Photo Stories

Portrait Photography With A Telephoto Lens

We all enjoy taking photos of people.  Unfortunately the majority of photos are just snapshots taken with a cellphone where people put very little thought into the outcome of the image.  But that’s not you because you are a student of photography and want to know how to improve the images you capture. 

There are so many variables to capturing a fantastic image, and one of those is the focal length of the lens you choose. It is important that your photos of people pop and are flattering.  The best way to do that is with a fast f/2.8 telephoto lens.  Remember, the key to great photographs is shooting with great glass.

The Importance of Focal Length

The reason you are shooting a portrait is to create a personal image that is flattering to the subject.   Wide angle lenses create distortions whereas shooting with a long focal length removes distortions by compressing the image and blurring the background to make your subject pop.  The longer lens compresses facial features so noses stick out less, foreheads are not as prominent, and everything else in the image is more compressed when shooting from a distance.

A long lens also removes distracting backgrounds.  With a fast wide angle lens such as a 24mm f/1.4 it is difficult to separate your subject from the background unless you focus really close.  Even if you can get great background bokeh with a fast lens wide open your focal plane is so narrow that the nose and ears can be blurred while the eye is sharp.  This would not make for a nice portrait.

Another reason that you would not want to use a wide angle lens for portraiture is that you need to be well within the subjects personal space in order to fill the frame.  If this is your spouse or a close friend, shooting from 2 feet away may not be a big deal.  However, when I was shooting Uncle Fuggles at 17mm (24mm on a DX sensor), he was a bit uncomfortable with me standing so close.

Separate Your Subject From The Background

Blurring the background is important with portraits because it allows you to isolate the subject from the background.  When everything is in focus the background is too distracting and your eye is not drawn to the subject.  A great photo leads your eye to the subject in the image.  Below are two images that are similar.  One has a more depth of field while the other has less and is more compressed.

Disappear Into The Crowd

A long focal length lens allows you, the photographer, to blend into the background.  Standing further away allows you to get great candid shots.  When you are up in someone’s face with a 35mm lens they know you are there and will react as such.  When you are shooting from 10 to 20 feet from them they will act more natural.  

Shooting across the room when children are playing is great because their attention is on having fun rather than on the camera.  It helps you capture them in their natural state.  Shooting at a distance with a fast long lens can also help isolate someone from a group of people.  Imagine you wanting to photograph a girl singing in a choir.  You can separate her from the rest of the crowd.  Unlike photos where you play 'Where's Waldo' blurring the crowd will help lead your eye to the subject adding interest to the photograph.

Photos In Space

Shooting with a long lens can remove spatial distortions.  When shooting close you may be above or below the subject and wide angle lens will show your spatial difference.  But when moving further from the subject the differences in height vanish.

Finally, shooting with different focal lengths keeps your brain working by causing you to think about each photo you take.  Know your lens, and put your camera in manual mode.  Think about your settings.  Then predict what you think may work for the lighting conditions.  Take the shot and see how accurate your guess was.  Think about the exposure triangle and make any corrections in stops of light to improve the image. 

One caveat when shooting with a long lens is that you don't want to shoot with a shutter speed lower than the length of the lens.  So a 200mm should have a shutter speed 1/200 or greater.  Remember, the crop factor.  If you are shooting with a cropped sensor Canon at 200mm you need to have your shutter speed no lower than 1/320 of a second (1.6 x 200mm = 320mm).

Uncle Fuggles was kind enough to step in as a portrait model. The images below were taken with the Nikon D7100 , the Sigma 17-50mm f/2.8 EX DC OS HSM , and the Sigma 50-150 mm f/2.8 APO EX DC OS HSM . The camera settings remained constant for each image and I only changed the focal length. The camera was set to 100ISO, f/4.5 at 1/1000 shutter.

Why does the background change while the subject remains the same?

The two images below demonstrate the difference between the 17mm and the 150mm focal lengths.  Using your imagination you can see how the wider lens captures more of the background when compared with the longer telephoto lens.  The longer lens is more narrow, so it gets right in the face of the subject without any ancillary noise from the background. 

