Understanding Aperture in Photography

Aperture
Aperture refers to an adjustable opening in your camera lens that is able to limit the amount of light passing through the lens and hitting the camera sensor. Just think of it like your eyes. When you open your eyes, light enters through your cornea, and is bent through the pupil, which is a round opening in the center of the iris. The iris and pupil works exactly like the aperture of a camera, controlling the amount of light being emitted.

To control your camera’s aperture, switch your camera mode to aperture priority. In this mode, you are able to manually control your camera’s aperture. The camera will change the shutter speed automatically to match the aperture that you had selected to create a picture that is properly exposed when the shutter release button is clicked.

Aperture is measured in F-stops. The lower the F-stop (e.g. f/2.8), the wider the opening of the aperture. While the higher the F-stop (e.g. f/22), the smaller the opening of the aperture. This concept can be confusing for beginners to understand as it is counter intuitive. However, it should not be too hard to understand once we know exactly what aperture is and how it affects the outcome of your pictures.

When the aperture is wide open (e.g. f/2.8), more light will enter through the camera’s lens, therefore, less time is required for proper exposure which meant faster shutter speeds. Wide aperture will also cause a shallow depth of field in your picture, where the foreground and background of your picture is blurred except for the subject which you are focusing on. However, the opposite applies when the aperture is small.

 
When the aperture is small (e.g. f/22), less light will enter through the camera’s lens, therefore, more time is required for proper exposure which meant slower shutter speeds. Small aperture will also cause a deep depth of field in your picture, where everything in the picture is in focus.
Wide aperture (e.g. f/2.8) is useful for taking pictures in low light conditions as more light gets to enter and hit the camera’s sensor. It allows you to use faster shutter speeds as well that can be used to freeze action on moving subjects such as a running dog. It is also suitable to use when you want to take portraits or macros where you want a shallow depth of field so that the subject will be sharp and stand out in your picture.
Small aperture (e.g. f/22) is useful for taking pictures in good light conditions as there is more than enough light that will enter and hit the camera’s sensor. It allows you to use slower shutter speeds which can be used to give your subjects a motion effect in your picture. Remember the running dog example? We can use slower shutter speed to create a motion effect of the dog, running in your picture, bringing your picture to live.

A small aperture is also suitable to use when you want to take landscapes or group shots so that everything in the scene is considerably sharp.

About the Author
Roy Lee is a freelance photographer residing in Malaysia, who specializes in wedding, portrait, and landscape photography.

Digital SLR Terms

Megapixels	Cameras with more megapixels give you the freedom to make huge prints and to crop your photos, but they do not necessarily have higher image quality.
ISO and Image Noise	Increasing the ISO setting lets you take clear photos in dim light without having to use a flash, but it also degrades the image quality.
Dust Control	Dust that lands on an SLR sensor appears as small black spots in every photo you take. Dust controls systems attempt to prevent and eliminate this.
Image Stabilization	There are two types of stabilization: one that's included inside the camera and one that's inside the lens. Regardless of the type, stabilization helps to eliminate blur in your photos caused by camera shake.
Live View	With a live view system, you can compose photos using the LCD screen on the back of the camera in addition to the viewfinder.
Dynamic Range	Your eyes have exceptional dynamic range and can see details in a scene even when there's extreme contrast. Unfortunately, an SLR doesn't work quite as well as your eyes.
HDSLR	An HDSLR is a single camera that can capture both still images and High Definition (HD) video.
Crop Factor	A digital SLR sensor is smaller than a frame of 35mm film, so only a portion of the image that passes through the lens is captured by the sensor.
Autofocus	Autofocus systems can include anywhere from 3 to 9 individual focus points. More important that the number of points is the accuracy of the system.
Continuous Drive	A continuous drive lets you take multiple photos in rapid succession. More expensive cameras have faster continuous drives.
JPG and RAW Files	JPG is the standard format for digital images, and is easy to e-mail, upload and print, but RAW offers significantly more creative freedom.
Aspect Ratio	Wonder why your digital prints never turn out exactly like the image on your computer monitor? The culprit is aspect ratio.

