Disparity between 18% gray cards

medformatjunkie · May 25, 2016

Not sure if this is the right forum to post this but seemed correct. I'm getting back into black and white photography after a very long hiatus and I'm starting to pick up supplies. My main interest is pinhole so I recently got a Black Cat exposure guide that has a gray card on the back. The other day I ordered a couple of Analogbooks and they also have gray cards on the back. Right away I noticed there is a difference between the two. One was slightly darker than the other.
I decided to check them with my spot meter in direct sun and there was a difference of half a step. I'll have to experiment to see what effect this has on my exposures, if any but was wondering if anyone else have experienced this?

RalphLambrecht · May 26, 2016

medformatjunkie said:
Not sure if this is the right forum to post this but seemed correct. I'm getting back into black and white photography after a very long hiatus and I'm starting to pick up supplies. My main interest is pinhole so I recently got a Black Cat exposure guide that has a gray card on the back. The other day I ordered a couple of Analogbooks and they also have gray cards on the back. Right away I noticed there is a difference between the two. One was slightly darker than the other.
I decided to check them with my spot meter in direct sun and there was a difference of half a step. I'll have to experiment to see what effect this has on my exposures, if any but was wondering if anyone else have experienced this?

neutral gray cards can be different from one manufacturer to the next depending on their QC. There are also not always 'neutral' in color. I make my own by printing a 56%lack on my Epson 3880.measured with my densitometer,the reflection density is always exactly0.75,which is equivalent to an 18% reflection.Judging by eye ,it is also color neutral as expected.

DREW WILEY · May 26, 2016

They not only differ between manufacturers, but even lot to lot, or due to fading. Basically, the quality control of routine gray cards tends to be awful.
I keep on hand a carefully stored MacBeath color checker chart with its own gray scale. This is one of the good ones. In other words, buy an expensive gray card as a reference to check any of your casual ones. But a secondary problem is that meters do not themselves have identical spectral sensitivity, so any deviance from true neutral gray on a card will also affect readings (and in this respect also, most of them are way off,
so one more reason to have color-correct hues and neutral on a MacBeath etc chart).

Chan Tran · May 27, 2016

You can get a cheap reflection densitometer from ebay. They are the dying breed. The printing industries now use photospectrometer. Film processing industries is small now so I don't see densitometer being made any more.

RalphLambrecht · May 27, 2016

Chan Tran said:
You can get a cheap reflection densitometer from ebay. They are the dying breed. The printing industries now use photospectrometer. Film processing industries is small now so I don't see densitometer being made any more.

Luckily for us Heiland Electronics in Germany still makes very good densitometers and BTW ,there are lots of uses for them in d***** too

DREW WILEY · May 27, 2016

There are all kinds of industrial uses for densitometers. The companies that make them (like X-Rite) are doing better than ever due to the technology
branching out into digital measuring instruments, color matching machines, biotech applications, etc. Simple transmission density readers are still readily available new, though used ones are abundant. But that's not the kind of machine I used when comparing stacks of gray cards. I used a high
end spectrophotometer that went a full step both directions past the visual spectrum. In other words, I could plot precise hue and not just reflection density. There is absolutely no need for this kind of instrument in a typical photo lab, even if you could afford one. I simply had one available to me,
so what the heck...

dasBlute · May 27, 2016

medformatjunkie said:
... I decided to check them with my spot meter in direct sun and there was a difference of half a step.

You can get that just by varying the card orientation in relation to the sun. I was never able to use the
'meter off the grey card' technique to any degree of success. I'd rather meter the shadows.

gone · May 27, 2016

I had the same experience. After trying a grey card one time I abandoned it, and simply bought a good hand held meter that could be used as a reference for other cameras and meters. I've never been in a situation outdoors that I couldn't find a middle value somewhere. Those cards are just something else to slow you down, and as noted, will vary considerably depending on the angle they're held. Besides, is it an 18% grey card or a 12% grey card? They make both, which probably accounts for your different readings.

medformatjunkie · May 27, 2016

Well, I have been enlightened. I guess I was naive enough to believe that all gray cards were created equal. I appreciate the info. I think it's about time I end my dependency on them!

DREW WILEY · May 27, 2016

With color film I'm concerned with hues properly saturating how I want them to. So I am mainly concerned with things equivalent to midtone readings, along with how far up I can expect highlights to hold color. There is only so much you can do with shadows under such circumstances,
especially when shooting chromes. Otherwise, one simply gravitates to cooperative lighting situations, unless working in a studio where light ratios
can be artificially controlled. With black and white film you can significantly futz around with development to help the film match to scale you need.
So the most important thing is to make certain the neg contains sufficient shadow content: "expose for the shadows, develop for the highlights".
Therefore the most critical measurement is in fact the lowest shadow value where you wish to retain gradation, followed by the highest value where you want recognizable texture. Of course, after awhile you might become so accustomed to a particular type of lighting and subject matter that this
becomes rote. But when it comes to meters, what counts is sheer familiarity with how your own meter behaves in relation to your chosen films,
and then, reliability of the meter itself. And these do need to be checked for accuracy from time to time. That's why I keep around a fresh spare
meter - both to periodically check my other meters, and to serve as a backup when one of them finally wears out.

benjiboy · May 27, 2016

i suggest you buy a pack genuine Kodak 18% Grey Card they are correct, I bought one about forty years ago and am still using it http://www.bhphotovideo.com/c/product/27715-REG/Kodak_1903061_Gray_Cards.html

Ronald Moravec · Aug 23, 2016

Kodak grey cards are used to set a print exposure in the red channel. If you want a true neutral grey, get a WhiBal card which is true grey and 18%. They are made to WB a digital camera and are very very accurate. These are my most used and the other is the large color checker.

The checker is excellent for finding filter corrections. Find the correct exposure for grey, then adjust f stop the get the same density thru the filter. Repeat for sun, and tungsten, flash.

AgX · Aug 23, 2016

Have a look at
www.fotowand.de

A one-man show of a guy who is obsessed with gray (and thus with colours). He started 31 years ago manufacturing grey-cards just because he got fed up by discrepancies between and shortcomings of the cards marketed so far.
The site is a mess, but his offer of cards is amazing.

darkroommike · Aug 23, 2016

It's tough to make a perfect gray card, most of the processes used can produce pretty darn good cards, it's an individual call to determine if PDG is good enough. The Kodak cards, produced with offset printing, and as others have said, were originally intended to balance color prints. When we were leaning to print in One Hour Lab School we were warned about chasing ourselves by trying to overcorrect the process, this can create a positive feedback loop, which is never a good thing. Close is usually close enough. Consistent is better than perfect (since perfect does not exist). And evaluate all your field use cards against one master reference is also a good idea.

wiltw · Aug 23, 2016

Ronald Moravec said:
Kodak grey cards are used to set a print exposure in the red channel. If you want a true neutral grey, get a WhiBal card which is true grey and 18%. They are made to WB a digital camera and are very very accurate. These are my most used and the other is the large color checker.

The checker is excellent for finding filter corrections. Find the correct exposure for grey, then adjust f stop the get the same density thru the filter. Repeat for sun, and tungsten, flash.

Oh no, some horridly bad information! Even WhiBal lets people know that their product is specifically for WHITE BALANCE. One should NOT base EXPOSURE measurements from their card, it is specifically made to be NEUTRAL but it is NOT 18% midtone.

Disparity between 18% gray cards

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