Friday, September 26, 2008

How to create a photo with a pure black background

I recently posted an image on Flickr with an all black background. One of the first comments (by basswulf) asked if I shot the image with a black background or if I did it in post processing. It was actually some of both; most of it was handled in camera with a black background supplemented by a minor bit of touch up after the fact. I thought I'd share here how I typically do this type of shot.

My buddy, super photographer and all around great guy, Rich Legg, wrote an article about creating a photo with a pure white background. My technique is similar but slightly different because I use Paint Shop Pro instead of Photoshop and I'm doing a black background instead of a white one.

I start by shooting against a black background. In this case, the background simply consists of a black piece of fabric suspended by the overhead floor joists in my unfinished basement. I try to put a bit of space between my lights and the background to eliminate light spill onto the fabric. I also try to orient the lights so they are not pointing at the background. Doing this helps give a nice even black background and minimizes the amount of touch up work required.

1 Black background startHere's the starting image exposed at f/14 with a 1/160th shutter speed and ISO 100. Without flashes, this exposure setting would cause the entire image to be almost completely black, even with the overhead lights on. Exposing this way helps produce a black background and lessens post processing work. As can be seen, the background is very close to black. In spite of all this, if you look closely, you can see a bit of detail on the right side. This is where the fabric ended and some of the items in storage in my basement can be faintly seen. A combination of ambient, a little spill from the strobes and being stopped down caused them to start fairly dark but visible.

2 Black background by faceAbsolute black, in RBG color space, is when all three color components are zero. Zooming in close to the face on the left side, we can see the background has values close to black but not entirely black. In fact, it's a very, very, very dark gray.

3 Black background hand detailLooking at a zoomed in portion of dark detail on the hand, we can see the green and blue components are very similar to the black, but the red is a bit higher. This means its similar to the background but has some additional information providing subtle details for the eye.

4 Black background histogram adjustmentSince the goal is to get the background black, I want to adjust the image so the background's three components are all zero while maintaining the relative value of red component in the hand. The best tool I've found for this is the Histogram Adjustment. This tool allows a number of adjustments, but for the purposes of this image, we just want to adjust the lower bound. By sliding the black pointer on the left side up from 0 to about 10, we cut off all the very small variations on the black side of the image without significantly changing the lighter portions.

5 Black background by faceNow, when we look at the background, we can see it's gone to pure black.

6 Black background hand detailBut we still have some red component in the details, so we haven't completely lost them.

I didn't post an overall image at this point, but the faint portions of unwanted background detail on the right side of the image are greatly reduced. In fact, I couldn't see them at all. But when I ran the color picker over that area of the image, I did see RBG values other than 0, 0, 0, so I knew there was still some more work to be done.

7 Black background negative pre touchupA cool trick is to change the image into a negative. By doing this, the mostly invisible details in the black background suddenly show up as tints when the background is made white. The blue/gray details clearly visible here on the right were nearly impossible to see in the positive version.

9 Black background negative by faceAs can be seen in this close up, the previously all black section is now pure white.

8 Black background negative post touchupThe next step is to select the paintbrush and set its color to pure white. Now I just paint out the details I don't want on the right side.

10 Black background finishedOnce all the background that I want to finish as pure black is painted a pure white, I again select the negative image adjustment and everything changes back to the proper colors. At this point the background is pure black and the image is ready for any further processing I may want to do to it.

Note: Click on any image to see a larger size.

Monday, September 22, 2008

Full Photographic Finale (for the week)

This last weekend was full of photographic culture for me. Friday night I went to a career retrospective by Sam Abell, a National Geographic contract photographer for 30 years. Saturday afternoon, I joined the Photowalking Utah group to view a presentation by Kenneth Linge, a wedding and portrait photographer. Both these photographers have a long history of exceptional work and both are about as different as Bob Newhart and Robin Williams.

Sam Abell's photography is very documentary in nature. His goal is, as an observer, to record places and events as they are. His presentation followed this style with a scripted slide show and an allotted time that he finished to the minute. It was a documentary of his career. This is not to imply a dry lecture. Far from it. He held a room of over 100 people spell bound for two hours as he showed images and regaled us with stories from his personal family life as well as tales of adventure from his professional travel. Interspersed with all this were tips for improving our photos: use strong diagonals, bad weather means good photos, put peoples' heads and shoulders above the horizon line, compose and wait, take pictures from behind people to respect their privacy.

As a portrait photographer, Kenneth Linge's photography is highly personal. With the goal to capture the individual's personality at its best, he employs copious amounts of personal interaction to surface their inner beauty. Like Sam, his presentation followed his photographic style. The opening "Hi I'm Kenneth. What do you want to talk about today?" exemplified our entire time with him. It was highly interactive with participants' questions and comments driving the direction of the discussion as we covered topics ranging from the color of his studio walls to the psychology of photographing people.

Even with the great differences in picture and presentation style, I thoroughly enjoyed the time spent listening and learning from each. If you ever get a chance to see either one, I highly recommend it.

Monday, September 15, 2008

Using Focal Length in Composition

As photographers, we frequently use the zoom feature to adjust the size of the main subject without moving the camera position. In this article, I will explore other aspects of zoom, also known as focal length, in composition.

Loosely defined, focal length is the zoom setting on the lens. It is indicated by a number, measured in millimeters, indicating the distance of the lens from the sensor. Smaller numbers, meaning the lens is closer to the sensor, produce a wider field of view. Conversely, larger numbers, meaning the lens is further from the sensor, produce more magnification with a narrower field of view.

FocalLengthCompWideAngleFocalLengthCompHighMagnificationTo get an intuitive understanding of what's happening, think about two rods that are a fixed distance apart on one end and connected by a sliding ring. As you move the ring closer to the fixed end, the free ends will move apart. As you move the ring further from the fixed ends, the free ends will move closer together. By analogy, the fixed end is the sensor in the camera, the lens is the ring and the free end represents the field of view.

Besides the obvious size of the main object, there are two other effects caused at the extremes of focal length spectrum. The first happens at short focal lengths and is called foreground expansion. The second happens at long focal lengths and is background compression.

42/52 Pointing the fingerForeground expansion magnifies items close to the lens to look proportionally larger than other items in the image. This can be used to emphasize one object over another. This image is taken at a focal length of 18mm with the finger about 2 inches from the camera lens; my body and face are at arms length. With this setup, my hand is about twice the size of my face.

Background compression happens at larger focal lengths with a narrower field of view and is where perspective causes the background to pull in closer to the subject. Here are several shots at progressively longer focal lengths: 18 mm, 55 mm, 100 mm, 205 mm and 300mm. The camera position was moved back so the main subject is the same size in all the shots. With the narrower field of view and increased magnification, even though the subject is the same size, the background is significantly changed. This can be seen best by paying particular attention to the fence and trees.
18 mm55 mm100 mm205 mm300 mm

Using zoom can make things more convenient by changing the size of the main subject from a fixed position. But next time your out shooting, remember that by moving around it can also be used to change the composition and overall feel of the image.