Digital Photography: The Exposure Triangle

The Exposure triangle is the most important aspect of photography.  Its three primary components are, Aperture, ISO, and Shutter Speed, but before we move further let me discuss a few things in detail.

Shutter speed is easy to understand, but it's complicated in practice. In its simplest form shutter speed is how long the shutter will remain open when pressing the shutter release button. It is represented as fractions of a second to as long as minutes or hours.  The shutter controls three things.  

1. Shutter speed controls the length of time light is let into your camera to correctly expose the frame. While looking at your light meter you can see how under or overexposed the image will be based on a set amount of time, and is directly related to how open the lens iris is (your aperture setting) and the sensor's light sensitivity (your ISO setting).  Increase the speed and the exposure will darken. Decrease and it will lighten.

When exposing for low light with a slow shutter speed it's recommended you use of a tripod and a remote trigger to avoid camera shake.

2. Shutter speed either freezes or blurs action.  If you are photographing live action sports and you want to freeze movement you want a fast shutter, or you could slow the shutter to create motion blur.

3. A slow shutter speed can show how slow moving objects change over time. For example, in the film days when photographing star trails you would keep the shutter open for an hour or more.  

One thing to note is that long exposure photography is a relic from the films days. Today, long exposure photography is done by taking many photographs of the same scene then compiling them with software. So instead of leaving the camera's shutter open for two hours to capture star trails you would instead take 1,440 five second exposures stitching them together with software to achieve the same affect all while making a cleaner image. 

The Reciprocal Rule With A Twist

Zooming with a telephoto lens can cause unwanted camera shake leading to blurry images. To avoid this you need to employ the Reciprocal Rule. That is, your shutter speed should not be slower than the focal length of your lens as measured in fractions of a second.  This is to avoid motion blur when hand holding a telephoto lens.

For example, if you are shooting at a 100mm focal length then your shutter speed should not be less than 1/100 of a second. If you are at 200mm you should shoot at a minimum of 1/200 of a second.  

But here's the twist!  If you are not shooting with a full frame camera then you have a camera with a cropped sensor. This adds a multiplier that is based on the size of your camera's sensor (i.e., Nikon = x1.5, Canon = x1.6, Lumix & Olympus micro 4:3 = x2).  

For example, you have a 200mm focal length with a Nikon DX then your are effectively shooting at a 300mm equivalent and should not lower your shutter below 1/300 of a second. A Lumix or Olympus would be at 1/400 of a second. This takes a little thought, but with practice you can quickly do the calculations and be on your way to making tack sharp photos.

Stops of Light

Light is designated with an f/number where f represents doubling or halving the amount of light entering the camera.  You most often see this on your lens with an f/number designation (e.g., f/2.8, f/4, f/5.6, etc.). One stop from f/2.8 to f/4 will cut the amount of light entering your camera in half. Opening your aperture up from f/11 to f/8 will double the amount of light.

This is the primary reason why large aperture lenses are so expensive. A fast f/2.8 telephoto lens requires a lot of glass, and is big and heavy. Whereas, slow kit lenses are much less expensive because they have variable apertures. To learn more, I wrote extensively comparing single aperture with variable aperture lenses. 

Exposure Triangle

Armed with these three pieces of information (Shutter Speed, Aperture, and ISO) you create the Exposure Triangle.  Keep in mind, the exposure triangle is always in flux.

Think of it this way.  Proper exposure is in the center of the triangle.  If you move up or down on one side you need to move in the equal and opposite direction for one of the other sides. Or a half stop on both opposite sides to maintain the correct exposure.

For example, your camera's sensor has a specific native sensitivity for a properly exposed image.  If you have a correctly exposed image with the settings of 1/125 shutter speed, aperture set to f/5.6, and ISO 800, and you speed up the shutter to 1/250 to freeze action then you either need to open the aperture or increase the ISO by one stop, f/4 or ISO 1600 to maintain the correct exposure.  If your camera is capable of half stops then you can do one half stop of each instead of a full stop of one or the other.  

