stability of 'sunny 16'

[cowanw]

43.25 degrees north full sun today EV 14.7

 

[RalphLambrecht]

Florida: 15.1 at high noon. We are at 28.9 Northand as always full sun and clear skies.

 

[David A. Goldfarb]

Since you've posted this, we've had two unusually cloudy days here in Honolulu. Maybe later it will clear up.

 

[polyglot]

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

EV = log2(N2 / t)
EV = log2(1/t) + 2log2(N)

log2(100) = 6.64
2log2(16) = 8
=> 14+2/3

27 = 128 not 100. 1/125 is a pretty good approximation of 1/128, so f/16 1/125 is EV15. That Wikipedia link above even has a nice table showing that EV15 at f/16 is t=1/125. Or you could look at the EV dial on a spot meter, like the Pentax DSM has.

 

[Chan Tran]

Ralph! How do you figure that f/16 and 1/100 s is EV15? It's 14.66666666666 as Polyglot pointed out but if you read it off a meter it would either show 14.7 or 14 and 2/3 depending on which meter you use.

 

[chiller]

This may have been covered but isn't the sunny 16 rule derived from the reciprocity of the iso at f16? therefore f16 @ 1/100 for iso 100. Not 1/125th which is .3 EV difference. Also how are people arriving at their EV readings? Incident or reading a grey card and are you basing the reading angled incident to the camera lens or directly at the sun?

If you are using a grey card and a reflected meter how you position the card can vary the EV reading or calculated reading. Practically an incident meter is the only consistent way to determine sunny 16

 

[chiller]

I type too slow.

 

[David A. Goldfarb]

Honolulu, 21.3° N, 3:40pm

EV 15.0 at ISO 100, Minolta Flashmeter III, incident reading

 

[Steve Smith]

This may have been covered but isn't the sunny 16 rule derived from the reciprocity of the iso at f16? therefore f16 @ 1/100 for iso 100. Not 1/125th which is .3 EV difference.

No. As I wrote earlier, its the closest shutter speed to 1/ISO which on modern cameras would be 1/125.

It's not supposed to be something accurate to two decimal places! It's a close approximation to get acceptably exposed negatives in the normal range of daylight in the absence of a light meter.


Steve.

 

[mauro35]

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

Indeed, the autumn is so dark people need some medication...I am actually not originally from Finland, so it doesn´t work for me, I try practicing long exposure skills instead..
It´s a shame I don not own a good exposure meter, cause with sunny f/16 I tend to get a bit too low a shadow density. I prefer sunny f/11 in summer and even f/8 in autumn without snow. But OTOH who knows how accurate is my shutter speed.

 

[pdeeh]

how are people arriving at their EV readings? Incident or reading a grey card and are you basing the reading angled incident to the camera lens or directly at the sun?

If you are using a grey card and a reflected meter how you position the card can vary the EV reading or calculated reading. Practically an incident meter is the only consistent way to determine sunny 16

Ralph's OP asks for the following:

Please take your incident meters,meters,step outside,point the dome directly into the sun and take an EV reading.

 

[Steve Smith]

Please take your incident meters,meters,step outside,point the dome directly into the sun and take an EV reading.

Whilst this method will probably give a more consistent reading of the sun's intensity around the world, a real incident reading should be with the meter pointing at the camera from the subject rather than directly at the light source.


Steve.

 

[RalphLambrecht]

Whilst this method will probably give a more consistent reading of the sun's intensity around the world, a real incident reading should be with the meter pointing at the camera from the subject rather than directly at the light source.


Steve.

good;then we are OKbecause,the consistency of the sun's intensityaround the world is what I'm trying to verify.
thank you ll for your help and comments.

 

[pdeeh]

But you're not being asked to measure your palm

 

[DannL.]

But you're not being asked to measure your palm

Problem solved.

 

[bdial]

New Hampshire, USA
12:00 p.m. EV 15

 

[Chan Tran]

No. As I wrote earlier, its the closest shutter speed to 1/ISO which on modern cameras would be 1/125.

It's not supposed to be something accurate to two decimal places! It's a close approximation to get acceptably exposed negatives in the normal range of daylight in the absence of a light meter.


Steve.

That's modern camera of the 80's. More modern cameras do have shutter speed of 1/100 as they are in 1/3 stop increments.

 

[RalphLambrecht]

New Hampshire, USA
12:00 p.m. EV 15

perfect,thanks for that;we've got EV15 from Southern Australia all the way to Northern Canada.I think ,it's save to say 'sunny 16' works!

 

[Curt]

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.

Steve, you just missed the shot! The ship sailed right past while you were looking up the correct exposure!

 

[Steve Smith]

That's modern camera of the 80's. More modern cameras do have shutter speed of 1/100 as they are in 1/3 stop increments.

You mean old modern cameras!


Steve.

 

[E. von Hoegh]

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

Yesterday was an uncommonly clear day without a single cloud. EV 15 on the nose.

 

[RalphLambrecht]

Yesterday was an uncommonly clear day without a single cloud. EV 15 on the nose.

same thing in Florida yestwrday and today,other than clrear days very common hereand it was a hot one again.

 

[RalphLambrecht]

Indeed, the autumn is so dark people need some medication...I am actually not originally from Finland, so it doesn´t work for me, I try practicing long exposure skills instead..
It´s a shame I don not own a good exposure meter, cause with sunny f/16 I tend to get a bit too low a shadow density. I prefer sunny f/11 in summer and even f/8 in autumn without snow. But OTOH who knows how accurate is my shutter speed.

shutter speeds can easily vary by 1/3 stop,depending on temperature. on the other hand ,apeture settings are usually very accurate and consistent+-0.1 stops.if you can measure your shutter speedsand trust your aperture settings.

 

[wiltw]

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

The problem is that 'right' can mean a deviation of about 1/3 EV, measuring the same light with a dozen different meters...the ISO calibration equation allows meter manufactures to choose their own 'constant', resulting in 1/3 EV difference from brand to brand. Then, if you take multiple units of the same brand and model, deviations between even units of the same brand and model can result in not perfect agreement!

So if the experiment is to read location specific differences, you immediately have lots of error -- even if the sun was IDENTICAL at all sample locations (or the folks were standing side by side)!

BTW, for the experiment, location latitude N37 degrees 31 minutes, observation at 13.30 PDT: EV15.9

 

[wiltw]

on the other hand ,apeture settings are usually very accurate and consistent+-0.1 stops.if you can measure your shutter speedsand trust your aperture settings.

It used to be that Modern Photography and Popular Photography both measured actual max aperture (as well as the true FL) vs. the rated max aperture and FL, and they would publish the results. Here are some examples, and notice the two examples of lenses tested by BOTH magazines...sample-to-sample variations!

• Rated OM 35mm f/2.8, actual 35.51mm f/2.73 (Popular Photography)
• Rated OM 35mm f/2.8, actual 35.1mm f/2.81 (Modern Photography)
• Rated OM 100mm f/2, actual 100.83mm f/2.1 (Popular Photography)
• Rated OM 100mm f/2, actual 100.65mm f/2.05 (Modern Photography)
• Rated OM 21mm f/2, actual 20.15mm f/1.91 (Modern Photography)
• Rated OM 24mm f/2.8, actual 25.1mm f/2.93 (Modern Photography)