Using the Aperture

 

If you’ve been following this blog recently, I explained what the whole deal was about the quintessential term APERTURE. If you need a refresher or want a hopefully simpler explanation than you’ve heard so far, do head back to the post: Technical Terms in Photography – Aperture.

Now that we know what Aperture is, its time to see what Aperture used for. As we saw, the Aperture is the opening in the lens which controls the amount of light coming onto the image sensor. The larger the aperture, the greater the amount of light falling on the image sensor and hence, the “brighter” the picture.

Let’s see the difference visually. The three photographs are from my window and shot in sequence at the same time of day. I varied the aperture setting on my camera and the setting is shown on each photo.

The photo in the middle is typically as close as possible to a correct exposure. Most of the detail is visible and the colours are well balanced out. This was on a bright day at a medium size aperture, f5.6.

The photo on the top is an overexposure. This means that there is more light in the photograph than is necessary. The result is a washed out image as if the whole scene was enveloped in a mist. As can be seen, the details are suppressed and the colours are very light. This is at a very large aperture size, f 3.7.

The photo at the bottom is an underexposure. As you might have guessed, this is due to inadequate light falling on the image sensor. The camera sensor is unable to capture the details and hence the image looks like it was captured at dusk under fading light. Again, the details are lost in the dark tones and colours are very dull. This is at a very small aperture size, f 8.

Exposure is a term that comes from the days of film photography. The amount of light to which the film is exposed to would determine how good the photograph is. This amount of light is controlled by the size of the aperture and how long the film is exposed [shutter speed]. Getting a correct exposure manually is the holy grail of photography.

So in conclusion, the ability to get good detail and correct colours depends on the aperture being open at the right size for the existing light available. While it is also important to consider for how long the image sensor is exposed [The shutter speed], the aperture size will determine the correct amount of light needed for the scene to be captured well.

What aperture settings to use when?

The main determinant of aperture size, just like the human eye’s iris, is incoming light. Depending upon the amount of light in the scene, either the camera or you will have to adjust the aperture size. If the lighting is bright, the aperture should be small. If the lighting is low, use a bigger aperture.

A list of typical subjects being captured and the typical aperture size is given below:

f-stop	Used in situation when
f 1.4	Dark night landscape
f 2	Moon lit night landscape, stars
f 2.8	Night photos
f 4	For most situations in artificial light, like a bulb lit room
f 5.6	For most situations
f 8	For most situations with bright light, like a spot-lit performer or an outdoor shot on a bright sunny day
f 11	Sun lit objects other than snow like light coloured walls
f 16	Snow landscape on a bright sunny day, well lit white objects
f 22	Bright light, Sun lit snow

If your camera allows you to adjust aperture settings, it is important you learn to do this manually. This would not only give you more control on the photograph, but will also allow you to get more creative with the photographs.

A note to point and shoot camera owners: If your camera does not allow you to change aperture settings, do not feel bad. This essentially allows you to concentrate on composing good pictures, while ‘outsourcing’ the technical work to the camera. Your camera will have a number of SCENE modes which essentially are presets of aperture and shutter speed. So in a way, when you use each scene mode in the appropriate situation, you are effectively adjusting your aperture and shutter speed, with a little help from the camera :)

Another very important aspect of photography that is dependent on the aperture is Depth of Field [DoF], but that is the subject of another post.

Until then, do leave your comments and suggestions. I’ll also be happy to answer any questions that you might have.

Technical Terms in Photography - Aperture

 

One of the most important terms you will hear on any photography related website or blog is camera aperture. Whenever you encounter a good photograph exhibited by a photographer, either in a gallery or in a magazine, chances are you will see a series of numbers alongside, describing the camera settings while taking that particular shot. One of those numbers, usually prefixed with the letter ‘ f ’ is the aperture setting.

So what does the term ‘Aperture’ mean anyway?

In the strictest sense, Aperture means a hole or opening through which light is allowed to pass. So a camera aperture is the hole in the front of the camera through which light is focussed onto the image sensor. Simple?

The best way to understand this is to compare a camera with the camera inside the human body, the eye.

The circled area termed aperture is the hole through which light gathered by the lens is focussed onto the image sensor.

