Sunny 16 rule

Chan Tran · Mar 2, 2014

what math equation do you use to determine the number of stops darker in doors than outdoors if a photograph is properly exposed photograph is taken indoors at ISO 800, f/2.8, and at 1/50 of a second ?

Im trying to calculate sunny 16 rule and compare how much darker it is.
For instance if I do Sunny 16 rule on one picture
and use f2.8 ISO 640 and 1/50 second, is this how to calculate this?
f/16 is 5 times darker. And for reference I pick out 100, 1/1000.
5 times lighter for iso. and 4 times lighter for shutter. So it would be 4 times lighter?
I don't see 1/50 second for shutter speed though.

I have seen these 2 questions posted on another forum. It appeared to me that the question is a homework question rather something the poster really wanted to know. It it is the case how would the instructor taught the students to get answer to these kind of question. I know there are many ways to come up with the right answer but someone who teaches a photography class and put such a question in the homework how would that person teaches the students to solve the problem?

markbarendt · Mar 2, 2014

Wow, that equation could give an art major a migraine.

snapguy · Mar 2, 2014

bean counters

My answer would be this is a question for a light meter, not math. Is it after dark outside? Is it rainy with black skies? Would you be photographing bright snow all the way to the horizon? If you take your camera outdoors will it be wall to wall jungle canopy? If you venture outdoors and you are in Syria, will someone shoot you? Or mug you, in a big city, or arrest you if you are in North Korea?

Sirius Glass · Mar 2, 2014

It is called a light meter used correctly not a mathematical equation.

ntenny · Mar 2, 2014

I guess they meant to stipulate that it's sunny-16 conditions outside, which means they're basically asking "how many stops difference between f/2.8 at 1/50 and f/16 at 1/800?" Seems like a reasonable exercise for someone learning to do calculations in stops, though it's not expressed in the clearest way (which could be down to the asker or the original exercise).

-NT

benjiboy · Mar 2, 2014

+1, The human eyes and the brain are very poor instruments to evaluate light because they react too quickly and imperceptibly to changes of light intensity for us to notice them.

Jeff Kubach · Mar 2, 2014

I like to use a lightmeter in those cases.

Jeff

Chan Tran · Mar 2, 2014

I think the OP's posted the questions rather poorly but really the question has nothing to do with determining correct exposure. It only asks the difference in stops for 2 camera settings.

In the first post is really asking between f/16@1/100@ISO100 and f/2.8@1/50@ISO800 how many stops difference are there?
In the second post is really asking between f/16@1/100@ISO100 and f/2.8@1/50@ISO640 how many stops different?

That's all has nothing to do with getting proper exposure and that is why I think it's an academic question and not something the OP wanted to know.

markbarendt · Mar 2, 2014

Chan,

For a photography class that first question is truly a mess. An art teacher is asking a complicated math question.

The teacher doesn't ask for the answer/the difference; he/she is asking for the equation. Essentially asking them to write the equation to find the logarithmic difference between two settings.

Prof_Pixel · Mar 2, 2014

9 stops darker

removed account4 · Mar 2, 2014

Chan Tran said:
I think the OP's posted the questions rather poorly but really the question has nothing to do with determining correct exposure. It only asks the difference in stops for 2 camera settings.

In the first post is really asking between f/16@1/100@ISO100 and f/2.8@1/50@ISO800 how many stops difference are there?
In the second post is really asking between f/16@1/100@ISO100 and f/2.8@1/50@ISO640 how many stops different?

That's all has nothing to do with getting proper exposure and that is why I think it's an academic question and not something the OP wanted to know.

the way it was worded was difficult to understand
but the end answer isn't very difficult to figure out ... i think ?

markbarendt · Mar 2, 2014

jnanian said:
the way it was worded was difficult to understand
but the end answer isn't very difficult to figure out ... i think ?

Yeah the answer isn't tough.

What we understand is that the difference between f2.8 and f16 is 5, not 13.2. The first question is asking us to write the equation that gets us 5 when we look for the difference between 16 and 2.8; and show that 4 is the difference between 1/50 & 1/800.

Steve Smith · Mar 2, 2014

benjiboy said:
+1, The human eyes and the brain are very poor instruments to evaluate light because they react too quickly and imperceptibly to changes of light intensity for us to notice them.

