Inverse Square Law

1) OVERVIEW: WHY USE FLASH?

2) THE INVERSE SQUARE LAW - What does it mean?

3) THE INVERSE SQUARE LAW Shoot

The video below explains and demonstrates this principle in effect very well. 

Assignment: INVERSE SQUARE LAW

See the student example below? That's basically your job.

You are to submit a single image that is actually a side-by-side compilation of six photographs of your partner at different distances from the backdrop.

HOW TO SET UP THE SHOT

You will need a wide backdrop, a single studio light with softbox (raised fairly high, angled a bit downwards), a transmitter (paired to the light), and your camera.

Start with your subject right up against the background. The light (and camera) can be a few feet in front of them.

CAMERA SETTINGS

• M Mode

• ISO: 100

• Shutter Speed: 1/200s

• Aperture: start with f/11, be prepared to adjust

• Light power: start with 1/2, be prepared to adjust

WHAT TO DO

1. Set up the shot as described above. Take some test shots until the exposure of the subject looks OK.

2. Take a series of six images. After each image, the photographer can take one big step backwards, the light can be moved the same distance backwards, and the subject can move in the same direction by the same distance. The background stays in the same place.

WHAT SHOULD YOU SEE?

Your subject's face should be exposed the same in all six images, provided you both moved the same distance after each shot. The backdrop, however, should fade from view as it gets further away from the light source (your flash).

The "fading" backdrop is demonstrating the Inverse Square Law.

HOW TO MAKE A FILMSTRIP IN PHOTOSHOP:

1) Open all files at once by going to File > Scripts > Load Files Into Stack. Select the files you want and open them.

2) If the images are inconsistent in their composition, you will want to align them a bit better. You can start with a pair of layers turned on, and reduce the opacity of the upper one to 50%. Then you can choose whichever layer needs to move to match by using the CTRL-T (Free Transform) command and repositioning or enlarging/shrinking the layer. Restore opactity to 100% when done, then move on to the next pair of layers. You may need to crop your overall image after doing all this, if any layers are no longer covering the whole canvas.

3) Go to Image > Canvas Size. Set the width and height values to be given in percent instead of pixels or inches).

4) Set the width to 600%. The height should not change. If it does, you may need to "unlink" the height value from the width.

5) One by one, drag your layers to the proper spot (left to right). Be aware that Photoshop is generally helpful in showing purple guidelines that "snap" to what it perceives as the edges of other objects/images. 

6) You may wish to create a black background layer in case there are visible "cracks" around the edges of the individual images. To do this, simply create a new layer (bottom right, next to trash can button), drag it to the bottom of your layer stack, then select Edit > Fill and choose Black. This will hide those cracks.

7) Time to re-size this image, now that it's 6x bigger than we need. Go back to Image > Image Size and change the resolution to 72 ppi. This should work. The issue is that jpgs larger than 20MB won't post on your site properly. You can check this when you save in the next step and go back and reduce the image size if necessary.

8) Save once as a .psd (for you), and then again as a .jpg! (File > Save a Copy).

HOW TO HAND IN

1) Open this project in Classroom

2) Add your completed .jpg "filmstrip" image.

4) Complete the self-evaluation rubric then TURN IN.