Sunny 16

Sunny 16 is just a convenient starting point. Your exposure is determined by 3 factors, shutter speed, aperture and ISO sensitivity. So if you want to change any of these factors you need to adjust either or both of the other two to compensate.

For example starting from f16, 1/100th sec and ISO100 you want to use a faster shutter speed. OK change it to 1/200th sec and you now have half the exposure you had before so you need to change the other factors. Either open up the aperture one stop to f11 or change ISO to 200 will have the same effect. Not a fast enough shutter speed yet? Just keep opening up by one stop every time you half the exposure time.

As long as you keep the changes in step you will get the same exposure.

--
Steve

http://www.pbase.com/steephill

The Sage Knows said:

If you mean, how would you shoot at 1/500s at ISO 100 on a clear sunny day while basing the exposure on the Sunny 16 rule,

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Yes this is an example of what I meant.

The Sage Knows said:

then "without memorizing a chart of values", you just count the clicks from 1/100s to 1/500s as you turn the shutter dial on your camera (seven 1/3 stop clicks). The you click as many time going the other way with the aperture dial from f/16....seven 1/3 stop clicks ....f/7.1

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Perfect, thanks. I've heard before that a 'stop' is a 'stop' but I wasn't sure if it really was that easy.

Nightfury said:

OK so I understand from DPR forums and wikipedia that sunny16 is such that you set your aperture to f16 with shutter speed being the reciprocal of the ISO setting.

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Nightfury said:

exs f16 iso100 ss1/100 or f16 iso200 ss1/200 etc etc

Without memorizing a charge of values, is there any rule of thumb if you want to start using shutter speeds and ISO values that are not reciprocals? Is this just not done?

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For any one strength of incident light (Light Value), and any one ISO setting, a whole gamut of equivalent shutter-speed and aperture settings will pass the same volume of light to the sensor.

So, if just ONE correct exposure setting can be identified, it can be used as a stepping stone to any other practical shutter-speed and aperture combination that might be a more convenient equivelant.

Here is an example, one specific Sunny 16 case broken down, the 100-ISO one...

• Strength of light (or Light Value) Clear Sun
• Sensor or Film sensitivity in ISO values 100
• Shutter-speed (duration of opening) 1/100th sec
• Lens opening known to be correct for the 3 conditions above f/16

Any of these values can change, with the exposure being held correct and equivalent by making an equal and opposite adjustment to one or other of the remaining three factors. It is your choice, except that mostly you can't change the weather, and you cannot move any setting past the end of its range, either!

Let's take 'em in turn...

1) Changed levels of light intensity...

• In an earlier post I already showed how the aperture should be varied for the different light values arising from different degrees of cloud cover, or different light volumes bounced on to subjects from their surroundings.. (snow or sand).

2) Changed ISO levels...

• I hope it is also clear that changing ISO to, say, 200-ISO, could also be accommodated by simply increasing shutter speed to 1/200th second, without having to alter anything else at all. Indeed, in Clear Sun light levels any ISO can be returned to correct exposure by setting shutter-speed to the reciprocal of the ISO and using f/16.....

... which doesn't mean for a moment that you HAVE to return to correct exposure by way of a reciprocal shutter speed.... It just happens to be an incredibly convenient and serendipitously easy way of remembering what correct exposures are, which is what we are trying to do here.

No...you can, if you wish, break with the ISO and simply select a more convenient shutter speed, which you accommodate by making the appropriate adjustment to one of the two remaining components in your control... as follows

3) Changed shutter-speed...

• Example speed change from 1/100th to 1/800th second, say, is 3 stops less exposure... so the aperture will need to be opened up by a commensurate 3 f-stops to keep exposure correct.. [OR increase ISO reciprocally after all!]

4) Corrected aperture (lens opening)...

• Lens opening correct for the above shutter speed, (at current light level, and ISO value)... is 3 stops wider than f/16, therefore f/5.6

Does that make sense now?
--
Regards,
Baz

"Ahh... But the thing is, they were not just ORDINARY time travellers!"

I used to carry around a table of equivalent exposures and a list of guidelines similar to what Barrie listed for other lighting conditions until I finally memorized most of it. Use it a few years and you will get pretty good at it. I don't think many people nowdays will find it as accurate or as reliable as just learning how the meter in your camera works in various situations and then using exposure compensation as necessary.

Thanks for that write up Barrie. I just wanted to let you know that I did come back to this thread and read it, and your typing did not go in vain.