# Online exposure calculator!



## poopingfish (Apr 3, 2008)

Found this looking for a calc for my math homework.
It may be of some use, not sure. Personally never heard of an ISO of 6400 but im still relatively new. Click here.

Is this thing right?


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## Big Mike (Apr 3, 2008)

That is based on the 'Sunny 16 Rule'.  It does work, but it relies on your ability to accurately identify the light levels.  

If you have a camera with a built-in light meter (99% of modern cameras do) then you don't really need to use this.  But it's certainly handy to know.


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## KhronoS (Apr 4, 2008)

Big Mike said:


> That is based on the 'Sunny 16 Rule'.  It does work, but it relies on your ability to accurately identify the light levels.
> 
> If you have a camera with a built-in light meter (99% of modern cameras do) then you don't really need to use this.  But it's certainly handy to know.



Mike, i think that it will become handy to shoot very dark scenes ( night scenes ), because you will be forced to use  BULB, and you have to know how much time to keep the button pressed 
What do you think?


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## poopingfish (Apr 4, 2008)

Haha. Khronos got you there!
Ah, the ol sunny 16 rules huh? I mustve over looked that somewhere.

Wait-How is this reliant on the S16 rule? It says when you click "calculate" what is needed for each stop. From f/1 to f/64.


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## Big Mike (Apr 4, 2008)

> Wait-How is this reliant on the S16 rule? It says when you click "calculate" what is needed for each stop. From f/1 to f/64.


The Sunny 16 rule is; in bright sun with an aperture of F16, your shutter speed should be the reciprocal of your ISO.  So for ISO 100, it would be 1/125.  

You can use those values to extrapolate to any circumstance.  If your aperture is F4, that's 4 stops larger, so your shutter speed at ISO would need to be 1/2000.

So it's not just a rule for F16.

The problem with that calculator, is that you are choosing a light level based on a description...."Subject lit by dim or indirect artificial light"...that could mean something different to everyone...like I said, you would have to be very good at identifying the light level.

I do see that you can also enter the light level value in different measurement values...but you would need a light meter for that anyway.

Seems like a lot of trouble when most cameras have a built-in meter anyway.


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## Socrates (Apr 4, 2008)

Big Mike said:


> That is based on the 'Sunny 16 Rule'. It does work, but it relies on your ability to accurately identify the light levels.
> 
> If you have a camera with a built-in light meter (99% of modern cameras do) then you don't really need to use this. But it's certainly handy to know.


 
I still have a slide-rule type device _*(from 1964!)*_ for this purpose. It factors ASA, f-stop and shutter speed for a hundred night exposures (each one with an extremely detailed description). It's about as far away from "sunny-16" as you can get. I cut it out of a magazine and glued to pieces of cardboard

I still use it occasionally. Under certain circumstances, it's actually better than my camera's built-in meter. First, the camera's meter doesn't know that the scene is _supposed_ to be dark and second, I can use it for exposures as long as thirty seconds.  Bracketing is, of course, essential.


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## Big Mike (Apr 4, 2008)

What about reciprocity failure?  Each film is somewhat different when it comes to longer exposures...slower film can be more sensitive than faster film etc.


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## skiboarder72 (Apr 4, 2008)

poopingfish said:


> Personally never heard of an ISO of 6400 but im still relatively new.



My D300 goes up to ISO6400, the D3 goes up to ISO25,600 :thumbup:


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## 68Whiskey (Apr 4, 2008)

skiboarder72 said:


> My D300 goes up to ISO6400, the D3 goes up to ISO25,600 :thumbup:



More like :thumbdown:, I could take a pencil and etch the picture better than the D3 can take on at ISO 25,600, with that said I am buying one soon LOL.


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## Socrates (Apr 4, 2008)

Big Mike said:


> What about reciprocity failure? Each film is somewhat different when it comes to longer exposures...slower film can be more sensitive than faster film etc.


 
After you get the theoretical value, you factor that in manually.  Hey, this was the sixties - what do you want?  I don't worry about it anymore because digital sensors don't have reciprocity failure.  However, I still bracket, bracket, bracket.


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## Big Mike (Apr 4, 2008)

> However, I still bracket, bracket, bracket.


Amen.  Me too.


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## KhronoS (Apr 4, 2008)

Big Mike said:


> The problem with that calculator, is that you are choosing a light level based on a description...."Subject lit by dim or indirect artificial light"...that could mean something different to everyone...like I said, you would have to be very good at identifying the light level.



Yeah you're right... exact numbers can't be equal with a simple description.

But hey... at least you know around how much time you need to press that button  ... and from there... as you said... bracket, bracket, bracket


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## Big Mike (Apr 4, 2008)

On a side note, I had a photography instructor that said he (and his associates) could tell the light level they were in...usually down to within one or two tenths of a stop.  They always had a light meter with them and they would 'guess' the reading it would give.  The one who was farthest away from the actual reading had to buy lunch.


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## JerryPH (Apr 4, 2008)

Big Mike said:


> On a side note, I had a photography instructor that said he (and his associates) could tell the light level they were in...usually down to within one or two tenths of a stop. They always had a light meter with them and they would 'guess' the reading it would give. The one who was farthest away from the actual reading had to buy lunch.


 
Do that for 5-6 years, and it would not surprise me if they indeed could do that!


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