18% Grey Card. To use it or not.

[DREW WILEY]

He didn't own either an SEI or Pentax spot meter at that point, in 1941. They weren't invented yet. If they had been, it would have been an easy problem. But he COULDN'T LOCATE whatever meter he did use at that time quickly enough, so did a mental calculation based on the footcandle value of the moon as a high value, and worked down from there in his guesstimate of the rest of the scene - at least if what he stated in his own books was correctly reminisced.

The point isn't if he did that technically correct or not in his head, but simply, that it historically worked good enough to bag a workable negative. Why overcomplicate the story? Lots of his methodology was questionable in certain particulars, but worked good enough for him and his students. And apocryphal or not, that story is now entrenched in the pedigree of that famous image itself.

Today, if someone wants a footcandle incident reading, just use a lux meter like lighting pros do. Photographic exposures are far more easily done using EV readings instead.

 

[Chan Tran]

th
Today, if someone wants a footcandle incident reading, just use a lux meter like lighting pros do. Photographic exposures are far more easily done using EV readings instead.

Although Adams said Footcandle he really meant Cd/ft^2 which is a luminance and not an Illuminance unit like footcandle. This is the reason why photrio member Davidave was confused about.

Ansel Adams Exposure Formula?

So in p.66 of Book II, Ansel Adams outlines his exposure formula: Square root of your ASA give you the key stop Take your meter reading in c/ft^2 (foot-candles) and the inverse is the shutter speed at the key stop. So if shooting ASA100, the key stop would be f/10. And if luminance value...

www.photrio.com

 

[Alan Edward Klein]

He didn't own either an SEI or Pentax spot meter at that point, in 1941. They weren't invented yet. If they had been, it would have been an easy problem. But he COULDN'T LOCATE whatever meter he did use at that time quickly enough, so did a mental calculation based on the footcandle value of the moon as a high value, and worked down from there in his guesstimate of the rest of the scene - at least if what he stated in his own books was correctly reminisced.

The point isn't if he did that technically correct or not in his head, but simply, that it historically worked good enough to bag a workable negative. Why overcomplicate the story? Lots of his methodology was questionable in certain particulars, but worked good enough for him and his students. And apocryphal or not, that story is now entrenched in the pedigree of that famous image itself.

Today, if someone wants a footcandle incident reading, just use a lux meter like lighting pros do. Photographic exposures are far more easily done using EV readings instead.

The moon is always in the sun (except at New Moon when you can;t see it). So it's values are a constant.

 

[DREW WILEY]

Alan, it's not a dependable constant because of intervening atmospheric conditions, which can be fog like here, or smog, or smoke, jet contrails, pollen haze, etc. But the dry desert air of interior New Mexico was probably remarkably clear back when AA took that famous picture. I don't think he had any personal means to directly measure the moon's luminance. He claimed he got it from an astronomer, or else astronomical publication, and remembered it.

And Chan - Even AA's incorrect usage of terminology became influential, or at least got interwoven into photographic history and lingo of the photographic community, for better or worse. If I asked my Astrophysics Professor friend about it, he could write out intricate math formulas all day long, and describe great telescope projects one after another, but can't himself take a decent picture.

My own attitude about correct exposure of the moon would simply be to bracket some test exposures in advance of any serious project. But I haven't done even that. I seem to bag it correctly anyway.

 

[Bill Burk]

Use the square root of your film speed as the f/stop and the candles per square foot as the shutter speed. Pretty easy to do in your head.

 

[wiltw]

My own attitude about correct exposure of the moon would simply be to bracket some test exposures in advance of any serious project. But I haven't done even that. I seem to bag it correctly anyway.

Oh no...Moony 11 varies, too?!

 

[Alan Edward Klein]

Alan, it's not a dependable constant because of intervening atmospheric conditions, which can be fog like here, or smog, or smoke, jet contrails, pollen haze, etc. But the dry desert air of interior New Mexico was probably remarkably clear back when AA took that famous picture. I don't think he had any personal means to directly measure the moon's luminance. He claimed he got it from an astronomer, or else astronomical publication, and remembered it.

And Chan - Even AA's incorrect usage of terminology became influential, or at least got interwoven into photographic history and lingo of the photographic community, for better or worse. If I asked my Astrophysics Professor friend about it, he could write out intricate math formulas all day long, and describe great telescope projects one after another, but can't himself take a decent picture.

My own attitude about correct exposure of the moon would simply be to bracket some test exposures in advance of any serious project. But I haven't done even that. I seem to bag it correctly anyway.

