Meanwhile, CCD sensors tend to produce less noise which translates to images appearing sharper. This goes hand in hand with CCD sensors being more sensitive in lower light conditions. Because CMOS sensors are much more available and costs less to manufacture than CCD sensors, cameras with CMOS sensors are usually less expensive.

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Medium format is the largest sensor type in digital cameras for photographic applications. However, it doesn’t come in just one size. Medium format has its own group of sensors, with its own equivalents to the four thirds, APS-C, and full-frame formats. There are a variety of sensor sizes for medium-format cameras, and typical sizes range from around 43.8×32.9mm to 53.7×40.2mm.

The general rule for maintaining sufficient shutter speed for a given focal length, to avoid the appearance of image shake, is to simply use a shutter speed quicker than 1/focal length. Therefore, you should try to shoot a 300mm lens at a shutter speed quicker than 1/300 of a second and adjust aperture and/or ISO to help you achieve that shutter speed.

There’s also the medium-format cameras—the lesser known of the group. These cameras have the largest sensors out of all the available digital cameras for photography, which means they can get pretty expensive.

The Four Thirds System uses a 4:3 image aspect ratio, hence the name, and is featured in cameras like the Blackmagic Design Pocket Cinema Camera 4K. The Micro Four Thirds System uses the same ratio but can also record 16:9, 3:2, and 1:1 formats. It is included in cameras like the Olympus OM-D E-M1 Mark III and Panasonic Lumix G9.

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The APS-C or crop-sensor format is the most well-known and most versatile of the bunch. The APS-C sensor is popular in DSLR and mirrorless cameras alike. Beginners and professionals alike use it thanks to its adaotability.

Focal distance vs focallength

One “side effect” of focal length is image, camera, or lens shake. When you handhold a camera, no matter how steady your hands, between your hands and arms and the mechanicals of the camera, things will be moving when you depress the shutter release. This movement causes blur in an image at varying degrees; sometimes not noticeable and other times, ugh.

As an additional layer of complexity, each bucket has a filter on it that only lets in red, green, or blue light. In essence, each bucket can only collect 1/3 of the total light trying to enter it. For each bucket, the amount of the other colors is approximated. All this information is then converted to the final image you see on your screen.

In relation to focal length, there is not much more you can say about a zoom versus a prime, but it is important to know that there are usually optical tradeoffs for the convenience of a zoom. For a more thorough discussion about the applications of different focal length lenses and the debate between prime lenses and zoom lenses, see my article “Going Beyond the Kit Lens.”

Different digital cameras have different-sized sensors. This causes an effective change in the field of view of the camera, but not in the focal length of a given lens.

Before I go on, I need to say a quick word about “crop factor.” Different digital cameras have different-sized sensors. This causes an effective change in the field of view of the camera, but not in the focal length of a given lens. Because the sensor size is independent of focal length, we often speak of the different field of view produced by a smaller sensor as a “35mm equivalent” field of view or focal length. I will be covering crop factor in an upcoming article but, for the purposes of this article, we will be talking about focal length in relation to 35mm film or a full-frame digital sensor, as it is a standard baseline for discussions on focal length.

The typical APS-C sensor size is different across camera brands. Canon APS-C sensors are usually 22.3×14.9mm, while other brands like Nikon, Sony, Pentax, and more usually feature APS-C sensors with 23.6×15.6mm dimensions. Many cameras including the Canon EOS M50 Mark II, Fujifilm X100V, Sony Alpha a6600, and Nikon Z50 all hold APS-C sensors.

At first, you might think that to achieve the same field of view with different focal length lenses, all you need to do is move closer or farther from the subject. This is partially true, but the way your image changes will be very obvious, even if the subject is about the same size in an image taken with a wide-angle lens and then a telephoto lens.

The groundbreaking EOS-1D was the first Canon camera to carry the APS-H sensor type was, and it launched in 2001. Canon released four more cameras (all members of the 1D line) with the same sensor type before discontinuing it.

focal length是什么

Again, there is no simple yes or no answer to this question. In the last decade or so, CMOS sensors have become a lot more prevalent than CCD sensors. Most consumers cameras and cell phones manufactured today use CMOS sensors. CMOS sensors, in general, use less power, therefore the camera battery will last longer.

