Silly Question of the Day

[wingflapp]

Ok, I have a question that may sound incredibly ridiculous, but I'm gonna ask it anyway.

It's kind of hard to explain (if you don't know what the heck I'm trying to ask) so hopefully this little explanation will help my question to make sense.

I dabble a little bit in aviation, and one piece of information that we use is called a 'standard day'.. meterologically speaking. Basically its a day that is 15 Celsius, and 29.92 Barometric Pressure. This actually almost never happens, but it is the standard datum from which most other measurements are made so we can determine performance and decide on any number of aircraft configurations. It's to keep everyone on the same page, no matter what level of experience, or aircraft type.

As far as photography goes - I have read a lot of the rules, and a lot of the discussion and articles on aperture, ISO and shutter speed. I can't help but be curious if there is any such thing akin to the 'standard day', except from a photographical perspective. For lack of a better term, is there a 'standard picture' from which we deviate?

As an example - Subject 10 feet from the camera, with X amount of light, and an aperture setting of Y = a basic picture where a new person should begin experimenting.

The reason I ask this silly question - A starting reference and direction generally helps a person to know which changes will help them to reach their goal. (from a technical standpoint)

Man, I hope that question makes sense. This was hard to put into words.

[zona5101]

I suppose... I can think of the "Sunny 16 Rule" that might be kinda like that...

[ravncat]

sunny 16 rule is what popped into my head as well..

It states - For a subject in direct sunlight - set aperture to F16 and Shutterspeed to the (nearest) Reciprocal of the ISO. so f16 at 1/100th for iso 100 (though back in the day, with only full stops of shutterspeed one had to go to 1/125th because 1/100 was not an option)

One would also use some other basic guesses based on the weather condition and strength of shadows - it still works fairly well - this was how many got by with out a light meter.. All you had to do was increase or decrease by a stop per level, so i`ll adjust aperture so that 1/iso still works for shutter speed. With a good understanding of the exposure triangle, it becomes fairly easy to do a decent job of guessing a nearly correct exposure.

With film`s lattitude, it was often good enough. With Slide film / digital - it would be better to bracket around the guestimate - though with digital one usually has a light meter available - and otherwise a histogram. I still practice guessing exposures with manual before shooting, just because It`s neat to be able to do


f/4 Open Shade/Sunset definitely no shadows +4 stops
f/5.6 Heavy Overcast No shadows +3 stops
f/8 Overcast very hard to see shadows +2 stops
f/11 Slight Overcast slightly soft shadows +1 stop
F/16 Sunny (and thus sunny 16)
f/22 Snow/Sand Strong Sharp Shadows -1 stop

And then we`d add a stop or so for backlighting.

[wingflapp]

Great info. It definitely gives me the starting point I was hoping for. Thank you so much.

Still, I am brand new to photography, so it also raised 2 questions.. I hope you have the time to touch on them, perhaps.

You discussed setting 1/100 shutter speed for a 100 ISO... the 2 are apparently reciprocals. So, for a 400 ISO (I'm guessing here) I would use a 1/400 shutter speed (if such a shutter speed exists)...Sensor is 4 times more sensitive, so I'm reducing the time the shutter is open by roughly 75%. ish. maybe. Somewhere in there. Do I have that correct?

Also, I was curious about the stops you listed. From your example, for heavily overcast skies I would start with an aperture setting of 5.6. You also added "+3 stops". I was curious what "+3 stops" refers to. I know we talk about the aperture setting using the word stops, but I'm not sure what the +3 is.

Thank you in advance!

[wingflapp]

I did some searching, and I think I got it. The Plus values represent the # of stops from the standard, which was f/16.


I think.

[dalmorloson]

I hope I'm correct in saying...a + or - stop does not necesarily have to be changed with the aperature. A stop is double the light or half of the light hitting the sensor. This can be achieved with any of the three factors (aperature, shutter speed, or ISO). From 1/100 to 1/200th is a stop, 5.6 to 11 is a stop, ISO 100 to 200 is a stop. Not that these were all in the same direction (+-), just giving examples.

[wingflapp]

Originally Posted by dalmorloson

I hope I'm correct in saying...a + or - stop does not necesarily have to be changed with the aperature. A stop is double the light or half of the light hitting the sensor. This can be achieved with any of the three factors (aperature, shutter speed, or ISO). From 1/100 to 1/200th is a stop, 5.6 to 11 is a stop, ISO 100 to 200 is a stop. Not that these were all in the same direction (+-), just giving examples.

Gotcha! Thanks so much!

[ravncat]

That`s right, i only gave varied aperature in the examples above - so that the general idea of 1/iso for shutter speed was right - you could of course vary iso or shutter speed to increase or decrease exposure.


But using this - is a rough guide - it would be more accurate to use the cameras meter.

[Henry Wilt]

Originally Posted by dalmorloson

I hope I'm correct in saying...a + or - stop does not necesarily have to be changed with the aperature. A stop is double the light or half of the light hitting the sensor. This can be achieved with any of the three factors (aperature, shutter speed, or ISO). From 1/100 to 1/200th is a stop, 5.6 to 11 is a stop, ISO 100 to 200 is a stop. Not that these were all in the same direction (+-), just giving examples.

Forgive me for jumping in here, I want to clarify this for myself as much as anything else, is f/5.6 to f/11 not 2 stops? I thought f/5.6 to f/8.0 was one whole stop.

[ravncat]

5.6 to 11 is two stops