Do I need a grey card?

[Pookeyhead]

@DG Phototraining

It;s very rare you need to be this accurate. Having done a great deal of commercial product photography, I can assure you that some clients will actually give you a pantone colour swatch and INSIST that it's accurate. The only way I can deliver on such a promise is to shoot raw and balance in post.


For everything else... it's utterly subjective. However... I still tend to use a grey card and have a reference shot even though it's rare I stick to reality and accuracy in the final image. I like to start with a neutral image, as switching between neutral and your adjusted shot keeps you grounded and stops you going too far one way or the other. Without this you can suffer from "creep" and end up with a "**** me, that's warm" type image.

 

[DG Phototraining]

even though it's rare I stick to reality and accuracy in the final image

My point exactly

'true WB' is merely a reference point

In the past I handed my grey card to the Groom in church prior to his Bride arriving, or even used the Expo from the spot they will be standing at. But during a typical service the light can change so much using the original measured setting is pointless; then they can be moved about a bit from side to side meaning the light changes again. I've even had both the exposure level and WB be hugely different between a B&G that are stood 2ft apart !!!

Dave

 

[ecoleman]

But you can do exactly the same with a grey card... just fill the frame with it.

I've never said you can't, as I've said before, they are both tools. You pick which one you prefer.

Besides.. either method is only as accurate as the camera's auto white balance if you think about it.

I get much better results from my Expodisc than I do from AWB. AWB can struggle in mixed light whereas the Expodisc is spot on.

I still have an Expodisc, I bought it when they first came out - £10 to anyone who wants it (I think I paid about £90 at the time !!!);

I would never have paid £90 for one. I got one when they dropped to £30

 

[HoppyUK]

It's worth noting that not all grey cards are neutral grey, depending on their intended use. For exposure, perfect neutrality isn't necessary, and for white balance, 18% reflectance (or whatever) isn't needed. Some will do both, but the Kodak grey card for example is not guaranteed neutral on the grey side (mine is a touch green) and it's the white side that is recommended for white balance.

Agree with David's post #41. WB cards etc are very useful as a reference starting point, but then go with whatever looks best. I use an X-Rite ColorChecker, and keep meaning to treat myself to the handy little Passport version.

BTW, those ridiculously expensive ExpoDiscs were originally marketed as an incident light metering attachment for SLRs. They're no different to the lens cap type things you can get on ebay for a fiver. Or you can DIY it with a coffee filter cone over the lens, or a few sheets of white paper. As I recall, it took three sheets of Tesco Value copy paper to create an exposure and WB attachment that was a pretty accurate 18% grey

I don't agree with the notion that it's always better to do things in-camera. It's not a bad rule of thumb, but some things are often done better/easier in post production. White balance is one example of that.

 

[kendo1]

I'd go with that, Richard

 

[Canon Bob]

........ but some things are often done better/easier in post production. White balance is one example of that.

It's worth mentioning here that any time that you're pushing the Iso levels into noisy territory with artificial light (street lights/floodlights) then there's some benefit it getting the WB correct at the point of shooting. Once the noise is in the file then PP adjustment of WB isn't going to remove it.

Bob

 

[Carlh]

In the case of weddings where you can't go measuring white balance because of the lighting setup in the church and then switching to something else outdoors, I use the white-balance tool in Camera Raw and providing the dress is white, I'll select that to set my white balance and if its not a white dress, the groom usually has a white shirt on, so I'll select their cuff or collar and 90% of the time it gives a good representation of the colours. I use the faithful settings as the default white-balance in camera anyway and that can get me another good representation if there is nothing "pure white" to help set the wb.

 

[HoppyUK]

It's worth mentioning here that any time that you're pushing the Iso levels into noisy territory with artificial light (street lights/floodlights) then there's some benefit it getting the WB correct at the point of shooting. Once the noise is in the file then PP adjustment of WB isn't going to remove it.

Bob

Do you have any more info/links on that Bob?

 

[Canon Bob]

Do you have any more info/links on that Bob?

No specific links, Richard, but maybe an explanation will suffice?