Remember, when you are comparing a camera lens/photograph to looking at someone up close with your eyes, you are still viewing them through a wide angle lens...your own wide-angle lens—the eyeball. Your eye experiences that same larger delta between light rays at the edges and the center of the "frame." You would see it more if the eye had a closer minimum focus distance.

Created by Olympus and Panasonic, the Four Thirds System is a standard that allows for the compatibility of lenses and bodies across participating camera makers. Image sensor size is 17.3×13mm with a crop factor of 2.0 when compared to full-frame camera sensors.

Any sensor that is about 1.5 to 1-inch in size or smaller can be found in non-interchangeable lens cameras (your typical point and shoot) and smartphone cameras.

When you shoot through a telephoto lens, you will see the image get virtually “flattened.” This means that the image will appear to have less depth—the background behind your subject will appear much closer, and your portrait will be more flattering to the subject.

Essentially, a sensor is made up of tiny individual photosites. Think of each photosite as a bucket covered by a lid. When an exposure is initiated (press of the shutter button), the lid is uncovered to collect photons of light. When the exposure stops, the lid is placed back on the buckets (photosites). The collected photons are then converted to electrical signal, and the strength of that signal is determined by how many total photons were collected.

The family of wide-angle lenses includes fisheye lenses that can provide more than a 180-degree field of view; much greater than the human eye, including the periphery, so much that if not conscious of it, you can photograph your feet in the frame when holding the camera to eye level. Telephoto lenses, especially extreme “super telephoto” lenses, can narrow the field of view to where it feels like you are looking through a soda straw, albeit a really big and heavy soda straw!

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If you're still craving more, be sure to watch this episode of FocusEd, which discusses lens focal length for photographers. You will learn about what focal length is, how sensor size and lens focal length affects your angle of view, and more!

On a 35mm film camera, it turns out that the angle of view afforded by a 50mm lens provides a field of view that is approximate to the field of view produced by the human eye. (When we say “35mm film camera” we are referring to the size of the frame of film, not the focal length.) We all know that our eyes have a wide field of view and that we also see things off to the periphery of where we are looking—peripheral vision—but, when you look through a 50mm lens on a 35mm camera, what you see is very similar to what your eye sees. Therefore, the 50mm lens, and lenses measured close to 50mm (say 35mm to 70mm, opinions vary) are known, collectively, as “normal” or “standard” lenses.

However, a smaller sensor allows added reach (zoom). For example, on a micro 4/3 sensor, which is has a crop factor of two compared to a full frame sensor, a 200mm lens becomes the equivalent of a 400mm lens. Smaller sensors also allow for an overall more compact camera and lens system, which is convenient for travel and long hikes. Finally, smaller sensor cameras are generally less expensive.

The Canon EOS R5, for example, is a full-frame mirrorless camera option, and the popular Nikon D850 DSLR has a FX full-frame sensor.

I wrote this article as an introduction for photographers new to the world of photography. Therefore, I chose not to dive too deeply into the technical.

Again, unless you are designing a lens from scratch, you, as a photographer, are free from knowing the nuances of measuring focal length and you should keep in mind how lenses of different focal lengths affect the way your images look in terms of proximity, distortion, and perspective. Thankfully, on this subject, the bulk of the math can remain with the engineers!

Unfortunately, when you venture into the telephoto realm of focal lengths, this movement is amplified by the fact that the field of view of the lens is smaller than that of wide-angle or normal lenses. Therefore, it is more difficult to get a sharp image at telephoto focal lengths, especially extreme focal lengths.

The answer to this question isn’t a simple yes or no. It all depends on what’s most important to you. In general, the larger the sensor the better the image quality because it can acquire more light, generates less noise, and can create a shallower depth of field (more background blur) which is preferred my many for portraiture work.

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To counteract this shake, you can stabilize the camera on a tripod or other support and reduce the duration your shutter is open. The faster the shutter speed, the less movement will be captured. In order to maintain the same exposure, you may need to increase the size of your aperture opening or increase your ISO sensitivity.

