CFA level 1

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Photography for Newbie

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Basic Techniques What is a “stop”? A stop in photography term is the measurement of light (measured in EV). +1 stop means that the light is double from the current value. Similarly, -1 stop means half of the light entering your camera. Of course you can have 1/3 stops or 1/2 stops. What are the common ISO values for a film? ISO is the measure of the sensitivity of the film, and the common ISOs are: 50, 100, 200, 400, 800, 1600, 3200, and 6400. Each of these is 1 stop away from the next, e.g. ISO200 is double the sensitivity of ISO100. There are other ISO films/settings available in between. What is a shutter? Shutter in most SLRs is film plane shutter and it is the blade in front of the film plane that controls the amount of light hitting the film. It is normally closed and opens briefly when you press the shutter release button to expose the film. Another type of shutter is diaphragm shutter and it is usually mounted on the lens. A 3rd type of shutter is electronic shutter used in some digicams. What are the common stops for shutter speed? Common shutter speed goes like this: 30”, 15”, 8”, 4”, 2”, 1”, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000, 4000. Each of these is 1 stop away from the next. Notice that they roughly double the value from the next, as when we double the time, double among of light will enter the camera. What is an aperture? Aperture is the diaphragm located in the lens for controlling the amount of light entering the lens. Aperture sizes are stated as (focal length)/(f-stop value), e.g. f/8, meaning the area of the opening is the current focal length of your lens divided by 8. Notice that at a given f-stop, e.g. f/8, the aperture opening is smaller for wide angle when compare to telephoto. Since we are talking about area, when it doubles it is multiply by square root of 2 of the previous one. Hence it goes from 1 to 1.4 to 2 to 2.8, etc. (see below). What are the common stops for aperture (f-stop)? Common aperture goes like this:  f/1 (widest), f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32 (narrowest). Again, each is 1 stop away from the next. An easy way to memorize them is that they multiply in pairs. ( 1-2-4 , 1.4-2.8-5.6) How do we calculate stops? Assuming the light entering the camera remains constant, we can play around with the value of the ISO, shutter speed and aperture value while maintaining the same exposure. Ex 1: Assuming ISO 100 is constant. f/8 at 1/250s is equivalent to f/11 at 1/125s. Why? When we set the aperture from f/8 to f/11, we are reducing the light by 1 stop (half the amount of light now enters the camera). So to maintain the same exposure, we need to increase 1 stop from the shutter speed, hence 1/250 to 1/125 (time now is double, so we have double the light). Ex 2: Assuming shutter speed is fixed at 1/250 and initially ISO is 100. Aperture is f/5.6. If we change the aperture to f/11, what is the ISO value we need to maintain constant exposure? Since from f/5.6 to f/11 are -2 stops, we need +2 stops from ISO, hence we need ISO 400. How do shutter speed and aperture affect a picture? High shutter speed is used to freeze a motion while slow shutter speed is used to create “motion blur”. Smaller aperture has a greater depth of field (DOF) and larger aperture a shallow DOF. Shallow DOF is useful for subject isolation. 3 factors that affect DOF are: aperture size, focal length, and object to camera distance. Wider aperture size (smaller f-stop number), longer focal length, and shorter object to camera distance all decrease DOF, resulting in a blurer background. How can I reduce camera shake? A few things you can do. Fist of all, learn the correct shutter release squeezing technique. The way to do it is to lightly tap on the shutter release button to achieve autofocus. Once everything is in order, lightly squeeze the button all the way down. Second, pay attention to the shutter speed. As a rule of thumb, the minimum shutter speed is 1/focal length, so e.g. you are at 200mm, the shutter speed should be above 1/250s. If not, you’d better find something stable to support your camera (e.g. top of car, railing, lamp post) or use a tripod. Thirdly, tug your elbows in to form a triangle to support the camera. If you are using an SLR, use your forehead to support the camera too. Why is my digicam having deeper DOF at the same focal length and f-stop