# How to choose between a Grey Card, Expo Disk or Light Meter?



## nikonusersince2007

What is the difference between a grey card, an expo disk and a light meter?

Do I need all 3 or a cobination of 2 or just 1?


*Does a light meter set custom WB or do I set custom WB with a grey card and then take the light measurement with the light meter with the camera now set with the custom WB...do the grey card and light meter work together or do I just need 1 of them to take a correctly exposed image?

So confused.  Thank for the help!


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## cbarbero

A grey card and light meter works best for me.  This also depends on the light meter used. There are some cameras out there with better meters than some of the lesser handhelds.


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## MLeeK

If I can only have one? The light meter is the most useful. The grey card is the cheapest and you can toss it in your bag for setting white balance as long as it is true neutral gray.


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## Big Mike

Two different issues here.  Getting proper exposure and getting proper White Balance.

A light meter is the best tool for getting proper exposure...mainly because most (hand held) light meters are incident meters.  They measure the light falling on the scene, not the light reflecting off of the scene.  This gives you accurate exposure settings.  A hand held light meter is also good for metering different parts of a scene, or lighting ratios etc.  Also, if you need to meter flash/strobes as well, many hand held meters are flash meters as well.  
You don't set White Balance with a hand held light meter.  You could get a hand held color meter, and then dial in that setting to your camera, but that is for super accurate white balancing (and it's expensive) so it's usually only something you'd see on a movie set.

A grey card is a calibrated target for when using a reflected light meter.  The meter in every camera is a reflected light meter.  The way a reflected light meter works, the reflectivity (brightness) of the scene/subject will influence the reading, which can cause you to get improper exposure.  By 'metering' on the grey card, you are using the tone that the camera is calibrated for, thus you will get setting for proper exposure.

Also, because a true grey card is color neutral, you can use it for setting a custom white balance.
There are also white balance targets that might have white/black/grey areas or even a patch of color swatches.  You can use photos of these targets to set your WB/color on the computer, after the shoot.  (shoot in RAW).

There are WB aids, like the expodisk, which help to set a custom WB.


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## KmH

The Expodisc fits certain size lenses (they make 7 sizes). So you may need several of them to accommodate the lenses you have. Expodisc is just a white balance tool, which is how they advertise it.

Or you can get just *one* gray card that works will all your lenses.


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## GeorgieGirl

KmH said:
			
		

> The Expodisc fits certain size lenses (they make 7 sizes). So you may need several of them to accommodate the lenses you have. Expodisc is just a white balance tool, which is how they advertise it.
> 
> Or you can get just one gray card that works will all your lenses.



I have an expo disc and I still can't figure out how to work it. Custom WB no problem.


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## 480sparky

GeorgieGirl said:


> I have an expo disc and I still can't figure out how to work it. Custom WB no problem.



Adjust camera to set custom white balance, install Exposdisc.  Aim at light source, snap shutter.  White balance now set.


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## GeorgieGirl

480sparky said:
			
		

> Adjust camera to set custom white balance, install Exposdisc.  Aim at light source, snap shutter.  White balance now set.



So it's the receiving light not the reflecting light with the expo?


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## 480sparky

GeorgieGirl said:


> So it's the receiving light not the reflecting light with the expo?



The camera is set using the light coming through the Expodisc.  The disc goes on the front of the lens, just like any other filter (that's why they're sold in common filter sizes).


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## nikonusersince2007

Does setting a custom WB with a grey card help to get correct skin tones?
What does setting a custom WB do?  It affects all colors not just white-correct?


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## 480sparky

nikonusersince2007 said:


> Does setting a custom WB with a grey card help to get correct skin tones?
> What does setting a custom WB do?  It affects all colors not just white-correct?



A gray card is usually used to set the WB _in post_.  Exposdiscs (and similar devices) allow precise WB setting _before you shoot_.

A 'Custom WB" means just that... the WB is set precisely to the color temperature of the light source.  If the light is 5818°K, the camera sets itself to that.  Not something close, like 5800 or 5825, but 5818.

WB affects all colors in the frame.


The difference between an Expodisc and a gray card is _when you set the WB_.  If you use something like an Expodisc, your WB is set at the beginning of your shoot.  As long as the light doesn't change, you won't have to fiddle with any WB issues again........ either in the field or in post.

A gray card is used to correct WB _in post_.  You take a photo of it during your shoot, and use an 'eyedropper' in your post software to adjust the WB.


