Kodak grey card usage

Diapositivo · Mar 22, 2016

RobC said:
Actually its says if your subject is quite light(???) then decrease exposure by 1/2 to 1 stop and if subject is quite dark(???) then increase your exposure by 1/2 to 1 stop. Thats a lot of use to people using slide film and only marginally better for people using negative film.
??? What does quite light and quite dark mean. I presume it measn high or low contrast but how high or how low. Its just another pointless ball park guesstimate approach.

I presume it means so high as to be near the toe (when you use slide film) or so dark as to risk to block shadows.
That's exactly the same advice given with incident light meters.
If you have a grey cat and you measure exposure with the grey card (or the grey cat) everything is fine and dandy.
But if you have a white cat (one of those who seem to have come out from the washer) and you use an incident light meter (or the grey card method) you end up placing the cat somewhere in a zone of your slide film which might not have a very good rendition of the texture.
So you decrease a bit the exposure.
That's normal practice when photographing flour, sugar, snow, bride dress etc.
People will instantly know it's a white subject and will compensate, in their brain, for the slight hint of grey. But that slight hint of grey will allow you to record all the texture very clearly.

It all sums up with the fact that the measure of the incident light meter (which is what is attempted when using a grey card) works very well for normal subjects but can lead to trouble with non-normal subjects (high contrast of illumination, high reflectivity ratio, high-key subject, low-key subject). Those are all situations where the subject can "fall" outside of the best zone of rendition and only a spot meter gives you certitudes. IMHO.

RobC · Mar 22, 2016

Old-N-Feeble said:
spot meter... no gray card

its grey, not gray. They can't even get the spelling right.

DREW WILEY · Mar 22, 2016

I'm so glad that I learned to use a spotmeter on a wide range of natural subjects a long time ago. Don't need to use a gray card at all, and my brain
doesn't work anymore. All my meters are the same kind and read identically. That should last me for the long haul. Now all my exposures are based on sheer inertia in a vacuum. Fine until I run into an asteroid. Maybe gray cards are like gray hair. As you age, the less you like to think about it.

BrianShaw · Mar 22, 2016

I always thought it was "grai" but that was beaten out of me by the nuns.

Old-N-Feeble · Mar 22, 2016

RobC said:
its grey, not gray. They can't even get the spelling right.

Ha ha... you Brits never kood spel rite!!

RobC · Mar 22, 2016

fact is the kodak grey card being representative of the average subject luminance, only works for subjects of average luminance. What you need is a meter which tells you if your subject s average luminance. Oh, we've got one, a grey card. Only problem is you need to use it to detrmine lighting ratios which involves using it at several angles, taking several readings and getting the angles correct and then yo can adjust your exposure based on those several readings.
But if you have calibrated your film speed, dev and printing, then you can use a spot meter whilst standing at camera, and not running backwards and forwards between camera and subject to place grey card, and just meter anything you like and expose it on whatever tone(zone) you like without using a grey card.
I know which is a lot easier.

Stephen Benskin · Mar 22, 2016

Gray or Grey
The colour ("color" if you're an American) between black and white can be written gray or grey.

In the US, the spelling gray is far more popular than grey, and this has been the case since at least the early 19th century. As a result, many Americans consider grey to be a spelling mistake.

Outside the US, the spelling grey (which has been around for nearly 1,300 years) still dominates.

RobC · Mar 22, 2016

Old-N-Feeble said:
Ha ha... you Brits never kood spel rite!!

You don't have german ancestry do you? This is why we want to get out of the EU...
Native Germans of a sensitive nature should not read below here.

The European Commission have just announced an agreement whereby English will be the official language of the EU, rather than German, which was the other possibility. The Germans were initially reluctant to accept this but conceded after negotiations with Her Majesty's government.
The agreement was that the English spelling had some room for improvement and it was accepted that a five year programme of change would be done to implement these spelling changes in a new "EuroEnglish".
In the first year, "s" will replace the soft "c". Sertainly, this will make the sivil servants jump for joy. The hard "c" will be dropped in favour of the "k". This should klear up konfusion and keyboards kan have 1 less letter.
There will be growing publik enthusiasm in the sekond year, when the troublesome "ph" will be replaced with "f". This will make words like "fotograf" 20% shorter.
In the third year, publik akseptanse of the new spelling kan be expekted to reach the stage where more komplikated changes are possible. Governments will enkorage the removal of double letters, which have always ben a deterent to akurate speling. Also, al wil agre that the horible mes of the silent "e" in the language is disgraseful, and they should go away.
By the 4th year, peopl wil be reseptiv to steps such as replasing "th" with "z" and "w" with "v".
During ze fifz year, ze unesesary "o" kan be dropd from vords kontaining "ou" and similar changes vud of kors be aplid to ozer kombinations of leters. After zis fifz year, ve vil hav a realy sensibl riten styl. Zer vil be no mor trubls or difikultis and evrivun vil find it ezi to understand each ozer.
Finali ve hav von!

Old-N-Feeble · Mar 22, 2016

^^^ Well, ain't that better 'n Orson Welles' 'new speak'? Das ist gut, ya??