when compare to an SLR? Anybody like to answer this? Since the sensor size digicam is much smaller then the standard 35mm size on the SLR, its lens has a shorter “equivalent focal length” then the SLR’s. Remember from above, the aperture size is (focal length)/(f-stop value)? Now at f/8, the actual aperture size on the digicam is much smaller then that on the SLR, resulting a deeper DOF. What is the relationship between focal length and perspective? When we zoom from wider angle to telephoto, if we tried to maintain the same subject size, the background will appear to be further away from the subject at wide angle and closer at telephoto. This is called perspective compression and is also a useful technique for subject isolation. What other techniques are available for subject isolation? Some other effective ways for subject isolation is by using contrast and/or color difference between the main subject and the surrounding/background. What are program, aperture priority, shutter priority, and manual mode? In program mode, the camera sets both the aperture and shutter speed according to the exposure value measured by the meter. In aperture priority mode, you set the aperture you want, and the camera selects the shutter speed according to the metering. In shutter priority mode, you select the shutter speed while the camera sets the aperture. In manual mode, you control both shutter speed and aperture. Note that the meter does not come into play in manual mode (except for indication), hence exposure compensation has no effect in this mode. Metering What are the different metering modes? In matrix (evaluative) metering, the camera uses multiple segments of sensors divided across the frame to measure the scene and decides the best exposure value based on the data pre-stored in the camera’s firmware. In center-weighted metering, the measurement is based primarily on a center circle in the viewfinder (how big is the circle depends on your camera). Spot metering determines the exposure by concentrating on a small area at the chosen metering spot. When to use each mode? Matrix metering is generally the easiest and most commonly used. However, in tricky lighting situation, the camera can be fooled (e.g. backlight or snow condition). In this case you can use the spot meter to help you achieve the proper exposure. Center weighted mode is used when your subject is large and you want to use the average of the entire object for exposure. What is mid-tone and what is its relation with the meter? Mid-tone is 18% gray when we go from black to white. Our eyes see things in logarithm manner, so middle gray is at 18%. Mid tone is not limited to gray, and can be red, green, blue, or other colors, as long as it is at 18% value. How does this relate to the meter? All meters measure the exposure and give the result in 18% gray. This means that if you use spot meter and white piece of paper, the paper will appear gray in your pic. Matrix metering will try to correct it by referring to the data stored in the camera. So how do we use spot meter? You can get the exposure value of a given lighting condition by taking measurement off an 18% gray card. Or, you can learn to compensate by experience (e.g. pure white is about +2 stops then mid tone, while pure black is –2 stops). When is spot metering useful? One example where spot metering comes in handy is when you have backlit situation. In this case, the light source is behind the subject (e.g. a model), so what you do is spot meter off the model’s face. You then compensate the exposure depending on the skin tone of the model. What is bracketing? When you turn on bracketing, the camera will take 3 consecutive pictures: the normal one, one with a lower exposure compensation and one with a higher compensation. E.g. if you set the bracketing value to 1/3EV, the shots will be taken with –1/3EV compensation, normal, and +1/3EV compensation. This is done when the photographer isn’t quite sure of the actual exposure value, and kiasu a bit doesn’t hurt. J Flash Why are some people turning on the flash in broad daylight? What they are doing is called “fill flash”. In very strong sunlight under sunny day, the subject’s (e.g. a model) face is unevenly lit. To have a more natural look, fill flash is used. In auto fill flash mode the camera will automatically determine the correct amount of flash to fire to properly expose both the subject and the background. Another way of doing this is by using one or more reflectors. When should I not