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## MLeeK

I use my grey card for setting WB in the field-not post. Especially when I am working in a particularly crappy gym. 
Fill the frame with the grey card, take the shot, set the WB. 
No matter what way you are using it (for setting in camera or in post) you have to make sure the shot of the grey card is not getting any reflection from a color cast onto it, it is exposed well in the light you will be shooting in. If your light begins to change... you need to re-set. 
When you are using it for setting WB in camera fill the frame with the grey card.


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## nikonusersince2007

I have the sekonic light meter model 300something-how do I get my WB to be correct using a light meter instead of an expo disk?  Or do I need to use both the light meter and an expo disk?


480sparky said:


> nikonusersince2007 said:
> 
> 
> 
> Does setting a custom WB with a grey card help to get correct skin tones?
> What does setting a custom WB do? It affects all colors not just white-correct?
> 
> 
> 
> 
> A gray card is usually used to set the WB _in post_. Exposdiscs (and similar devices) allow precise WB setting _before you shoot_.
> 
> A 'Custom WB" means just that... the WB is set precisely to the color temperature of the light source. If the light is 5818°K, the camera sets itself to that. Not something close, like 5800 or 5825, but 5818.
> 
> WB affects all colors in the frame.
> 
> 
> The difference between an Expodisc and a gray card is _when you set the WB_. If you use something like an Expodisc, your WB is set at the beginning of your shoot. As long as the light doesn't change, you won't have to fiddle with any WB issues again........ either in the field or in post.
> 
> A gray card is used to correct WB _in post_. You take a photo of it during your shoot, and use an 'eyedropper' in your post software to adjust the WB.
Click to expand...


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## Derrel

A gray card works quite well at the time of shooting...

I've also taken custom white balances off of a white cloud in the sky, using a tele-zoom, and defocusing the image...works like a charm...works a lot like the expodisc works...


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## 480sparky

nikonusersince2007 said:


> I have the sekonic light meter model 300something-how do I get my WB to be correct using a light meter instead of an expo disk?  Or do I need to use both the light meter and an expo disk?



99.9999999% of light meters are only capable of reading the _amount_ of light.... so they are only used for setting exposure.  There are _color temperature_ meters available, but they're *very* pricey!  4-digit price tags to start with.

If you want to be accurate, use a light meter and an Exposdisc.  Gray cards can be thrown into the mix if you want, especially given they're relatively inexpensive.


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## nikonusersince2007

can you please walk me through the process of using both a light meter and an expo disk to get the correct exposure and wb for a shot? (which do I set first, do I take the expo disk off the lens before taking a picture of my subject, etc...)



480sparky said:


> nikonusersince2007 said:
> 
> 
> 
> I have the sekonic light meter model 300something-how do I get my WB to be correct using a light meter instead of an expo disk? Or do I need to use both the light meter and an expo disk?
> 
> 
> 
> 
> 99.9999999% of light meters are only capable of reading the _amount_ of light.... so they are only used for setting exposure. There are _color temperature_ meters available, but they're *very* pricey! 4-digit price tags to start with.
> 
> If you want to be accurate, use a light meter and an Exposdisc. Gray cards can be thrown into the mix if you want, especially given they're relatively inexpensive.
Click to expand...


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## 480sparky

nikonusersince2007 said:


> can you please walk me through the process of using both a light meter and an expo disk to get the correct exposure and wb for a shot? (which do I set first, do I take the expo disk off the lens before taking a picture of my subject, etc...)



I usually set WB first, then worry about exposure.  As long as the light temperature doesn't change, I don't need to worry about WB.  If you're shooting in a studio environment, you probably will learn what the color temp of your lights are early on, and never have to reset it for months.  if you're shooting in the field, WB can change just as rapidly as exposure can (sun is suddenly covered by clouds, for instance).


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## Josh66

480sparky said:


> nikonusersince2007 said:
> 
> 
> 
> can you please walk me through the process of using both a light meter and an expo disk to get the correct exposure and wb for a shot? (which do I set first, do I take the expo disk off the lens before taking a picture of my subject, etc...)
> 
> 
> 
> 
> I usually set WB first, then worry about exposure.  As long as the light temperature doesn't change, I don't need to worry about WB.  If you're shooting in a studio environment, you probably will learn what the color temp of your lights are early on, and never have to reset it for months.  if you're shooting in the field, WB can change just as rapidly as exposure can (sun is suddenly covered by clouds, for instance).
Click to expand...

