Digital SLR Lens Reviews / Slr camera lens

In this age of the general purpose digital camera, the concept of focal length, lens aperture, focal ratios, and many other photographic technical terms have become somewhat obsolete for most digital camera users. One basis reason for this is the fact that most basic digital cameras used these days do not require such knowledge as the knowledge might not be able to be applied to a basic digital camera, let alone a digital phone camera.

The situation is very different for the serious amateur photographer. Specially those using digital single lens reflex cameras (from now on in this article shortened to DSLR). Serious starting out amateur photographers will need to understand such terms as focal length, aperture and focal ratio. Particularly they need to understand these terms in order to get the best results. Okay, what do these terms mean?

- Focal length is simply the distance from the lens to the focal plane of the imager.

- Aperture is the usable diameter of the lens opening.

You need to understand both terms…focal length and aperture as each has a relationship to the other. The relationship between focal length and aperture is referred to as the “focal ratio”. The “focal ratio” (f-number) is calculated by dividing the focal length of a lens by the camera lens aperture .

Example:

The lens system of a camera has an aperture( usable diameter of the lens opening) of 50mm. The focal length of the lens is 500mm Therefore the focal ratio = 500/50 = 10. The focal ratio is generally written as f/10. e.g. the lens has a focal ratio of f/10

Now you understand how to calculate the focal ratio the next question should be “So what?”. Well, for the serious amateur photographer, particularly those using DSLR cameras, the “focal ratio” is essential knowledge due to a photographic concept referred to as “lens speed”.

Okay…what is meant by “lens speed” and why is it important?

The term lens speed refers to the “maximum aperture diameter”, or “minimum f-number”, of a photographic lens or lens system. When using a lens possessing a larger maximum aperture (that is, a smaller minimum f-number) the lens would be nominated as a fast lens. The reason being it delivers more light intensity (illuminance) to the focal or image plane, permitting a faster shutter speed. If the lens has a smaller maximum aperture (larger minimum f-number) then the lens would be classified as “slow” because it delivers less light intensity and needs a slower shutter speed.

Camera lenses are classified as “fast” or “slow” . This is vital information for photographers as the Llns speed given by the minimum f-number, or conversely maximum aperture diameter, or maximum numerical aperture, is a vital quantitative method in order to compare lenses.

Knowing the lens speed is essential information when photographing in dim light, and moreso when using long telephoto lenses. Being aware of lens speed is also particularly important in order to determine depth of field when undertaking portrait photography. Lens speed is a major variable in tandem with other photographic variables such as focal length and camera format size.

The photographer who understands these terms and knows how to apply them to their qw in varying photographic situations will produce excellent results.
Autor : ROSS ST QUIN TIN

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Your digital camera will last longer if you take steps to take care of it from the beginning. Your lens is your digital camera’s eye to the world. It is a very sensitive part of your camera. Your digital camera will last longer and take better photos if your keep your lens clean.

Some preventive measures you can take are not to touch the lens with your fingers. Once the lens is scratched, you will need professional assistance to repair the damage. Your fingers can also leave oils from your skin, which are not easy to remove. When your digital camera is not in use, always put on the lens cap. This is such an easy task but it will save your lens from getting dusty or dirty. Many new point and click digital cameras have an automatic cap that closes over the lens when the camera is turned off. This is a great added feature to look for when buying a digital camera.

You need to keep the body of your digital camera clean and free of dirt and dust. Keep your camera in a case or bag when you are not using it. If the digital camera does get soiled use a soft lint free cloth to wipe it off.

Clean your lens only when necessary. A little dust won’t affect your photos. These hint may help you clean your lens.

* Before cleaning your lens, hold your digital camera upside down and use a bulb brush (a bulb blower and brush combination tool) or lens pen to get any dust off your lens. The lens pen has a moveable brush on one end with non-liquid cleaner on the other end to remove fingerprints and smears.

* Or you could use a can of compressed air to remove dirt or dust. Be careful with the compressed air by suddenly lower the temperature it can crack or damage the lens. The can of air can blow contaminates on your lens along with the air. If you decide to use the can of air instead of the bulb, hold the can straight and start blowing before you aim it at the lens. This should remove the dust from your lens.

* Now for any stuck on dirt you will need to use a lint free cleaning cloth and lens cleaning fluid. Never use a dry cloth on your lens. And never a use a napkin, paper towel, facial tissue or eyeglass tissues. These may scratch your lens. Always put the cleaning fluid on the cloth never on the digital camera. Don’t take the chance of getting the fluid under the lens. Use a light circular motion to clean your lens.

* You can also buy a microfiber cloth, which is antistatic and won’t scratch, streak or smear the surface. This microfiber cloth will only needs lens cleaning fluid for stubborn smudges.

A little care and proper tools can keep your digital camera taking photos for a long time.

Submitted By: CARL WILSON

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Digital cameras are one of the greatest inventions of modern times. We are so fortunate to have this modern convenience called Digital Photography. To be able to capture a precious moment or beautiful scene at the click of a button, is something we should not take for granted.

Many beginners find digital photography rather challenging and rightly so. Today, more and more digital cameras are being created and it seems like the more digital cameras they make, the more difficult they become to use.

I own a Canon Powershot S3 IS. I purchased this digital camera about a year ago and I still haven’t utilized all of the awesome little features this camera has to offer. Now you may not want or even need a camera with tons of features. It really depends on the type of pictures you plan on taking.

Regardless of the camera you own or are planning to own, you should have a well rounded knowledge of digital photography. I hope the following 20 tips for taking digital photography will prove to be useful in your quest for taking better photographs.

