White Card Balance - Meter from White Paper

[nldunne]

This image is done by aiming the cam at a GREY CARD - about 30 or so degrees between the subject and roof lights. I worked the EV setting until the HISTOGRAM BAR is in the CENTER of the HISTOGRAM BOX. This gave me an EV @ PLUS 0.3.

For a P and S cam, the result is not too bad overall.

[Don Hoey]

Originally Posted by nldunne

When did this come about? When digital video and stills came about, they used white discs to set the WB and I am sure I have seen it = in print - mentioned that digitals were set up for white.

If the newer models have been set up for mid grey - that I do not know. I will enquire of some cam shops for currrent info. At the time the digis came out, I thought, why did the calibration change?

Norm,

I am slightly confused reading this, but then my brain is slightly out of gear from research for a previous thread.

Two separate things appear to be involved here. White Balance which affects colours, and Exposure which ranges from white to black tones.

As Duncan says light meters are calibrated for 18% grey and always have been. So provided the WB is accurate, and metering is taken from an 18% grey card the white card will appear white. However if the WB is off, but the exposure is accurate, then the white card would have a colour cast.

Don

[nldunne]

Don

I went back to the web search and tried to find material dealing with Grey Cards and Digitals.

Some sites suggested taking images of the Grey Card (I added the white paper). This I did - setting the EV from the G C by making my HISTOGRAM PEAK in the HISTOGRAM BOX line up right in the MIDDLE of the HISTOGRAM BOX. This I did using the EV control and I used the resulting EV (o in this case) to do the G C and white paper. My WB I set at FLUORESCENT DAY WHITE setting. This is just outside a window, but gives good example of the white paper and G C by it - going into shade - plus a bit of skin tones as well. We had hazy bright light.

[robski]

Like Don I feel there is some confusion with using a grey or white card to set the exposure and colour balance.

Using a tool such as http://www.speedgraphic.co.uk/meter_...e/16356_p.html can be used to set the camera exposure and in post processing check and correct the brightness and contrast levels. This is because the steps in grey level are know on the target and the image can be adjusted in post processing to match the the target. Thereby getting the image to match the scene.

Colour balance is about removing colour casts caused by different temperature lighting conditions.

In either case the RGB values of various parts of the image need to be measured and adjusted as required to the desired value.

Norm it good that you are attempting to use reference targets such as the web wheel and grey and white cards. However, I am somewhat confused by your methods in post processing.

You don't say what editing software your using. If it limited to just editing brightness, contrast and saturation then that may go some way to explain your methods. It sound like you are adjusting by eye rather than using your editor as an instrument to measure and adjust.

To start with your method of scanning the white card for a reference to compare against your image is flawed. Your scanner is going to introduce one set of distortions and your camera another set. You will never know which is nearest to being correct.

Your photo has a number of know reference points so make use of them and measure these points and correct accordingly.

On one of your recent posts with the grey step wedge it has a yellowish cast. I have used Photoshops colour balance tool to make some crude adjustments based on reading from the shadow, mid tone and highlight areas of the grey scale wedge. If the grey step levels were know (i.e one stop) then the contrast could have be adjusted to match the target.

On your last post the white balance looks good because the camera had a large area of neutral tone to work with. The thing to remember is that digital camera Auto White balance algorithms are not fool proof and normally work well within a limited range. They do not cope well with mixed light sources.

[nldunne]

Since I did this idea, I searched some webslites - dealing with digial cams and the Grey Card. My thought is that - except for a bit of a color cast I have to deal with, the material in the articles shows this is a better way to go than what I did try at first.

I do confess that I am wrong in the fact digi's are based on the tone of white. I had heard that mentioned but it may be only for the WB - not meter calibration.

As for the program - I used an old version of PICTURE IT as I am so used to it. However, I also have GIMP to play with as well. Right now, I like some things in both - so I can go from one to the other when I need something from each.

As for the color cast you worked on - I have to say this - I did the original by house lights - and did not color correct it to keep the look of working under house lights. Either program would have given me the option to color correct the image.

Not selling work or worrying about everything being nth degree accurate in general, I stay as natural as possible for most all images. I realize many people like everything nth degree accurate - and I accept that - if that is their desire.

Also, I want to do my images in a way that I can sit/stand back from them and let them SPEAK TO ME - as if I was speaking to the artist. When I have visited art galleries overseas, I have learned many a strong lesson - not to stand close and count errors. Most images are the biggest collection of strokes and styles that make no sense. One loses the strong feel of the image doing that - and I will always stand/sit back from any image. Myself, I do not know why people sit close and count errors instead of sitting/standing back from the image and seeing what the author of the piece - right or wrong - is trying to say through the image.

[robski]

If I recall correctly I believe it was said that Monet wanted to repaint some of his work after he had his cataracts removed. He was very disappointed that the paintings did not match the scene.

When photographing subjects where the colours are well known it does help if you can try and keep them faithful. Colour calibration has played a part in various jobs I have had over the past 40 years. I have been lucky that my colour vision has been good but not blessed with the colour vision that most women have.

As for selling my photos - I wish

[nldunne]

I wonder - I will not be included - how many of us will have work lung in galleries and admired after as many years as the Old and Dutch Little Masters? Some art colleges even use their work for the basis of their art courses today. Is it any wonder why they are some of the best artists from which to learn ones skills by follwoing them?

I am happy your eyes have stayed strong this long.

[jzhao1688]

Hi Norm,

Yelvertoft is right, because in photography when started long time ago, it always had the mid gray card 18%-19% and never was a white card. You probably mean a white balance card to calibrate the white balance of the camera metre?