White balance anomalies

[topcat07]

I have been taking a few pictures of a grey card amazing i know

when putting those photos into lightroom and using the pipette for white balance on the grey part it would show a reading of 2600 but when clicking 'auto' white balance in Lightroom this would increase it up to around 150 more so 2750?

I have tried this in a few different places and the software always thinks it is a bit more.

Is the grey card more accurate and the software is guessing?

Or am i shooting the grey card wrong (out of focus, max focal length, near to the lens) ?

 

[AJQS]

I dunno, but my version of lightroom likes to make everything purple regardless so I'd stick with setting WB using the dropper.

 

[HoppyUK]

WB dropper is a measurement, anything else is just a guess. Assuming your grey card is actually neutral grey (some are not quite) and not under-exposed with some colour noise that may influence the reading, then it cannot be wrong.

Whether or not the colours then 'look' right is another question. WB is an art as well as science, and for example you wouldn't want technically correct colours in candle light, or fire light, or a sunset.

Our eyes can be quite forgiving of slightly inaccurate colours, but very intolerant of inconsistent colours. For example, in a wedding set, it's a very good idea to get the bride's dress right, but even more important to keep it the same shot to shot.

 

[russellsnr]

If you an 18% Grey card then trust it.

 

[Russ77]

Another factor may be how your screen is set up, it is calibrated?

 

[woodstock163]

I realise the importance of WB and do use the icon variations. To set manually though I do get somewhat confused. Why the white and grey card...New here so sound a bit ignorant no doubt. I have done 4 weddings using the icon changes for the large difference in light ...Manually settings confuse me ....I relise one takes a pic of the card ...then what ?

Once you have the camera set whether manually or otherwise why the need to alter it in Lightroom of Photoshop ? .

 

[StewartR]

New here so sound a bit ignorant no doubt.

Welcome to TP. And don't worry about sounding ignorant. Better by far to know that you're ignorant, and ask questions, than to carry on blissfully unaware of your ignorance!

Why the white and grey card?

White card is for correct WB. Grey card is for correct exposure or correct WB. If you have a grey card - and it's a true neutral grey - then you don't really need a white card.

Manually settings confuse me ....I relise one takes a pic of the card ...then what ?

Two options.

One is to set the WB in camera. How you do this depends on your camera. For my Canon DSLR, I take a photo of the entire white/grey card, then select that as the source for the custom WB. The camera calculates what adjustments are needed to make the card a true neutral white/grey, and uses that as the WB setting.

The other is to set the WB in Lightroom or whatever post processing software you use. Call up the image of the card, click on it to set the WB, and then apply that to the other images taken in the same light.

Once you have the camera set whether manually or otherwise why the need to alter it in Lightroom of Photoshop ? .

Because WB isn't an exact science and you might prefer a different tone (typically a warmer tone) than would be strictly correct. See HoppyUK's comments about sunsets and candlelight.

Or because the light is actually varying a little bit over time and the WB you set at one point in time isn't necessarily correct for all the shots. Outdoors, the proportion of cloud cover can affect the WB. Indoors, even if the lighting is constant, the WB for any shot can be affected by the colours of reflective surfaces (walls, ceiling etc.) in the vicinity of the subject.

 

[HoppyUK]

I realise the importance of WB and do use the icon variations. To set manually though I do get somewhat confused. Why the white and grey card...New here so sound a bit ignorant no doubt. I have done 4 weddings using the icon changes for the large difference in light ...Manually settings confuse me ....I relise one takes a pic of the card ...then what ?

Once you have the camera set whether manually or otherwise why the need to alter it in Lightroom of Photoshop ? .

The white card or grey card is just a known reference that contains equal amounts of red, green and blue light, that the camera is calibrated to replicate. The theory being that if the camera is zeroed to this, all other colours will naturally fall accurately. You could take a WB reference off any colour card and the camera would then make it appear grey, but then all other colours would be skewed. You can actually buy WB accessories that do this deliberately, being a very light blue which makes skin tones warmer (and everything else warmer too).

Here's an example of difficult white balance. I just googled snooker player, and as you can see the guy has a green face, but the shot looks natural http://www.bbc.co.uk/sport/0/snooker/21127300 This kind of effect happens all the time, though thankfully to a much lesser extent. You might get something similar photographing children sitting on green grass. Or in a room lit by daylight but with brightly coloured walls or furnishings, near the window the correct white balance will be close to the daylight, but as you get further into the room the light picks up more and more reflected colour from the surroundings, and if there's also some artificial light, then that's going to change things too.

In situations like that, 100% colour accuracy is simply not possible and the best compromise is usually set by eye and on the whole this works well enough and our eyes compensate and tolerate quite a lot. As I said above, colour consistency shot to shot is more important than absolute accuracy.

If 100% colour accuracy is necessary, for maybe a fashion shoot or catalogue work, then the photographer must control all the light at source and ensure there's nothing in the environment that can affect it.

 

[omens]

I've always been puzzled by the suggestion of a grey card for WB. I've always thought that if you wanted an accurate white colour, you used a white card to set the WB. If you wanted accurate metering of the scene, you used a grey card.

I say accurate but obviously the tog has the ability to override this - you might actually want to make it obvious that the sodium lamps are making the car look orangey (which is probably more accurate of the scene).

Can anyone explain to me why you'd want to use a grey card for setting WB than a white card?

 

[HoppyUK]

I've always been puzzled by the suggestion of a grey card for WB. I've always thought that if you wanted an accurate white colour, you used a white card to set the WB. If you wanted accurate metering of the scene, you used a grey card.

I say accurate but obviously the tog has the ability to override this - you might actually want to make it obvious that the sodium lamps are making the car look orangey (which is probably more accurate of the scene).

Can anyone explain to me why you'd want to use a grey card for setting WB than a white card?

If the card is truly neutral grey or neutral white, the only difference between them is that there's a slightly greater chance of the grey card being under-exposed with some colour noise that could skew the result. On the other hand, over-exposed white, ie blown, is useless.

White is generally more convenient, as there's often some fairly neutral white found in a lot of typical scenes. White paintwork, white tablecloth, white shirt etc and they'll give you a pretty good reference with the WB dropper in post processing. Finding a neutral grey in a typical scene is very rare.