1. Know your camera. One of the biggest mistakes you can make is not taking time to learn about the features of your camera. Don’t be lazy. Read your instruction manual.

2 - When shooting sunny outdoor shots, try adjusting your white balance setting from auto to cloudy. The auto setting will make your shots appear too cold. When you change it to cloudy, it will increase the warmth of your pictures.

3 - If you are looking for superior image quality, the ability to use a variety of lenses and print large high quality photos, then considering a Digital SLR Camera.

4 - Use your flash outdoors. Sometimes, even on a sunny day outdoors, there is still a need for a flash. If the sun is directly over head or behind your subject, this can cause dark shadows to appear on the face. The flash will help lighten the subjects face.

5- Sometimes simply turning your camera and taking vertical shots can make a world of difference. Experiment more with vertical picture taking.

6 - Do not put your subjects directly in the center of your shot. Move your subject off center to inject more life into your photos.

7 - Learn how to hold your digital camera. One of the most common problems beginners face is the shaking of the camera because they are not holding it properly. Of course, the best way to avoid shaking the camera is to use a tripod. If you don’t have a tripod, then you should be holding your camera with two hands. Put one hand on the right hand side of your camera where you actually snap the photo and the other hand will support the weight of your camera. Depending on the camera, your left hand will either be positioned on the bottom or around your lens.

8 - Learn about the “Rule of Thirds”. This is a well known principle of photographic composition that every beginner should become familiar with. Do a search online and you will find many tutorials on this subject.

9 - Look at other photographers work. Just spending time studying the work of other photographers can provide loads of inspiration.

10 - Join online photography communities. Get active and ask questions.

11 - Do not compare your photography to anyone else.

12 - Do not copy the work of other photographers. Try and develop your own unique style.

13 - Do not leave your batteries in your camera if you don’t plan on using your camera for long periods of time. Some batteries run the risk of leaking and this can damage your camera.

14 - Subscribe to a good photography magazine. Read books on photography.

15 - Find experienced photographers to go out on shoots with.

16 - Post your photographs in online forums. Learn to accept criticism.

17 - Try taking your pictures in RAW format. RAW is a powerful option available in today’s digital cameras where no in-camera processing takes place. This allows you to do all processing using your favorite image editing software.

18 - Don’t buy the most expensive photography equipment right away. Practice and learn about photography using cheaper equipment first. After you have been taking pictures for a while, you will then know what kind of equipment you will need.

19 - Invest in a tripod. Some of us have very shaky hands. If you can’t stop the shakes, then get a tripod. It will make a world of difference.

20 - If you are not able to carry your equipment with you everywhere, make sure you have a note pad handy. This way if you find a nice shot, you can write it down and visit that location at a later date.

Author: Ralph Serpe

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Camera Lenses

In the last section, we saw that at any one point, a lens bends light beams to a certain total degree, no matter the light beam’s angle of entry. This total “bending angle” is determined by the structure of the lens.

A lens with a rounder shape (a center that extends out farther) will have a more acute bending angle. Basically, curving the lens out increases the distance between different points on the lens. This increases the amount of time that one part of the light wave is moving faster than another part, so the light makes a sharper turn.

Increasing the bending angle has an obvious effect. Light beams from a particular point will converge at a point closer to the lens. In a lens with a flatter shape, light beams will not turn as sharply. Consequently, the light beams will converge farther away from the lens. To put it another way, the focused real image forms farther away from the lens when the lens has a flatter surface.

Increasing the distance between the lens and the real image actually increases the total size of the real image. If you think about it, this makes perfect sense. Think of a projector: As you move the projector farther away from the screen, the image becomes larger. To put it simply, the light beams keep spreading apart as they travel toward the screen.

The same basic thing happens in a camera. As the distance between the lens and the real image increases, the light beams spread out more, forming a larger real image. But the size of the film stays constant. When you attach a very flat lens, it projects a large real image but the film is only exposed to the middle part of it. Basically, the lens zeroes in on the middle of the frame, magnifying a small section of the scene in front of you. A rounder lens produces a smaller real image, so the film surface sees a much wider area of the scene (at reduced magnification).

Professional cameras let you attach different lenses so you can see the scene at various magnifications. The magnification power of a lens is described by its focal length. In cameras, the focal length is defined as the distance between the lens and the real image of an object in the far distance (the moon for example). A higher focal length number indicates a greater image magnification.

Different lenses are suited to different situations. If you’re taking a picture of a mountain range, you might want to use a telephoto lens, a lens with an especially long focal length. This lens lets you zero in on specific elements in the distance, so you can create tighter compositions. If you’re taking a close-up portrait, you might use a wide-angle lens. This lens has a much shorter focal length, so it shrinks the scene in front of you. The entire face is exposed to the film even if the subject is only a foot away from the camera. A standard 50 mm camera lens doesn’t significantly magnify or shrink the image, making it ideal for shooting objects that aren’t especially close or far away.

Lenses in the LensA camera lens is actually several lenses combined into one unit. A single converging lens could form a real image on the film, but it would be warped by a number of aberrations.

One of the most significant warping factors is that different colors of light bend differently when moving through a lens. This chromatic aberration essentially produces an image where the colors are not lined up correctly.

Cameras compensate for this using several lenses made of different materials. The lenses each handle colors differently, and when you combine them in a certain way, the colors are realigned.

In a zoom lens, you can move different lens elements back and forth. By changing the distance between particular lenses, you can adjust the magnification power — the focal length — of the lens as a whole.

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