Principles of Exposure: Capturing Action and Controlling Motion Blur

Exposure: Shutter Speed, Aperture, ISO:

Exposure is the measure of light falling on the media, be it film or CCD. It's controlled by three factors namely shutter speed, aperture and sensitivity of the sensor (ISO). Let me try to explain each of these in a greater detail.

Shutter Speed is the amount of time the shutter screen remains open, in other words, it is the duration for which the light hits the media. Shutter speed is the feature of the camera and not the lens. Faster the shutter speed, lesser the duration for which light hits the sensor, so lesser amount of light is captured.

The shutter speeds range from 1/4000th of a second (1/8000 on a pro camera) to 30seconds, with a special "B" (bulb) mode wherein the shutter could be kept open as long as the photographer wishes (of course, constrained by battery).

The shutter speed controls another most important aspect - freezing the subject in time. Simply stated, you shoot a speeding car with slow shutter speed, you tend to see the trails of the car resulting from motion blur. On the other hand you shoot the same car with higher shutter speeds, the car will appear as though it is stationary. In case you're wondering what magic, the photographer has done to capture those long trails of headlights, the answer is simple: he would have just kept the shutter open long enough to capture the trails.

When you're shooting with slower shutter speeds (under 1/100th of a second) holding the camera, it is highly likely that you end up with a blurred photograph. Why? It's obvious that when you're shooting at lower speeds, even the slightest camera shake will contribute to the blurring of the photograph. Solution for this problem is to mount the camera on a tripod or try to find a platform nearby to place the camera and shoot.

The answer for the question "What shutter shutter speed to use for a particular shot?" is "It entirely depends on the kind of shot and it can't be generalized". If you're shooting birds, wildlife, sports, street shots etc. which require the moment to be captured tack sharp use high shutter speeds. Night shots, trail capture, abstract photographs, light painting, milky waterfall photographs etc. require slow shutter speeds.

Aperture is the feature of the lens and has nothing to do with the camera, except that the aperture values are set/controlled by the camera. As the name itself suggests, aperture is an "opening" at the rear end of lens through which the light enters the camera. Earlier days, the lens barrel had an aperture ring to set the required aperture values, but these days the aperture could be controlled by the knobs on the camera or changing a setting on the digital menu of a DSLR.

The maximum and minimum value of aperture depends, as mentioned earlier, on the lens and not on the camera. You may find a lens with aperture as big as f1 or f1.4 or as small as f45 or f64. Aperture is measured in terms of f-stops and hence the f. It's notated f/1.8 or f/5.6 as well. As you can see the size of the aperture is inverse to the value of f-stop, higher the f-stop smaller the aperture, smaller the f-stops bigger the aperture. So at f1.8 the light received by the medium will be more than f5.6; least light will be received at the smallest aperture say F22 of F45 or whatever your lens supports.

Like shutter speed, aperture also controls one other aspect, apart from the amount of light, it's called Depth of Field (DOF). You maybe confused by amateur photographers who are fond of terms like DOF, Bokeh, Hyperfocal distance etc. Just remember this rule of thumb & don't get lost in the jargon: Bigger the aperture, smaller (shallower DOF) the region of focus; smaller the aperture larger (deeper DOF) the region of focus. You may, therefore, want to open up the aperture for a portrait shot wherein you want a focused and sharp face and blurred background and close down the aperture for a landscape shot wherein you want the entire landscape to be focused. Also in macro shots, the amount of DOF is very critical since the available DOF is very less. DOF is used sometimes to give artistic effects to the photographs.

Photo credit: Seth Wilson 2013

Portraits would come out well with bigger apertures (smaller f-stops) for it makes the subject really sharp against a background of soft background, Also night shots usually require bigger apertures which would allow lot of light to enter.

Landscapes need smaller apertures (bigger f-stops) for most times it wouldn't have a specific focus point. Smaller apertures help on a very bright day to cut-off excess light entering (of course this could be controlled by shutter speed too).

