Ansel Adams Exposure Formula?

[Paul Howell]

Ansel Adams wrote two articles for the 1963 edition of the Encyclopedia of Photography, Vol 8, in the same Vol John Carroll writes about exposure and Exposure Meters, followed by Adams' Exposure Meters How to Use Them, then Exposure With the Zone System. Although at time I don't find that at time Adams to be clear, reading all the articles one after the another does help.

 

[Alan Johnson]

I think this is a non-sequitur... "before nominal speeds were doubled" affected the film speed ratings, not the computation of f/stop and shutter speed.

I'm looking at my Weston Master II and Weston Master III side by side. They only differ by 1/3 stop in their markings. This difference is a "method" difference.

I find the Weston Master III follows the Ansel Adams Exposure Formula exactly, and if you just remember the key stop for your EI, you set your shutter speed to the number the needle points at... that's as simple as it gets.

Yes, Bill, you are right. The reading on the meter dial is not affected by what is set on the calculator dial, which is not connected to it , sorry about that mistake.

 

[Alan Johnson]

What a load of bollox.

St Ansel was right.
Are you a pictorialist?

 

[Cloudless]

New poster here, I was reading my copy of The Negative also and had many of the same questions.

I think the main point of the OP was missed in some of the later discussion, and that is that Ansel was saying that the formula using c/ft^2 only requires you to be able to estimate a square root for your iso. He mentions that for his Moonrise photo he used just this formula essentially (with some adjustments for filters and a shift to a different zone). Page 66 describes the formula, pg 127 goes into detail of said photo.

He even mentions how to come up with a table for your meter, LV to c/ft^2, on pg 66. The point of that being, once you can point your meter, and get a c/ft2 reading, you don't need to fuss with the dials anymore if you get fast at the formula.

On my weston master v, I worked out just this. I set the dial to 100 iso, which has a sqrt of 10, so fstop 10 is the key. I then set my dial to LV 10, and the shutter is 1/25, which means that LV 10 is around 25 c/ft^2. You repeat this and make yourself a chart for all LV values.

How practical this would be is certainly up for debate, but it can't hurt to understand this at it's base level.

 

[pentaxuser]

St Ansel was right.
Are you a pictorialist?

I cannot find cliveh's quote in your post, Alan, anywhere in this thread about whatever he was referring to in what may be adjudged as rude thus deleted?. Where has it gone and what was he referring to?

pentaxuser

 

[Truzi]

I cannot find cliveh's quote in your post, Alan, anywhere in this thread about whatever he was referring to in what may be adjudged as rude thus deleted?. Where has it gone and what was he referring to?

pentaxuser

Interesting, when I click the arrow that takes you to the post quoted, I get an error about not having permission to view the post or perform that action. This is only for cliveh's post to which you were referring.

 

[MattKing]

I expect this thread has been "moderated".

 

[cliveh]

I don't even remember commenting on this thread.

 

[darkroommike]

This may have been good advice when exposure meters were much less facile than current models, today I just whip out a spot meter with a Zone Dial, and incident light meter or the good old Luna Pro.

 

[Eric Rose]

At the end of the day you can do all the fancy math you want but I believe AA like Weston developed by inspection. So in the end it all boils down to a subjective evaluation under a green light.

 

[Doremus Scudder]

Adams developed by time, tray developing in complete darkness and shuffling through the stack to agitate (just read "The Negative" for his methods).

As for the Exposure Formula: it seems superfluous these days, when meters spit out info in EVs, not foot candles or the like and are hugely more reliable than they were in Adams' day. I could get out the table and convert the EV values on my Pentax spot meter into foot candles and do the calculations, but by then I could have metered, exposed and moved on to the next shot...

Best,

Doremus

 

[silveror0]

Doremus, I agree that the spot meters reading in EV values is certainly a “happy place” to be in, but I hope you’re never tempted to convert EV to foot-candles (a measure of incident Illuminance), rather than the subject luminance in c/ft^2 required for use in the Exposure Formula). Admittedly, I feel a bit cursed that my S.E.I. photometer (1/2-deg spot) is still going strong; AA described how to use it to directly get c/ft^2 readings and to arrive quickly at camera settings from there. But it always hurt my hair (what’s left of it) to do the mental mathematical gymnastics to get from those settings to the preferred combination of settings for a shot (done in haste was error prone). So I’ve kept in my field records notebook a chart for converting c/ft^2 to EV for each of my preferred films; it’s easier and quicker to use the linear calc than the geometric one – but then LF isn’t a particularly speedy world anyway. EV does permit a quicker assessment of the subject's luminance range and dev expansion/contraction needed for Zone System work.

 

[Doremus Scudder]

My mistake! Candles per square foot (or meter) it is, indeed. I was being a bit careless with my terminology.