I agree that the human eye cannot detect actual light levels due to the 'automatic exposure' mechanism in the eye. However, we can judge contrast very well by the distinctiveness of shadows.

As the sun is a constant, the only variable during daylight hours is the amount of diffusion given by the clouds and this can be judged very well by eye.

Steve.

Mark Crabtree · Mar 2, 2014

Steve Smith said:
I agree that the human eye cannot detect actual light levels due to the 'automatic exposure' mechanism in the eye. However, we can judge contrast very well by the distinctiveness of shadows.

As the sun is a constant, the only variable during daylight hours is the amount of diffusion given by the clouds and this can be judged very well by eye.

Steve.

And the amount of the subject in shade, which is what seems to me is often left out by the Sunny 16 rule. Sure the main subject may be in full sun, but it is generally agreed (I'm sure not by every single person though) that you expose negative film for the amount of shadow detail you need. To me, Sunny 16 is more a useful snapshot rule where the nuiances of shadow detail may not matter, or for transparnency film. 1/500 @ f11 is about the least exposure I ever use for Tri-x (ISO 400) in full sun, though I can picture situations where f16 would be adequate. So my rule of thumb is Sunny 11. Doesn't have the same ring to it, but it gives me exposures I like better. I actually am often likely to give more than that in many cases. And more diffusion often doesn't change that exposure for me since it often doesn't change the shadow level.

As has been pointed out, the differences between the old and new shutter speeds are small and ignorable. Thinking in half stops for aperture is perfectly adequate. For me, when in between, give move the dial in the direction of exposure rather than less, at least if using Sunny 16.

To be clear, I'm not disagreeing with anyone, just expressing my feeling about the adequacy of the Sunny 16 rule, and how that impacts the OP's question.

Chan Tran · Mar 2, 2014

jnanian said:
the way it was worded was difficult to understand
but the end answer isn't very difficult to figure out ... i think ?

No the answer is easy but I am wondering which method would a teacher teach students to do this? So many ways to figure out the answer which way it was taught?

Prof_Pixel · Mar 2, 2014

It's really very simple.

Indoors with ISO 800 film: 1/50 sec at f/2.8

Outdoors with sunny 16 rule and ISO 800 film: 1/800 sec at f/16

1/50 sec to 1/800 sec is 4 stops (1/100, 1/200, 1/400, 1/800)

f/2.8 to f/16 is 5 stops (4, 5.6, 8, 11,16)

4 = 5 = 9 stops darker

RalphLambrecht · Mar 2, 2014

It's esy. All you have t to do is multiply the indoor exposurewith the temperature difference to get he outdoor exposure;in F for asa and in Cfor iso.

markbarendt · Mar 2, 2014

RalphLambrecht said:
It's esy. all you have tto do is multiply the indoor exposurewith the temperature difference to get he outdoor exposure;in F for asa and in Cfor iso.

Thanks Ralph I new there was a way.

benjiboy · Mar 2, 2014

It stands to reason if "sunny 16" was so accurate and produced such perfect exposures nobody would ever have ever invented light meters.

Mark Crabtree · Mar 2, 2014

benjiboy said:
It stands to reason if "sunny 16" was so accurate and produced such perfect exposures nobody would ever have ever invented light meters.

It does? People don't take pictures other than in the sun?

erikg · Mar 2, 2014

Mark Crabtree said:
It does? People don't take pictures other than in the sun?

Somebody is being sarcastic here.

lxdude · Mar 3, 2014

RalphLambrecht said:
It's esy. All you have t to do is multiply the indoor exposurewith the temperature difference to get he outdoor exposure;in F for asa and in Cfor iso.

Ah, but don't forget about the difference in color temperature between inside and outside, too!

John Koehrer · Mar 4, 2014

lxdude said:
Ah, but don't forget about the difference in color temperature between inside and outside, too!

Cloudy or sunny too. 6k+ vs. 55k
It can be pretty noticeable. Or not.

wiltw · Mar 4, 2014

lxdude said:
Ah, but don't forget about the difference in color temperature between inside and outside, too!

What if we're shooting B&W film?

markbarendt · Mar 4, 2014

wiltw said:
What if we're shooting B&W film?

Which one? They have different responses.

Sunny 16 rule

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