Sunny 16 Rule Question

[ptpdprinter]

The ancient definition of A.S.A. (as opposed to ASA and ISO) was the inverse of the shutter speed that produced the correct exposure at mid-day on the first day of summer in Washington D.C.

So the definition would change annually depending on whether the first day of summer in Washington, D.C. that year happened to be rainy, cloudy, partly cloudy, partly sunny, or sunny? Who was in charge of making the annual pronouncement? How did they determine "correct" exposure?

 

[Bill Clark]

Hi Roger,

You’ll probably chastise me, but what I did with film and do now with digital is light balance each photograph with my photography. I didn’t want to spend time in the darkroom correcting this! It doesn’t always work with some photography.

What I try to do is to have more than one area of a photograph with proper exposure (example, faces) and avoid having another with either over (blown out) or under exposure. I see so much of this going on with folks photographs.

During the film days it took time to get this correct. But I did it by propering planning and seeing the places I would be making photographs during the time I would be doing the gig. For a while I’d use a Polaroid back to check things out! Whew! That was a lot of work.

I usually made my negatives about a half to one stop over and transparencies about a half stop under.

There are many variables with film photography. But, for sure, I didn’t want to work with under exposed negatives or over exposed transparencies.

With digital, I find it so much easier as I can see it immediately, using the histogram as an important tool.

Thanks for your thoughts.

 

[johnnyrod]

Well I am bemuse to see the return of Roger Hicks (hello!) as I was just about to post a link to one of his pages, that gives a good run-down. It's a very long page, go to the bottom and page up a couple of times:
http://rogerandfrances.com/subscription/ps expo neg.html
As noted above, sunny 16 ignores shadows, Roger suggests this works when the sun is at your back, overexpose by a stop when it's from the side and two stops when it's in your face.

 

[Dwig]

...ASA (the same as A.S.A.)...

Actually, they are not identical. The original A.S.A spec. was based on technical specifications, but the numbering system derived from the old seat-of-the-pants system used on earlier cameras like the one using a Kodak Ball Bearing Shutter that was pictured earlier in the thread.

ASA, without the periods, appeared later (~ late '50s ?) and involved some small refinements. I remember Tri-X being rerated from A.S.A 200 to ASA 400 as a result, even though there was no change in the film itself. The standard for what was the proper reference density had changed.

 

[ptpdprinter]

The ancient definition of A.S.A. (as opposed to ASA and ISO) was the inverse of the shutter speed that produced the correct exposure at mid-day on the first day of summer in Washington D.C. Mid-winter and/or at extreme latitudes the light can be 1/2-3 stops lower. Many of the old charts would include a Summer/Winter conversion.

The original A.S.A spec. was based on technical specifications, but the numbering system derived from the old seat-of-the-pants system used on earlier cameras like the one using a Kodak Ball Bearing Shutter that was pictured earlier in the thread.

So for A.S.A. which is it: technical specifications or first day of summer in Washington, D.C.

 

[David Hughes]

I might as well throw this into the nixture...

One appeared every month then. Meters were, of course, also available but were very expensive at about 5 or 6 pounds each and in those days there were 4 US $ to the pound. Also great to see the amount of work put into this page by the magaine and then to keep it up to date.

EDIT; it's nearly midnight here and so I'll just type this fttb and come back tomorrow morning. The film speed system changed in 1960, or rather started to change then. I've a guide by Johnsons of Hendon dated 1964 explaining it and will try and summarise it then. There was also a punch up over it in the 1930's in which politics played a big part and I'll look for that as well but the heap of old papers etc is a mile high...

Regards, David

 

[Roger Hicks]

Actually, they are not identical. The original A.S.A spec. was based on technical specifications, but the numbering system derived from the old seat-of-the-pants system used on earlier cameras like the one using a Kodak Ball Bearing Shutter that was pictured earlier in the thread.

ASA, without the periods, appeared later (~ late '50s ?) and involved some small refinements. I remember Tri-X being rerated from A.S.A 200 to ASA 400 as a result, even though there was no change in the film itself. The standard for what was the proper reference density had changed.

Not exactly. ASA and A.S.A. both refer to the American Standards Association, now ANSI, the American National Standards Institute. There is no significance in the use or non-use of the full stops (periods).

In the late 1950s the American Standard in question was changed to a fixed minimum density criterion, bringing it into line with the DIN standard and replacing the theoretically superior but difficult to implement fractional gradient criterion devised by Jones and Condit. At the same time, as far as I recall, the DIN standard adopted in effect the ASA contrast criterion instead of gamma infinity.