The point about it reflecting the sun, is that should there be no fog or haze, you could calculate the exposure so you don;t clip it if it;s at it;s higest (normal) brightness, or use the Sunny f/16 rule.

 

[DREW WILEY]

Just the adjust the Moon Dimmer Switch plugged into your multi-outlet strip.

 

[MattKing]

The luminance of the moon does vary with how much atmosphere you are viewing it through. Low in the sky will be less bright than high above. That issue is compounded by additional atmospheric contaminants like dust, smoke and water vapour.
Of course when Hernandez was shot, that sky would likely be far clearer than most skies that many/most of us encounter now.

 

[reddesert]

The point about it reflecting the sun, is that should there be no fog or haze, you could calculate the exposure so you don;t clip it if it;s at it;s higest (normal) brightness, or use the Sunny f/16 rule.

Unfortunately, this is not correct in practice. There are two issues:

- the reflectance of the moon's surface is below average (low albedo), IOW the moon is darker than an 18% gray card, so "sunny 16" doesn't hold. wiltw referred to "Moony 11" which I think is an attempt to compensate for this.

- the moon's reflectance is highly dependent on angle - the technical term is non-Lambertian. It backscatters light more effectively at a 180 degree bounce (opposition) than at oblique angles. For this reason, the full moon is noticeably more than twice the brightness of quarter moon, for example.

See for ex the brief discussion of the moon at https://en.wikipedia.org/wiki/Albedo#Optical_or_visual_albedo

 

[Alan Edward Klein]

Unfortunately, this is not correct in practice. There are two issues:

- the reflectance of the moon's surface is below average (low albedo), IOW the moon is darker than an 18% gray card, so "sunny 16" doesn't hold. wiltw referred to "Moony 11" which I think is an attempt to compensate for this.

- the moon's reflectance is highly dependent on angle - the technical term is non-Lambertian. It backscatters light more effectively at a 180 degree bounce (opposition) than at oblique angles. For this reason, the full moon is noticeably more than twice the brightness of quarter moon, for example.

See for ex the brief discussion of the moon at https://en.wikipedia.org/wiki/Albedo#Optical_or_visual_albedo

I agree with you. But the story is how Adams used his knowledge of the moon's light to calculate in his head an approximate best exposure for the shot. If he didn't want to clip the moon and overexpose, using a form of the Sunny 16 could get him in the ballpark.

What calculation did Adams actually make to determine his exposure?

 

[Chan Tran]

I agree with you. But the story is how Adams used his knowledge of the moon's light to calculate in his head an approximate best exposure for the shot. If he didn't want to clip the moon and overexpose, using a form of the Sunny 16 could get him in the ballpark.

What calculation did Adams actually make to determine his exposure?

I hope you can read it. It's from his book "Examples The Making of 40 Photographs"

 

[BrianShaw]

Ansel's Anecdotes - The Making of Moonrise, Hernandez

The story of the making of Ansel Adams' Iconic Moonrise, Hernandez, 1941. Three perspectives from Michael Adams, Alan Ross and John Sexton.

articles.anseladams.com

 

[BrianShaw]

It’s really wasn’t a “calculation” but, rather, an estimation and a hope for success.

There were 2 tellings of that story. EXAMPLES being a later, somewhat more embellished, recollection. We’ve discussed this before…

 

[Stephen Benskin]

Good story, but the negative was still underexposed and later chemically intensified. My understanding is Adam's charged more for Moonrise because printing was so difficult. At that time, exposure guides and tables were widely used because of the high costs of meters. Those photographers probably would have memorized the exposure settings for many lighting conditions throughout the day. For them, it would have just been another Saturday.

 

[BrianShaw]

The Kodak Master Photoguide tends to give very good advice. I’ll bet Ansel had one and if time permitted would have used it.

 

[Vaughn]

Good story, but the negative was still underexposed and later chemically intensified...

Selectively selenium toned, actually (so half of the neg was exposed 'properly', I suppose). I shamelessly stole the idea from him for the below image (top half of 4x10 negaitive toned.)

Snow, Merced River
Carbon Print

 

[Milpool]

Well, in his earlier tellings he used a meter.

I agree with you. But the story is how Adams used his knowledge of the moon's light to calculate in his head an approximate best exposure for the shot. If he didn't want to clip the moon and overexpose, using a form of the Sunny 16 could get him in the ballpark.

What calculation did Adams actually make to determine his exposure?