Differences between DSLR cameras and digital compact cameras

The first major difference between digital SLRs and digital compact cameras is what prevents most people from buying a digital SLR: price.
Even though digital SLR prices have come down each and every year, they are still significantly more expensive than their compact cousins.
Let me put it this way: an inexpensive digital SLR camera start around $450 without a lens. Then you get to track on an additional $100 for a kit lens or $500 for a high-quality zoom lens.
If you can't fathom spending $500 to $1000 on a digital camera, then digital SLR is definitely not your choice.
However, if you've been saving you pennies for months and are perfectly aware of how much these cameras cost, then let's take a closer look at some of the other differences between digital SLR caneras and digital compact cameras.

Size and Weight
Size and weight is the second most obvious difference between digital SLR cameras and digital compact cameras after price. Even a small-sized digital SLR camera is double up the size and price of a compact camera.
While there are many new digital SLR models that are more portable (and are easier to travel with) the addition of a lens to your camera ensures that you'll never be able to stow it away in your shirt, pocket or purse.
If you'd like the higher image quality of a digital SLR camera but don't want a huge heavy camera, then consider a mirrorless DSLR - they're more the size of compacts but capture DSLR-like photos (and you can change lenses).

Professional Movies
Prior to 2008, digital SLRs with video did not exist.
Digital SLR cameras could only take stills, and many people were suprised that these big expensive cameras could not capture video clips like their tiny compact cousins.
All that is now in the past: virtually all DSLRs released since 2008 included a High Definition (HD) video capture mode.
But the one thing that really sets DSLR video apart from compact video is the ability to change lenses.
Since you can change lenses on your DSLR, you can capture videos that look more like movies:
- Extreme wide-angle shots, close-ups and backgrounds thrown nicely out of focus can all be achieved with digital SLR.
This explains why many small independent film companies now use DSLRs as their camera choice. Compared to the price of a high-end digital video camera, a DSLR is pretty cheap.

Manual Zoom
Compact digital cameras have electronic zooms: push a button (or level) and the camera's lens zoom in and out.
Since all digital SLR lenses can be removed from the camera body, the zoom mechanisms are entirely manual: to change the view you have to twist a ring on the lens.
This manual zoom actually results in a faster zoom: you don't have to wait for the motors to move the lens in and out, you can twist the zoom ring as fast or as slow as you like.

Zoom Range
Since we are on the topic of lenses, let's talk about another difference between digital SLR and digital compact cameras: zoom range.
There are many digital compact cameras on the market today with "mega-zooms". These cameras have 10x or 12x zooms and are capable of taking both wide angle and telephoto shots.
In order to cover a similar range with a digital SLR camera you have one of two options:
- Buy a mega-zoom lens: these give you the same zoom power as a 10x zoom on a compact, but also cost about $600 USD.
- Buy two zoom lenses: with one wide-angle zoom and one telephoto you can cover a lot of range, but at significant cost ($800 USD or more)
If tons of zoom range is important to you, the compact is clearly the more economical solution.

So what should you buy?
Even though I've talked about the difference between SLR and digital compact cameras you still might be on the fence.

Here are a few question that might help you make up your mind:
- Do you want to take more professional-looking photos?
- Do you want to create high-definition home movies?
- Do you want to be able to change the lens attached to your camera?
- Do you want more control over the photos that you take?
- Are you sick and tired of the slow speed of your digital compact camera?
- Do you want to take a lot of photo in low light?

If you answered YES to every question, get a DSLR. You'll be happier in the long run.
If you answered NO or MAYBE to one or more, then consider a digital compact or mirrorless DSLR instead.

What is DSLR?

Digital Single-Lens Reflex (Digital SLR or DSLR) are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of camera.

DSLRs are often preferred by professional still photographers because they allow an accurate preview of framing close to the moment of exposure, and because DSLRs allow the user to choose from a variety of interchangeable lenses. Most DSLRs also have a function that allows accurate preview of depth of field.