use the flash? When taking night scenes! Your flash won’t be powerful enough to light up the whole building/mountain especially when they are so far away! Use a tripod instead. Only use the flash when taking foreground objects that are within your flash range (see 21 and 23 below). What is “guide number”? Given a focal length and an ISO, guide number of a flash = subject distance * f-stop. The higher the guide number, the more powerful your flash is and the further away it can shoot. For example, for a flash of GN = 12 (at ISO 100, m, 50mm), it means that using a 50mm lens and an ISO 100 film, at f/4 your flash can reach a distance of 12/4 = 3m away. What is flash sync speed? When the flash fire, it only fires for a very short moment. For camera with film plane shutter, the shutter actually opens and closes by 2 blades. The 1st blade opens up the film plane and the 2nd one closes it. So there exists a time when the 1st blade just finish passing the plane when 2nd one just start to close up. This is the flash sync speed of the camera. Any shutter speed higher then this would mean that the 2nd blade closes in before the 1st one leaves the plane. This resulted in a slit narrower then the original film plane, and if the flash fires momentarily, it will only illuminate part of the film exposed by the slit. Different camera has different flash sync speed. Diaphragm and electronic shutters do not exhibit this limitation. What is slow sync mode? In this flash mode, the camera continues to open the shutter after firing the flash to illuminate your main subject, so that the darker background can be captured. E.g. you can use this mode at night to shoot people with a night scene, without which the background would appear dark. To use this mode, you must set up a tripod. What is rear sync mode? In this flash mode, the camera fires the flash at the end of the exposure of the slow sync mode. This mode is effective in capturing a subject that moves, resulting the subject leaving a trail of light behind. Tips for taking better pictures What makes a good picture? A good picture is always produced by a photographer who thinks ahead of what he/she wanted to express before pressing the shutter. Think of each picture as an essay to describe something. Ask yourself what do you want to write in the essay. You’ve not succeeded if the viewers look at your picture and never say “wow!” What is “rule of thirds”? When a subject is placed at the center of a frame, it usually looks boring and static. A better way of placing the subject (or anchor points) is to put it (them) at the “thirds”. Looking into your view finder/LCD, try to imagine the frame is divided into 3 equal parts both vertically and horizontally. These dividing lines are the “thirds”. Try it out now. Why is it important to keep the horizon level? The horizon of the earth represents the ground, and we are used to seeing them, well, horizontal. Imagine a picture with the sea horizon slanting one side. Won’t you naturally expect the water would pour out of the picture? J Can the above rules be broken? Of course you can, rules are meant to be broken! Once you mastered these rules properly, you can break them to achieve more creative form of photography. In other words, a subject doesn’t always need to be at the 3rd! Try to use your imagination, be creative, and experiment. How to make effective use of space in the picture? The amount of space placing in the picture is normally related to personal taste and what the photographer would like to express. For a landscape picture, placing the horizon at the upper 3rd (resulting more space below the horizon) brings a sense of distance, while placing it at the lower 3rd would show the spaciousness of the sky. For a person/subject that is moving, you would probably want him/it to move into the frame, so you leave more space in front of him/it. If you do it the other way, the person would look like he is trying to walk out from your picture. What is framing? Framing is another method to bring attention to your subject. You enclose the subject with some surrounding objects.  