If you changed any one of the three without changing either of the other two then your image may be over or under exposed by one stop of light.  To see this in action put your camera in manual mode and start turning the shutter and aperture dials while leaving the ISO constant.  You will see your light meter move from a proper exposer to under and over exposed.  

Exposure is always in flux as light is never constant. With a strong understanding of the exposure triangle you will capture great images.  To get out of Auto and into Manual I recommend you shoot in Auto first to see what your camera is doing, then emulate those settings and adjust them by one or two stops up or down to see how each setting affects your image. 

Now get out there and make great pictures.

Digital Photography: ISO Explained

It seems everyone has a digital camera these days. Unfortunately for most people it's a cellphone. Believe it or not people still use "real" cameras, and you may be one of them. There are a lots of reasons why you want to take pictures with one, but the number one reason is that you can get out of auto and take control of the settings for each picture.

This all begins with the exposure triangle (shutter speed, aperture, and ISO). From previous articles I've written you know that shutter speed controls the length of time the image sensor is exposed to light, and aperture (f/number) controls the amount of light that enters the camera. Aperture also controls your depth of field while ISO is the sensitivity of the image sensor to light. A change in one requires a change in at least one other to maintain proper exposure.

On its face ISO is easy to understand - The higher the number the more sensitive your camera is to light. But it’s not that simple, and increasing your camera's ISO comes at a cost. What is ISO and why do you need to know about it?  Let’s find out.

What Is ISO?

International Standards Organization (ISO) is the standard measure of light sensitivity of your camera’s imaging sensor whether that’s film or a digital sensor.  It is a standard designation that all camera manufacturers agree to.  Film may also have a sensitivity rating called ASA, but for the scope of this article I will only talk about ISO.

ISO is also known as “film speed”.  When we look back to antiquity known as “The Film Days” you may recall having the choice of 100, 200, 400, 800, etc. ISO ratings when purchasing a roll of film.  Today, digital cameras use a similar designation, and can go as high 25,000 ISO or more.

A film's ISO rating is a reference to the light sensitivity of the film emulsion. It’s speed represents the amount of time the film needs to be exposed to light to get a proper image, which is controlled by the length of time the shutter is left open. Aperture plays a role here too with the amount of light the iris lets in.  

The higher the ISO number the more sensitive the film is to light. That is, 800 ISO is more sensitive than 400 ISO by one full stop of light.

Film sensitivity is a simpler design when compared with a digital sensor’s light sensitivity.  Higher speed films were more sensitive to light because the silver crystals in the film emulsion were larger allowing them to capture light faster when compared to smaller crystals. The tradeoff however, was that the larger crystals were visible and made the image look grainy. 

Digital image sensors have a similar problem. As the pixels become more sensitive to light they too become "grainy". Here is where we make the comparison between the crystals in the film emulsion and the digital imaging pixels. Larger emulsion crystals increases the grain. Whereas, a stronger electrical signal increases the electrical noise (grain).  

The Digital Photo Sensor

A digital photo sensor is made up of millions of smaller sensors called pixels. Each one of these pixels independently gather light in the red, blue, and green spectrum. When a pixel is active and highly sensitive (6400 ISO) with no light coming into the camera (your lens cap is on), there will be a small amount of color sprinkled throughout the background of the black image. This is electrical noise (grain) from the increased electrical signal that is stamped into your image when snapping the photograph.

Below are two images with the lens cap on. To the right is 100 ISO and to the left is 25,000 ISO.  Click the image to enlarge.  You may need to dim the lights in your room, but the electrical noise is noticeable. 

The below diagram represents the image quality of one properly exposed pixel at 200 ISO on a digital sensor. It demonstrates a representative amount of red, blue, and green light (shown as red).  The electrical noise is represented as blue. 

Notice how much of the pixel is in the "red" with a small amount of electrical noise in "blue". This would create a tack sharp image.

Now let's consider what would happen if you took a picture in low light with the camera set to 200 ISO. When you increase the ISO from 200 to 3200 the pixel increases the light sensitivity by four times, but it also increases the amount of digital noise by that same amount. It does this by increasing the electrical signal to boost the sensor's light sensitivity.