At the same time, the old "safety factor" was removed from the ASA film speed. Just as today there are those who say that films "aren't really" as fast as their ISO speeds indicate, there were plenty in the 1950s who said that films were "really" faster than their ASA ratings. Both are right, because film speeds are a matter of opinion and compromise. This is why most negative film speeds apparently doubled -- but it meant you had to meter more carefully, and most people don't. Indeed, many don't know how.

As for "the old seat of the pants system" and its relationship to old Kodak shutters, I'm not sure what you mean by this. It's a subject I've studied in some depth, and even written a book about ("Perfect Exposure" from David & Charles) and I don't recognize what you are talking about. This probably means one of two things.

Either there is a small but interesting fact I have never encountered (which happens all the time) or there is a myth which has been propagated widely by those who have not researched the subject much. This also happens all the time, the most celebrated being the myth that an "average" subject reflects 18% of the light falling on it instead of the actual 12-14%. See "The 18% Grey Card" for more on this.

Then again, most people don't even ask what "average" might mean. As far as I know, it refers to outdoor subjects near Rochester, New York, but that might be a myth too.

Cheers,

R.

 

[David Hughes]

As promised...

As promised...

This is a summary taken, mainly, from "The Johnson Photographic Year Book" of 1964 and they start by explaining that there were four main systems in use in Britain before 1960.

ASA and BS which were agreed as a common standard by the British Standards Institute and the American standards Association in 1947 and were designed to give logarithmic and arithmetical scales. The first doubles the speed by an increase of 3° (mainly used in Britain) and the arithmetical scale by doubling (for the USA).

The Weston scale was based on tests carried out by the makers of the well known meter and, finally,

DIN (Deutsche Industrie Norm) mainly used in continental Europe and which closely looks like the BS scale. Add 10° to DIN and you get BS, good enough for everyday use.

All of these included a safety factor and using them to set a meter "would indicate exposures rather more than double the bare minimum" for a "satisfactory" negative.

And so they eliminated the safety factor, which would seem to double the film speed...

Some of the reasons were;

35mm film works best with exposures near the minimum;

Automatic printers worked best with less dense negatives and

Reversal film (meaning colour slides) have a very limited latitude and exposure cannot include a safety factor.

NB This change applied to black and white negative material only. Colour slide and negative film speeds did not change.

As a clue "BS (log)" and "BS/ASA (arith)" mean the new standard, as does "20DIN" instead of "17°DIN" (the DIN examples are for the same film as new and old labels).



Regards, David

 

[Roger Hicks]

Hi Roger,

You’ll probably chastise me, but what I did with film and do now with digital is light balance each photograph with my photography. I didn’t want to spend time in the darkroom correcting this! It doesn’t always work with some photography.

What I try to do is to have more than one area of a photograph with proper exposure (example, faces) and avoid having another with either over (blown out) or under exposure. I see so much of this going on with folks photographs.

During the film days it took time to get this correct. But I did it by propering planning and seeing the places I would be making photographs during the time I would be doing the gig. For a while I’d use a Polaroid back to check things out! Whew! That was a lot of work.

I usually made my negatives about a half to one stop over and transparencies about a half stop under.

There are many variables with film photography. But, for sure, I didn’t want to work with under exposed negatives or over exposed transparencies.

With digital, I find it so much easier as I can see it immediately, using the histogram as an important tool.

Thanks for your thoughts.

Dear Bill,

Far from chastising you, I agree completely. I do exactly the same, except perhaps that I used 1/3 stop instead of 1/2 stop for transparencies, though the 1/6 stop difference between 1/3 under and 1/2 under is negligible. I just wondered if "a bit" or "a little" meant the same to you as to me. It does!

Cheers,

R.

 

[David Hughes]

...Then again, most people don't even ask what "average" might mean. As far as I know, it refers to outdoor subjects near Rochester, New York, but that might be a myth too.

Cheers,

R.

Yes, exactly; I've often wondered what it meant but based on the pictures on the exposure guides of the 1930's cameras and so on I think it was meant for someone's mum taking a picture in the park or on the beach in August. Selo's guides and books (1930's and 40's) use a park a lot for the examples and there's young lady on the beach on the front of the Zeiss Ikon AG table (the printer's code suggests May 1931).

Regards, David