ISO is the measure of sensitivity of the media (film) and digitally is a camera dependent feature. ISO values are typically in the range of 100 to 3200 (on a pro camera it can have an extended range from 50-102400)

When the ISO is set to 100 the sensor is the least sensitive, it can sense less light. When it's set to 1600 or 3200, the sensor can sense a much more light. Which means for a given condition if ISO 100 gives a standard exposure with F8.0 & 1/250th of a second, ISO 1600 may give a standard exposure at F8.0 & 1/1000th of a second. ISO comes very handy while shooting hand-held under low light conditions, it gives an advantage of slightly faster shutter speeds which helps in avoiding motion blur.

An obvious question may arise to a novice, "Why should I shoot at low ISO when higher ISO gives an advantage of faster shutter speed?" Though ISO seems to be such a cool feature, it carries with it something very undesirable - NOISE. Higher the ISO, higher the noise.

Brighter the ambience smaller the ISO (unless you want grainy effect), darker the ambience higher the ISO.

To Make It Easy Just Remember The Rule of Equivalent Exposure: Each Change In ISO Is Equal To One Full F-Stop

Imagine you've pointed your camera at a scene and it's recommending the following settings:

1. A shutter speed of 1/100s 
2. An aperture of f/5.6 
3. A sensitivity setting of ISO 400 

We could make the photo appear twice as bright by doing any of the following:

1. Doubling the shutter speed to 1/50s 
2. Doubling the area of the aperture by increasing it one full f-stop, to f/4 
3. Doubling the sensitivity setting to ISO 800 

Any of these could be described as increasing the exposure by 1 stop.

Likewise, to make the scene appear half as bright, we can reduce the exposure by 1 stop by taking one of the opposite steps: 

1. Halving the shutter speed to 1/200s 
2. Halving the aperture area by reducing it one full f-stop, to f/8 
3. Halving the sensitivity to ISO 200. 

Note that we use the word "stop" even when we're not adjusting the f-stop (aperture) setting. It's just become a general term to mean a factor of 2.

That's about it. For even more information, read this page here at Cambridge In Colour.

Key Assignment: Capturing Action

Students, your new assignment is a challenge for you to demonstrate an understanding of the basics of exposure through capturing action and controlling motion blur. Create images that meet the criteria listed below

Assignment Deliverables:

This pelican was shot with a fast shutter speed to capture it in motion, even the water droplets splashing up are frozen in time. Photo credit Will Tierney 2015

1- Object Frozen in Time: Create 2-3 images of a moving object that is frozen in mid-action, this image must show no motion blur. For each image write a short description of the process used in taking the photo, what settings were used to create the visual effect and describe the affect the image may have on the viewer.

A fire spinner creates a silhouette of herself through motion blur. Photo credit Seth Wilson 2005

2- Object in Motion: Create 2-3 images that show an object in motion. The moving object must show motion blur. For each image write a short description of the process used in taking the photo, what settings were used to create the visual effect and describe the affect the image may have on the viewer.

3- Tracking Motion: Create 2-3 images that shows an object in motion with the background behind the object showing motion blur. For each image write a short description of the process used in taking the photo, what settings were used to create the visual effect and describe the affect the image may have on the viewer.

4- Zoom Blur: Create 1 image that shows zoom blur by cranking the zoom and taking a photo at the same time, try it a few times and post your best. For each image write a short description of the process used in taking the photo, what settings were used to create the visual effect and describe the affect the image may have on the viewer.

Post all images with accompanying written content to the flickr group when complete.

Due by following thursday...

- Mr.W

Post Processing Enhancement Exercise

Hello Students,

Your new assignment is to enhance a portrait with the methods detailed below. Use a good portrait and a good landscape image and work through the following tutorials. Read through the color enhancement assignment and find a way to enhance the colors in your image to make it rich and vibrant. Next try the process listed afterward to modify additional images using the cross processing, tilt-shift affect and the "Dragan"method to create deep shadow and gritty detail in your images.