Please ask the instructor to demonstrate. J How would lines and S-curves affect the photo? S-curves and lines that exist in nature or man made buildings can be used to lead the eyes to your subject. A photo with an s-curve normally looks more graceful. What is anchoring? Anchoring refers to insertion of point of interests into your picture to hold the picture together. E.g. you are shooting a seaside sunset. The picture would be rather plain if it is just the sun, the sky and the sea. Now if you include one or 2 seagulls or silhouette of a couple into the picture, they become the anchors and make the scene more interesting. What is layering in landscape photography? Layering is a technique used in landscape photography to divide the picture into 3 parts: foreground, center and background. This injects a sense of dimension into the otherwise rather empty picture, and leads the viewers’ eye. Why is subject isolation important? Each photo is supposed to have one and only one subject/topic. The topic can either be an object, a person, an expression, a relationship, a feeling, or a view that you, the photographer, would like to tell your audiences, the viewers. By picking out the subject that you want to photograph and isolating it from the surrounding, you are focusing the viewers’ attention to what you want to express. Any other objects in the photo that is not part of your topic or at least complement your main subject are just distraction and shouldn’t be there. If they do complement the subject, they should not overpower it. Why is lighting important? When god created light, there came along the shadows. A good mix of light and shadows can usually add a lot mood to a picture. Different lighting will give different feel and impact. A few of the different lighting: spot light, high/low key light, backlight, moody light, and colorful light. Use them effectively to create beautiful pictures. (Please ask the instructor to illustrate). Any other composition tips? If possible, try shooting a subject from different angles. Eye level is usually the most common but unimpressive angle. Try an angle higher then the eyes by climbing on top of something (e.g. going to the 2nd floor of a building) or a lower angle close to the ground. Look around the subject to find a clean background so you can better isolate the subject. Choose an angle that minimizes the distractions. Move your feet, walk around. Simple is great. Simple is better. Try to keep your picture simple and uncluttered A common mistake made by most newbies (myself included) is to try to include too many things in your picture. As mentioned above, try to isolate your subject, remove all the irrelevant stuffs and include only those that support your subject/topic. Others How to take fireworks? Use lower ISO so that you can open up your shutter longer. Find yourself a good position, set up the camera on the tripod, and use a shutter release string and bulb mode. If possible, anticipate when the next firework will shoot, and open the shutter before that so that you’ll catch the “tail”. Use f-stop of f/11 or f/16, and approximate exposure time of 2-5 secs. How to make “silky water” out of the river/waterfall? Depends on how “silky” you want the water, use a shutter speed that is slow enough for your taste. You can experiment by starting from 1/30s and longer. Remember to use a tripod. In sunny days you might have trouble achieving low shutter speed – in this case, an ND (neutral density) filter will help. NDx2 will reduce a stop, NDx4 2 stops, and NDx8 3 stops. They can be stacked. How to shoot the “streaks of lights” on city streets? Again, the trick is using long exposure. Set your camera to shutter priority mode and choose a shutter speed that is “long enough” to make the streaks of your liking. Take care to check the aperture value such that it is not out of your camera capability. Put your camera on a tripod, and release the shutter when the traffic is moving. You can either use a shuttle release string or the timer, but with the timer capturing the right moment can be tricky. Experiment and shoot until you are satisfied. How to proceed from here? Take more photos! Think before you shoot, and when you are not shooting, look at other people’s photos. If you like them, ask yourself why is it good. If not, ask yourself why not? Learn the good and bad points about them, and do the same for your own photos. Recommended books for reading: John Shaw’s Nature Photography Field Guide John Shaw’s Closeups in Nature That’s all. Good luck and happy shooting. And thanks for coming. DOF Meter Please print out 2 copies of the following. Cut out the outer circle on one piece and the inner circle on the other. We’ll use this as a rotating chart during the course. This chart is optimized for DSLR with 1.5x multiplier (circle of confusion = 0.020mm) Where to get the DOF Meter: http://dfleming.ameranet.com/custom.html

