This is page 2 of 2. "Digital Film Speed" begins here.
Film speed and shutter speed are proportional. As you decrease film speed your shutter speed decreases by necessity.
You will want to use the slowest film speed possible. But not so slow that the matching shutter speed causes the image to blur. That is why you switched from 100 ISO, while shooting the flowers, to 600 ISO for the Heron.
You started in Aperture priority. When you increased the film speed, the camera left the aperture where is was because of the program you were in. Remembering that film speed, aperture and shutter speed are interdependent; the camera balanced the change in film speed by setting the shutter speed for you in order to correctly expose the Heron. Isn't that cool?
With practice and experience you will learn what works best for you.
The ISO number is film speed.
That is the speed at which a given film can capture a picture for you. All other variables being constant, a higher film speed allows you to capture a moving object that would otherwise blur.
The following information on digital film speed is applicable to pictures taken in natural lighting.
Not those taken with a flash unit. Flash is another subject all together, though some of the information overlaps.
Another way I use a higher film speed is as the sun is getting low in the sky, or any low light situation. I can continue shooting a moving subject in the lower light. And I can hand hold the camera later in the day with a faster film speed.
In other words it extends the daylight hours I can shoot. And it offers more times I can shoot without the need of a tripod. Though I lose quality, the loss will only show if I am enlarging the prints.
I shot this carousel on a rainy day, inside the protective enclosure. This is a very low light situation. Film speed 640 ISO, Aperture setting 5.6 and shutter speed of 1/10th of a second.
Normally 1/60th of a second is the slowest you want to hand hold your camera. I hand held the camera by perching myself against the railing. A higher film speed, but at this size and at least up to about 8"X10" the quality is great.
I don't like to use a tripod. They are too restrictive for me.
I could have used a much faster digital film speed for this shot in order to increase the shutter speed and be sure to get a sharp shot. I chose 640 to maintain as much quality as possible. And I had to perch myself in order to keep it from blurring.
Here’s how I choose film speed.
If you have a subject that is completely still like landscape 100 ISO is normally a good choice. Many times one will want to crop and/or enlarge a landscape picture.
Shooting at a slow film speed the camera captures more of the details. (As in the gas can picture above) This allows you to crop and/or enlarge while retaining a crisp finish.
Shooting people, even if they are posing I start at 200 ISO. Invariably people move! In the brightest of lighting you can still shoot at 100 ISO should you so choose, but the difference in quality is negligible.
You can even use 400 ISO if you are posing children and want to ensure sharp pictures.
Moving on up to active children and pets, I start at 400 ISO and go up from there. In good lighting 400 does a good job. In shade or on a cloudy day, you may even want to go up to 800 ISO.
On the other hand if you are shooting a speedboat slamming past you down the river you will never get a crisp picture at 100 ISO. That is when you will want to use something closer to 1,000 ISO.
Now it’s time to enter another variable.
Sunlight. If the sun is high in the sky and shinning brightly you will use a lower ISO than if it is cloudy or the sun is near setting.
Early in the morning and as the sun sets you will increase your ISO setting.
There you have it; some guidelines…
for different types of photography and what film speeds work well. This will give you the highest quality prints in each type of shot.
As I always say, if you will be cropping or enlarging your pictures you will want to make sure you use the appropriate digital film speed for each type of shot. This will give you the best quality possible in each shot.
If your pictures will be used only for 4”X6” prints or on a digital screen you need not concern yourself about the noise caused by fast digital film speed.
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