Many professionals also prefer DSLRs for their larger sensors compared to most compact digitals. DSLRs have sensors which are generally closer in the size to the traditional film formats that many current professionals started out using. These large sensors allow for similar depths of field and picture angle to film formats, as well as their comparatively high signal to noise ratio.

The term DSLR generally refers to cameras that resemble 35mm format cameras, although some medium formats cameras are technically DSLRs.

The Advantage of Digital SLR Cameras:
- Build for speed
So why are some compact cameras so slow and digital SLRs so fast? It is electronics vs mechanics.
There's a device called shutter that located in front of the digital SLR sensor for blocking it from light. When you take a photo, the shutter (made up of two curtains) opens and closes. This is different from a compact camera, when there is no shutter mechanism. In compact cameras, the sensor is electronically activated every time you take a photo. The advantage of the mechanical solution is that it is instantaneous: you press the shutter button and the shutter snaps open. There's never a delay when you want to capture that photo of a lifetime. If this was the only advantage of digital SLR cameras, it might be enough for everyone who's frustrated with a sluggish compact camera.

- A Lens for Every Occasion
The ability to exchange lenses, to select the best lens for the current photographic need, and to allow the attachment of specialized lenses, is a key to the popularity of DSLR cameras.

- High Quality in Low-Light
One clear advantage of digital SLR cameras is that they are able to capture photo even when there is not a lot of ambient light.
So what? Every camera can take a photo when there's not a lot of light - just turn on the flash.
Here's the trick: digital SLR cameras can do it without the flash.
Digital SLRs are able to take photos when there's little available light because of a feature called ISO: it makes the digital sensor more sensitive to light.
As you increase the ISO (and increase the camera's sensitivity to light) you also add grain or "noise" to the image.
The advantage of digital SLR cameras when it comes to ISO is that even at high ISO settings they produce very little noise. I can't say the same about compact cameras.
If you really enjoy taking photos when there's not a lot of light, the image quality of a digital SLR will exceed a compact cameras any day of the week.

-You Have Control
This is my favourite advantage of digital SLR cameras.
I don't like a machine to be making decisions for me. While it's right most of the time, it isn't right ALL of the time. The human brain will always be better at judging a scene then a camera set to automatic.
With a digital SLR, you have complete control over every photo you take, and don't have to rely on the camera to make choices for you.
Even if you're not ready to make the jump to a fully manual camera, don't be frightened off/
Every digital SLR camera lets you use an automatic setting, and provides you with the intermediate steps that offer increasing levels of control over your images.

Why do capacitors sound different?

In the past capacitors were just capacitors and sound quality was determined by the dialectric material with polypropylene considered by many as "the best" seeing as this type of capacitor had the lowest losses. But technology of the 21st century has brought us new measuring techniques and insights and there seems to be more to it. We can now measure things that were not possible a few years ago. In a nut-shell: microphony is the keyword - the mechanical resonance, a key feature of audio capacitors. This is a physical deformation of the capacitor walls which occurs as a result of the audio signal passing through the component - much like an electrostatic speaker. This resonance is dependent on the size, shape, materials and manufacturing parameters of the capacitors. This effect has been known about for years as it plays a part in the impulse strength of capacitors. However, the effect has never been considered read the white paper on mechanical resonances inside capacitors. Another interesting article was written by Martin Colloms back in 1985 in which he tested several capacitors on their sonic differences. Also look at the equivalent circuit diagram of a capacitor, this also explains a lot!

Phase

Speakers are a complex electromechanical machine that vibrate and move air to produce sound. Sounds simple. But what many people do not understand is just how a speaker receives a signal from the radio or amplifier which powers it.

All electronics in a vehicle will operate on 12 Volts DC, or direct current battery voltages. But, a speaker will not operate properly if DC voltages are applied to a speaker. So what happens? The amplifier, whether internal to the radio or a separate amplifier connected to the radio, will convert an audio signal from the radio to a very low AC voltage.

For a speaker to make sound, it must move IN and OUT. But to do this, the audio signal that is given to the speaker through speaker wires must change polarity. Or more simply, the voltage waveform of the audio signal must switch between (+) positive and (-) negative polarities very quickly. When a this happens, the speaker will move in for (-) negative signal and move out for (+) positive signals. This is a simplified overview of how a speaker vibrates in and out, producing sound. This is a very important concept in mobile electronics.