Post Processing Project:

• Work through the 3 methods below, color enhancement, cross processing and dragan effect
• Use pictures you have taken for the exercise, look for colorful images to enhance
• Work through the tutorials carefully and follow each step. Your results should show similar improvement. Experiment for best results!
• Post your 3 processed images to the flickr group, along with the 3 unedited images as well

Part 1: Color Enhancement Post Process:

• Choose your favorite colorful images from previous photo shoots and create a copy of it, open the copy up in Photoshop (it's always a good idea to edit copies and keep backups of your original images)
• Read the entire tutorial below and try each step out on your photo, adjust settings as needed to boost and enhance the image for best results, this will be different for each image
• Create an image border

For many beginning photographers, any version of the image editor, Photoshop, can look quite daunting to use. With all the menu options, palettes, tools, filters, layer styles and various changes you can make to an image, it’s difficult to know where to start. This article provides some ways to get started.

Here’s a photo I took at the San Jose Rose Garden. Notice it’s lacking control and saturation of color. It’s a little flat and lacks depth. We can adjust it with Photoshop.

To get started, simply open a colorful photo that could use a little enhancement, or an image that needs a lot of improvement...

1. Duplicate The Background Layer

The first thing you want to get used to doing is making a copy of the background layer of your image. The Layers palette should open by default, but it is also found by clicking on Windows>Layers in the menu bar of Photoshop.

Select the Background Layer and click on the little triangle at the top right of the palette. When the palette options open, click Duplicate Layer, or you can use the shortcut keystroke, Command+J.

By duplicating the background layer, you can make all types of adjustments to duplicate layers without permanently changing the original layer. If you make some adjustments you don’t like, you can drag the duplicate layers (with all the adjustments and effects you made to them) to the trash at the bottom right of the layer palette and restart the process.

2. Automatic Image Adjustments

When you start learning how to use Photoshop to improve your photos, you might want to try out some of the automatic adjustments that can be made, even if you don’t understand the tools themselves.

The basic image enhancement and adjustment tools in Photoshop are found under Image>Adjustments in the menu bar. In the Adjustment palette, there are various tools like Levels…, Auto Contrast, Curves, Brightness/Contrast.

To introduce you to these adjustment tools in this introductory photoshop tutorial, I’m going to suggest that you use the automatic and preset features of these tools. As you begin to understand them more, you will make use of manual adjustments. Try sliding the adjustments around, by exploring and experimenting you will become more fluent in expressing your artistic vision in your images.

So with your background layer duplicated and selected, click on Image>Adjustments>Auto Levels in the menu bar. When you release the mouse of the menu item, the automatic Levels adjustment should enhance or at least affect the shadow (dark), midtones, and highlights (bright) areas of your image. Often, a photo can be improved in Photoshop with just the automatic adjustments applied.

3. More About Layers

Now let’s revisit how layers work. Go back to the Layers palette and click on the little eye next the Duplicate layer that you just applied the Auto Layers adjustment to. When you toggle that little eye off, it means that you’re turning off the adjustment or effect that you made in that layer. Since the adjusted layer is on top of the background layer like a clear transparency, you can toggle the eye off and on to see how the adjustments are applied to the background layer (also remember: you can drag the duplicate layer to the trash to get rid of the adjustment(s) all together).

4. Automatic Curves

Okay, let’s return to a few other automatic adjustments and enhancements you can make to your photo. Go back to Image>Adjustments and then click on Curves. The Curves box will open. This box may look seriously scary with its grid, points, lines, and ear droppers. But don’t worry about that. We’re simply going to use some automatic adjustments to see how Curves can impact your photo.

Click on the button next to the word Preset. In the drop-down box, select Medium Contrast (RGB). If you don’t see much of a change in the contrast of your photo, go back to the Preset button and try Strong Contrast. You should be able to see the effect of the Preset on your photo before you click OK. Curves works similar to Levels but with more intensity in contrast.

