Photography Basics – Understanding ISO and Stops

A Digital SLR Guide to Camera Tips and Techniques

Oct 4, 2009

It's difficult to keep up with all the modern technology today, but here is a DSLR beginner's guide to help new photographers get started.

This is a continuation from a previous article which covered photography basics like shutter speed and aperture. This guide will continue with some next steps in learning to use a Digital SLR camera.

ISO for Digital Cameras

ISO is a term that was used to indicate different film speed on film cameras, and although there is no film in digital cameras, the effect on the final photograph is similar, so the same term is still used with digital cameras. For a basic understanding, know that the higher the ISO, the less light necessary to take a shot, but the quality of the photo will be reduced and look more grainy. 100 ISO is the typical starting range for a camera's capability, with numbers going up to 1600 and far beyond in today's modern cameras.

For consumer grade DSLRs most photos should be taken in the 100-400 range, because higher numbers will get noticeably grainier. However, for photographers wishing to take low light shots without a flash, using 800, 1600 or more can yield acceptable results. In recent years, DSLRs have seen vast improvement in image quality even at high ISOs. All DSLRs will produce better photos than point-and-shoot cameras because of the larger sensor size.

Stops: Putting Together Shutter Speed, Aperture and ISO

Putting the factors of shutter speed, aperture and ISO together makes an incremental scale indicated by "stops." Put as simply as possible, doubling one will mean another needs to be halved to keep the same exposure. Playing each of these factors up or down allows the photographer to get the right combination for their desired shot whether it is an action, landscape, portrait shot, etc.

With shutter speed and ISO, the numbers are straightforward and easy; 1/100th of a second is half 1/50th of a second and 400 ISO is double 200 ISO. With aperture things get more complicated. The aperture scale in full stops goes f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, etc. This means that taking a picture on f4 will allow half as much light as the same picture on f2.8. Photographers wishing to make the most out of their photographic opportunities should learn how each of these, shutter speed, aperture and ISO effect each other.

Most DSLRs have a quick option called exposure compensation to toggle up or down stops, usually in 1/3 increments. This allows photographers to quickly make a photo darker or lighter depending on their preference.

The copyright of the article Photography Basics – Understanding ISO and Stops in Digital Photography is owned by Christopher Brown. Permission to republish Photography Basics – Understanding ISO and Stops in print or online must be granted by the author in writing.

Oct 10, 2009 1:26 PM

Yuen Kit Mun :

I recommend ISO 400 minimum for friends who are starting out with DSLRs. Their kit lenses are quite dark so ISO 400 helps them use higher shutter speeds and reduce camera shake.