Where does 18% gray originate (Page 3): I do agree about the white balance part, if the card is truly color neutral, but the original use of a 18% grey card in the Ansel Adams zone...

bleirer

Dale Evans - Amaetur wrote:

Grey cards are for setting the color balance, not the exposure. ASA100@f8x125 second will always give you a good daylight exposure but it will not the correct color balance. A grey card is the best way to do that.

I learned about using grey cards after wasting a 4 hour drive to the mountains to shoot some snow scenes.
I was shooting ASA100 B&W film and used the camera meter. When I made my contact sheet all of the exposures were spot on but the snow was grey instead of white.

I do agree about the white balance part, if the card is truly color neutral, but the original use of a 18% grey card in the Ansel Adams zone system was to consider it as an exposure reference for zone V, the middle of the tonal range. It can still be useful in tricky lighting and contrast situations because metering the card in the same light as the subject is similar in effect to using an incident meter, it gives a reading independent of the reflectance in the scene. In your grey snow example, the snow would be white if you has metered off a 12% grey card or added a half stop to a 18% card reading. It was grey because it was underexposed and it was under exposed because the meter's job was to set the camera assiming that the overall scene was an average of middle grey. You turned the white snow into zone V by metering it.

Dale Evans - Amaetur Loc: Baton Rouge, La

OK, same answer, just a different way of saying it.

But,

I turned the snow into zones 9-10 by metering my card, and then because I knew the middle gray point, expose so that the snow would be the tone I wanted it to be.

The Zone System allowed the photographer to pre-visualize the image and expose for it. It saved a ton of time and expensive paper in the darkroom.

bleirer

Dale Evans - Amaetur wrote:

OK, same answer, just a different way of saying it.

But,

I turned the snow into zones 9-10 by metering my card, and then because I knew the middle gray point, expose so that the snow would be the tone I wanted it to be.

The Zone System allowed the photographer to pre-visualize the image and expose for it. It saved a ton of time and expensive paper in the darkroom.

I must have misunderstood you, I though you said grey cards were for color balance not for exposure, but it sounds like you did use it for exposure after all.

On digital, once I got to know the boundaries of my gear, I find I can push the brightest white I care about as much as 3 2/3 stops above whatever my camera calls middle, if I'm being bold (don't try it with jpeg though) or more like 3 1/3 with confidence that i didn't over saturate a color, and my deepest shadow that I want detail in I can drop about 3 1/3 below middle. Those are the limits my gear gives me. So in practice it is just pushing the histogram to the right until the leading edge just starts to jump off the edge, and if the left side is over the edge taking a backup shot if time with the shadows in a safe place.

Dale Evans - Amaetur Loc: Baton Rouge, La

Rule 1 - When using film always expose for the shadows,

Rule 2 - When using Chrome and now Digital always expose for the highlights.

wjones8637 Loc: Burleson, TX

Thank you to all that responded to the question. Your remarks and explanations are very helpful. I have been a bit slow replying due to getting my wife around to Drs. so she can have a knee replaced in about two weeks.

Thanks again,
Bill

bleirer

Dale Evans - Amaetur wrote:

Rule 1 - When using film always expose for the shadows,

Rule 2 - When using Chrome and now Digital always expose for the highlights.

I can't tell you how many hundreds of rolls of film I exposed while practicing my 'zone system previsualization' Velvia was my choice. I am so happy to have exposure simulation and a color histogram right there in the viewfinder, it's a whole other way of previsualizing.

MW

rfreudenheim wrote:

It’s the color of the sky in Rochester, NY (home of Kodak) :)

Having lived in Rochester for four years once This explanation is more than a little plausible!

Wallen Loc: Middle Earth

Photec wrote:

One thing every (old zone system) film photographer who has transformed to digital RAW photography will agree on, getting desired images is SO much easier and quicker. The other advantage is that the darkroom being digital smells much better!

And no cursing when someone opens the light or door LOL

mdougc Loc: Sarver, PA

rfreudenheim wrote:

It’s the color of the sky in Rochester, NY (home of Kodak) :)

😁👍👍

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

Just as an aside- the Shirley card is the breason for metering the palm of your hand trick works

Fotomacher Loc: Toronto

wjones8637 wrote:

A while back there was a discussion where a graph showed that an 18% gray card reflected 50% of the light falling on it. This makes sense, since it is used for setting mid tones. My question is where did the 18% originate? Is this the percentage of a pure black pigment mixed with a pure white pigment?

A curios mind had time to wander.

Thanks,
Bill

Fotomacher Loc: Toronto

My curious mind has better spelling. A well balanced scene with a variation of shades and tones will reflected about 18% of the light falling on it, thus light meters were calibrated to the 18% “standard”. It’s a guide, not a rule. BTW everything that you see or photograph is reflected light.

BebuLamar

Fotomacher wrote:

My curious mind has better spelling. A well balanced scene with a variation of shades and tones will reflected about 18% of the light falling on it, thus light meters were calibrated to the 18% “standard”. It’s a guide, not a rule. BTW everything that you see or photograph is reflected light.

Not always! Some subject emit light so it's not reflected light.

nekon Loc: Carterton, New Zealand

But as it's coming towards the camera, it is classed as reflected light ,as opposed to light falling on the subject

nekon Loc: Carterton, New Zealand

Don't forget the fact,as Kodak told us in the 50's all meters are calibrated at 12.9%so your 18% onlyn applies to grey cards.