Now, comparing the cross section of the human eye with the simple cross section of the camera, it is easy to see how closely the camera is designed like the human eye. In the human eye, the iris (pictured below) is a muscular ring like structure which opens and closes depending on the amount of light the eye senses. This opening, called the pupil (the dark hole in the centre of the iris), controls the amount of light entering the eye and falling on the back of the eye, the retina.

 (Image courtesy: Petr Novák, Wikipedia)

Similarly, in the camera, a diaphragm controls the size of the aperture, the hole through which light passes and falls onto the image sensor on the back.

 

What does the aperture do?

Just like the pupil in the eye, the aperture controls the amount of light falling on the image sensor. The larger the aperture, a higher amount of light is allowed to fall on the image sensor.

Adjusting the aperture allows the image sensor to record the right quantity of light to capture the subject perfectly. Too large an aperture would cause too much light to fall on the image sensor, causing the image to become very bright and white, a condition photographers refer to as a washout.

On the other hand, too small an aperture causes the captured image to be under lit, in other words, much darker and low detail than the scene really is.

 

Making sense of aperture numbers

On a camera, the aperture settings are defined as f-numbers or f-stops. this is usually denoted as the letter ‘f’ followed by a number, e.g. f4.4, f22

Typically the f-number can be varied to any number, but practically this type of continuous adjustment is difficult to achieve given the mechanics of the lens. Hence, certain preset ratios have been identified and universally adopted in most lenses. These presets are known as f-stops.

The main f-stop numbers which are universally available in all lenses are a range between these numbers:

f-stop	Relative Size	Used in situation to capture…
f 1.4	Very large	Dark night landscape
f 2	Large	Moon lit night landscape, stars
f 2.8	Large	Night photos
f 4	Medium	For most situations
f 5.6	Medium	For most situations
f 8	Medium	For most situations
f 11	Small	Sun lit objects other than snow
f 16	Very Small	Snow landscape, well lit white objects
f 22	Very Small	Bright light, Sun lit snow

These particular f-numbers are chosen as presets for a very interesting reason. When you switch from a f-number to the next f-number in this series, the effective amount of light falling on the image sensor is reduced by exactly half. So the aperture size at f5.6 allows half the amount of light to fall on the image sensor as compared to the amount of light the aperture size at f4 would allow.

Fixed lens cameras and point and shoot cameras would have a small range of f-stop settings, typically f-4 to f-8. The dSLR Cameras with interchangeable lenses do not have a aperture range of its own, it is the lenses that each have their own range.

 

How do you adjust aperture? 

Almost all cameras today allow the aperture size to be handled by the camera. This way, a light sensor on the camera reads the light level in the scene, the camera figures out the appropriate size of the aperture required to let in the right amount of light. So you just set up your shot, the camera figures out the settings and depressing the button, you have a pretty picture.

Some cameras allow you to select the aperture size. This is done either digitally using a joystick or buttons on the back of the camera, or manually by rotating a ring on the lens. This gives a photographer better control on the amount of light falling on the image sensor and if necessary, allows him to be creative by deliberately underlighting a scene or slightly washing out the scene.

We will look at how the aperture actually affects the photo and how to use aperture in a future post. Until then, do send in your comments and suggestions.

Understanding Camera features - Zoom

 

Since we checked out the myth of Megapixels in a past post, you know what to look for in terms of megapixel count for the new camera you want to buy.

Today we look at another of the camera salesman’s favourite buzzwords – The camera zoom.

Zoom, in terms of a camera, is the ability of the camera lens to focus on a subject at progressive distances from the camera. The ability of the camera to magnify the subject so as to capture greater detail or to very simply, get close to the subject, which in reality can be very far off.

In my past post about focal lengths, we saw how zoom or subject magnification actually worked. By varying the distance between the lens and the image sensor, the angle of viewing is narrowed down. This focuses the camera’s image sensor on a smaller portion of the subject, thus causing it to magnify.

So very simply, the greater the ability of the camera to magnify subjects further away, the better the zoom capability of the camera.

However there is a catch. There are in reality two types of zoom in digital cameras, optical zoom and digital zoom.

