stability of 'sunny 16'

[NedL]

I just looked it up. The minimum distance is 1.471e8 km and the maximum is 1.521e8 km. Unless I'm making a mistake, inverse square leads to ~7% variation of over the course of a year. That's much higher than I would have guessed ( although not so much on the log2 EV scale ).
Clive was right.

 

[MattKing]

This may be more of a test of our meters than a test of the consistency of light intensity.

But it is still quite interesting.

Earlier today I was shooting some ISO 100 slide film under the sun. Incident meter readings were right on Sunny 16 here in Delta, BC, just northz of the 49th parallel.

 

[Maris]

EV 15.2 by Sekonic L-758D right now here in Noosa, Australia. I guess that's why they call this area the Sunshine Coast

 

[lxdude]

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.

Except at high noon.

 

[mauro35]

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

That cannot be true. Here in Finland at 4pm in December the sun has already long set. It´s night already.

 

[Steve Smith]

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.

Sunny 16 is never that accurate. It is usually quoted as the closest shutter speed to 1/ISO. Therefore EV15 is close enough.


Steve.

 

[Xmas]

Well my exakta 11a has a 1/100... and half click stops.

But in London there is sufficient particulates to need more exposure easy to judge depending on how many antihistamines, tabs I need to take to breath ok.

I use sunny side /11!

And sunny side and similar slide rules or tables have two hours of sunrise/sunset rules.

 

[Steve Smith]

I have found these to be very accurate:

http://www.earlyphotography.co.uk/site/entry_E40-6.html


Steve.

 

[pdeeh]

I had one of those and I wish I knew what happened to it

 

[michaelbsc]

I had one of those and I wish I knew what happened to it

No need for paper ones.

http://www.fredparker.com/ultexp1.htm

 

[Steve Smith]

You don't actually need a Johnson's Exposure Disc to make use of it.

I reverse engineered mine to give this (which I have posted here before):

Start with a number depending on ISO used:

ISO 25 8
ISO 50 9
ISO 100 10
ISO 200 11
ISO 400 12
ISO 800 13
ISO 1600 14

Add a number depending on the scene:

Strong sun with white clouds +4
Strong Sun +3
Weak, hazy sun +2
Dull +1
Very dull 0


Add a number depending on the time and date:

May to August, 10 am to 3 pm +4
May to August, 8-10 am, 3-6 pm +3
May to August, 7-8 am, 6-7 pm +2
September, October, March & April, 10 am to 3 pm +3
September, October, March & April, 8-10 am, 3-6 pm +2
September, October, March & April, 7-8 am, 6-7 pm +2
November to February, 10 am to 3 pm +2
November to February, 9 to 10 am +1


And finally, subtract a number depending on the scene:

Open sea and sky and scenes from the air 0
Distant landscapes and beach and snow scenes -1
Open landscapes and scenes with light foreground -2
Groups in the open and near views of houses and trees -3
Distant buildings and wide streets -4
Scenes with heavy foreground and near landscapes -5
Close up portraits in the shade and scenes in heavy shade -6
Bright interiors -7
Dull interiors -14 (disc says rotate twice)

As a test, put in some standard sunny 16 settings:

ISO 100, start with 10
Bright sunny day, use strong sun setting adding 3 = 13
For mid day in June, add 4 = 17
For an open landscape, subtract 2 = 15

The numbers are EV or Exposure value numbers. EV 15 is 1/125 at f16 which is what sunny 16 recommends for these conditions



Steve.

 

[pdeeh]

Oh I just liked it because its a nice object and it had sentimental value

 

[pentaxuser]

Sunny 16 is f16 1/125 @EI100

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.

I wonder what explains this. It seem contrary to eveything I thought I had read. Isn't the "reductio ad absurdum" of this that in summer the worse place to be for sunburn is the South Pole. Come to think of it the South Pole might be bad because there is very little to prevent the UV rays penetrating the atmosphere. Might the same have been true of that day in Tasmania?

All I know is that the incidence of extreme sunburn is much greater for Scots who holiday in say Greece and don't take precautions than those who holiday in Scotland and don't take precautions, all other things being equal

Could your worst sunburn be caused by any other factors?

pentaxuser

 

[RalphLambrecht]

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

not between 10am and 4om.the point of this exercise is how stable the light soutce sun actually is.Please participate.

 

[Nuff]

I wonder what explains this. It seem contrary to eveything I thought I had read. Isn't the "reductio ad absurdum" of this that in summer the worse place to be for sunburn is the South Pole. Come to think of it the South Pole might be bad because there is very little to prevent the UV rays penetrating the atmosphere. Might the same have been true of that day in Tasmania?

All I know is that the incidence of extreme sunburn is much greater for Scots who holiday in say Greece and don't take precautions than those who holiday in Scotland and don't take precautions, all other things being equal

Could your worst sunburn be caused by any other factors?

pentaxuser

The North Pole doesn't have much of an ozone hole. But the South Pole has huge one. Just do an image search on google.

 

[Steve Smith]

the point of this exercise is how stable the light soutce sun actually is.

The sun is very stable as a light source. The variables are our angle to it and the cloud cover.


Steve.

 

[RalphLambrecht]

I have found these to be very accurate:

http://www.earlyphotography.co.uk/site/entry_E40-6.html


Steve.

me too;I agree. My Dad never owned a lihtmeterand still had perfect exposuresat all hours of the day.He was a genius!

 

[RalphLambrecht]

thanks for the link.

 

[RalphLambrecht]

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.

I assume the inaccurances to average out.

 

[RalphLambrecht]

The earth’s orbit around the sun is elliptical, not circular.

and that makes nodifference at all.In fact, we are closer to the sun in wintr than in summer.the orbit is nnot a significant variable for this test.:munch:

 

[RalphLambrecht]

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.

How did you get to 14.66.I get an even 15 at f/16 and 1/100/s

 

[RalphLambrecht]

That cannot be true. Here in Finland at 4pm in December the sun has already long set. It´s night already.

Is that why you guys drink so much?I know, I would.

 

[RalphLambrecht]

great mthod!thanks for sharing!

 

[FrancoisM]

It depends maybe on how he was holding the lightmeter ?

Francois.

How did you get to 14.66.I get an even 15 at f/16 and 1/100/s

 

[E. von Hoegh]

Clear sunny day with scattered clouds, about a needle's width above EV 15 on my LunaSix.