Sunny F 16 rule beginner’s question

Stephany

Today around noon (partly sunny) I took my very first photo with Canon SX 120 ( lens 36-360 mm; F2.8-4.3). The Auto settings the camera chose puzzle me:

ISO 160; 1/800; F/4.3; 60 mm. If I was to manually set the camera to ISO 100 should I change the setting to about 1/500 to comply with the camera’s logic? Following the Sunny rule, I'd probably choose 1/1000 not 1/500. Sorry, for asking such a rudimentary question, but I am lost.


http://www.flickr.com/photos/54054082@N08/4994843230/

pathfinder

Hi Stephany,
I wrote this thread a few years back about Sunny 16 - It is still a good trick to know.

From the table in the link I posted about Sunny 16, at ISO 100, the correct shutter speed for f4 at ISO 100, is about 1/1600th to 1/2000th. Since f4.3 is about 1/3rd stop slower than f4, the shutter speed would need to be a little longer, maybe 1/1200th or so. For ISO 160, it would be about a 1/2 stop faster, so maybe 1/1,800th or so - call it 1/2000th.

Look at it this way - f4.3 is about 1/3 stop slower than f4.0, and ISO 160 is about 1/2 stop faster than ISO 100, - combine them and the difference is less than 1/6 th of a stop - 1/2 minus 1/3 = 1/6th of a stop or usually insignificant. Hence the shutter speed would still be between 1/1600th to 1/2000th.

Why not shoot an image of two and check your histogram. Or shoot a 16 step grey scale and see if you captured all the 16 different levels of grey with one exposure....

pathfinder

My error for confusing you.

While F4.3 is indeed about 1/3 stop smaller (hence "slower" aperture - requires a longer shutter speed than a full f4.0), ISOs do indeed mean faster film as they get larger.

Apparently I was asleep when I suggested ISO 160 was slower than 100. You are correct, ISO 160 is indeed about 1/2 stop faster, and would require a shorter shutter speed not a longer one. I will re-edit my post to correct my error.

Think of it this way - f4.3 is about 1/3 stop slower than f4.0, and ISO 160 is about 1/2 stop faster than ISO 100, - combine them and the difference is less than 1/6 th of a stop - 1/2 minus 1/3 = 1/6th of a stop or usually insignificant. Hence the shutter speed would still be between 1/1600th to 1/2000th.

Sorry for my confusion in my precious post.

Stephany

Pathfinder, no problem. I've found a paper writtten by Mr. Fred Parker explaining Exposure Values and it has a Table in it, which I also find quite helpful. Thank you, again, for your help.

pathfinder

I suspect this is the link you are referring to, isn't it, Stephany? http://www.fredparker.com/ultexp1.htm

Stephany

Pathfinder,

yes, it is. But, I would like to modify the Exposure Value table for my camera lens 6mm-600mm F/2.8-F4.3 which includes in-between F/Stops (up to F/8), ISO speeds and a limited range of shutter speeds so, I do not have to calculate much.
I am not sure exactly how to do that yet, but may be there is an equation I could use and do it in Excel? Please let me know if you have any suggestions.