense to point it toward the light source.)

However, Jan's pictures that he's posted here previously and on the
Expo Disc website seem to indicate that flash is where the Expo
Disc excels. I guess that's part of the reason he keeps on
insisting that the disc is best used as a reflective measuring
device.

But personally, in my use of the Expo Disc I've never been able to
replicate the same excellent WB when using flash that Jan
demonstates...at least not on a consistant basis. And when the
Expo Disc causes the shots to be off...I've found they are WAY off.

So that, coupled with the same lack of consistancy in non-flash
shooting situations, keeps the Expo Disc in the bottom of my camera
bag...which is too bad. I so wanted to like this little device and
the convenience it provides. But I guess I should realize that
there's no "free lunch" when it comes to a proper WB.

--
Peter Sills
Digital Focus
http://www.digitalfocus.net

jan sanders44123 · Nov 24, 2002

Taz said:
JohnM said:

I hold it in front of the lens & shoot an image pointed straight at
the light source(IE: straight in to the sun).

This is not really what the directions say, but it usually works
great.

Click to expand...

If indeed the best results are obtained when the Expo Disc is used
as an incident reading device, then this would seem to make it not
very useful for on board (or on bracket) flash. (And btw, I agree
that it seems to make sense to point it toward the light source.)

However, Jan's pictures that he's posted here previously and on the
Expo Disc website seem to indicate that flash is where the Expo
Disc excels. I guess that's part of the reason he keeps on
insisting that the disc is best used as a reflective measuring
device.

But personally, in my use of the Expo Disc I've never been able to
replicate the same excellent WB when using flash that Jan
demonstates...at least not on a consistant basis. And when the
Expo Disc causes the shots to be off...I've found they are WAY off.

So that, coupled with the same lack of consistancy in non-flash
shooting situations, keeps the Expo Disc in the bottom of my camera
bag...which is too bad. I so wanted to like this little device and
the convenience it provides. But I guess I should realize that
there's no "free lunch" when it comes to a proper WB.

Here are two images, one in the studio and one outside. These two images show three skin types...black...white...brown. Images are unadjusted for color. Custom WB using the ED pointed at the subject.
This method provides a perfect 18% gray frame to use for Custom WB.

The outside image was shot with fill flash, so there was two types of light factored into the gray frame. I don;t understand why some of you are having problems grasping this device. It is so simple to use and get your color right from the start.

Jan Sanders
http://www.jansanders.com
http://www.hollywoodheadshotstudio.com

Taz61703 · Nov 24, 2002

Peter Sills said:
However, if you want to use the ExpoDisc to determine proper WHITE
BALANCE, then you would aim it at the subject, as the subject is
being hit with not only direct light, but reflected light, and
potentially more than a single light source.

Peter...

Don't know if you caught hm's post above http://www.dpreview.com/forums/read.asp?forum=1019&message=3828581 but what he says here seems to make a lot of sense:

"If you place an expodisc on the camera, it diffuses the
incoming light and averages together the light from various
sources. So you put the camera in front of the subject in
"incident light meter" position, and shoot the incoming light,
and you'll get an averaged reading of the various light sources
in the correct proportions. This removes the color of the subject
from the equation, so it removes the requirement of having a
perfectly neutral subject to shoot. This is how the expodisc
would give most reliable results, I'd think"

When it comes to the Expo Disc, we seem to have two schools of thought in the method that gets the best results. I had previously used it by pointing it AT the subject, but just wasn't happy with the results. I tired using it in incident fashion (pointing at the light source)...and while better, it just wasn't as useful in this manner (e.g., flash).

This thread, though, has inspired me to give the Expo Disc another go. This time I'll try and make careful notes about my shots and see if I can discover what works best (for me, anyway). As I say...I WANT to like this little goodie as it would be such a convenience boost.

-Taz

David Lawson · Nov 24, 2002

Not sure I follow your logic here. You say photograph scene to get correct WB. Now if I put myself where the subject is and use the Expo disc as an incident light meter, surely the light falling on it is the almagamation of all light sources affecting the subject. To put it in your words it is being hit by all the light, direct and reflected, falling on the subject. Now say I am shooting a model laying on grass, I am above her (Just fantasizing a little) so the light falling on her is from the sky ( predominantly grey in the UK) will be used to affect WB. Using your method there would be a lot of green affecting the WB, however, this would not be reflecting on her, so why should it be taken int account. I know this is not what the expodisc manual says and I could be wrong. But as I remember from a lot of old threads it was decided light falling on the disc was best metod. I do use an expodisc, in the manor I describe, and have nothing but admiration for it's late inventor, and respect for his wdow who is carrying on the business. David

Peter Sills said:
However, if you want to use the ExpoDisc to determine proper WHITE
BALANCE, then you would aim it at the subject, as the subject is
being hit with not only direct light, but reflected light, and
potentially more than a single light source.

Does this clear it up? It is invaluable for the D30 or D50 user.
It is less important, though still quite helpful for the 1D/1Ds
user as there is essentially a small ExpoDisc built into the camera
(the reflected White Balance sensor on the outside of the camera).

Peter

Taz said:

JohnM said:

I hold it in front of the lens & shoot an image pointed straight at
the light source(IE: straight in to the sun).

This is not really what the directions say, but it usually works
great.

Click to expand...

