How to position a Grey Card (Landscape)

[Lachlan 717]

Can anyone assist with advice on how to position an 18% Grey Card?

Many threads refer to "...place your grey card and..." without explaining [I]exactly[I] how this should be done.

Should I lace the card so that it is parallel to the film plane? Do I tilt it towards the sun?

Thanks in advance for any help!!

Lachlan.

[lenser]

Hi, Lachlan.

The card needs to be placed in light that is like that on the scene. If that means full sunlight, be sure you DON'T tilt the card so it is shaded and vice versa.

Often you can just stand at the camera position and do a reflected meter reading off the card to set your exposure.

If you are using the Zone System and want to use the card to adjust the gray scale values of a scene. Move it from light to shadow (like is in the scene) check the readings and make your plus and minus decisions for both exposure and development.

You can use the card with both a spot and a hand held reflected meter.

Some cards have Zone System directions on the back that help with those decisions.

Good luck.

Tim

[steve simmons]

Forget the gray card and learn to meter the scene. Regardless of whether you are working with color or black and white you should meter the highs and lows and place your values accordingly. You can't do this by using a gray card.

Just my 2 cents

steve simmons

[Lachlan 717]

The card needs to be placed in light that is like that on the scene. If that means full sunlight, be sure you DON'T tilt the card so it is shaded and vice versa.



Thanks, Tim.

So, to put this into a real life situation, if I was shooting a creek with some round-ish grey rocks in it, and I want to get the area under the crown of the rock as Zone V, I would lay the card on this area of the rock? This assumes that the card will assume a plane equal to the zenith of the rock...

Hope this makes some sense!!

Lachlan.

[steve simmons]

So, to put this into a real life situation, if I was shooting a creek with some round-ish grey rocks in it, and I want to get the area under the crown of the rock as Zone V, I would lay the card on this area of the rock? This assumes that the card will assume a plane equal to the zenith of the rock...


What about the values in the rest of the scene?

steve simmons

[Lachlan 717]

Forget the gray card and learn to meter the scene. Regardless of whether you are working with color or black and white you should meter the highs and lows and place your values accordingly. You can't do this by using a gray card.

Just my 2 cents

steve simmons

Thanks, Steve. I agree with learning to meter a scene.

This question relates to understanding the margins of the highlights and the lows relative to the assumed mid point (18%). As you wrote, "The 18-percent gray card is used as a standard, artificial tone for the meter reading, and it matches Zone V on the zone scale."

I want to use the grey card reading as a starting point (i.e. Zone V), and gauge the high/low readings against this.

As such, I am interested as to the angle of the card, as tilting it can reflect or shadow the light falling on to it.

Lachlan.

[Walter Calahan]

Try to put the gray card parallel to the film plane facing directly towards the lens with no tilting. Place it in the light that you judge to be falling on the dominate areas of the image. Take a reading.

Then read your white with detail and your shadow with detail to calculate off the gray card exposure.

Or, take an incident meter reading in the main light, and then a spot reading of the white with detail and shadow with detail. You get the same results, and won't have to worry about the gray card.

[lenser]

First of all, I agree totally with Steve that you need to learn to meter the variations in the scene. For that, a spot meter is possibly your best tool. I also agree that you would not necessarily limit using the card for only the one tonal value in a scene. That's why I mentioned metering a shadow position as well as a highlight and then applying the Zone System to make creative exposure decisions.

Steve's book "Using the View Camera" has some terrific information about the Zone System and about exposure control.

Now to your question about positioning the card in the scene. Yes and no!

Yes, you can put the card in the scene, but you must position it several ways so you meter not only the highlight (off a three dimensional object) but also the shadow. You also need to move the card into a fully shadowed part of the scene. In general, you will decide on an exposure based on making a shadow area fall into a printable zone and then processing the film to maintain detail in the highlights. Failing to account for shadow detail will cause dead blacks instead of a living detailed part of your image.

The qualified 'NO' is for two reasons. One is that you can get the same metering at the camera position by changing the tilt of the card from highlight to shadow while you monitor the changing meter readings. (Avoid being near anything reflective like a car or light colored building or clothing) There is no need to have the card actually in scene which might be either difficult or dangerous in some circumstances.

The second reason for the "NO" is that you should be aware of the glare effect of tilting the card too far into the direction of the source of the light.

It's somewhat like catching a bad glare off a car's windshield or wax job. If you are not familiar, it has to do with the angle of incidence and the angle of reflectance which works on either shiny or matte surfaces.