Much more could be said about Curves and Levels, but this is just an introduction. You can play around with the points in the Curves box and see how they affect your photo. Remember, the changes you make are non-destructive to your photo, so you can experiment as much as you like. The illustration below explains a little about how the three main points in the grid function. If you make a mess of things, simply click Cancel and start over, or click OK when you’re satisfied with how the photo is looking.

5. Make Colors Pop

Okay, now lets move on to learn about other enhancements that can be made. One of the tools I use on nearly all the images I bring into Photoshop is one called Soft Light. Here’s how it works.

Go back to the Layers Palette, drag all the layers, except the background layer to the trash. Click on the Background layer and create another duplicate of it. Now click on the Normal button at the top of the Layers Palette. In the drop-down box, select Soft Light. When selecting this adjustment, it should make the colors of your image pop, or at least intensify the contrast of your images. The contrast of most digital images always need to be improved. This technique does that job extremely well without too much loss to detail.

If the Softlight application is too strong, select the Opacity button at the top of the Layers Palette and decrease the opacity of the layer/effect.

6. Image Border

Another tool that beginning Photoshop users might want to know is how to add a border around an image. Again there are a few ways to do this. One way is to select the top layer in the Layers palette. Next click on Image>Canvas Size. In the dialogue box that opens up, change the Width and Height to both to .2. Choose a color for your border. Make sure the center of the Anchor box is selected. Click OK and you should see a border around the image.

Part 2 and 3: Cross Process and Dragan Method:

Take your favorite images from your recent portrait assignments and create 3 different versions of each image by working through the online tutorials posted below. Post your 4 post-processed images and 4 unprocessed images (before and after) to your blog when complete:

Cross-Processing:

Cross processing is an effect where the film is developed with the wrong mix of chemicals. Work through the tutorial to recreate this effect and make your photo look like it's source was film and not digital. The border around the film is called the "film rebate". Search for one on google images to use on yours.

Link: Dragan Effect:

Andrzej Dragan's photography is known for having an intensity in detail and tonal depth. Try to mimic his technique with photoshop by working through the video tutorial.
Prefer a plain tutorial? Check out this link: Dragan Effect in 5 steps

Have fun!

 - Mr.W

New Assignment: Rule Of Thirds

Rule Of Thirds Project Details:

A detail from the Tilden Park Carousel in Oakland Ca. Photo by Seth Wilson

Your next assignment is to compose 4 different images that demonstrate the rule of thirds. Your images must be properly lit, have the right levels of exposure and must be in focus. You must apply the Rule Of Thirds to each images composition. Try to compose your image in camera, and only crop your image if needed. These must be new images, not previous work examples.

You can shoot any subject you like, such as landscape, portraiture, still life, pets, architecture... but each of your 4 final images should be different subjects. 

You should shoot many images and choose the best... on average you should shoot about 15-20 shots and choose the single best example from each set.

Assignment Deliverables:

1- Four images that demonstrate the use of the Rule of Thirds in their composition. Each image must be a different subject matter, the subjects could be landscape imagery, portrait, still life etc. Take many photos of each subject and post your best.

2- Written Synopsis of the Rule of Thirds as you interpret it. Write a short description of this principle and how you used it in your images. Tell me what/where the focus point in each image is... where is the eye drawn to? Include these details in each image posted.

Grading:

• Your work will be evaluated on its ability to demonstrate this principal in a creative and informative fashion and to meet all deliverables on time.
• Image enhancement (color, B&W, color tweaking) is allowed as long as it enhances and does not detract from clearly demonstrating the principal. 
• These images must not be over or underexposed and must be in focus. Use a tripod to ensure a jitter/blur free image.
• Your images must demonstrate proper exposure techniques

Deadline:

This assignment is due at end of next weeks class.

Links:

Tutorial: How to Crop an Image in Photoshop with the Rule of Thirds

Reading: Cambridge in Colour - Rule of Thirds

Student Work Examples:

Have fun with your new assignment!

  - Mr. W