Using an Expodisk (or however you spell it), I think I would do it the other way around.

Use the light meter to set the exposure, then put the Expodisk on and set the WB.  What good will a custom WB do you if it was taken with the wrong exposure?

And yes, you'll need to take the Expodisk off before taking pictures of the subject...  You can't see through it (it wouldn't work very well if you could).  It's kind of like a translucent lens cap.


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## Big Mike

> can you please walk me through the process of using both a light meter and an expo disk to get the correct exposure and wb for a shot? (which do I set first, do I take the expo disk off the lens before taking a picture of my subject, etc...)


Read and re-read your manual on how to set a custom WB. 

What you need, is a picture of something that is color neutral.  That's why a grey card works, but you could also use something that is pure white or pure black...or something that is any shade of grey that is color neutral (same amount of red, green & blue).  You take the shot (fill the frame).  Then go into your menu, to where you set the custom WB.  It will ask you to choose a photo, so you pick the one you just took.  You have now set the custom WB.  To use it, change your WB setting to custom (Pre on a Nikon).

As for how to use a grey card, I have a nice little example on my blog here. How to use a Grey Card ~ Mike Hodson Photography


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## 480sparky

O|||||||O said:


> Using an Expodisk (or however you spell it), I think I would do it the other way around.
> 
> Use the light meter to set the exposure, then put the Expodisk on and set the WB.  What good will a custom WB do you if it was taken with the wrong exposure?
> 
> And yes, you'll need to take the Expodisk off before taking pictures of the subject...  You can't see through it (it wouldn't work very well if you could).  It's kind of like a translucent lens cap.



So you would take a meter reading, set the exposure on the camera, put on the Expodisc, adjust your camera to a custom WB to set your white balance, then take the ED off, then go back to your exposure mode to take the shot?


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## Josh66

"Go back to my exposure mode"?  Why would I have left it?

I guess (if I understand the question) my answer is yes.

Set exposure.  Set WB.  Take pictures.  How is that complicated?


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## 480sparky

O|||||||O said:


> "Go back to my exposure mode"?  Why would I have left it?
> 
> I guess (if I understand the question) my answer is yes.
> 
> Set exposure.  Set WB.  Take pictures.  How is that complicated?



Either way is correct.  WB/Exp or Exp/WB.

To-MAY-toe, Tuh-Mah-toe.


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## Josh66

I liked your previous reply better, before the edit.

I still say that a custom WB set using the correct exposure is better than one set without it.  I mean, if you're going to go through the trouble of setting a custom WB - I assume that means you want the colors to be as accurate as possible.  Why then, would you not make sure that your custom WB was set using the proper exposure?  Seems backwards to me...
BTW, the Expodisc can also be used to set exposure.


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## 480sparky

O|||||||O said:


> I liked your previous reply better, before the edit.
> 
> I still say that a custom WB set using the correct exposure is better than one set without it.  I mean, if you're going to go through the trouble of setting a custom WB - I assume that means you want the colors to be as accurate as possible.  Why then, would you not make sure that your custom WB was set using the proper exposure?  Seems backwards to me...
> BTW, the Expodisc can also be used to set exposure.



Setting a custom WB has nothing to do with exposure.  I just put on the ED and fire away, camera settings be damned.  The color temp of the light isn't going to change, regardless of my exposure settings.


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## 480sparky

A video might explain the three a little better:







Custom WB, using ExpoDisc:









Using Auto WB:


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## APHPHOTO

I use both the expo disk and the calibration target. To use the expo disk, you simply set the camera up to get custom white balance and aim it at the light falling on subject. The calibration target is usually placed in the area alluminated by the light source being used and you aim at it. I personally dont see a reason for a light meter if your shooting digital.


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## unpopular

The light meter in your camera will work just fine, it's just a matter of finding a correct reference. Perhaps having a flash meter would be useful if you plan on shooting with external flashes. But I sold my Gossen Starlight a long time ago and haven't missed it since. It was great with film cameras that lacked a spot meter tho.

As for color meters, you can get older minoltas on ebay for about $500 which will meter both color, intensity and can be used with flash.


