The only three things you need to know about DSRL

The Only Three things you Need to know about DSLR
A practical guide to exposure
Guilherme Zühlke O’Connor
twitter.com/guioconnor
facebook.com/guioconnorPhoto

Once upon a time…

Once upon a time…
… there was SLR

SLR – Single Lens Reflex

A camera with a single lens

A camera with a single lens
Use of reflection to send the image to the viewfinder

Back in the old times…

The body of the camera was responsible for the exposure time

The lens was responsible for the aperture

The lens was responsible for the aperture
The film was responsible to hold the projected image for eternity (or a sub-period of it)

The camera body
Tipically, a camera body would be set to expose the film for a period of time ranging from 30 seconds to 1/2000 of a second (but your mileage may vary)
http://www.flickr.com/photos/buou/4884738437/

The Lens
Has a diafragm that controls the area of the aperture through which the light enters the camera
The amount of light is proportional to the area of the aperture
http://www.flickr.com/photos/cycleologist/1454436980/
(*) See previous presentation on aperture at
http://www.slideshare.net/guioconnor/aperture-in-photography-or-how-boheh-happens

The Film
The film has an emulsion containing silver salts that react to the presence of light
The more light it receives, the more grains of salt will react
The coarser the grains of salt the less light you need but the lower the definition of the resulting image(*)
http://www.flickr.com/photos/remediatethis/4353934129/

(*) That’s the ISO setting for ya

The correct exposure needs a certain amount of light.

The correct exposure needs a certain amount of light.
If you want a faster shot, you need a wider aperture. And vice versa.

Alright, alright. What about DSRLs, then?

Alright, alright. What about DSRLs, then?
Same thing but with a sensor in place of the film.

Manual Mode
Most DSLRs have a manual mode setting

Manual Mode
You set the exposure time

Manual Mode
You set the aperture

Manual Mode
You set the aperture
Settings are based on the photometer indication

Aperture priority mode
Most DSLRs have an Aperture Priority Mode

You set the aperture you want to take the picture on

The camera works out how fast (or slow) it needs to be

The camera works out how fast (or slow) it needs to be
Ideal to control the depth of field

f/4.8
f/32

Shutter Priority Mode
Most DSLRs have a Shutter Priority Mode

You set the exposure time of the shot

The camera works out the aperture

The camera works out the aperture
Ideal to control motion blur

1/500 s
1/90 s

But also for extreme light conditions

Exposure time 104s, barely visible with the naked eye. Shot with ISO 50.
See more at http://www.facebook.com/media/set/?set=a.224883254190744.71882.119779558034448

The ISO setting
Just as in film

The ISO setting
Just as in film
The higher the ISO the less light you need

The ISO setting
Just as in film
The higher the ISO the more noise you have

The ISO setting
Just as in film
Different sensors have different qualities for a given ISO value

The ISO setting
Just as in film
Different sensors have different qualities for a given ISO value
ISO is based on the amount of light needed, not the amount of grain/noise produced

ISO 1600
ISO 200

All fancy exposure settings on your DSLR are based on these three basic principles.

?
Questions
Further reading
http://www.z-oc.com/blog/2007/08/understanding-cameras-and-photography/
http://www.slideshare.net/guioconnor/aperture-in-photography-or-how-boheh-happens

The only three things you need to know about DSRL

by Guilherme Zühlke O'Connor on Jun 02, 2011

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