The increased ‘noise’ (electrical signal represented in blue) is the digital equivalent of the larger crystals in the film emulsion. This is your grain.

Benefits Of Digital Camera ISO

One benefit of using a digital camera when compared to film is that the digital camera can adjust ISO on the fly to meet the lighting demands of your current environment.  This occurs because the output of the photosensor is able to be electronically amplified on demand.  Whereas a 36 exposure roll of 800 ISO film had you locked in at 800 ISO for the entire 36 exposures.  

Amplifying the sensitivity of the image sensor does not change it's native light sensitivity. When you change the ISO from 100 to 1600 what you are actually doing is electronically amplifying the output signal making it more sensitive to a given amount of light. 

Here’s the key to this whole thing. When the photosensor ISO increases for low light the electrical signal increases and you lose image quality. Is this a bad thing?  Not necessarily. Grain can add an artistic effect, especially with black and white photos.

Notice how Uncle Fuggles is tack sharp at 400 ISO and how the image degrades at 25,000 ISO. Both photos were taken at 50mm with my Nikon D7100 and Sigma 17-50mm f/2.8 lens.

400 ISO                                                                                    25000 ISO

Why Do You Need To Increase The ISO?

The primary reason you need to up the ISO is to increase the photo sensor's sensitivity to light to keep the shutter speed fast enough to avoid motion blur when hand holding or during fast action. If your subject isn't moving you can turn down the ISO and mount your camera on a tripod to shoot a longer exposure.

One thing to note is that you want to lower the ISO when shooting flash photography, but flash will often alter the artistic impression of the image you are trying to create.  

When Do You Adjust The ISO?

Well, it depends. It depends on what you are trying to do with the image you are trying to create. Grab your camera and work through the examples below to help you better understand what the settings do.

Turn up the ISO when…

1. You are in low light situations without a flash.

Example: 1/100 shutter speed; f/2.8 aperture; 6400 ISO

2. You need a fast shutter to freeze fast action.  This can also occur in low light.

Example: 1/500 shutter; f/5.6 aperture; 3200 ISO

3. You want to shoot a landscape while hand holding the camera with the majority of the image in focus without any bokeh.

Example: 1/125 shutter speed; f/22 aperture; 1600 ISO

4. You want to create an artistic black and white photo

Example: 1/500 shutter speed; f/1.8 aperture; 6400 ISO

5. You are using a variable aperture lens.  At 55mm your aperture is f4.5 whereas at 200mm you are shooting at f5.6.  You need to adjust the ISO for the number of stops of light you are reducing your aperture by as you zoom. There is also the rule of thumb that as you zoom your shutter speed should not drop below the length of your lens in millimeters.

Example 1: 1/125 shutter speed; f/4 aperture at 55mm; 1600 ISO

Example 2: 1/250 shutter speed; f/5.6 aperture at 200mm; 6400 ISO

Turn down the ISO when…

1. You are trying to recreate an image just as you see it without any grain whatsoever.

Example: 1/125 shutter speed; f/4 aperture; 100 ISO (bright light or with flash)

2. You are outside on a bright day

Example: 1/250 shutter speed; f/8 aperture; 100 ISO

3. You use a flash (direct or indirect).

Example: 1/200 shutter speed; f/5.6 aperture; 200 ISO

4. You change from a ‘slow’ lens to a ‘fast’ lens.  That is, when you use a larger aperture lens to let in more light.

Example: 1/125 shutter speed; f/1.4 aperture; ISO 100

Late model cameras can handle ISO’s as high as 3200 ISO with little grain. Each sensor generation is better than the last, and many of the new models can handle low light well, especially when you use quality glass.

One last note regarding noise, and photography with high ISO.  It can be argued that 'some' noise is not only an acceptable part of imaging, but can lend character that can add to an image's artistic qualities rather than detract.  

Consider old World War II era photographs.  If they were tack sharp like today's digital images would they possess as much nostalgia if they didn't have that grainy texture?  That sepia tone?  That point is of course debatable.  What you must consider when capturing an image is whether you are creating a photo documentation, or are you looking at photography as an art form?  The choice is yours and ISO will help get you there.