Digital Photography

Part 1:  Advanced learning

fujifilm digital cameras
When to Change ISO
Mood lighting, anyone?
Being able to change ISO on the fly is one of the most significant advantages that digital cameras have over their film counterparts.
This brings us to an important question: why should you change the ISO rather than letting the camera decide for you?
More importantly: when should you change the ISO setting on your camera?
The answer will significantly increase the quality of the photos you take.
When the Lights are Low
I’m not going to define ISO here. I’ve already done that on a different page where I talk about ISO and image noise.
I will provide a short definition: ISO is an indication of how sensitive your camera’s sensor is to light. The higher the ISO number, the greater the sensitivity.
Put another way: increasing the ISO of your digital camera helps it to “see” in the dark.
I just tipped you off to the answer to the question I posed above…
You want to manually increase the ISO setting on your camera when you are taking photos in dim light conditions AND you don’t want to use the flash.
I’ll get into more details about this in just a moment. Before I do, take a quick look at this chart to see the relationship between certain lighting conditions and the ISO setting:
Lighting    ISO
Bright sunshine    100
Mild shade or overcast    200
Deep shade    400
Indoors on a sunny day    800
Indoors at night    1600
The important thing to note: as the light gets dimmer, the ISO must increase accordingly.
It’s All About Shutter Speed
Let’s delve a bit deeper into the specifics of when you should change the ISO setting.
First, a question for you: don’t you just hate it when a prime photographic opportunity comes up and your photo turns out a blurry mess?
I certainly do. It drove me crazy when I first started using digital cameras that half my photos were blurry. So many shots that could have turned out great were immediately deleted.
That’s because I didn’t know how to properly leverage my ISO setting to get a fast shutter speed.
A slow shutter speed is what causes a blurry photo.
Here’s a more detailed description: a shutter speed that is not fast enough to freeze the motion of your subject will result in a blurry photo.
This means that you can take a perfectly clear portrait using a shutter speed of 1/60th of a second (because your subject is still) but a photo of a running horse at 1/60th of a second will be a blurry mess.
Here’s a quick table to help you determine the approximate shutter speed required for different subjects:
Subject    Shutter Speed*
Landscape    60
Portrait    125
Children    250
Animals    500
Sports    1000
Race Cars    4000
* Shutter speeds are measured in fractions of seconds, so 60 is really 1/60th of a second.
One factor that contributes to blurry photos is how fast your subject is moving.
The Focal Length Factor…

Fuji Finepix S1000fd 10MP Digital Camera with 12x

The second key player in any blurry photograph is the focal length of your lens.
Focal length indicates the telephoto capacity of your lens. For example, a lens with a focal length of 100mm is a more powerful telephoto lens than a 50mm. Zoom lenses have variable focal lengths.
Here’s the rule:
IF you are holding the camera in your hands and IF the shutter speed is less than the focal length, a blurry photo will result.
But what’s causing the blur? If you’re taking a portrait of a non-moving subject why should the ENTIRE photo come out blurry?
The problem is that when you hold the camera in your hands the CAMERA is shaking.
Camera shake is magnified by longer focal lengths.
The way to negate camera shake it to always use a shutter speed that is faster than your focal length:
Focal Length    Shutter Speed (for no blur)
28mm    30
50mm    60
100mm    125
200mm    250
300mm    350
The only time that this rule doesn’t apply is with cameras that have built-in anti-shake or if you’re using an anti-shake lens.

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