A typical sensor will be neutral around 5200k (there will be some variation but it's a good enough value to use). At the 'neutral' value then the gain (iso) of all three channels (RG&B) are equal. If the processor decides that the light source is a different temperature then it compensates by varying the gain on the three channels but keeps the average equal to that which gives the correct exposure response to the iso value selected.

Example;
If we assume a halogen source (3000k approx) then the blue channel gain is increased and the gain of the other two channels is decreased thus maintaining the average gain for the the selected iso value.....the blue channel becomes the noisier of the three as a consequence but there's nothing we can do about it. If the true temperature is 3300k and the calculated temperature is 3000k then we will bring the WB in the RAW file back 300k....but the file already contains '300k's worth' of extra/unneccesary noise (as a result of over adjustment of the blue channel gain) that doesn't disappear when the WB slider is pushed back up.

At lower iso values where the sensor comfortably produces noise free files then there's nothing to worry about and WB changes in PP have little or no ill effects. Once we get into the uglier regions, things can be improved by getting it right before the event.

Hope that all makes sense.

Bob

 

[Canon Bob]

Oooops...appeared twice

 

[HoppyUK]

No specific links, Richard, but maybe an explanation will suffice?

A typical sensor will be neutral around 5200k (there will be some variation but it's a good enough value to use). At the 'neutral' value then the gain (iso) of all three channels (RG&B) are equal. If the processor decides that the light source is a different temperature then it compensates by varying the gain on the three channels but keeps the average equal to that which gives the correct exposure response to the iso value selected.

Example;
If we assume a halogen source (3000k approx) then the blue channel gain is increased and the gain of the other two channels is decreased thus maintaining the average gain for the the selected iso value.....the blue channel becomes the noisier of the three as a consequence but there's nothing we can do about it. If the true temperature is 3300k and the calculated temperature is 3000k then we will bring the WB in the RAW file back 300k....but the file already contains '300k's worth' of extra/unneccesary noise (as a result of over adjustment of the blue channel gain) that doesn't disappear when the WB slider is pushed back up.

At lower iso values where the sensor comfortably produces noise free files then there's nothing to worry about and WB changes in PP have little or no ill effects. Once we get into the uglier regions, things can be improved by getting it right before the event.

Hope that all makes sense.

Bob

Yes, makes perfect sense Bob - when shooting to JPEG. But not with Raw. WB adjustments are only applied on JPEG conversion so when shooting Raw the in-camera WB setting makes no difference.

 

[Canon Bob]

Yes, makes perfect sense Bob - when shooting to JPEG. But not with Raw. WB adjustments are only applied on JPEG conversion so when shooting Raw the in-camera WB setting makes no difference.

We'll have to agree to differ on this, Richard. You beliefs would be based on in-camera WB correction being solely at the digital amplification stage unlike iso level adjustment which is achieved with a mix of analogue and digital amplification/attenuation....a reversible change in PP. Mine, on the other hand, are based on some or all of the WB correction being achieved at the analogue stage and thus affecting the sensor output before the A/D converters are sampled.

Bob

 

[Blank_Canvas]

We'll have to agree to differ on this, Richard. You beliefs would be based on in-camera WB correction being solely at the digital amplification stage unlike iso level adjustment which is achieved with a mix of analogue and digital amplification/attenuation....a reversible change in PP. Mine, on the other hand, are based on some or all of the WB correction being achieved at the analogue stage and thus affecting the sensor output before the A/D converters are sampled.

Bob

I think you're getting a little to hung up on on technicalities and getting a little confused in the process. Richard is correct in what he's saying in respect to RAW.

 

[Canon Bob]

I think you're getting a little to hung up on on technicalities and getting a little confused in the process. Richard is correct in what he's saying in respect to RAW.

I'm not hung up at all, Nick. I believe that having a greater understanding of how things work will assist in optimising results when the shooting conditions become challenging. I believe that when Canon invoked their dual layer metering sensor the methodology for WB correction changed whilst you seem to think differently. As with most things, the individual should follow what works for them.

