stability of 'sunny 16'

RalphLambrecht · Aug 17, 2014

my dear friends on APUG,
I need your help for a world-wide experiment.the sun is known to be an extremely stable light source and has been for he last 4.5 billion yearswith promise to do the same for another 4.5 billion yearson a clear sunny day, it provides bout 82klux,measured on a perpendicular(normal)plane to the sun.this can be measured with an incident lightmetercapable of eadind in EVsat 100ISO,atich it should read EV 15.I have done this in Northern Europe and in North Amrikaand never had more than a 0.1 deviation from 15EV .Let's see how stable this is world-wide.Please take your incident meters,meters,step outside,point the dome directly into the sun and take an EV reading. Then please report it here with your location.I'll start:Florida, USA,yesterday3pmEV15.1;today11am14.9EV.
tanks for the effort

Nuff · Aug 17, 2014

I just started trying to memorise sunny 16 to minimise my metering. Last Friday at 1pm Sydney, Australia time. I metered and it was bang on f16. I have no idea about the actual EV and I don't expect to see sunny day for a while.

pdeeh · Aug 17, 2014

51N 2W
2014:08:17 16:25Z
EV 15
Gossen digisix

gone · Aug 17, 2014

While the sun MAY be a stable light source, that doesn't mean the light in Portland is the same as the light in New Mexico. Every place has it's own native light (the sea shore is notoriously soft and diffused, while the desert is notoriously hard and glarey). You have to make your own adjustments w/ or w/o a meter to taylor your exposures to your locale. Consider the American Southwest sunny 22.

Chan Tran · Aug 17, 2014

With the Minolta flashmeter III and VI I have EV14.7 both in Chicago, IL and Dallas, TX.

snapguy · Aug 17, 2014

Hummm

I think your scientific experiment, although interesting, is flawed. How do you know all these light meters are giving correct readings? Some have got to be ancient. I know the hand held ones I own are creaking with age.

mgb74 · Aug 17, 2014

I assume you need a clear, sunny day with the sun unobstructed by clouds. But does time of day have an impact?

markbarendt · Aug 17, 2014

15.1 @ ISO 100
Durango CO USA
Readings matched on both of my Sekonic L358s

ic-racer · Aug 17, 2014

RalphLambrecht said:
my dear friends on APUG,
I need your help for a world-wide experiment.the sun is known to be an extremely stable light source and has been for he last 4.5 billion yearswith promise to do the same for another 4.5 billion yearson a clear sunny day, it provides bout 82klux,measured on a perpendicular(normal)plane to the sun.this can be measured with an incident lightmetercapable of eadind in EVsat 100ISO,atich it should read EV 15.I have done this in Northern Europe and in North Amrikaand never had more than a 0.1 deviation from 15EV .Let's see how stable this is world-wide.Please take your incident meters,meters,step outside,point the dome directly into the sun and take an EV reading. Then please report it here with your location.I'll start:Florida, USA,yesterday3pmEV15.1;today11am14.9EV.
tanks for the effort

Ralph,
Have you seen this paper?
http://ccfg.org.uk/conferences/downloads/P_Burgess.pdf

Truzi · Aug 17, 2014

I certainly don't have the equipment to test, and my own subjective attempts at Sunny 16 are by no means accurate. However, the few times I dabbled with the concept, it seems F11 gave me the best results. Of course, being in the Greater Cleveland Area of Ohio may have something to do with it.

aRolleiBrujo · Aug 17, 2014

snapguy said:
I think your scientific experiment, although interesting, is flawed. How do you know all these light meters are giving correct readings? Some have got to be ancient. I know the hand held ones I own are creaking with age.

Isn't this scientific experiment? Isn't the purpose to establish the validity of a Hypothesis? I guess I might be wrong, since I haven't studied the Scientific method in ages, especially with an understanding!

markbarendt · Aug 17, 2014

aRolleiBrujo said:
Isn't this scientific experiment? Isn't the purpose to establish the validity of a Hypothesis? I guess I might be wrong, since I haven't studied the Scientific method in ages, especially with an understanding!

The grand majority of meters are probably very close to right.

FrancoisM · Aug 17, 2014

46.88 -71.52
2014:08:17 20:00Z
EV 15.4
Sekonic 308S

cliveh · Aug 17, 2014

mgb74 said:
I assume you need a clear, sunny day with the sun unobstructed by clouds. But does time of day have an impact?

The time of day will have an impact, as will the weather and the meter. As we don't all have a sunny day at the same time in the month/season such an experiment is flawed.

RalphLambrecht · Aug 17, 2014

Nuff said:
I just started trying to memorise sunny 16 to minimise my metering. Last Friday at 1pm Sydney, Australia time. I metered and it was bang on f16. I have no idea about the actual EV and I don't expect to see sunny day for a while.

the EV for sunny 16 is EV15I had 14.5 at 5pm in Florida today.

