Monday, 20 August 2012

What is ISO in Photography?

During the good old days of film photography, our ISO was known as ASA (the American Standards Association, Presently ANSI – American National Standards Institute). And was the measure of sensitiveness of the film to light. Films were available in different ASA ratings like 50, 100, 200, 400, 800 and 1600 ASA films. The higher the number, the more sensitive to light the film is and vice versa. The lower the number, the lower will be the sensitivity of the film and the grain in your shots will be finer.

Photography ISO
Photography ISO

In Digital Photography ISO (abbreviation for International Standards Organisation) measures the sensitivity of the cameras image sensor. Same as in case of film photography; the lower the ISO number the less sensitive your camera's image sensor is to light and vice versa. Similarly lower the ISO settings, finer the grain in photos and vice versa.

What does ISO sensitivity mean?

Low ISO Sensitivity means that the film / image processor has to be exposed to light for a longer period of time than a film with a high sensitivity / an higher ISO setting in order to properly expose the image. 100 ISO is considered standard and will give you nice clean images under most conditions.

All digital cameras when set to Full Auto mode are programmed to take pictures at different lighting conditions with the least noise. So although they do pump up the ISO when in low light conditions they do it with the least possible setting there by maintaining a balance between sharpness and the amount of grain.

Most cameras give you the option to choose your ISO manually but before you do so, make up your mind as to what are the conditions under which you are shooting and what is your desired result and to what purpose are your going to use your shots.

Before deciding upon the ISO settings for a particular shot, be clear about the following.

Photo By Steve Kelly

1. Grain – This is the primary consideration, what is the intended use of this picture, if it is to be printed in small sizes, say 6 by 4 or so then even if there is grain in the picture it won’t be visible in print. But if you need bigger prints then grain is definitely a problem. So small prints happily bump up your ISO and for larger prints go through the following points.

2. Existing Lighting Conditions – How well is your subject lit, will you get decent shutterspeeds in the desired aperture value to handhold the camera.

3. Can I Improvise Upon Existing Lighting –
Do I have a flash with me? Is the use of flash permitted at the given scene? Or can I turn on a couple more lights, maybe open a window, use a reflector etc and get better exposure figures?

4. Do I Have a Tripod – If you have a tripod or any place where you could set your camera and shoot avoiding camera shake then you could do without bumping up your ISO settings. But that depends on one more factor which is our next point.

5. Is My Subject Stationary – If you are shooting a stationary subject and if you have a tripod at your disposal then all is well, no need to fiddle with ISO settings. But if you have a moving subject then your options are limited.

what is iso in photography
Photo By Chuck Burgress

Situations that Demand Higher ISO Figures

I need a grainy picture – plain and simple if you wish to reproduce some classic shot with grain in it or plan to use the purposefully induced grain creatively.

At Temples, Churches, Mosques, Museums, Art Galleries etc; use of flash is prohibited inside of most religious sites and they tend to be a bit on the darker side for photography.

I need to shoot action in low light.

If you need to capture the ambience of a particular scene – Certain situations have a bit of ambience which people like to capture in film, for example a setting of a candlelight dinner. So use of flash is ruled out and ISO settings go up.

ISO photography
Photo By Sinu S Kumar Shot at ISO 3200, 500mm, F 6.3, Speed 160

Most modern cameras handle higher ISO better than their earlier counterparts, It is not only the ISO setting but the quality of light (remember quality and not quantity) available at the scene also plays a major role in determining how good or bad the resultant image will be. So mastering the ISO settings and the results will go a long way in helping you out of tight situations and take better pictures where earlier you would have end up with images which could not be salvaged. There are several software’s available in market which will help you get rid of noise in post production. So it is always better to play with ISO and get your picture then fix noise problems later. Better than getting any shots at all.

In the next article we will discuss about Photography - Tips For Beginners - Aperture

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