If indeed the best results are obtained when the Expo Disc is used
as an incident reading device, then this would seem to make it not
very useful for on board (or on bracket) flash. (And btw, I agree
that it seems to make sense to point it toward the light source.)

However, Jan's pictures that he's posted here previously and on the
Expo Disc website seem to indicate that flash is where the Expo
Disc excels. I guess that's part of the reason he keeps on
insisting that the disc is best used as a reflective measuring
device.

But personally, in my use of the Expo Disc I've never been able to
replicate the same excellent WB when using flash that Jan
demonstates...at least not on a consistant basis. And when the
Expo Disc causes the shots to be off...I've found they are WAY off.

So that, coupled with the same lack of consistancy in non-flash
shooting situations, keeps the Expo Disc in the bottom of my camera
bag...which is too bad. I so wanted to like this little device and
the convenience it provides. But I guess I should realize that
there's no "free lunch" when it comes to a proper WB.

Click to expand...

--
Peter Sills
Digital Focus
http://www.digitalfocus.net

gary ng · Nov 24, 2002

Jan,

How do you handle situation where there is an object that has a strong color say as mentioned by Johanathan like a forest ? So instead of measuring average of light falling on the scene(thus the color cast), it would be the color of the subject itself that is being measured.

jan sanders77139 said:
No variations are possible with the EP, such as shadows, angle of
card, reflections. Also as noted, white is not always white when
you try and use paper or other things such as a wall etc. The EP is
calibrated to exact standards and noted on every case. I don't know
about everyone else but the reduction in work flow is priceless!
The bet $50 I ever spent on camera equipment!

Jan Sanders

DavidP #28649 · Nov 24, 2002

As I recall, the color of the light is NOT the same thing as the "color temperature" of the light.

And I believe that reflected light (even off a colored object) doesn't change its "color temperature" nearly as much as the actual color changes.

Try an experiment with an ExpoDisc. Shoot a bright red object through the expodisc to get a custom white-balance.

Then, shoot with that custom white-balance.

I don't think you'll end up with a gray object in the resulting photo.

gary ng said:
How do you handle situation where there is an object that has a
strong color say as mentioned by Johanathan like a forest ? So
instead of measuring average of light falling on the scene(thus the
color cast), it would be the color of the subject itself that is
being measured.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

gary ng · Nov 24, 2002

David,

I don't have Expodisc yet but just did a simple experiment with a semi-transparent white plastic bag.

Seems that because of the diffused nature, the color of the object would have little if any effect, even in the case of my plastic bag. As the expodisc seems to be even more opaque, I believe this would be a non-issue except for close subject like macro shooting.

However, if this is the case, the instruction on the expodisc web site is wrong as it should be used in incident mode rather than facing the subject.

DavidP said:
And I believe that reflected light (even off a colored object)
doesn't change its "color temperature" nearly as much as the actual
color changes.

Try an experiment with an ExpoDisc. Shoot a bright red object
through the expodisc to get a custom white-balance.

Then, shoot with that custom white-balance.

I don't think you'll end up with a gray object in the resulting photo.

gary ng said:

How do you handle situation where there is an object that has a
strong color say as mentioned by Johanathan like a forest ? So
instead of measuring average of light falling on the scene(thus the
color cast), it would be the color of the subject itself that is
being measured.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

jan sanders44123 · Nov 24, 2002

gary ng said:
I don't have Expodisc yet but just did a simple experiment with a
semi-transparent white plastic bag.

Seems that because of the diffused nature, the color of the object
would have little if any effect, even in the case of my plastic
bag. As the expodisc seems to be even more opaque, I believe this
would be a non-issue except for close subject like macro shooting.

However, if this is the case, the instruction on the expodisc web
site is wrong as it should be used in incident mode rather than
facing the subject.

DavidP said:

And I believe that reflected light (even off a colored object)
doesn't change its "color temperature" nearly as much as the actual
color changes.

Try an experiment with an ExpoDisc. Shoot a bright red object
through the expodisc to get a custom white-balance.

Then, shoot with that custom white-balance.

I don't think you'll end up with a gray object in the resulting photo.

gary ng said:

How do you handle situation where there is an object that has a
strong color say as mentioned by Johanathan like a forest ? So
instead of measuring average of light falling on the scene(thus the
color cast), it would be the color of the subject itself that is
being measured.

Click to expand...

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Click to expand...

Colors have no bearing on results. You are concerned with the light. When you move to new light or change light set ups then you re-meter with the Expo Disc and set your custom WB again. You can also meter many different light situations and keep the resulting frames indexed on a flash card to reference back to. I used an old 16MB card to do this and carry it with me.

Both methods of metering work, shoot your frame facing the subject or shoot facing the light source if you can. Here are the studio and outside location shots again.

Jan Sanders

Scott Sanders · Nov 24, 2002

jan sanders said:
For perfect color on my D60 and D-30 I use an Expo Disc, end of story.
Much discussed here as well as WB issues. Now there is a review of
the Expo Disc available, you can find it here:

http://www.digitalfocus.net/sections/reviews/ColorManagement/Expodisc/Expodisc_1.htm

at the Digital Focus site.
Enjoy!

Jan Sanders
Los Angeles

DavidP #28649 · Nov 24, 2002

http://www.expodisc.com ?

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise

Expo Disc Review

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