EXPOSURE - PART 2

Exposure Part 2

Correct Exposure in Photography, of course, depends on shutter speed, aperture value and ISO.

Most of the technical terms in Digital photography have been adopted from Film photography. The emulsion coated on the film has got some of the characteristics which present day sensors have, for recording images. However, there is no big difference in optics of Film Photography and Digital Photography. The glaring difference must be understood about light sensitivity. There is different film for different sensitivity which measured in ISO units. In Digital photography the same sensor will change its sensitivity using digital technology and circuitry.  The size of one frame of 35 mm film is 36mm x 24mm for all cameras of 35 mm format cameras. Where as the size of the sensor is different for various digital camera models.

Though the optics is generally same, as said above, there are of course, some difference because of the size of the sensors. Due of this, in digital cameras, there are numerous sizes of Digital cameras

The correct exposure can be achieved with correct combination of shutter speed and aperture for a particular lighting of the subject. It is interesting to study this subject with examples normally highlighted during Film Photography era.

The correct exposure can be achieved with the following combination with constant ISO value.[ Shutter Speed – Aperture Relationship].

Shutter speed in seconds------------Aperture[f/stop]

1/ 1000--------------------------------------f/2.8

1/500-----------------------------------------f/4

1/250-----------------------------------------f 5.6

1/125-----------------------------------------f/8

1/60------------------------------------------f/11

1/30------------------------------------------f/16

It should be understood that same amount of light will strike the sensor in all the above COMBINATIONS.

The above combinations give an idea of choosing higher shutter speed, say 1/1000 at

 f/ 2.8 to freeze an image of a fast moving object. For normal stationary subject, a shutter speed of 1/ 125 at f/8 is recommended.

In the present digital technology, cameras are having much finer controls than the illustration shown above.

It will be a nice idea to study the EXIF details after transferring the image to the computer.