As a new photographer you have undoubtedly heard the phrase, "Stop of Light", but what is it? A stop of light is a measure of light to gauge exposure. If some thing is underexposed or darker than it should be, you need to add stops of light. If an image it too bright you need to reduce stops of light. 

Watch this 1 minute quick tip video. If you already know about stops, then you will be done, if not, read after this and see them explained. 

Why do you need to know exact stops?

     Say you have got the perfect exposure but you want to change the noise, or depth of field, or freeze the motion better . Knowing how to create reciprocals of exposures allows you to do this. 

For instance

ISO 100, F2.8, 1/500 = ISO 200, F5.6 1/1000 = ISO 100, F4, 1/250

These are all equal in exposure, the things that change will be noise (ISO), motion freezing (Shutter Speed) and Depth of Field (aperture), but will all look identical in exposure. 

    Stops are relevant to ISO, Shutter Speed, and Aperture. On ISO and Shutter Speed they are very simple to figure out because it is just a 2 x's multiple. Aperture is a little trickier just because it does use while numbers, but super easy with a  bit of practice. 


Raising the ISO from 100 to 200 Increased it by 1 stop. So your picture will be 1 stop brighter. Farther increasing it from 200 to 400 is 1 stop as well. It continues on until you reach max ISO on your camera, usually around 25,600 on most cameras, some a bit less. 


Shutter speed works the same as ISO. Halving and doubling will either increase light or reduce light respectively. If you slow your shutter by half (1/500 to 1/250) you are gaining 1 stop of light. If you increase your shutter speed by 1 stop (1/80 to 1/160) you will lose light. It is true for all numbers in the shutter speed. 


Aperture is where it is a little trickier to remember since it isn't working in whole numbers. Then you increase the aperture by a stop, you are technically opening the whole in the lens (aperture) and doubling its area in size. There is an actual formula for aperture ( it actually get pretty complex since it factors in depth of field so we won't cover it this time. That is a lesson all on its own.) So just know the numbers represent the opening size. 1 being wide open and 22 being a very tiny whole for sake of this discussion. 


    Each green number represents a whole stop, the number in-between represent 1.3 of a stop. 

     The larger the number the smaller the diameter of the aperture, resulting in less light and a deep depth of field. The smaller the number the bigger the diameter of the whole, resulting in more light and a shallower depth of field. 


     I hope this short analysis of stops of light cleared up some of the confusion. I know it was one of the hardest parts for me to truly grasp in photography and using the cheat in the video helped me determine stops while out in the field. 

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