Saturday, December 27, 2014

Shutter, Aperture, and ISO, Part I

In this exercise, you'll adjust Shutter Speed, Aperture, and ISO separately, to learn what the visual effects of each setting are. You'll actually start taking pictures and looking at them in this exercise.

There are actually three separate exercises here, you can do them in any order.

Exercise 1.

In this exercise you'll be changing the Shutter Speed to see what the effects are.

Find a place where things are moving. Perhaps people or cars passing by.

Set the shutter speed to about 1/30. Alter Aperture and/or ISO settings to get the meter to "just right", centered. You will now take a series of photographs.

Holding the camera quite still, squeeze the shutter button. Do not "push" it, squeeze the grip, exhale gently, and allow the shutter button to compress, until the camera takes a picture. By squeezing the camera rather than pushing the button, you minimize the amount the camera moves around while you're taking a picture. This is a good thing, and should become natural to you.

Ignoring the meter, now, adjust the shutter speed one or two clicks in one direction. Take another picture. Go another couple clicks in the same direction, and take a third picture. Perhaps go a couple more clicks and take one more picture.

Now return the Shutter Speed setting to where you began, the meter should be more or less "just right" again.

Repeat the previous steps, clicking the shutter speed in the other direction.

Examine the resulting pictures. As the Shutter Speed gets faster and faster (1/60, 1/125, 1/250) the pictures should get darker and darker. As the Shutter Speed gets slower and slower (1/15, 1/8, 1/4, 1/2) the picture should get brighter and brighter.

What happens to the objects in motion past the lens?

Exercise 2.

This exercise follows the same pattern as Exercise 1, except you will be adjusting the Aperture.

Find a location with nearer objects, and farther ones. A longish table with objects spread out along it is a good choice. Sit or stand near one end of the table, so there are objects quite close to you (a couple feet, one meter) and objects farther away, past the table (ten feet or three meters, maybe).

Focus on something about middle distance, maybe six feet or two meters away. Make sure there are things farther away, and things closer to you, visible in the pictures you're about to take.

You may choose to set your lens/camera to Manual Focus at this point, to keep the point of focus the same from one shot to the next, as you do the exercise. If you cannot or don't want to, make sure that you focus back on the same object at the same distance for each shot in the exercise.

Set the Aperture setting to about f/8.0. Using the Shutter Speed and ISO settings, get the meter in your camera to read "just right". Now take a picture.

Ignoring the meter, adjust the Aperture settings one or two clicks in one direction. Take another picture. Adjust it another couple of clicks in the same direction, and take another picture. Continue until the Aperture setting will go no farther in that direction.

Return the aperture to f/8.0, the meter should return to "just right" or close to it.

Repeat the steps above, this time adjusting the Aperture one or two clicks in the other direction between each photograph.

Examine the resulting pictures. As the Aperture gets numerically larger (11.0, 16.0, 22.0, 32.0) the pictures should get darker and darker. As the Aperture gets numerically smaller (5.0, 4.5, 2.8) the picture should get brighter and brighter.

What happens visually to objects that are very near you, and very far away from you?

Exercise 3.

This exercise follows the same pattern as Exercise 1, except you will be adjusting the ISO.

The location here is anywhere with a good detailed scene, and not too much light. People always seem to use a bookshelf for this. It's not a bad idea.

Set the ISO to 800. Use the Aperture and Shutter Speed settings to get the meter on to the "just right" position. Take a photo.

Now you know the drill, right? Adjust the ISO a couple of clicks in one direction, ignoring the meter, and take a photo. Continue until the ISO can be adjusted no further in that direction, or until you get bored.

Put the ISO back to 800, and do the same again, adjusting the ISO in the other direction.

Examine the resulting pictures. As the ISO gets numerically larger (1600, 3200, 6400, HI, HIGHER) the pictures should get brighter and brighter. As the ISO gets numerically smaller (400, 200, 100) the picture should get darker and darker.

What else happens? Look closely. It should be apparent at the larger ISO numbers, at least, but it's a somewhat more subtle effect. Pay attention to the way colors look, and to how grainy the picture looks (especially if you zoom in).

Lessons Learned

At this point you should have a pretty good handle on how the three settings we're using affect the resulting picture, visually.

Putting these exercises with the previous one, you should be able to think through, for instance, what the visual effect of the following might be, for example:

Center the meter on "just right" and take a picture. Then change the Aperture a couple of clicks in one direction (which will change the meter), and the Shutter Speed in a suitable direction to get the meter back to "just right". Take a second picture.

How will the first and second pictures be different?

What if you used Aperture and ISO? What about ISO and Shutter Speed?

The effect you see with slower shutter speeds is motion blur. The motion of objects appears as a smearing of the object along the path of motion. In addition, tiny movements of the camera, which are inevitable, will become more and more apparent as an overall softness or smeariness to the picture.

The effect you see with aperture is called Depth of Field. In general, the larger the numerical aperture (8.0, 11.0, 16.0 etc) the more objects closer and further away than whatever you focused on will appear sharp, the Depth of Field will be greater. Smaller numerical apertures will, of course, produce shallower, less Depth of Field.

The effect is more dramatic close up, and less dramatic farther away, which is why we started with a table-top (this is pretty close up, the effect should be quite visible in your pictures). With a numerically small aperture like 2.8 or even 4.0, the only objects that appear sharp are those quite close to the one you focused on.

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