Assignment 2 - Sports and Action

Always pacing, this lion at the San Francisco Zoo provided plenty of practice when learning to blur the background in a panning action shot.

Photo by Michael Broxton

Motivation

One of the first problems you will encounter as a photographer is that the world doesn't stand still and wait for you to take a photo. Many interesting compositions are fleeting, so the photographer has to be somewhat opportunistic. Sometimes you will take a hundred photos and only get a handful of good ones.

The key difficulty in capturing moving objects is getting enough light. The shutter speed needs to be short enough to prevent motion blur. You usually compensate for this by using a large aperture and increasing ISO. However, you quickly encounter trade-offs. For example, increasing the aperture shortens the depth of field and makes precise focus more important (and challenging). Autofocus takes time and a slow autofocus system may not be able to keep up with the action you are trying to capture with your fast shutter speed, resulting in a missed shot. If you're able to set up the shot, one good trick is to prefocus at the depth you're expecting, so that the photograph can be captured at the instant the object moves through the point of focus. As you can see, capturing a unique photograph often involves manipulating several of the camera's control systems at once!

Instructions

This assignment is similar in format to the first one. There are four requirements this week, which you will meet by taking photographs, uploading them as a new album to Google Photos (under your corporate account) as an album, organize the album however you like, and add a caption to each photo describing which requirement it satisfies. You must meet each requirement in at least one photo, and every photo should meet at least one requirement. Upload from 5 to 10 photographs in total. Finally, post thephotos in your album to the course's Google+ community as explained in Assignment #1, giving your post a title, like "Submission of assignment #2 (Sports and Action) by <my name>" (substituting your name).

• 1. Requirement 1: Freeze the action. Take at least one photo with a very short shutter speed to capture your subject during a split second in time. You'll need lots of light for this, so try this outdoors during the middle of the day. If you happen to have a very strong flash, you can also use it to freeze the action when there is less available light.

  2. Requirement 2: Show the action by blurring the foreground. Take at least one photo that uses motion blur to give a sense of how your subject moves. The main subject of the photograph should be motion blurred, but the background should be sharp.

  3. Requirement 3: Show the action by blurring the background. Take at least one photo with a sharp subject and a motion blurred background. Note in your comments how this gives a different sense of movement from requirement 2. (One way to do this is is to keep a moving object centered in your viewfinder as it passes you by panning the camera to match its speed. This takes some patience and practice, but it's worth the effort once you get it right!)

  4. Requirement 4: Show the action with a burst. Take a burst of photos (at least 3) one after another quickly, so that it shows a progression and tells a short story. Many cameras have a burst mode to make this easier. Once you've taken your action sequence, you should combine the burst of photographs into a single image using Photoshop or similar. Your combination could be as simple as placing all of the photos side-by-side into one larger photo, or it could be a blend of the photos, or it could be something fancier. The choice is yours!

Example Solution

As usual, we've posted an example solution to this assignment to let you know what we expect. Again, your comments should be entered as captions in Google Photos before posting to photos to the Google+ community, not as comments in the Google+ posting (despite the way it's done in the sample solution). For additional inspiration, you may want to peruse the best CS178 photographs (as selected by the TA's and instructor) from 2009, 2010, 2011, 2012, 2013, and 2014. However, you do not need to meet the assignment requirements in the same way as these solutions do - in fact, you should challenge yourself to come up with creative, unique compositions. There are plenty of possibilities out there. Surprise me (and your peers)!

Again, try to submit photographs taken by you specifically for this course. Do not reuse old photographs that you may have laying around, even if they perfectly meet one of the requirements.

Peer-to-Peer Commenting on Photos

After the assignment deadline, meaning on Monday, April 4, go to the Google+ Community, select the "Assignment #2" category in the left-hand sidebar, find 3 or more submissions that have fewer than 3 reviewers for them, open those posts, and add some comments on its photos. For each photo try to use the following schema: First, did the photographer satisfy the requirement he/she claims with that photograph? Second, was there something you particularly liked about the photograph? Third, is there something you thought the photographer could have done differently, and could therefore work on in the future? You don't need to comment on every photo, but try to comment on most of them. Keep your comments brief but constructive. Be Googley!

Finally and importantly, back out of slideshow mode and make a comment on the entire post - to the effect, "Andrew Adams has reviewed this album", so that others know without having to open the post that it has been reviewed by 1 more person. Of course, if you find a particularly awesome picture in a post, feel free to expand your comment: "Awesome shot of putting your head in a lion's mouth!"

Try to finish this commenting phase by the end of the week, i.e. by EOD on Friday, April 8, while the assignment is still fresh in everyone's mind.

Practice problems

Here's your second set of practice problems, related to Optics. Note: answers have now been marked in bold.

• • Problem 1. Holding everything else constant, widening the aperture of a camera lens means (check all the apply):

    • a) less depth of field

      • b) more depth of field

      • c) less light hitting the sensor

    • d) more light hitting the sensor

      • e) a wider field of view

      • f) a narrower field of view

  • Problem 2. You have a 50mm f/2 lens. Its maximum aperture diameter is:

    • • a) 12.5mm

    • b) 25mm

      • c) 100mm

      • d) 200mm

      • e) Depends on the sensor size

  • Problem 3. In order to compute the field of view of a lens/camera combination, you need to know the lens's focal length and the camera's sensor size. Mary has an old film camera that uses standard 36x24mm film. Joe has a new Nikon D3000 digital SLR with a sensor measuring 24 x 16mm. Mary puts a 60mm lens on her camera and Joe wants to get the same field of view with his camera. What focal length should Joe use?

    • a) 40mm

      • b) 60mm

      • c) 90mm

      • d) Not enough info

  • Problem 4. Which of the following can you easily reduce with software? Select all that apply. Assume that the photographs were taken with commercially available digital cameras, excluding light field cameras from Lytro.

    • • a) Depth of field

    • b) Vignetting

    • c) Lateral chromatic aberration

      • d) Longitudinal chromatic aberration

      • e) Focus error

Due Date

Assignment Deadline: 11:59pm, Sunday, April 3, 2016

Commenting Deadline: EOD, Friday, April 8, 2016

Assignments are generally related to the material from the week before they are assigned, and are due on Sunday at midnight at the end of the week in which they're assigned. This leaves you free to start thinking about the next assignment during the next week's lectures, which are about a different topic. It also ensures that you will get feedback on your photos from the peer-to-peer system.

Page authors: Marc Levoy, Andrew Adams, and Jesse Levinson, revised by Marc Levoy for the Google version of this course.