Optical zoom or mechanical zoom is the method of zoom explained above. The magnification is achieved by physically changing the distance between the lens and the image sensor. This needs a mechanical way to move the lens and is most commonly done using a telescopic mechanism like the one pictured below.

Because the optical zoom does not manipulate the captured image in any way, the result is a clearer and sharper magnification.

Digital Zoom is the cheaters way to zoom, available only to digital cameras. As there is no film in the digital camera and the captured image is electronic information, this allows the camera to manipulate the electronic image in many ways which were not possible with film.

The magnification of the picture is done by image manipulation rather than any physical movement of the lens. The area of interest in the digital image is cut out and magnified by expanding the pixels. Now while this technically works for a small expansion, doing this too much causes the picture to blur and lose focus, not to mention giving it a very grainy look.

As an example of the quality difference, look at the picture below. 

(Picture courtesy: Bob Atkins)

As can be seen, while a optical zoom would give you a sharper clearer magnified image, the digital zoomed image is blurred and pixellated. Even though the image is magnified to the same extent, the usability of such an image greatly reduces.

So, when you go out to buy a new camera, ask for one which has a larger optical zoom. Never settle for only a digital zoom even though these cameras are a lot cheaper. Most of the time the camera salesman may not know what type of zoom is present in the camera. In that case, ask to see the specifications of the camera and look for the word “Optical Zoom”.

Nowadays, most cameras have a combination of optical and digital zoom. The zoom range begins with optical zoom [with the telescopic mechanism coming out] till about 4X – 6X and then goes further to digital zoom. While this effectively would give you a large combined zoom range, remember that the useful zoom is the optical part. The digital zoom for around 2X more would help, but anything more than that is a gimmick.

Usually 4X to 6X optical zoom is good for any point and shoot camera and should cover most photography situations. Special prosumer cameras, called super zooms, feature optical zoom ranges of up to 20X. These are useful for the hobbyist.

dSLR cameras have the option of interchangeable lenses. As a result, special lenses and lens attachment combinations enable the camera to have an incredible zoom factor. These lenses have the telescopic mechanism within and allow fine adjustment of the zoom to enable tack sharp images. Some of these lenses cost more than the camera body itself !!!

The rule of thumb in the shop is – Buy as much optical zoom that is possible within your budget.

As always, please leave your comments. Until next time……………………

Technical terms - Focal Length

 

If you were to read through the specifications of a camera or even a lens, one of the first things you would notice is Focal Length. Engineers in the audience will immediately be taken back to their Physics class in Optics, and sometimes even they will not be able to clearly remember what this term means. Trust me, I’m an engineer :)

Very simply put, Focal length of a lens is the distance between the lens and the image sensor, while focussing on the subject. The image sensor is where the photographic image is recorded inside the camera.

Let’s look at the picture below:

There are three lens positions in this diagram. Position 1 or X, is the closest the lens can be placed next to the sensor. In camera terms, this is the base focal length. Notice that when the lens is in this position, more of the subject is captured on the sensor due to the wide angle of viewing.

Position 2 or 2X, is about 2 times the base focal length. This causes a smaller angle of viewing, thus capturing a smaller portion of the subject to fill the whole image sensor. As a result, that particular portion of the subject appears magnified or zoomed.

Position 3 or 4X is about 4 times the base focal length. This position narrows down the viewing angle even more, causing more magnification of the subject.

Hence the position of the lens determines how much of the subject is captured on the area of the image sensor. Farther away from the sensor means less of the subject is captured onto the whole sensor, giving the effect of magnification.

The most common way a camera manufacturer can introduce a variation in focal length in a camera is by installing a telescopic lens mechanism like the one shown below:

This mechanism telescopes out to change the distance between the lens at the front of the telescope and the mage sensor housed inside the camera body. The result of this movement can be seen on the LCD screen behind as a magnification of the subject. 

While looking for a camera, it is best to buy one with a good range of focal lengths. This would allow you to zoom closer to the subject without physically moving close. A range of 3X to 6X is good in a compact point and shoot camera.

We shall dwell on the matter of zoom in another post.