The angle of incidence is from the light to the subject and the angle of reflectance is from the subject to the eye or camera or meter cell. When those angles are low, you get glare because the light is skipping directly toward the meter. Even on a matte surface like a gray card, it can give a falsely light exposure reading of the actual brightness in scene.

To avoid this, make sure the card is in the light, but at a steep angle (near perpendicular to the meter) rather than a shallow one.

For my field kit, I trimmed a gray card down to 4x5 (about the size of my holders) to make it easy to carry in the camera bag. The full card can be a little bulky unless you stay with your car all the time.

In a pinch, you can also meter from the palm of your hand if you remember that it is about one stop brighter than the gray card.

Have fun. It's really part of the enjoyment when you see those prints developing.

Tim

[Ed Lajoie]

Thanks, Steve. I agree with learning to meter a scene.

This question relates to understanding the margins of the highlights and the lows relative to the assumed mid point (18%). As you wrote, "The 18-percent gray card is used as a standard, artificial tone for the meter reading, and it matches Zone V on the zone scale."

I want to use the grey card reading as a starting point (i.e. Zone V), and gauge the high/low readings against this.

As such, I am interested as to the angle of the card, as tilting it can reflect or shadow the light falling on to it.

Lachlan.


The best starting point is to use the gray card to do an ASA test. After you've done that, I'd leave it in a drawer at home and meter the scene at hand. If your test is trustworthy, you'll exercise the proper control over exposing the scene. If you insist on a standard, place your hand in EXACTLY the same light as your subject, meter off the palm of your hand, and open one f stop. That method will prove as accurate as metering off your gray card. Neither will work if you don't know your true ASA (ISO). Good luck.

[Joe Smigiel]

Thanks, Tim.

So, to put this into a real life situation, if I was shooting a creek with some round-ish grey rocks in it, and I want to get the area under the crown of the rock as Zone V, I would lay the card on this area of the rock? This assumes that the card will assume a plane equal to the zenith of the rock...

Hope this makes some sense!!

Lachlan.

I don't understand why you would even want to put the gray card in this scene to meter. You've already decided what you want to be middle gray in the scene, i.e., "the area under the crown of the rock as Zone V." You've visualized (previsualized if AA) the rock as zone V and so meter it and set your exposure to the suggested meter reading. If your ISO is set correctly, the rock will be middle gray. Other values may be off, but the rock should be middle gray.

Now suppose you used the gray card to meter. Further assume the rock doesn't actually match the 18% desired. Let's say it is darker. If you meter the gray card and expose accordingly, the rock will be darker than the gray card. That's not what you envisioned. So, regardless as to whether the rock matches the gray card or not, you want to meter and place the rock on zone V, not the gray card, if you want the rock middle gray.

The zone system revolves around metering and exposing for the shadows and determining development based on where the highlights (or in your example,, the important middle tones) fall. But, that's a much more involved topic. IMO, the gray card is more useful in the studio where lighting and subject values can be controlled, lighting ratios adjusted, etc.

While the following might seem way off topic here, I think it is relevant to the concept of visualization. As an exercise in metering & visualization set up several gray cards on light stands with the white side towards a photoflood in an otherwise darkened room. Set the lights in a line at distances equivalent to whole f/stop values. Elevate successive cards so they don't cast a shadow on each other.

You might have a light at 16', another at 11', a third at 8' and another at 5.6' from the lamp. Each of these will be approximately one stop or zone darker than the previous one as distance increases from the lamp. Looking down the line you can actually see the white cards take on different values.

You could use another gray card closer to the lamp (probably around 4.5') and its gray side to match tones with one of the white cards further out (11'). You've just made that single white card represent zone V in your visualization. The adjacent cards appear as zone IV (farther away) and zone VI (closer to the lamp) and zone VII for the closest. You can easily see the difference and how placing one luminance affects the visualization/reproduction of the other cards. Now here's the kicker: while looking down the line, turn the free gray card around so that its white side is at 4' from the lamp. Your entire perception and visualization of the tones of the other white cards will change as the nearer card becomes a whiter white perceptually. Take the card at 4' and put it at 22' and the entire scale shifts perceptually again.

If you wanted to, you could meter to place specific cards on specific zones and see the effect on where the other cards would fall in relation to that decision. This is very similar to what you do in the field when metering and placing values. It takes some practice but eventually becomes second nature.

As far as the gray card in the landscape, it might help you identify which objects match the brightness of the card or show which are lighter or darker, but it isn't going to really help you if you decide to do anything other than an average exposure. You may as well use an incident meter in that situation (and here's where the BTZS people take over the convo).

Hope this helped clarify rather than confuse.