POLARITY: is the part of the voltage waveform that is currently active. The part of the waveform that is (+) is considered positive polarity, and the part of the waveform that is negative is considered negative polarity. You might notice that speakers connections are marked (+) positive and (-) negative so that you connect the (+) positive speaker wire to the (+) positive speaker connection and that you connect the (-) negative speaker wire to the (-) speaker connection.

In reality, a speaker is NEUTRAL or doesn’t have a (+) positive or (-) negative to it. The marks on the speaker indicating (+) positive and (-) negative are there so that you connect ALL of your speaker the same way. WHY? Well, polarity. When all speakers are connected the same, all (+) positive speaker wires connected to (+) positive speaker connections, etc., then all speakers will move out at the same time and move in at the same time. When all speakers are connected the same, the speakers are said to be “in polarity”. What happens if speakers are “out of polarity”? Lets say there are (4) four speakers in a vehicle, (3) three of which are connected the same, but (1) one is connected “out of phase”. That one speaker will move opposite of the other three and cause problems. The amplifier that is powering the four speakers will, internally, see an “out of phase” problems. When an “out of phase” problem exists, the overall sound from the speakers will sound different. What happens inside the amplifier is that the AC voltage waveform powering the “out of phase” speaker will be opposite of the other “in phase” waveforms. When this happens, the “out of phase” waveform signal will CANCEL out one or more of the “in phase” waveform signals powering one of the “in phase” speakers. When two waveforms cancel each other out, a flat waveform exists. Speakers will reproduce this flat waveform in the form of dull or lifeless music.

Many amateur installers or listeners cannot tell when a speaker is out of phase. To these people, the music reproduced by the speakers sounds odd, but they do not know how to solve the problem - finding the speaker “out of phase” and flipping the wires until the speaker is “in phase” with the rest of the speakers. When this happens, the sound immediately improves and the amp is not fighting itself internally.

AC Voltage Audio Waveforms

Low ESR Capacitors

What is ESR?

ESR is an abbreviation for Equivalent Series Resistance, the characteristic representing the sum of resistive (ohmic) losses within a capacitor. While ESR is undesirable, all capacitors exhibit ESR to some degree. Materials and construction techniques used to produce the capacitor all contribute to the component's ESR value. ESR is a frequency dependent characteristic, so comparison between component types should be referenced to the same frequency. Industry standard reference for ESR is 100KHz, +25°C. ESR is an important characteristic, as the power dissipation (watts) within the capacitor, and the effectiveness of the capacitor's noise suppression characteristics, will be related directly to the ESR value.

What's driving demand for Low ESR?

An industry wide trend towards lower voltage - higher current circuit design, fueled by lower voltage silicon devices is causing designers to specify capacitors with minimal ESR. Higher levels of functionality in today's designs means that despite voltage level falling, circuit power levels have not dropped accordingly. Ohms law tell us, in every simple fashion, that at the same power dissipation level, lower voltage operation will mean higher current levels. This greatly increases the demands on the power management circuit (power supply or DC/DC converter) to deliver energy during periods of high current load stepping. Lower voltage circuit operation also imposes greater restrictions upon the output voltage variation level as well. The output capacitors or capacitor bank, used in the power management circuit, need to exhibit low ESR characteristics. Ripple voltage (noise) on the output supply voltage will be directly proportional to the ESR of the capacitor used. By considering the formula: Vr = I x R, where Vr is the ripple voltage and R is the ESR, we can see that if the current (I) increases from say 4A to 20A then the ripple voltage will also increase by a factor of five. Increased ripple voltage (Vr) cannot be toleranted in todays and next generation designs. This is fueling demand for very lower ESR capacitors.

What types of Low ESR Capacitors are available?