BTW, most people don't know (including most Americans) that English was adopted, as the official USA national language, won by only one vote against German.

I sometimes wonder how that might have affected WW2.....

BrianShaw · Mar 22, 2016

Hilarious, Rob!!!!!!!!

Old-N-Feeble · Mar 22, 2016

And BTW, I'm Irish and Scottish... so DON'T PISS ME OFF!!

Poisson Du Jour · Mar 22, 2016

Stephen Benskin said:
Gray or Grey
The colour ("color" if you're an American) between black and white can be written gray or grey.

In the US, the spelling gray is far more popular than grey, and this has been the case since at least the early 19th century. As a result, many Americans consider grey to be a spelling mistake.

Outside the US, the spelling grey (which has been around for nearly 1,300 years) still dominates.

Differences in spelling is a bit of a grey area...
There are people in Australia (particularly in medicine) who do take a tilt at the American gray, perhaps on account of reading too many books published in the US which adhere to the US spelling doctrine.

RobC · Mar 22, 2016

Old-N-Feeble said:
And BTW, I'm Irish and Scottish... so DON'T PISS ME OFF!!

No need to, it's a natural trait

wiltw · Mar 22, 2016

Diapositivo said:
If you have a grey cat and you measure exposure with the grey card (or the grey cat) everything is fine and dandy.
But if you have a white cat (one of those who seem to have come out from the washer) and you use an incident light meter (or the grey card method) you end up placing the cat somewhere in a zone of your slide film which might not have a very good rendition of the texture.
So you decrease a bit the exposure.
That's normal practice when photographing flour, sugar, snow, bride dress etc.
People will instantly know it's a white subject and will compensate, in their brain, for the slight hint of grey. But that slight hint of grey will allow you to record all the texture very clearly.

It all sums up with the fact that the measure of the incident light meter (which is what is attempted when using a grey card) works very well for normal subjects but can lead to trouble with non-normal subjects (high contrast of illumination, high reflectivity ratio, high-key subject, low-key subject). Those are all situations where the subject can "fall" outside of the best zone of rendition and only a spot meter gives you certitudes. IMHO.

RobC said:
But if you have calibrated your film speed, dev and printing, then you can use a spot meter whilst standing at camera, and not running backwards and forwards between camera and subject to place grey card, and just meter anything you like and expose it on whatever tone(zone) you like without using a grey card. I know which is a lot easier.

I just thought I'd do this as described, to see how 'infallible' the incident meter would be...
Subject: a bit of flour and a bit of sugar on a white plate
Sunlight late afternoon (4:45pm) meter pointed straight up to the sky (and at the lens)...
ISO 400, 1/1600 f/5.6 +0.3EV metered.
Shots at ISO 400 f/5.6, shutter speeds 1/1600 (0EV) 1/2000 (-0.33EV) 1/2500 (-0.66EV) (left to right)...

Sure enough, the exposure made at -0.66EV from incident metered resulted in the 'best' rendition of sugar and flour.
So then I angled the hemisphere and metered the result....
The best result, for incident meter which best matches the actual exposure in the above series, required the hemisphere to be pointed to the SUN, not pointed at the camera lens (contrary to popular opinion, but matching the aim-at-source technique which I believe to best protect highlights for transparencies or digital!) Yet even then the incident meter suggested +0.2EV more exposure than the right most shot was exposed in the series above.

BrianShaw · Mar 22, 2016

Since the white plate and, umm, mysterious white powder are nearly 2-D... shouldn't you have used a flat disk diffuser instead of the dome?

markbarendt · Mar 22, 2016

silveror0 said:
And then there's roll film with multiple exposure situations and only one compromising development possible.

Not a compromise, a transfer of work to the enlarger.

RobC · Mar 22, 2016

I think that if you are going to point meter at light source you should use the flat disc and not the hemisphere.
maybe your lighting was "quite light".

The hemisphere was designed specifically for pointing at camera with the intention of metering the average luminance whereas the flat disc is for metering the light source direct which is why you use the flat disc for metering lighting ratios, especially in the studio with more than one light source.

And metering light source direct with flat disc should be closest to metering grey card angled to reflect 16% with reflection meter. Now all you need to know is what angle to use to get a grey card to reflect 16% to the camera
Once you've tested for which angle to use then you have it nailed to get your grey card to work like an incident meter. Might just be easier to use an incident meter and not bother with reflection meter.

Oooops Brian beat me to it.

wiltw · Mar 22, 2016

BrianShaw said:
Since the white plate and, umm, mysterious white powder are nearly 2-D... shouldn't you have used a flat disk diffuser instead of the dome?

Nice idea, here is the result...

Hemisphere at lens f/5.6 +0.3EV
Hemisphere at sun f/5.6 +0.8EV
Flat disk at lens (sun has lowered in a sky by 5:25pm): f/4 + 0.7EV
Flat disk at sun: f/8.0 +0.0EV

So the best result matching the actual exposure for best result was #4 aimed at the source, not parallel to the 'flat' subject!

markbarendt · Mar 22, 2016

wiltw said:
I just thought I'd do this as described, to see how 'infallible' the incident meter would be...
Subject: a bit of flour and a bit of sugar on a white plate
Sunlight late afternoon (4:45pm) meter pointed straight up to the sky (and at the lens)...
ISO 400, 1/1600 f/5.6 +0.3EV metered.
Shots at ISO 400 f/5.6, shutter speeds 1/1600 (0EV) 1/2000 (-0.33EV) 1/2500 (-0.66EV) (left to right)...