Article by David Wong 2004

30D Tutorial

1. Ken Rockwell

• 30D General
• 30D Control

Polarizer tricks… and links

Source

There are some caveats in using the polarizer. It can be really useful at times but I would not advise to keep it on your main lens at all times. The main reason for this is that it will make the use of a tripod compulsory with slow film or low light conditions. There are specific cases when you should not use a polarizer.

Situations where the use of a polarizer is not desirable

• Overcast weather
  The polarizer does not make the clouds “stand out” in uniformly overcast weather. All it does is turn them a little darker. You still lose 1.5 stops of light, though.
• Evening light
  In the evening, the skies naturally turn darker. It would be tempting to keep the polarizer on your lens to get dark blue skies, but the risk is to overdo the effect and get unnatural things.
• Night
  Honestly, I have never really tried to use a polarizer at night. Apart from potentially ruining side effects, I would be concerned by the fact that the filter tends to turn the viewfinder darker. As I generally focus manually at night, it would make it even more difficult.

Other potential gotchas

Here are some situations where you should be careful in using a polarizing filter.

• White or clear buildings
  The metering system of most modern SLRs is calibrated to take a medium gray as a reference for metering. If you take a reading from a lighter area – typically a building occupying most of the image – you are likely to underexpose your shot. With a polarizing filter, it will be even worse. You will get really dark – almost black – skies.

  This is more likely to happen with slide film as digital pictures have less contrast. In that case, take the filter off or turn it around so it has no effect and overexpose a bit. Use bracketing to make sure you have at least one acceptable image.

• Uneven effect
  When shooting outside with an ultra wide lens, you are likely to cover a wider sky area and will certainly get both darker and lighter zones in the sky, depending on your orientation.You will also have a difference between the area close to the horizon and the top of your image in vertical views, because of haze.
  These differences are amplified by the polarizer and can get distracting.
• Vignetting
  Be careful when choosing a filter to fit on a wide angle, especially on a zoom. At the wider angles, there can be a visible light falloff on the edges. To avoid this, get a polarizer specially designed for wide angles. Singh Ray makes a wide angle polarizer and Hoya has a range of “slim” filters. Be aware that the price for these will be all but slim!

More polarizers… and links

Some makes propose filters that do more than usual polarizers. Some add an UV filter to the polarizing effect, others a color filter. I have not tried them yet, but the warming polarizer looks tempting. You will find information on the following websites:

• Thkphoto proposes Hoya filters (if you find an official Hoya website, please let me know!)
• Singh Ray has a whole range of polarizing filters including
  - Gold n Blue polarizer
  - Warming polarizer
  - Red-Ray™ Polarizer
• Cokin proposes circular polarizers in addition to its famous range of P and A mount filters
• Some camera brands such as Canon also have a range of polarizers.

Other articles

Here are other articles about polarizers

• Naturephotographers has a great article in its online courses section.
• Luminous Lanscape has an intersting article called “understanding polarizers”

Polarizing filter tips

Source

The polarizing filter is one of the most useful filters for outdoor photography. It should really be in every serious photographer’s camera bag.
Polarizing filters exist for most camera types, from medium format to digital point and shoot cameras. Autofocus SLRs (like the ones I use) need circular polarizers. In these, the front side rotates which enables the user to see the effect gradually appear in the viewfinder.

Polarizing filter effects

Porto gulf The polarizing filter has one main effect: it eliminates reflection from non metal surfaces. It is effective on:

• Skies
  By eliminating the reflection of light on the tiny water droplets present in the atmosphere the polarizer brings more saturated and slighly darker skies. However this does not work from any angle. You will generally be able to assess the effect visually, especially with a SLR camera, but keep in mind that it works best with the sun at 90° from your position. With the sun in front, a polarizing filter will have no effect.
• Water and reflective surfaces
  By eliminating reflections, the polarizing filter will tend to make water and other reflective surfaces more transparent. The effect will also vary depending on the angle to the reflective surface. If you place your camera very low above a river, the effect will be very limited. If you shoot from a bridge above it, the water will look totally transparent.
• Colors
  The polarizing filter also reduces reflection from other surfaces such as foliage and thus makes their colors look more intense. It also tends to make shadow areas darker.
• Light absorption
  The main side-effect of the polarizing filter is that it absorbs 1.5 stop of light. Thus if you shoot at 1/180th of a second and then add the filter, you will find yourself at 1/60th of a second. This happens whatever the orientation for a circular polarizer. This does not make a polarizing filter quite usable in low light or indoors but has some interesting uses as pointed out below.

Choosing a polarizing filter

On top a classic BW polarizer
below a wide angle HOYA polarizer.
Notice the difference in thicknessOn SLR cameras, the usual polarizing filter has to be screwed onto the lens. Of course, you need to pay attention to the diameter of the ring. It is generally mentioned on the lens itself.
The wider the lens, the more expensive the polarizer. I never purchased one for my 82mm wide Sigma 20 because of its price.
Cokin and Singh Ray both proposer filters that fit the Cokin filter mounts.

Autofocus SLR cameras need circular polarizers.

