Ansel adams moonlight equation

[Manuel Madeira]

Hi guys, I heard about that moon photo that ansel adams took, and I heard the story behind it to, he didnt had his light meter and did some tyoe of equation, can you guys explain that to me???

 

[MurrayMinchin]

May as well get it from here:

https://www.anseladams.com/ansel-adams-anecdotes/

 

[wiltw]

Just amazing Ansel Adams knew the luminance of the moon—250 c/ft2 !

 

[MattKing]

Just amazing Ansel Adams knew the luminance of the moon—250 c/ft2 !

Not as surprising as you might think.
The moon is a common element in a fair number of landscape photos, and he would have had experience working in those units when working with exposure.

 

[wiltw]

Not as surprising as you might think.
The moon is a common element in a fair number of landscape photos, and he would have had experience working in those units when working with exposure.

Matt, I have a very long history in photography, 58 of my 71 years as a serious hobby and professionally. I have never dealt with luminance apart from reading about it in photography testbooks...never on a practical level. And that is why I find his knowledge so remarkable...it is not normally the knowledge of exposure determination. I do know the Moony 11 rule of thumb. It makes me wonder how many know what a candela is, without looking it up!

 

[RalphLambrecht]

Hi guys, I heard about that moon photo that ansel adams took, and I heard the story behind it to, he didnt had his light meter and did some tyoe of equation, can you guys explain that to me???

I read it in his book (The Negative?)but, since he explained it in foot-candles, I didn't care to remember it.

 

[reddesert]

Ansel, clearly, had studied the technical aspects of photography intensively. I also expect that the Old Ones who took up photography when films and meters were more primitive, either did it entirely by the seat of their pants, or were more familiar with luminance than we are now.

Another way of looking at the moon is the "looney f/11" rule - the full moon is in direct sunlight, but its surface is fairly dark, so to correctly expose the moon a rule of thumb is to modify sunny-16 to be f/11 at 1/ISO. Let's try applying that to Ansel's situation. He had ASA 64 film, used f/32, and a yellow filter with a filter factor of 3x. This was 1941 before ASA was redefined to eliminate the safety factor, so his film was really ASA ~ 125 in today's terms. So looney f/11 would put the moon at Zone V at f/11 at 1/125. He put the moon at Zone VII to make it lighter, so that's f/11 at 1/30 sec. He used f/32, so f/32 at 1/4 sec. And there was a filter factor of 3x, so that says f/32 for 3/4 sec. Which is surprisingly close to what Ansel used, f/32 at 1 sec.

Of course, I had to count stops on my fingers several times while doing that, and there is no way I could have gotten it right while focusing and pulling a dark slide.

 

[grain elevator]

Just amazing Ansel Adams knew the luminance of the moon—250 c/ft2 !

As reddesert mentioned, the moon is just another object in direct sunlight, and I seem to recall reading somewhere that A.A. used a light meter that read in c/ft² (one for motion picture use?), so it wouldn't be surprising that he thought in and used these units rather than "sunny 11" or "EV(100) 12".

 

[grain elevator]

As reddesert mentioned, the moon is just another object in direct sunlight, and I seem to recall reading somewhere that A.A. used a light meter that read in c/ft² (one for motion picture use?), so it wouldn't be surprising that he thought in and used these units rather than "sunny 11" or "EV(100) 12". And then he apparently opened up two stops t9 get a brighter moon, or more likely, to get as much exposure for the landscape as possible without blowing out the moon.

 

[BrianShaw]

I always, and still do, took that story as a bit of a tall tale.

 

[Carter john]

Here is something similar to what Murray posted with Roger Hicks take on 'Moonrise.'

Moonrise


Ansel Adams had mislaid his exposure meter, so he based his exposure on his recollection that the brightness of the moon at that elevation was 250 candles per sq. foot, from which he made a quick calculation and the exposure. The quick calculation in question was that the correct shutter speed in seconds to expose a given luminance on Zone V (the 18% grey mid-tone) is the reciprocal of the luminance expressed in candles per square foot at the key stop for a given film speed.


The key stop is the square root of the ASA or ISO film speed. With the ASA 64 film, the key stop is the square root of 64 or f/8, and the exposure is therefore 1/250 second if you want the moon on Zone V. This translates to 1/125 at f/11m 1/30 second at f/22 and 1/15 second at f/

32.


