Photography At Latitude 45 Or Higher - </Tinfoil Hat>

[canonloader]

The Theory...
I live roughly, at 45 degrees North Latitude and have noticed that while people in Florida can shoot the same camera/lens combo on a sunny day and get an easy 1/3200" shutter speed, I can only get like 1/1500 or 1/2000, and that is on a good day. So here I am, agonizing over this discrepancy for the last couple years, even sold perfectly good lenses, cause they were too slow for here, and blaming it on cloudy days.

And then it dawns on me, wait a minute. Even on the longest day of the year, the noon sunlight is still at not a 90 degree angle, but at 69 degrees. Thats almost 24 degrees for the tilt angle of the earth added to the 90 degrees straight up at the equator, minus the 45 degrees of latitude where I live. And that's on the longest day of the year when the sun is at it's highest. In Miami, at 25 degrees north, their sunlight is at 89 degrees at noon on the longest day of the year. And correspondingly higher even at sunrise or any other day of the year.

Has anybody else noticed this effect? People who travel regularly, or maybe you already know of this effect? I know it sounds odd, but at 69 degrees, each photon has to travel through a lot more atmosphere than when coming straight in, so, losing some of it's power and my f/stops. :)

[Sorarse]

Ah, but having too much light is not necessarily always a good thing.

[canonloader]

Well, that's what ND filters are for. :)

On the other hand, too little just puts me to sleep. :)

But I think I am on the right track in thinking that the strength of the light can effect the function of the camera. Think instead of being here at 45 degrees North, if you were at 90 degrees North, no light at all.

I guess the real question is, at what latitude does it really become a problem, slowing down lenses by a full stop?

[Mark_Cohran]

I've lived not very far north of the 45th parallel for over a decade and I routinely visit Arizona and California and lived for years in Florida, Georgia and South Carolina...I just don't see latitude as a significant factor in the amount of light on a bright sunny day. Sure, it has impact on the angle of the rays and the length of the day from solstice to solstice, but I've certainly seen no other impact.

[neumanns]

You should check out some of the shutter speed's obtained at altitude.

I have no referance handy but Look at some shot's taken at 12-14000 feet above sea level in bright sunlight.

But then again our sun glinting off the snow would even make a Floridian Jealous of our shutter speed's...But let's not talk about battery life or length of day!

[canonloader]

I just don't see latitude as a significant factor in the amount of light on a bright sunny day.
Your eyes may adapt, but I have also lived in San Diego, Miami, Phoenix, Seattle Presquile Maine and a number of places in betweem, Washington DC, NYC, Chicago. I would go blind in Phoenix or San Diego without sunglasses while I don't need them here. There is no doubt that light is weaker at higher latitudes, just a question of how much.

Altitude is another factor. At 10,000 feet you can burn to the bone in an hour of strong sun, while you might make it all day at sea level.

I wonder if there is some kind of chart or way to calculate what it is for a certain latitude/altitude?

[Mark_Cohran]

Your eyes may adapt, but I have also lived in San Diego, Miami, Phoenix, Seattle Presquile Maine and a number of places in betweem, Washington DC, NYC, Chicago. I would go blind in Phoenix or San Diego without sunglasses while I don't need them here. There is no doubt that light is weaker at higher latitudes, just a question of how much.

Altitude is another factor. At 10,000 feet you can burn to the bone in an hour of strong sun, while you might make it all day at sea level.

I wonder if there is some kind of chart or way to calculate what it is for a certain latitude/altitude?

Perhaps you're right. I'd be no help to you because I'm at nearly the same latitude, but if you could coordinate with somebody at near the same longitude but a lower latitude to take an outdoor meter reading with same type of handheld meter (on a gray card in sunlight on a cloudless day) at the equivalent time of day you could determine the difference directly.

[canonloader]

Your right. What it needs is some way to test the lumens, here then somewhere South of us. I have been searching for a couple hours and the basic concept is true, but I found no real numbers to tell what the actual difference is. I think if it was one stop, or even half a stop different, it would answer a lot of questions I have had for the last couple years. :)