RalphLambrecht · Aug 17, 2014

cliveh said:
The time of day will have an impact, as will the weather and the meter. As we don't all have a sunny day at the same time in the month/season such an experiment is flawed.

No,it's not.The purpose is to prove your statement wrong 'sunny 16' works from 10 am to 4pmalmost anywhere on the globe at all seasons,weather permitting of course and assuming properly working equipment; so far so good

cliveh · Aug 17, 2014

RalphLambrecht said:
No,it's not.The purpose is to prove your statement wrong 'sunny 16' works from 10 am to 4pmalmost anywhere on the globe at all seasons,weather permitting of course and assuming properly working equipment; so far so good

The earths orbit around the sun is elliptical, not circular.

pentaxuser · Aug 17, 2014

RalphLambrecht said:
No,it's not.The purpose is to prove your statement wrong 'sunny 16' works from 10 am to 4pmalmost anywhere on the globe at all seasons,weather permitting of course and assuming properly working equipment; so far so good

Won't we need a lot more meter readings especially from latitudes between 50 and 60N before we can conclude that EV15 applies as per your statement, Ralph for we Northerners?

I had always understood that the sunny 16 rule had to be modified for both latitude and seasons and that sunny 16 needed to be modified to sunny 11+ for any latitude above 50N.

Can we really assume that sunny 16 works on a sunny day at the winter solstice in say N Scotland even at 12 noon let alone as early as 10:00am or as late as 2:00pm. In N Scotland at say 57N it is almost dark at 4:00pm

I have been trying to meter grass on cloudless sunny days between 11:00am and 1:00pm at about latitude 53N in the last two months(mid June to mid August)and while a camera meter isn't an incident meter the best reading I got suggested that it was about sunny 13

pentaxuser

Chris G · Aug 17, 2014

EV 14.6 @ iso 100 at 4:00pm 49 degrees latitude. Vancouver, BC, Canada (Sekonic L-558)

polyglot · Aug 17, 2014

There is definitely a bit of variation at higher latitudes because the light has to travel through more atmosphere, and there are of course effects from haze and pollution. The spectrum of course changes because of the atmospheric differences too - in Australia we have far more UV than Europe due to the antarctic ozone hole.

I recommend having a look at some of these surveys and their techniques and some of these insolation maps. The latter are derived for the purpose of budgeting PV solar cell outputs and therefore include annualised weather patterns (cloud etc) so you should ignore the variations wrt sea/land and longitude. However, they do show a strong and uniform variation in insolation with latitude. Some of the papers show the variation throughout the day, and on a clear day, you can expect about 15-20% difference between mid-morning and noon, depending on your latitude, which is about EV0.3 difference.

I get EV14.8 in Adelaide in mid-summer, and about EV14.3 in winter. When I travelled Europe (Prague, St Petersburg) in late summer, it was more like EV13.8. I'd be interested to see a reading from inside a polar circle.

PS Sunny 16 is EV 14.66 not 15. EV15 would imply f/16 1/125 @ EI100.

Nuff · Aug 17, 2014

Sunny 16 is f16 1/125 @EI100 My measurement in 2nd comment was f16 1/60 @EI50.

I would also add that the further south in Australia you go the worse the UV gets. My worst sunburn was in Tasmania and I was only outside in sun for 15-20min. And that's from someone who grew up in QLD.

NedL · Aug 17, 2014

cliveh said:
The earths orbit around the sun is elliptical, not circular.

Ha! True Cliveh, but not very elliptical. IIRC, the eccentricity of earth's orbit is something like 0.01, so inverse square isn't going to vary much through the year...

ME Super · Aug 17, 2014

Right. Earth is actually slightly closer to the sun during the northern hemisphere's winter than it is during its summer.

Sunny 16 is not a 10:00 a.m. to 4:00 p.m. rule. It is a "two hours after sunrise to two hours before sunset" rule. If sunrise is 10:00 a.m. and sunset is 2:00 pm, then sunny 16 isn't going to work for you.

Chan Tran · Aug 17, 2014

RalphLambrecht said:
the EV for sunny 16 is EV15I had 14.5 at 5pm in Florida today.

The EV for sunny 16 is not EV15! As stated and assuming we're talking about ISO 100. The aperture is f/16 and the shutter speed is 1/100 that is equal EV 14 and 2/3. I understand the reason why you think it's EV15 because we often use 1/125 for the 1/100 shutter speed. But as the rule stated the shutter speed should be set to the reciprocal of the film speed. And since my measurements results in EV14.7 I think the sunny 16 is very good.

michaelbsc · Aug 17, 2014

NedL said:
Ha! True Cliveh, but not very elliptical. IIRC, the eccentricity of earth's orbit is something like 0.01, so inverse square isn't going to vary much through the year...

More like 0.0167, so that would round up to 0.02. Still probably not enough to notice in the shadows.

stability of 'sunny 16'

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