Capacitance values greater than 10ìF are often required to supply energy to today's electronic circuits, during load current stepping (low to high current stepping). This requirement is met through the use of single or multiple surface mount (SMT) electrolytic capacitors or combination electrolytic and high capacitance MLCC (ceramic chip) capacitor. Surface mount configurations are preferred as it allows closer component placement, reduces performance robbing series inductance and can reduce total PCB assembly costs. Recent low ESR electrolytic capacitor development has focused on techniques and materials designed to reduced the resistance of the cathode connection, either with a lower resistivity solid electrolyte. The cathode connection of electrolytic capacitors is the largest contributor to the electrolytic capacitors total ESR figure.

Low ESR SMT capacitors available today chiefly fall into 7 types.

ESR = Equivalent Series Resistance (ohm)

RCR = Ripple Current Rating (Amp)

1. LIQUID ELECTROLYTE, VERTICAL CAN CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Lowest cost solution.

Pros: High capacitance values, high voltage ratings, moderate to low ESR, moderate RCR and lowest cost.

Cons: Liquid electrolyte exhibits dry-out under high temperature, medium to large sizes.

2.HYBRID ELECTROLYTE, VERTICAL CAN CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Provides solid electrolyte performance (very low ESR) at much lower cost than solid electrolyte types.

Pros: Very Low ESR, High RCR, moderate capacitance values and moderate cost.

Cons: Liquid electrolyte component exhibits dry-out under high temperature, low voltage ratings and medium sizes.

3. SOLID POLYMER ELECTROLYTE, VERTICAL CAN CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Lowest ESR and highest RCR of the vertical can chip types, but at highest cost.

Pros: Very Low ESR, High RCR, moderate capacitance values and solid electrolyte for good long-term performance at high temperature.

Cons: High cost, low voltage ratings and medium sizes.

4. SOLID POLYMER ELECTROLYTE RESIN ENCAPSULATED FLAT CHIP ALUMINIUM ELECTROLYTIC CAPACITORS

Low ESR and high RCR, but at highest cost of all aluminium electrolytic types.

Pros: Very Low ESR, High RCR, Smallest size aluminium electrolytic type, moderate capacitance values and solid electrolyte for good long-term performance at high temperature.

Cons: High cost and low voltage ratings.

5. SOLID ELECTROLYTE, RESIN ENCAPSULATED FLAT CHIP MnO2 CATHODE TANTALUM ELECTROLYTIC CAPACITORS.

Standard tantalum chip capacitor construction processed for low ESR.

Pros: Moderate to Low ESR, Moderate RCR, Small size, Low ESR versions produced with manganese dioxide cathode (MnO2) construction and solid electrolyte for good long-term performance at high temperature.

Cons: Low voltage rating and limited transient (reverse or surge conditions) tolerance, could combust upon failure.

6. SOLID ELECTROLYTE, RESIN ENCAPSULATED FLAT CHIP POLYMER CATHODE TANTALUM ELECTROLYTIC CAPACITORS.

Standard manganese dioxide cathode (MnO2) is replaced by a highly conductive polymer (polypyrrole) cathode that considerably reduce ESR. The conductivity of polypyrrole is more than 100 times that of manganese dioxide.

Pros: Very Low ESR, High RCR, Small size, polymer cathode construction suppresses combustion = increased safety factor and solid electrolyte for good long-term performance at high temperature.

Cons: High Cost and low voltage ratings.

7. MLCC - SURFACE MOUNT CERAMIC CHIP CAPACITORS.

Capacitance values up to 100uF are available today in ultra-small sizes.

Pros: Ultra Low ESR, Moderate RCR, Smallest size, Non-polarized for applications where reverse operation or transient conditions occur, High temperature rating and good soldering heat exposure characteristics.

Cons: Low voltage ratings, Large effective capacitance loss under VDC operation, Capacitance decrease over time (aging), Piezoelectric effects.

Summary

Circuit designs incorporating lower voltage semiconductors and IC's are driving increasing demand for better and lower ESR capacitors. SMT low ESR type electrolytic capacitors offer the combined solution of high capacitance, to supply energy during high-speed load stepping, and low ESR to reduce the output filter ripple (noise) voltage to meet the needs of today's and tomorrow's power management design challenges.