Sure enough, the exposure made at -0.66EV from incident metered resulted in the 'best' rendition of sugar and flour.
So then I angled the hemisphere and metered the result....
The best result, for incident meter which best matches the actual exposure in the above series, required the hemisphere to be pointed to the SUN, not pointed at the camera lens (contrary to popular opinion, but matching the aim-at-source technique which I believe to best protect highlights for transparencies or digital!) Yet even then the incident meter suggested +0.2EV more exposure than the right most shot was exposed in the series above.

Your conclusion does not surprise me, Pointing the meter at the main light protects the highlights.
In contrast though the furthest left shot protected the mid/lower tones better so...

Kevin Caulfield · Mar 22, 2016

RobC said:
its grey, not gray. They can't even get the spelling right.

Sorry, but I can't resist...

It's "it's" not "its".

markbarendt · Mar 22, 2016

BrianShaw said:
Since the white plate and, umm, mysterious white powder are nearly 2-D... shouldn't you have used a flat disk diffuser instead of the dome?

There was a time I thought that too, not so much anymore.

wiltw said:
Nice idea, here is the result...

Hemisphere at lens f/5.6 +0.3EV

Hemisphere at sun f/5.6 +0.8EV

Flat disk at lens (sun has lowered in a sky by 5:25pm): f/4 + 0.7EV

Flat disk at sun: f/8.0 +0.0EV

So the best result matching the actual exposure for best result was #4 aimed at the source, not parallel to the 'flat' subject!

The big difference between sphere and disk is angle of view. You can be more specific about what the meter sees.

For example "Flat disk at lens (sun has lowered in a sky by 5:25pm)" is seeing just the sky so it protects the shadow detail. While "Hemisphere at lens f/5.6 +0.3EV" at the same time is seeing the sky and some sun so it compromises between the two light sources. "Flat disk at sun" protects the highlights at the expense of mid and low tones.

There isn't a wrong choice here, you just apply an artistic bias by choosing one metering method over another.

wiltw · Mar 22, 2016

markbarendt said:
For example "Flat disk at lens (sun has lowered in a sky by 5:25pm)" is seeing just the sky so it protects the shadow detail. While "Hemisphere at lens f/5.6 +0.3EV" at the same time is seeing the sky and some sun so it compromises between the two light sources. "Flat disk at sun" protects the highlights at the expense of mid and low tones.

There isn't a wrong choice here, you just apply an artistic bias by choosing one metering method over another.

I like your interpretation! It is similar in concept to my explanation of pointing at the source for transparency shot in studio, vs. pointing at the lens for portrait shot on color neg in the studio...it depends upon what you are 'protecting', neither iapproach s wrong if used at the right time, and neither approach is always 'best'.

markbarendt · Mar 23, 2016

wiltw said:
I like your interpretation! It is similar in concept to my explanation of pointing at the source for transparency shot in studio, vs. pointing at the lens for portrait shot on color neg in the studio...it depends upon what you are 'protecting', neither iapproach s wrong if used at the right time, and neither approach is always 'best'.

That my friend is the magic of getting a good exposure, understanding your intent and the light sources. There's no math involved in figuring out your intent, once that's decided the meter (any meter) is just a measuring stick.

The gray card and a spot meter can do the same thing. Just ask yourself what's the card seeing and what am I trying to protect?

Diapositivo · Mar 23, 2016

The flour rendition is lacking detail in the first picture because it sits on the beginning of the toe (for slide or digital).
My approach would be, as stated, to just move the exposure so as to place the flour in a zone of better texture.

So my procedure is:
1) always meter as you would normally do, using the normal dome normally aimed at the lens;
2) manually compensate according to subject. In the flour case (or any very white subject where texture matters), decreasing exposure by 0.5 EV should work to place it again in a comfort zone. For a black velvet I would open 0.5 EV more than the light meter indication normally taken.

Aiming the meter at the source IMHO might give erratic behaviour. In a cloudy day the exposure compensation would be different than in a sunny day.

I would personally never use the meter aimed at the source if not for checking illumination contrast (lighting ratio). And in that case a disc would be appropriate, and I don't even have it.

markbarendt · Mar 23, 2016

Diapositivo said:
Aiming the meter at the source IMHO might give erratic behaviour. In a cloudy day the exposure compensation would be different than in a sunny day.

"erratic" Giggle, those techniques aren't new. They are just different than today's norm.

The disk measurement is standard fare in a studio even today.

Aiming the meter at the light is one of the most accurate ways to meter, it just requires a little thought.

Practice with just the meter, leave the camera at home, just meter and try to see what it's telling you and see how many ways you can find to get to the same camera setting.

Kodak grey card usage

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