For wide angle lenses (24mm or less), you will probably need to pay attention to the filter you will purchase or you might get vignetting (darker corners on your pictures). On slower lenses, such as my 17-40L, this is not much of a problem, but I was told it would be different with the faster 16-35L.

The solutions are the more expensive slim filters or the more affordable wide angle polarizers, the latter being what I use on my 17-40L. Both generally do not have an outer ring, so you will generally not be able to use another screw-in filter on top of them or even use your regular lens cap.

Using a Polarizing filter

Using a circular polarizing filter on a SLR camera is easy. Just turn its front part to adjust the effect and watch it appear in the viewfinder.
Remember that the effect is stronger when you have the sun at 90° on your left or right. It will be less visible with the sun in your back and almost non-existant with the sun in front.

Here are the main situations in which I find a polarizing filter useful.

Bright sunny days
This is where the polarizer effects will be most interesting. The best effect will be achieved on a sky with small clouds.

	Without a polarizer – digital. The water keeps its reflections and the skies look a bit washed out.
	With a polarizer – digital. The water gets transparent and the clouds now stand out nicely. Also notice that the trees on the left have brighter colors. The water is not totally transparent as the effect fades with distance… in fact as the angle changes.
	With a polarizer – slide film. As slide film naturally looks more contrasted and punchy than digital pictures, the effect of the polarising filter seems to be more visible with really bright skies.

FTM

Question

How do I use Full Time Manual (FTM) focusing with my Canon 85mm 1.8 lens?

Canon lens manual says to “press the shutter button halfway and turn the focusing ring”. Is it necessary to press the shutter halfway as stated by manual? I have done FTM focusing with and without pressing the shutter halfway. FTM works fine without pressing the shuter halfway. But when I pressed the sutter halfway and use FTM, lens made a grinding noise – like changing gears. Is this normal? Why bother pressing shutter halfway when FTM focusing can be done without pressing the shutter? BTW this is a new lens.Also, is it OK to mount a cheap rubber hood ($3 hood)on the UV filter attached to my Canon 85mm 1.8 lens?

Answers

You can flip the AF/MF switch on the lens to MF and focus manually forever without any problems. “Full Time Manual Focusing”, as referred to in the EF lenses with USM motors, however, means you can manually adjust focus after autofocusing. Press the button, let the lens focus and then adjust focus with the manual focusing ring without lessening pressure on the shutter release. No need to flip the AF/MF switch. Be sure the camera is set to One Shot focusing. If you’re set on AI Focus or AI Servo, the lens will try to continue to autofocus while you’re trying to manually adjust focus. It sounds as if you’re probably set on AI Focus/AI Servo if you’re getting a grinding noise. That’s the internal autofocus mechanism eating itself up as it tries to fight back your attempt so manually focus.

Cheap rubber lens hoods don’t look cool. But they are better than nothing if you need a lens hood.

loneliness

It’s not the first time. It would not be the last.

Not because of no sunshine today. Not because of the depressing weather of January in a foreign country.

I’m still wandering in my life. Searching for what I have lost in the past. Though I know, what has been lost could never return again. Look around, I have nothing. The most precious thing I could ever have, is she. Though between us were rows and conflicts, what we had are just unforgettable. Just a matter of time, just the problem that we were too young, too immature to understand and overcome. I let her go, let my precious thing in life slip away. And I could never get it back. There were others who came into my life after her, but after all, I still couldn’t find the same person. The burning love, sacrifice, smartness, craziness, just everything …

I’m just afraid that day will happen, the day someone will send me … an invitation …

Deep in sorrow

Sleep Secrets

Found this from google. A good article for people who haven’t known about that before . Take note of REM sleep, remember that waking up time is Stage 1 and 2!

Recommended sleep length is 5 hours/day. The biggest problem is overcoming sleepiness. @ction Point!

Stages of sleep: the sleep cycle

Sleep is a periodic state of rest during which consciousness of the world is interrupted. Additionally, sleep is marked by:

• decreased movement of the skeletal muscles;
• a relaxed posture, usually lying down;
• reduced response to stimulation, such as sounds and touch;
• slowed-down metabolism; and
• complex and active brain wave patterns.

