CS178 Assignment 4 - Architecture and Interiors

Kneeling figure, Humayun's Tomb. Photo by Marc Levoy.

Motivation

Good photography often shows us the familiar in an unfamiliar way. Taking macro photographs last week, we made small things larger on our computer screens, and saw a level of detail not usually visible to the naked eye. For this reason, it's not too difficult to take a macro photograph that makes a non-photographer gasp. Capturing a compelling image of Architecture can be much harder. This week you'll be looking at the spaces where people live and work and trying to fit them into a frame.

Architecture is typically more geometric than natural scenes, so this week is a good week to think about the geometry of your scene. Consider repeating elements, size relationships as they change under perspective, the lines induced by vanishing points, and the texture and weathering of man-made objects. One way to surprise people with architecture and interior photography is by using clever composition to highlight the geometric aspects of structures that are subliminal or even overlooked. The requirements this week will help you play with geometry and think about the practical concerns of people who need to represent an interior space in a photograph.

By now you should have a good handle on the controls of your camera, so put your extra effort this week into making your photos visually compelling. Go beyond simply meeting the letter of the requirements and try out some of the rules of composition that were discussed in lecture last week.

Instructions

There are five requirements in this assignment that you should meet by taking 5-10 photographs.

1. Requirement 1: Vertical vanishing point. In at least one of your photos, vertical lines in the world (e.g. corners of buildings) must visibly converge to a vanishing point either within or nearly within your frame. To do this, look up and use a wide field of view (a short focal length).
2. Requirement 2: No vertical vanishing point. In at least one of your photos, vertical lines in the world must appear parallel in your photograph. You can do this by looking straight ahead when you take the picture and fixing the composition by cropping later. Alternatively, as demonstrated in lecture, you can use Photoshop's perspective warp tool (found under Edit->Transform->Perspective) to make these lines parallel. You can also use the lens correction tool found in the Filter->Distort menu.
3. Requirement 3: Frame your shot. At least one of your photos should be shot through a door, window, archway, or other physical man-made frame. The frame should be visible in the photograph, but is not necessarily the subject. The frame need not be rectangular.
4. Requirement 4: Repeating patterns. Find some interesting repeating patterns in a building or other man-made architectural object and use them as the focus of a photograph. Try to be creative here -- don't just take a random photo that happens to have some repeating elements. Instead, make the repeating elements the obvious theme of the image. So while you should certainly explain your choices in your comments, the repeating patterns shouldn't be so obscure that the viewer would need to read your comments in order to ascertain the repeating theme of the photo. To keep things exciting, you may not use windows or Main Quad arches for this requirement!
5. Requirement 5: Interior Panorama. As real-estate agents know, it's hard to capture the interior of a room without making it look small, and it's usually impossible to fit the entire room in the frame (where would you stand?). We're going to solve this with an interior panorama. Stand in the corner of a small room, or at the center of a large room, and take a sequence of photographs that captures the entire room, rotating the camera about its center of perspective (somewhere in the middle of the lens). Make sure your photographs overlap by about 25-50%. Then, convert your set of photographs into a single panorama that better shows off the interior of the room. We want to see the panorama, not the source photographs. Try to find an interesting room to do this in. Interiors are often dim, so pay attention to your camera settings and the available light.

   Note: Some cameras have a mode for automatic panoramas. You should not be using the automatic mode for the purposes of this requirement. We would like you to stitch the panorama yourself.

   In Photoshop you can make a panorama by going to the File menu, selecting Automate, and then Photomerge. A cylindrical layout usually works best, but you should try the other ones too to see what they do. If the resulting image has obvious artifacts (eg edges that don't line up), you probably didn't rotate the camera about the center of perspective, and need to try again. For this reason, you may want to make multiple attempts at capturing the source photos for the panorama before you take your photos back to Photoshop.

   You can also use some other panorama stitching tool, such as autostitch, if you like.

Upload your photos and add comments.

In general we will penalize photographs with insufficient comments, and starting this week we will be stricter than we've been so far (and you should be in your peer reviews). You should write at least two paragraphs below each of your photos explaining what camera settings you used, why you used the camera settings you did, how you composed your shot and why, any interesting story behind the photograph, and any image processing done afterwards. As always, be sure to note which requirement the photograph meets. Show that you are being mindful of your camera settings while taking photographs. It's true that Vela will show these parameters for you, but we want to hear from you why you set them to what you did. Here are some examples of the types of questions we'd like to see answered in your comments.

• What did you focus on? Why?
• What aperture and shutter speed did you use, and why did you choose them?
• What settings did you let the camera determine automatically? Why?
• Why did you choose a particular focal length (zoom)?
• Why did you take the photo from where you did and include in the frame what you did?
• Did you color correct the image afterwards? Crop it? Sharpen it?

Note that there's no need to include all of these for every shot; just choose questions that are the most relevant to each composition. You can look at the example solution for more guidance.

Example Solution

Please remember that the photographs that you submit for each assignment must be 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!

If you have questions or comments about the photos we used in the example solution, feel free to add them as comments below the corresponding photograph in Picasa Web, or to email us.

Peer Grading

You should follow the same rubric as the previous 3 assignments.

Practice problems

Finally, here are some practice technical problems related to recent material. You do not turn these in; they're just for your educational benefit.

Note: answers have now been marked in bold.

• Problem 1. If sampling an image or scene leads to aliasing, what could you do to get rid of it (check all the apply):
  • a) Downsample the image in Photoshop
  • b) Pre-filter the light before it reaches the sensor
  • c) Blur the image in Photoshop
  • d) Upsample the image in Photoshop
  • e) Nothing

• Problem 2. According to sampling theory, what should be your minimum sampling frequency, when trying to record a signal with maximum frequency 'f', to avoid aliasing?
  • a) sqrt(f)
  • b) f
  • c) f^2
  • d) f/2
  • e) 2f

• Problem 3. An image convolved by the following kernel will (circle all that apply):

      0 0 0 
  
      0 0 2 
  
      0 0 0 
  
  

  • a) be shifted
  • b) become more blurred
  • c) become sharper
  • d) become brighter

• Problem 4. This question is not directly related to this week's material, but is meant to show you what the third type of question on exams - short answer questions - look like. You have purchased a 100mm lens and you are eager to see how well it performs as a close-up lens for macro photography. After reading the specifications online, you learn that the maximum image distance (between the sensor and the equivalent thin lens) is 120mm.
  (a) For this lens, what is the distance between the equivalent thin lens and the sensor when the camera is focused at infinity? 100 mm
  (b) Given it's maximum image distance, what is the closest object distance that will produce an in-focus image? 600mm. The maximum image distance (s_i) is given as 120mm and the focal length is given as 100mm. Using the Gaussian lens formula (1/s_i+1/s_o = 1/f), we compute that the object distance (s_o) is 600mm. From this, we can conclude that this telephoto lens cannot focus any closer than 0.6 meters.

Due Date

Assignments are generally 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 your next section. Sometimes lateness is unavoidable. In such circumstances, be sure to read the lateness policy from the course outline, or contact your TA.