Basic Techniques
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.
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.
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.
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.
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).
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)
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.
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.
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.
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.
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.
Some other effective ways for subject isolation is by using contrast and/or color difference between the main subject and the surrounding/background.
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
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.
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.
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).
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.
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
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 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).
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.
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.
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.
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
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!”
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.
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
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.
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.
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
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.
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.
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.
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.
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).
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
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.
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.
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.
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:
That’s all. Good luck and happy shooting. And thanks for coming. DOF MeterPlease 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: |
| Article by David Wong 2004 |
Archive for the ‘Photography’ Category
Photography for Newbie
Posted by 1rtxud on January 21, 2008
Posted in Photography | Tagged: Technique, Terminology | Leave a Comment »
30D Tutorial
Posted by 1rtxud on January 21, 2008
1. Ken Rockwell
Posted in Photography | Tagged: 30D, Tutorial | Leave a Comment »
Polarizer tricks… and links
Posted by 1rtxud on January 21, 2008
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”
Posted in Photography | Tagged: Filter, Polarizer | Leave a Comment »
Polarizing filter tips
Posted by 1rtxud on January 21, 2008
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.
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Without a polarizer – digital. The water keeps its reflections and the skies look a bit washed out. |
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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. |
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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. |
Posted in Photography | Tagged: Filter, Polarizer | Leave a Comment »
FTM
Posted by 1rtxud on January 20, 2008
Question
How do I use Full Time Manual (FTM) focusing with my Canon 85mm 1.8 lens?
Answers
Posted in Photography | Tagged: Technique | Leave a Comment »