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## unpopular

BTW- I don't use any of these. I spot meter off the brightest area and increase exposure to the outer limits of my camera's latitude. This approach works in preventing clipping, increasing signal (decreasing noise) and maximizes dynamic range, but requires adjustments in RAW developement.

Because white balance is determined at processing, not at the time of exposure, there isn't any need to be super precise about white balance either.


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## 480sparky

unpopular said:


> ...........Because white balance is determined at processing, not at the time of exposure, there isn't any need to be super precise about white balance either.



That's assuming everyone has all the time in the world to spend pushing a mouse around setting white balance to a file full of raws.  Not everyone has that luxury.


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## nikonusersince2007

Can I put the expo disc over a UV or circularizing filter and have the expo disc give a proper WB reading?  Or do you NEVER want to have an filter on when take a custom WB reading with an expo disc?  Why okay or why not okay?


480sparky said:


> GeorgieGirl said:
> 
> 
> 
> So it's the receiving light not the reflecting light with the expo?
> 
> 
> 
> 
> The camera is set using the light coming through the Expodisc. The disc goes on the front of the lens, just like any other filter (that's why they're sold in common filter sizes).
Click to expand...


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## nikonusersince2007

How does this work "BTW, the Expodisc can also be used to set exposure."?  Thanks


O|||||||O said:


> I liked your previous reply better, before the edit.
> 
> I still say that a custom WB set using the correct exposure is better than one set without it. I mean, if you're going to go through the trouble of setting a custom WB - I assume that means you want the colors to be as accurate as possible. Why then, would you not make sure that your custom WB was set using the proper exposure? Seems backwards to me...
> BTW, the Expodisc can also be used to set exposure.


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## 480sparky

nikonusersince2007 said:


> Can I put the expo disc over a UV or circularizing filter and have the expo disc give a proper WB reading?  Or do you NEVER want to have an filter on when take a custom WB reading with an expo disc?  Why okay or why not okay?



Technically, a UV or CP shouldn't affect your white balance, but a cheap filter might.  And to compound the problem, a cheap CP might change the tint it creates as it's rotated.  So if you're shooting with cheap filters, WB is always going to be a headache.  Shoot with the good stuff, and leaving the UV or CP on while setting WB with an ExpoDisc won't affect it.  You may just need a bit more light when you're setting it with the CP in place.


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## unpopular

^^ however, using the expo disk will compensate for any color drift from the filter that isn't desired. If the filter is intended to be neutral, like a UV CP or ND, it might be a good idea provided that you intend to use the filter with that particular reading.

Obviously, once you remove the filter the compensation will be incorrect.


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## unpopular

nikonusersince2007 said:


> How does this work "BTW, the Expodisc can also be used to set exposure."? Thanks



I'd imagine that you'd use it like a incident meter.



> When using a meter in incident mode on subjects that are front lit, just point the meter, with the diffuser cone in place over the sensor, towards the camera, making sure that the meter is positioned in the same light as that falling onto the subject. The reading will not be correct if you hold the meter in an area of shade, while the subject is basking in sunlight.


From: Guide To Using A Hand-Held Light Meter


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## 480sparky

unpopular said:


> ^^ however, using the expo disk will compensate for any color drift from the filter that isn't desired. If the filter is intended to be neutral, like a UV CP or ND, it might be a good idea provided that you intend to use the filter with that particular reading.
> 
> Obviously, once you remove the filter the compensation will be incorrect.



But, as I stated, the color of a cheap CP may change when it's rotated.  I doubt anyone wants to set a custom white balance every time they turn the ring on a CP.


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## unpopular

deff not. But it would get you closer until you get a Heliopan.


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## Josh66

nikonusersince2007 said:


> How does this work "BTW, the Expodisc can also be used to set exposure."?  Thanks
> 
> 
> O|||||||O said:
> 
> 
> 
> I liked your previous reply better, before the edit.
> 
> I still say that a custom WB set using the correct exposure is better than one set without it. I mean, if you're going to go through the trouble of setting a custom WB - I assume that means you want the colors to be as accurate as possible. Why then, would you not make sure that your custom WB was set using the proper exposure? Seems backwards to me...
> BTW, the Expodisc can also be used to set exposure.
Click to expand...

Read the description on their own site (or the description on B&H).  The Expodisc is neutral - AKA 18% grey, same as a grey card.  Put it on, zero the meter, take a shot.  You now have a correctly exposed WB reference shot.

edit
And yes, like unpopular said, I suspect that the reading it would give you would be closer to an incident meter reading than a reflected reading.  So, not _exactly_ the same as a grey card...


