Introduction to Exposure - Page 3

* All elements of exposure work together. *

Putting it all together.

• Here is a hypothetical exposure situation, it's dull day.
• For ISO 400 all the the following exposure combinations are valid.
• Remember * all elements of exposure work together *
• So if we change an aperture value we must change a shutter speed. Also remember changing aperture changes depth of field.
• IE - We go from F8 to F5.6 we let twice the amount of light in through the lens,
• so that means we need to reduce (halve) the amount of time the sensor is exposed to the light.
• It is always a balancing act.

• Which combination will we use?
• It depend on what you want.
• If you are wanting to stop action I would go with 1/500 @ F4 or 1/1000 & F2.8 - although depth of field (DOF) will be small at that aperture.
• If you want greater depth of field go with 1/30 @ F16 although you may find it difficult to hand hold the camera.
• If you want to shoot a waterfall with the flowing water effect than you will need to reduce the sensitivity (ISO) down to possibly 100 or even lower as per the pic below.
• .

• .
• For our waterfall shot we now can shoot down to 1/4 of a second.
• However we will need a tripod to support the camera.
• Also because we are now shooting at a lower ISO (sensor sensitivity) value, noise in our photo will be reduced.
• .
• Conversely if we need more depth of field and high shutter speeds we can adjust the ISO to 1600.
• This will allow us to shoot at 1/500 @ F8 or 1/1000 @ F 5.6 giving us better depth of field at the expense of more noise.
• If shooting city streets of an evening high ISO's will allow you to capture scenes without using a tripod or flash.

* All elements of exposure work together. *

So if you change one component you will need to change one of the others to keep everything in balance.

How do we use do different exposure settings.

• .
• I will use a Canon 350D (Rebel XT) as an example (I own one)
• Similar controls are found on some Canon point and shoot cameras
• First a comparison of what the camera will do through the "Automatic" settings and what we can do when we take control.
• Next will be how to use the manual settings.

Rule # 1 - Read the book! - the one that came with your camera.

• .
• On the top of the camera you will find a shooting "mode" dial.
• .
• The Canon manual divides the Mode dial into two functional zones Creative and basic.
• ... the Nikon equivalents would be P, S A & M where you want creative control over your camera
• .... otherwise from Auto to Night portraits the camera has control over your photographs. this is for Nikons D40 and D80
• (1) Basic - where the camera will control everything relating to exposure, including popping the flash if needed, except red eye reduction with the flash.
• You cannot control how the image is recorded - jpg only - not RAW (RAW will be another tutorial.)
• I only use these modes occasionally.

• (2) Creative - Where you have total or partial, if you want to, control over the camera functions to achieve the results you want.
• .
• Here are some comparisons between letting the camera doing its thing and you taking control.
• (1) Portrait mode - here the camera will try to blur the background by setting the widest possible aperture and ISE ISO 100.
• The photos were taken within a few minutes of each other with a Canon 350D with a 50mm F1.8 Canon lens and a tripod. ISO was 100. The lighting was similar but not identical.
• Full size originals are available by clicking on the pictures.
• *********** They are large files - 3mb to 6mb each. *****************

• Portrait Mode - The camera has selected 1/2000 @ F2 ISO 100
• Notice the out of focus background (good) and how shallow the depth of field is.
• If this was a person only the eyes would be sharp.
• The camera has controlled how the picture looks re colours and contrast.

• Here I have selected 1/3200 @ F2 ISO 100
• The depth of field is the same.
• The colours look different because I have processed the picture with DPP, The software that came with the camera, to achieve the results I wanted.
• Because I was controlling the camera I set the output to RAW which gives me a lot more control over the photograph.

• I have used 1/60 @ F13 - ISO 100
• Notice the increase in depth of field.
• The whole of the hoist assembly is now sharp as would be a portrait because we are now using a smaller aperture.
• The background has sharpened up as well which is a minus.
• Maybe if this was a real portrait I would have shot from a different angle to get a better back ground.
• If I was shooting hand held with this lens I would not have shot below 1/100 as I don't feel I could hold the camera steady enough.
• That may mean I needed to up the ISO to 200 to have a similar aperture.
• This was process by me in DPP.