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

[nikonusersince2007]

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

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.

 

[480sparky]

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.

 

[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.

 

[unpopular]

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

 

[480sparky]

^^ 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.

 

[unpopular]

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

 

[Josh66]

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

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.

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...

 

[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.

 

[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.

 

[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.

 

[Josh66]

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

 

[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.

 

[Josh66]

You don't have to convince me, lol.

 

[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.

 

[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: