Photography Lessons: Exposure

In the first lesson, we learned that photography is all about light–specifically recording  the light illuminating an object or scene.  In order to do this, there are three things you need to configure in order to capture the image or scene:

  1. Aperture – iris diaphragm opening
  2. Shutter speed – exposure time
  3. ASA or ISO rating – the film or image sensor sensitivity, respectively

When my uncle gave me his Pentax K-1000 camera back in the 90’s, it started my serious learning about photography.  The camera was film-based (naturally) and had no automation whatsoever.  After loading the film and setting the correct ASA film-rating on the dial, I would have to adjust the shutter speed and aperture accordingly, and make sure that the light meter (see that needle on the right side of the viewfinder illustrated below) is in the middle position (indicating that the object in the center is evenly lighted)–that was it! 

The K-100 Viewfinder (Meter on the right)

Look at the viewfinder above; on the right side (with the needle) is the light meter.   For the K-1000 and all the manual film based cameras, the needle should be at the middle.  As the needle moves up (toward the + sign), the scene gets progressively overexposed.  As the needle moves down (towards the sign), the scene gets progressively underexposed. 

In modern DLSRs, there would be a digital value somewhere on the viewfinder or LCD screen.  On the Pentax K-x, it’s on the lower right corner (indicated by the number 9 on the illustration below).  If the scene is evenly lighted (based on ISO, shutter speed, aperture, and exposure method), the value would read 0.0.  If the scene is overexposed the value would be preceded by a plus (+) sign.  If the scene is underexposed, the value would be preceded by a minus () sign.

Pentax K-x Viewfinder

On my old (film-based) K-1000, I’d know if I got the exposure right only after the film was developed and the pictures printed—man, talk about suspense!  My youngest brother, Sonny, joking called film-based cameras “suspense cameras”, because you were in suspense if you’ve taken the shot right…until after the film was developed and the negatives printed.  If I got it right, that would be great!  But if I got it wrong, the opportunity was lost.  This is especially frustrating if you’ve travelled a great distance, and know that it would be a long time before you can return and take another shot.

Before the age of digital photography, you’d have to have lots of film (with different ASA rating) with you, and take different exposure settings (aperture and shutter speed combinations given an ASA rating).  Hopefully, of the many shots you took, there was at least one that was just right—enough to put a smile on your face.  To have captured a fleeting moment or a rare occurrence is the essence of photography–an image available for all to see and enjoy.

In order to capture an image correctly (from a technical standpoint, we’ll get into composition in later topics), you’ll need to use the right mix of ASA/ISO (film/image sensor sensitivity), shutter speed, and aperture—some photographers call this the exposure triangle.

Next topic: the aperture…

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