Important Theory

When I stopped school I thought that my studying days were over. I guess I was wrong. Wanting to be a photographer theory is more important then it ever was. Knowing and understanding light comes with practice but the theory behind it, is equally important. The easiest way to learn about light is with the exposure triangle. This triangle shows the balance between shutter speed, diaphragm and ISO. Putting these settings in a camera is often a choose between a sharp photo or a photo with motion noise. It's a match between deep focus versus shallow focus and a not so difficult decision between sensitivity and noise. Not so difficult because you don't want noise.

So the theory. I'll keep it short. I talked about all these things before but I want to explain what it all means. The diaphragm determines how much light enters the sensor. The bigger the number behind F/, the smaller the diaphragm and the less light the sensor gets. The shutter speed determines how long the light enters the sensor. So the longer de shutter speed is, the more light the sensor gets. Downside is that there is more risk at motion noise because of vibration. The last component is the ISO, this determines how sensitive the camera will respond to light. The higher the ISO, the higher the chance at noise.

It all is a triangle so that means that if you change one thing it effects everything. Every change can means less light or a halving of the amount of light. Every change can mean more light or a doubling of the amount of light. This difference is the 'exposure value' or in human language 'stops'. One stop is the difference between two consecutive shutter speeds, diaphragm values or ISO values. The kind of lens you use gives difference as well. I have two images and some photos to make it all clear.



Exposure triangle

Some stops and there effect

F/11  1/125s  ISO100  @18mm
good depth of field, no motion noise, no noise

F/5,6  1/500s  ISO100 @18mm
shallow depth, faster shutter speed because of the
lower diaphragm and no noise

F/11  1/125s  ISO100 @18mm
3m distance of subject
good depth of field, no motion noise, no noise



F/5,6  1/500s  ISO100 @18mm
3m distance of subject
shallow depth, faster shutter speed because of the
lower diaphragm and no noise

F/5,6  1/500s  ISO100  @18mm
with my 18-55mm lens
shallow depth of field

F/5,6  1/500s  ISO100 @75mm
with my 75-300mm lens
shallower depth of field

F/5,6  1/500s  ISO100  @300mm
with my 75-300mm lens
shallowest depth of field



F/8  1/4000s  ISO1600 @55mm
high ISO more noise in the back
high shutter speed because of high ISO

F/8  1/2000s  ISO800 @55mm
high ISO noise in the back
high shutter speed because of high ISO

F/8  1/1000s  ISO400 @55mm
slight noise in the back
high shutter speed because of high ISO

F/8  1/500s  ISO200 @55mm
not much noise
 

F/8  1/125s  ISO100  @18mm
Good depth of field

F/4  1/500s  ISO100  @18mm
shallow depth of field (look at the bald guy)



Enjoy Photography

Caroline