But all that was needed was for the moon to read without burning out to a featureless white, so it was quite safe to give 2 stops more exposure than this: in other words, ¼ at f/32. Finally, figure in the 3x green filter, and you have just over 1 second f/32; and 1 second at f/32 was the exposure given.


An entirely, separate way to come to very much the same conclusion is via the ‘sunny f/16 rule’. The moon is illuminated by the sun: at ASA 64, the correct exposure is therefore about 1/60 second (1/ASA) at f/16 or 1/30 at f/22. This is the same figure as Ansel Adams arrived at with his convoluted calculations, and you now make the allowances for over-exposing the moon while retaining texture -2 stops and finally 3x for the filter.


From Roger Hicks

 

[MattKing]

Correct me if I'm wrong, but many of the Weston meters read in c/ft2.
And I think AA used Weston meters.

 

[Sirius Glass]

The Moon reflects the Sun. If the Moon was a mirror, it would be Moonie 16 or Loonie 16.
However the Moon is not a mirror but is has a rocky and dusty surface with Albedo less than 1.0 which makes Moonie 11 or Moonie 8, Loonie 11 or Loonie 8.

 

[wiltw]

Correct me if I'm wrong, but many of the Weston meters read in c/ft2.
And I think AA used Weston meters.

The illustrations of Weston meters like the Weston Master (and others) show that the needle pointed to a scale of Foot-Candles, with two selectable ranges, Low: 2 to 50, High: 25 to 1,600 foot candles, rather than displaying Candela. So one would need to do a conversion.

As for converting units:

"According to Spectra, a manufacturer of light meters, candelas are equal to the square of the distance multiplied by the number of foot candles. For example, if your light meter is 10 feet away from the light source with a reading of 10 foot candles, the number of candelas equals 10 feet squared (100) times 10, which is 1,000 candelas."
​

So converting for the moon...

(Note: Retraction about scale in Foot-Candles, see post 42)

 

[MattKing]

I used this site when I considered the Weston meters: https://www.westonmeters.info/light-units
Quoting: "Although not actually mentioned on the majority of Weston exposure meters, the unit in most common use is candles per square foot, or Candles/Ftsq."
"The luminance meters (not designed specifically for photography) however, do NOT use candles per square foot. In the main they use Foot-candles. But they also use Lux x 100 and Lumens per square foot. (Oh dear! Oh dear!)"

 

[BrianShaw]

Roger Hicks, God bless his little heart and God rest his soul, was quite a story teller too!

 

[BrianShaw]

Correct me if I'm wrong, but many of the Weston meters read in c/ft2.
And I think AA used Weston meters.

… and they are also 30 degree coverage.

 

[MattKing]

… and they are also 30 degree coverage.

Yes, but the discussion is about whether AA would have worked with candles/ft2 (and been fully familiar with a value for the moon).

 

[wiltw]

I used this site when I considered the Weston meters: https://www.westonmeters.info/light-units
Quoting: "Although not actually mentioned on the majority of Weston exposure meters, the unit in most common use is candles per square foot, or Candles/Ftsq."
"The luminance meters (not designed specifically for photography) however, do NOT use candles per square foot. In the main they use Foot-candles. But they also use Lux x 100 and Lumens per square foot. (Oh dear! Oh dear!)"

That text contains perhaps some key content in the puzzle:

" The Weston exposure meter can then be used to convert between the two units: From Candles per square foot to foot-candles. Simply put, it's a matter of multiplying the candles-per-square foot reading off the meter, by a factor of x4. So a reading of 10 candles per square foot would represent 40 foot-candles.
​

since the scale is foot-candles (clearly indicated on meter face), one can derive 250 c/sq.ft. readily from 1000 foot-candles.
But the meter is designed to work with foot-candles, so the question is why Adams would think in terms of c/sq.ft when the meter does not work that way?!

(Note: Retraction about scale in Foot-Candles, see post 42)

 

[MattKing]

But the meter is designed to work with foot-candles, so the question is why Adams would think in terms of c/sq.ft when the meter does not work that way?!

I think that that site is saying that many (most?) of the Weston meters do work with c/sq. ft, not foot candles.
That has always been my understanding.