Bob

 

[HoppyUK]

We'll have to agree to differ on this, Richard. You beliefs would be based on in-camera WB correction being solely at the digital amplification stage unlike iso level adjustment which is achieved with a mix of analogue and digital amplification/attenuation....a reversible change in PP. Mine, on the other hand, are based on some or all of the WB correction being achieved at the analogue stage and thus affecting the sensor output before the A/D converters are sampled.

Bob

I suspect that we both may be right Bob The common belief that Raws are the unmolested output from the sensor has never been strictly true, and although it may be a good enough working rule of thumb, manufactures differ in the amount of tweaking that goes on. I can think of a couple of brands I've tested where there is obvious and significant noise reduction and colour adjustments made to Raws at very high ISOs.

For the record, I did some quick tests last night with a Macbeth colour chart, and but couldn't see any noise or other difference at all between Raws taken at different WB settings when corrected in LightRoom. Canon 5D2, ISO6400, low tungsten light, sun and tungsten WB settings.

As an aside, out of interest I also shot JPEGs and what was very noticeable there was the dramatic loss of colour fidelity when trying to recover the image shot at the wrong WB setting. I only mention it because I was shocked at how bad it was! Frankly, it was unrecoverable.

 

[Canon Bob]

For the record, I did some quick tests last night with a Macbeth colour chart, and but couldn't see any noise or other difference at all between Raws taken at different WB settings when corrected in LightRoom. Canon 5D2, ISO6400, low tungsten light, sun and tungsten WB settings.

I suspect that the 5D2 was spec'd before the dual layer metering sensor was implemented and therefore the camera calculated WB was based on the data post-capture. Things changed and now the metering sensor can detect more than scene luminance, it can interpret individual channel (RGB) luminance and can therefore estimate WB pre-capture.

Bob

 

[alexkidd]

I'd use a colour checker card if it's really critical otherwise I'd just do it by eye, end product is always going to be off based on screen or metamerism anyway

 

[Moey]

Wow, I didn't realise there was so much to using a grey card? I simply thought that you shot a grey card to preset your white balance as oppose to using the auto ones built in camera?? Am I kind of right or should I refrain from joining in this discussion furthur, for fear of embarrassing myself even more?

 

[ecoleman]

Wow, I didn't realise there was so much to using a grey card? I simply thought that you shot a grey card to preset your white balance as oppose to using the auto ones built in camera?? Am I kind of right or should I refrain from joining in this discussion furthur, for fear of embarrassing myself even more?

You are right. Some people have gone overboard and off topic into colour correction.

 

[Moey]

Thanks for the confirmation Elliott, I don't feel as stupid as I thought I would.. .. I may look it, but don't feel it.. ..

 

[Blank_Canvas]

Wow, I didn't realise there was so much to using a grey card? I simply thought that you shot a grey card to preset your white balance as oppose to using the auto ones built in camera?? Am I kind of right or should I refrain from joining in this discussion furthur, for fear of embarrassing myself even more?

You're totally on the right track and you haven't embarrassed yourself !

 

[Pookeyhead]

Take a shot with a grey card in frame... load raw into ACR or LR... click on grey card with white balance dropper tool. Done.


Some people just like to complicate things it would seem

 

[Nod]

IF the grey card is absolutely neutral grey, yes.

 

[Pookeyhead]

IF the grey card is absolutely neutral grey, yes.

If you buy a proper grey card, it will be.

 

[sunnyside_up]

I haven't read all this thread, so I'm just going to say...

I always shoot an 18% grey card everytime, without question, with every light setup. I keep my camera's white balance on 'flash', never auto (unless I'm just taking snaps). Then I bring it all into LR and make any corrections in post in one swoop.

 

[Nod]

If you buy a proper grey card, it will be.

Again, IF!

 

[Pookeyhead]

Again, IF!

Errr. yes. Just buy proper one.

 

[Peter]

I haven't read all this thread, so I'm just going to say...

I always shoot an 18% grey card everytime, without question, with every light setup. I keep my camera's white balance on 'flash', never auto (unless I'm just taking snaps). Then I bring it all into LR and make any corrections in post in one swoop.

Bethy May I ask why 'flash' and does that apply in artifical light ?