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## unpopular

^^ being transmissive, I am not sure that this is accurate. It would essentially function like average metering in this way, so if the scene is mostly dark, it would want to place those mostly dark tones in the middle grey. It should, if i'm thinking right, work as in incidence metering, but that would be kind of a pain, I'd imagine, and being as inexpensive as incidence meters are a bit unnecessary.

I think the neutrality refers to color; it cannot determine an 18% reference without a referenced light source.


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## Josh66

I don't think it really 'knows' what it's pointed at though.  The light is so diffused by the time it gets to the other side of it, that in my mind it would work much like an incident meter...  I don't have one now (and it's dark anyway), but it would be fairly simple to test - point it at a bright object, then a dark object and see if the meter moves.  I suspect that it is just reading the light that falls on it.


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## unpopular

It definitely would, but you don't normally point incident meters are the subject except in certain situations. You point it back at the camera.

Incident meters are designed to measure available light, not reflected light. But without a domed surface, it's not going to be very good at this either.


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## Josh66

Yeah, I know (re: incident meters) - been a while since I've seen an expodisc up close, I might be wrong about them...


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## unpopular

I don't really get what the point of an expo disk is. A greycard will do everything an expo disk will, will provide a post-exposure reference, and will not ever be influenced by the contents of scene except maybe in really weird situations. 

They've been a proven technology for the last 70+ years.


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## Josh66

You don't have to convince me, lol.


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## unpopular

I think mishelle posted a link on a similar thread about how Wired Magazine awarded these placement on some kind of unnecessary products list.


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## 480sparky

Exposure set by camera meter:








Expsuure set by spot metering gray card:






Exposure set by placing ExpoDisc on lens and aiming at modeling light:


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## unpopular

480sparky said:


> unpopular said:
> 
> 
> 
> ...........Because white balance is determined at processing, not at the time of exposure, there isn't any need to be super precise about white balance either.
> 
> 
> 
> 
> That's assuming everyone has all the time in the world to spend pushing a mouse around setting white balance to a file full of raws.  Not everyone has that luxury.
Click to expand...


Perhaps. But every camera has a custom white balance which works fairly well against a white reference, like a sheet of paper. This gets you pretty close, and will be similar for the an entire set.

Honestly, i don't understand all this white balance madness. Most professional photographers didn't even own a full set of CC filters and a color meter with film. They chose the right film for the situation and maybe an FL filter. For 99.9% of applications, the built-in color meter will do just fine so long as you don't rely on "auto" mode.


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## Helen B

unpopular said:


> It definitely would, but you don't normally point incident meters are the subject except in certain situations. You point it back at the camera.
> 
> Incident meters are designed to measure available light, not reflected light. But without a domed surface, it's not going to be very good at this either.



The Expodisk never made sense to me either.

I remember the Expodisk as being introduced as an incident attachment for cameras with TTL meters - hence the name. Only later was it sold as a white balance device. Like you say, it isn't as good as a domed receptor - there's a good reason why the incident diffuser on light meters has a non-flat shape. The idea is that for almost all purposes the best form of incident metering is to point the meter at the camera (or where the camera will be), and use the shape of the incident dome to read light from the sides and some from the rear, but not directly behind, as well as the light from the front (orientations with respect to the meter). Hence the cardioid response designed in to the dome or invercone. 

Flat receptors, with a cosine response, are usually only used in studio situations to measure individual lights or the illumination of a flat object, but a shielded dome works just as well in that case (either designed in to the meter like many Sekonics, or shielded by your cupped hand). That's also why colour meters always have flat receptors - they are designed for measuring a source, not for measuring the average.

If you want to do incident metering with a TTL meter, just meter off the palm of your hand. It's a good, constant reference. For white balance there are plenty of things that are cheaper, faster and more convenient to use than an Expodisk. Except in the studio, my personal preference is to use a white reference and then set the WB for the whole batch in Lightroom.


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## Tee

I have a combo collapsable grey/white disc.  On scene, I set my white balance using the white side then have the model flip the card around and take a shot of her holding the grey side for post production (if needed). Takes about 20-30 seconds for the whole process and has worked well.  The expo disc has always appeared "gimmicky" in my opinion especially when there are cheaper options that provide the same results.


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