Sleep is divided into two types: REM (Rapid Eye Movement) sleep and NREM (non-REM) sleep. REM sleep is when we dream. NREM sleep is further divided into four stages. A typical night of sleep follows this pattern:

• Stage 1 (Drowsiness) – When you first fall asleep, you are in Stage 1 sleep (Drowsiness). Stage 1 lasts just five or ten minutes. Eyes move slowly under the eyelids, and muscle activity slows down. You are easily awakened during Stage 1 sleep.
• Stage 2 (Light Sleep) -Next, you go into Stage 2 sleep (Light Sleep). In Stage 2, eye movements stop, heart rate slows, and body temperature decreases.
• Stages 3 & 4 (Deep Sleep) – Then you enter Stages 3 and 4 (Deep Sleep). During stages 3 and 4, you are difficult to awaken. People who are awakened during Deep Sleep do not adjust immediately and often feel groggy and disoriented for several minutes after they wake up. Children may experience bedwetting, night terrors, or sleepwalking during Deep Sleep.
• REM sleep (Dream Sleep) – At about 70 to 90 minutes into your sleep cycle, you enter REM sleep. You usually have three to five REM episodes per night. Your eyes jerk rapidly in various directions under your eyelids, thus the name Rapid Eye Movement (REM) Sleep.

The first sleep cycles each night contain relatively short REM periods and long periods of deep sleep. As the night progresses, REM sleep periods increase in length while deep sleep decreases. By morning, people spend nearly all their sleep time in stages 1, 2, and REM.

What happens during the REM sleep stage?

During REM sleep, you dream actively, but your limb muscles are immobile. Your breathing is rapid, irregular, and shallow. Your heart rate increases, your blood pressure rises, males may have penile erections, and females may have clitoral enlargement. Your brain is at least as active during REM sleep as it is when you are awake.

Because your major muscles do not move during REM sleep, you will not act out your dreams. (Sleepwalking occurs during NREM sleep.)

Infants spend about 50 per cent of their sleep time in REM sleep; after infancy, you spend fifteen to twenty per cent of your sleep time in REM sleep.

The importance of deep sleep and dream sleep

Each stage of sleep offers benefits to the sleeper. However, deep sleep is perhaps the most vital stage, as it is the first stage that the brain attempts to recover when we are sleep deprived. If we do not get adequate deep sleep, we experience the strongest effects of sleep deprivation.

Deep sleep allows the brain to go on a little vacation needed to restore the energy we expend during our waking hours. Blood flow decreases to the brain in this stage, and redirects itself towards the muscles, restoring physical energy. Research also shows that immune functions increase during deep sleep.

REM sleep, or dream sleep, is also very important. This stage is associated with processing emotions, retaining memories, and relieving stress. Our brains suspend logic, and we lose all self-awareness – which is why we can experience ridiculous, irrational events in our dreams and believe them to be true.

If our REM sleep is disrupted one night, our bodies don’t follow the normal sleep cycle progression the next time we doze off. Instead, we often go through extended periods of REM until we “catch up” on this stage of sleep. But, if deep sleep has been lost as well, our brain attempts to catch up on this stage first – in fact, the brain will try and make up all of the deep sleep it has lost and only half of the REM sleep.

… Colder and Older, sometime …

Tự nhận thấy mình đang sống hơi đơn điệu. Ít bạn bè, thiếu đam mê, không có một mục tiêu thực sự trước mắt. Những điều xảy ra trong cuộc đời đến nay, hình như đều do số phận … Có bao giờ tự quyết định được cuộc đời (!?)

Bắt đầu blog mới, tự hứa rằng sẽ cố gắng ghi lại thường xuyên và đầy đủ những chuyện đang diễn ra. Ít nhất cũng giúp giảm đi thói đãng trí nữa mùa, cố tình hay vô tình, quên những thứ nên nhớ, phải nhớ và cả không nên nhớ …

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