Choosing a digital camera – camera types

With digital cameras getting cheaper and cheaper, its no wonder that with the coming holiday season, digital cameras come towards the top of the gifting options list. Most of the time, this consideration happens when one either wants to break into the bold new world of digital photography or when you want to move up to the next level of expertise.

Now before I go on, the statutory disclaimer. I am not a professional photographer. What I’m doing here is sharing my experience and method that I used when I went shopping. My advice is not the expert advice and I will not name any brands or camera models.

However what I will do is list out what I looked for when I bought my camera and how I chose it. I will also point you to places where you could find in-depth reviews of cameras carried out by experts in subsequent posts.

Here are some of the considerations to look for when you choose your camera:

How do you use your camera:

Before you go web surfing, you should go sit in your favourite chair, get a notepad and answer these few questions:

• What do I want to photograph? Am I only going to photograph people or nature or scenery or sports?
• When do I take photos? Am I going to spend a lot of time taking photos or just special occasions like birthdays and anniversaries?
• What am I going to do with my photographs? Keep them on my computer and share with friends? Print them and frame them? Sell them??
• How much time do I want to invest in learning to use my camera?
• And finally, how much money do I want to invest in my camera?

Digital cameras usually come in three main categories:

The “point and shoot” camera: This is the no-fuss no-nonsense camera. Specifically meant for people who just want to take some occasional pictures of friends and family and some sunsets. These cameras do not have a lot of settings and modes and are built to be simple to use, literally “point the camera at your subject and press the button”. These cameras are towards the lower end of the price spectrum and need very little time to learn to use. Usually these are the cameras you can gift away or use regularly.

The prosumer camera: This is the next level of camera complexity. The word prosumer is a portmanteau of the words proficient and consumer. Typically this camera is meant for people who want a little more control of their photography but do not want to be overwhelmed by a myriad of functions and settings. A prosumer camera gives the user more manual control on the photograph settings than the “point and shoot” and would need about a day or two and some tinkering to understand the different settings and modes available.

A user can very well buy a prosumer camera and use it like a “point and shoot” [In fact, a lot of show-offs do that ;-) ]. I personally feel that’s a waste of camera capability and money. A prosumer camera is somewhere mid-range on the price spectrum. Prosumer cameras are also alternately called fixed lens cameras, typically because the lens cannot be changed.

The professional dSLR: This is the big daddy in the camera world. At the very top end of the camera spectrum, the digital Single Lens Reflex camera is what photography professionals use. The dSLR has the advantage of multiple manual setting adjustments, interchangeable lenses and incredible control on every aspect of the photography process. It can take weeks to learn to use a dSLR to its full potential and usually with expert guidance in some aspects. These are also moderately to outrageously expensive and usually worth investing if one wants to graduate into commercial photography.

In conclusion, I’ll leave you with a handy table that’ll help you decide which camera is right for you:

FEATURE	POINT & SHOOT	FIXED LENS (PROSUMER)	dSLR
Typical Use	- Occasional photos	- Hobby photography - Experimentation and learning	- Professional or Commercial photography
Advantages	- Simple to use - Very affordable - Smaller and lighter	- Better manual control than P&S - Better zoom and picture quality	- Interchangeable lenses - Multiple accessories - Best manual controls and image quality
Disadvantages	- Too little control - Low image quality	- Not as much control as a dSLR - Lens is fixed, so not easily replaceable - Usually needs a camera bag	- Expensive - Always needs a camera bag for accessories - Heavier than the other cameras
Time to learn to use including reading the manual	A couple of hours	A day to a week with lots of experimenting	A couple of weeks with expert guidance sometimes
Price	Low [$50 – $ 200]	Medium [$350 – $ 650]	High [$800 upwards]
Buy this type of camera if…	- you want to take pictures once in a while - you want to take pictures quickly and easily - you want to carry your camera easily	- you want to learn digital photography - you want more control on your imaging - you like to get creative - you want the ability to click professional looking photographs on a budget	- you’re a professional photographer or want to be one - you want to gain mastery in digital photography - you want to sell your photos commercially - you have lots of money

So that’s my take on camera types. Do leave comments or queries if you have a specific question that needs answers. I promise I’ll either give you an answer or find you one.