did I make a useable "gray card"?
 

I live WAY out in the boonies with NO photo stores around so:

I lightly sprayed a white card with black paint until my reflected-light
meter read it the same as the meter (with the incident light bubble on it)
read the light source (sun) .

Have I now a usable "gray card"?

Nat

did I make a useable "gray card"?
 

Sounds like it.


nat wrote:
I live WAY out in the boonies with NO photo stores around so:

I lightly sprayed a white card with black paint until my reflected-light
meter read it the same as the meter (with the incident light bubble on it)
read the light source (sun) .

Have I now a usable "gray card"?

Nat

did I make a useable "gray card"?
 

"nat" wrote

I lightly sprayed a white card with black paint until my reflected-light
meter read it the same as the meter (with the incident light bubble on it)
read the light source (sun) .

Have I now a usable "gray card"?

Yes.

You can use just about anything as a grey card if you are willing to
'calibrate' it:

o Meter a white sheet of paper and meter a 'typical scene' or measure
the incident light. Note the difference in the reading from the sheet
of white paper - this is a the 'calibration factor'. Use the white
paper as a grey card and apply this calibration factor to the
meter reading of the grey card.

o One's hand makes a good grey-card substitute: meter the palm of the hand
and open up one stop.

A 'neutral' grey card - where the card has no color - is a sometimes useful
thing to have in color photography.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
Fstop timer - http://www.nolindan.com/da/fstop/index.htm

did I make a useable "gray card"?
 

"nat" wrote in message
...
I live WAY out in the boonies with NO photo stores around
so:

I lightly sprayed a white card with black paint until my
reflected-light meter read it the same as the meter (with
the incident light bubble on it) read the light source
(sun) .

Have I now a usable "gray card"?

Nat

If it reads the same its usable. Actually, you can use a
white card. Kodak gray cards are white on the back with
about 90% reflectivity. White paper withou brighteners is
around this. Simply devide the reading by 5, or set the film
speed for five times the value you want. I think you can get
sheets of art paper with better diffusing surfaces than the
usual gray card. My Kodak cards have a considerable amount
of specular reflection which makes it necessary to be very
careful of the angle of light vs: meter.


--
---
Richard Knoppow
Los Angeles, CA, USA

did I make a useable "gray card"?
 

Probably not, the Gray Card (my caps) reflects about 18% white light but
also about equal amounts of the red, green, and blue components (which I
guess is why white light is white). But your gray card is probably "gray
enough" for the real word (assuming that the meter in your camera is
calibrated to an 18% reflectance (and some are not) and that your camera
meter was looking only at the card and that there was no stray light coming
in the eyepiece of your camera while you metered the card you made and ...
oh heck ... it's fine ... never mind.

Real Gray Cards get dirty, change with time, etc. MacBeth Color Checkers
aren't perfect either and are not stable over time (and I think MacBeth
changed the standard a couple of times, too.).

So find what works, the only problem I have with you system is that it's not
very repeatable. Might be better to find a color of Formica that matches
18% and but a 3x6 foot sheet and cut it up into a pile of gray cards or a
shade of automotive primer (gray) that's close enough to live with. Or even
gray matt board. So that you have a supply of identical cards but that's
just me fussin' again.

--
darkroommike

"nat" wrote in message
...
I live WAY out in the boonies with NO photo stores around so:

I lightly sprayed a white card with black paint until my reflected-light
meter read it the same as the meter (with the incident light bubble on it)
read the light source (sun) .

Have I now a usable "gray card"?

Nat

did I make a useable "gray card"?
 

Probably not, the Gray Card (my caps) reflects about 18% white light but
also about equal amounts of the red, green, and blue components (which I
guess is why white light is white)....oh heck ... it's fine ... never
mind.

So find what works....

Thank you, Mike, for the learned treatise. You got me thinking(?) and I came
up with the memory of the suggestion to just use the palm of my hand for a
target. I went out and tried it....WOW...only 1/2 stop off the incident
reading.

Should work OK...I wash 'em every week or so, dirty or not.

Thanks again,

Nat nhooCLOTHESh616(at)yahoo(dot)com
Oxford, AR
(please remove CLOTHES to eee-mail)

did I make a useable "gray card"?
 

"nat" wrote in message
et...
Probably not, the Gray Card (my caps) reflects about 18%
white light but
also about equal amounts of the red, green, and blue
components (which I
guess is why white light is white)....oh heck ... it's
fine ... never mind.

So find what works....

Thank you, Mike, for the learned treatise. You got me
thinking(?) and I came up with the memory of the
suggestion to just use the palm of my hand for a target. I
went out and tried it....WOW...only 1/2 stop off the
incident reading.

Should work OK...I wash 'em every week or so, dirty or
not.

Thanks again,

Nat nhooCLOTHESh616(at)yahoo(dot)com
Oxford, AR
(please remove CLOTHES to eee-mail)
You may find the back of your hand is even closer. A
white card can be used instead of a gray card if its
reflectivity is assmumed to be about 90%. This will be
pretty close. Devide the reading by 5 or multiply the film
speed by 5.


--
---
Richard Knoppow
Los Angeles, CA, USA

did I make a useable "gray card"?
 

You may find the back of your hand is even closer.

Thanks Richard. I tried that, but my old hand is so wrinkled the angle
becomes fussy.


--
Nat nhoclothesop616(at)yahoo(dot)com
Oxford, AR
(please remove clothes to eee-mail)

did I make a useable "gray card"?
 

Hi all,

I've measured the palm of my hand against a Kodak 18% and I have just
under an f difference. Very handy. I also have a T-shirt that I bought
at the Kodak Museum in Rochester that is 18% grey and has 18% print on
the back. Actually it's .5f off from the Kodak Paper Card, probably
because the T-shirt is cotton and thus not very, very reflective.

Regards, Bogdan

Richard Knoppow wrote:

"nat" wrote in message
et...

Probably not, the Gray Card (my caps) reflects about 18%
white light but
also about equal amounts of the red, green, and blue
components (which I
guess is why white light is white)....oh heck ... it's
fine ... never mind.

So find what works....

Thank you, Mike, for the learned treatise. You got me
thinking(?) and I came up with the memory of the
suggestion to just use the palm of my hand for a target. I
went out and tried it....WOW...only 1/2 stop off the
incident reading.

Should work OK...I wash 'em every week or so, dirty or
not.

Thanks again,

Nat nhooCLOTHESh616(at)yahoo(dot)com
Oxford, AR
(please remove CLOTHES to eee-mail)

You may find the back of your hand is even closer. A
white card can be used instead of a gray card if its
reflectivity is assmumed to be about 90%. This will be
pretty close. Devide the reading by 5 or multiply the film
speed by 5.



--
__________________________________________________ ________________
Bogdan Karasek
Montr‚al, Qu‚bec e-mail:
Canada

"Wovon man nicht sprechen kann, dar�ber muss man schweigen"
"What we cannot speak about we must pass over in silence"
Ludwig Wittgenstein
__________________________________________________ ______________

did I make a useable "gray card"?
 

hm... did you wash your hands first ?
;-)

BTW I'd use a non-reflecting gray paint and make it cover the card
fully instead of spraying partially covering black paint.