Joe

[Jeff Conrad]

Directions included with Kodak gray cards indicate, for a frontlighted outdoor scene, to hold the card vertically, oriented halfway between the light source and the camera, and increase the metered exposure by 1/2 step. This is at best an approximation, because exposure meter calibration derives from integrated (average) scene luminance, and has nothing to do with a gray card.

I agree with Steve that it's far more important to know where the highs and lows fall; if they're under control, the midtones fall where they will, and can be adjusted in post-exposure processing if necessary. If the highs (for reversal film) or lows (for negative film) are out of bounds, the information isn't there and the image is lost.

[Helen Bach]

I don't have much to add to the previous answers, except that one advantage of using an incident meter instead of a grey card is that incident meters with domes or Invercones may make more sense for three-dimensional objects because they are three-dimensional in themselves, and they take account of light coming from the side and even from the back - they are generally considered to have a cardioid response instead of the cosine response of a grey card.

The other thing is that Minor White, in his Zone System Manual, covers the use of grey card readings for estimating subject brightness range.

Finally, here is a photo of Professor Karapetoff using the 14% Neutrowe Gray Card in '39 or '40. I didn't take the photo.

http://gallery.photo.net/photo/5322017-lg.jpg

Best,
Helen

[Brian Ellis]

Thanks, Tim.

So, to put this into a real life situation, if I was shooting a creek with some round-ish grey rocks in it, and I want to get the area under the crown of the rock as Zone V, I would lay the card on this area of the rock? This assumes that the card will assume a plane equal to the zenith of the rock...

Hope this makes some sense!!Lachlan.

Sorry but it doesn't make sense to me. If you want to get the area under the crown of the rock as Zone V, why not just meter the area? The resulting reading will be Zone V (approximately but as close as any meter reading gets given the fact that the zone system involves zones, not pin points). In other words, I don't see what purpose the gray card serves. I've used gray cards for color balance purposes but never to determine exposure. For that I find the darkest area in the scene in which I want texture or detail (i.e. that I don't want to appear as solid black), meter it, and stop down one or two stops. It's really pretty simple, at least with a spot meter.

[Lachlan 717]

It's really pretty simple, at least with a spot meter.

Thanks, Brian.

Whilst I understand how to use a spot meter and the Zone System, I was actually after advice on how to place a grey card. Seems my scenario has taken this post somewhat off topic.

Lachlan.

[vonstauren]

Can anyone assist with advice on how to position an 18% Grey Card?

Many threads refer to "...place your grey card and..." without explaining [I]exactly[I] how this should be done.

Should I lace the card so that it is parallel to the film plane? Do I tilt it towards the sun?

Thanks in advance for any help!!

Lachlan.

Take it with a common sense, it's enough. The gray card should logically be in the same angle toward the Sun as the subject surface you want to measure. If that surface were a huge gray card, you should have the same result.That is, if the church wall is 40° off the sun direction and you want to measure the exposure for it, you incline the gray card in the same way as the wall is directed. Were the wall of a gray color it would be a huge gray card to measure from. Of course, as the subject has many faces you will always get some parts that do not correspond to the measured angle but that's life. Then you have to average in whatever logical way...

[Brian Ellis]

Thanks, Brian.

Whilst I understand how to use a spot meter and the Zone System, I was actually after advice on how to place a grey card. Seems my scenario has taken this post somewhat off topic.

Lachlan.


You said you hoped your scenario made sense. I was responding to that. It doesn't make sense, at least to me. But if you insist on using a gray card then just aim the card at the camera lens and place it at an angle such that there's no glare coming from the card. I think that's about as good as you can do when you're using a gray card outdoors to determine exposure.

[Jorge Gasteazoro]

Jesus, why does everything has to be a pissing match lately?


So, to put this into a real life situation, if I was shooting a creek with some round-ish grey rocks in it, and I want to get the area under the crown of the rock as Zone V, I would lay the card on this area of the rock? This assumes that the card will assume a plane equal to the zenith of the rock...


You got it right, someone mentioned put the gray card in the same light as your subject, so for your scenario, yes you would place the gray card on the area of the rock that you want to be zone V, meter the card and the meter the rock and you can determine how much to vary the exposure.

If you have an incident meter, this is the same as a gray card, just place the dome towards the light source next to your subject and meter.

[GPS]

...
If you have an incident meter, this is the same as a gray card, just place the dome towards the light source next to your subject and meter.

Dear lovely Jorge, why would you place the dome toward the light source? Or do you mean just not to put the exposure dome the other way round, backward?:) The dome is there just to take care of the direction of the light source, it should face the camera as the subject does. I must be missing something in your expression...