 

[Manuel Madeira]

Ansel, clearly, had studied the technical aspects of photography intensively. I also expect that the Old Ones who took up photography when films and meters were more primitive, either did it entirely by the seat of their pants, or were more familiar with luminance than we are now.

Another way of looking at the moon is the "looney f/11" rule - the full moon is in direct sunlight, but its surface is fairly dark, so to correctly expose the moon a rule of thumb is to modify sunny-16 to be f/11 at 1/ISO. Let's try applying that to Ansel's situation. He had ASA 64 film, used f/32, and a yellow filter with a filter factor of 3x. This was 1941 before ASA was redefined to eliminate the safety factor, so his film was really ASA ~ 125 in today's terms. So looney f/11 would put the moon at Zone V at f/11 at 1/125. He put the moon at Zone VII to make it lighter, so that's f/11 at 1/30 sec. He used f/32, so f/32 at 1/4 sec. And there was a filter factor of 3x, so that says f/32 for 3/4 sec. Which is surprisingly close to what Ansel used, f/32 at 1 sec.

Of course, I had to count stops on my fingers several times while doing that, and there is no way I could have gotten it right while focusing and pulling a dark slide.

Where did you learn all of this? The thing that surprises me the most about analogic photography is that there is so much to learn. But i dont where to find all of this info XD

 

[removed account4]

That text contains perhaps some key content in the puzzle:

" The Weston exposure meter can then be used to convert between the two units: From Candles per square foot to foot-candles. Simply put, it's a matter of multiplying the candles-per-square foot reading off the meter, by a factor of x4. So a reading of 10 candles per square foot would represent 40 foot-candles.
​

since the scale is foot-candles (clearly indicated on meter face), one can derive 250 c/sq.ft. readily from 1000 foot-candles.
But the meter is designed to work with foot-candles, so the question is why Adams would think in terms of c/sq.ft when the meter does not work that way?!

weird
I always thought when Moe lit a match between Curly's great toe and it's lieutenant ( 2nd toe ) it was a "foot candle".
At least he wasn't measuring distance in Pinkwaters or Smoots... !
https://www.cartalk.com/radio/show/1334-pinkwater-measurement
https://en.wikipedia.org/wiki/Smoot

 

[Manuel Madeira]

Ansel, clearly, had studied the technical aspects of photography intensively. I also expect that the Old Ones who took up photography when films and meters were more primitive, either did it entirely by the seat of their pants, or were more familiar with luminance than we are now.

Another way of looking at the moon is the "looney f/11" rule - the full moon is in direct sunlight, but its surface is fairly dark, so to correctly expose the moon a rule of thumb is to modify sunny-16 to be f/11 at 1/ISO. Let's try applying that to Ansel's situation. He had ASA 64 film, used f/32, and a yellow filter with a filter factor of 3x. This was 1941 before ASA was redefined to eliminate the safety factor, so his film was really ASA ~ 125 in today's terms. So looney f/11 would put the moon at Zone V at f/11 at 1/125. He put the moon at Zone VII to make it lighter, so that's f/11 at 1/30 sec. He used f/32, so f/32 at 1/4 sec. And there was a filter factor of 3x, so that says f/32 for 3/4 sec. Which is surprisingly close to what Ansel used, f/32 at 1 sec.

Of course, I had to count stops on my fingers several times while doing that, and there is no way I could have gotten it right while focusing and pulling a dark slide.

Oh and, what those things you said about zones??

 

[MattKing]

Being inherently anally retentive, I went back to the source materials I had at hand - Ansel Adams 1948 book "Camera and Lens". He begins discussion of exposure meters on page 69. On page 70 he states that the Weston meters (No. IV and Ranger 9, which he prefers) give their readings in c/ft2.
He then spends pages of text on all sorts of other details.
I wasn't around in 1948, but I thought I remembered reading that he liked Weston meters that gave their readings that way.

 

[BrianShaw]

Yes, but the discussion is about whether AA would have worked with candles/ft2 (and been fully familiar with a value for the moon).

Indeed it does!

Then between the 2 facts, it’s irrelevant. He could not have metered the moon., especially if you accept the story that he forgot his meter. . Most meters have, either on them or in the manual, conversion between its units and real lighting units of measure.