When capturing a photograph of an object at very close range with a wide angle lens, you do experience distortion. This distortion is not caused by a rectilinear lens is suddenly distorting the view—recilinear is recilinear— the distortion happens because of the more oblique angles that the light is entering the lens. The closer the subject is to the lens, the more variation there is in the angles of entry of the light rays from an object. Subject-lens distance is the cause...not really a distorting lens. For the beginner, this is difficult to describe without encouraging the audience to study the inside of their eyelids instead of a lens diagram.

Keep in mind that camera sensor formats are not standardized across the different brands or models. Dimensions may vary slightly from the figures listed above.

In fact, if we were really being careful, the second image should be projecting an upside down car on the sensor as lenses flip the image!

A camera’s sensor dictates the quality of the images it can produce—the larger the sensor, the higher the image quality. Bigger image sensors have bigger pixels, which means better low-light performance, reduced noise, good dynamic range, and the ability to obtain more information.

This is exactly the answer I was looking for. Just to put it another way, this means if I have a shot taken on a 50mm prime, with a 1.6 crop factor sensor, it is still correct to say the lens' focal length for the image was 50mm, rather than 80mm? It's the field of view that has changed, effectively cropping the image, although it might be convenient to say the produced image "looks like it's been shot with an 80mm lens and 35mm sensor."

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Prime lenses are those that have fixed focal lengths. Zoom lenses are those that have variable focal lengths. This is accomplished by physically changing the length of the lens, internally or externally.

The use of the term perspective here is unfortunate. The only thing that can alter perspective is moving the position of the camera. A wide angle lens does not distort geometric perspective. That's what people look like up close. Take that photo of your friend and print it big. Now stand close enough so that it fills the same angle of view as the lens provided to the sensor. Nothing will be distorted. Check out the skull in Holbein's The Ambassadors. It looks undistorted from a certain angle, as would the corners of a wide angle shot when presented to a viewer in such a way as to match the FOV of the original shot.

Hello - Was hoping you could clarify something me.    In some instances (in the top image in the article) the focus point is shown at the image plane.    In other cases ( the lower image in this article) the image plane is shown to be behind the  focal point,  which would be out of focus.

The other thing that lenses of different focal lengths have an effect on is what is known as “perspective.” To put it very simply, wide-angle lenses distort the scene, and telephoto lenses compress the view.

As a photographer, it’s important to know the difference between camera sensor sizes, particularly if you’re planning on buying a new camera. Sensor size is the first and most important thing you need to consider. It is the main feature of your camera that will have the most powerful impact on your images.

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Due to their large image sensors, medium-format cameras are traditionally heavier and bulkier than their full-frame counterparts. But that changed, as brands like Hasselblad have come out with smaller mirrorless medium-format cameras like the X1D II to provide photographers with a lighter, more compact option. The newer Fujifilm GFX 100 is also a medium-format mirrorless camera and holds a whopping 102MP resolution.

The primary measurement of a lens is its focal length. The focal length of a lens, expressed in millimeters, is the distance from the lens’s optical center (or nodal point) to the image plane in the camera (often illustrated by a "Φ" on the top plate of a camera body) when the lens is focused at infinity. The image plane in the camera is where you will find your digital sensor or film plate. If you are an optical engineer, this is important stuff. For the photographer, however, we do not need to know about nodal points or why the 200mm lens in our closet is only 193mm long, to make great photos. What we need to know, as photographers, is what focal length means to our images. When we talk about lenses, the focal length is not only related to the lenses’ physical length, the linear measurement is representative of an angular field of view.

If the lens is shorter than 50mm, say, a 24mm lens, then the image produced by that lens will give the photographer a wide-angle perspective of the world before them—wider than your “normal” vision. The field of view of the lens is wider than that of the standard lens.

Full-frame sensors are available in both DSLR and mirrorless cameras. They have the same dimensions as the 35mm film, hence the name. The 35mm full-frame sensor type is the gold standard among professional photographers who want the highest-quality images.

We’ve all heard of the full-frame DSLR camera, of course, which is the gear of choice of seasoned professional photographers. For enthusiasts and beginners, the usual choice is the APS-C format or crop-sensor DSLR camera. However, some prefer to use mirrorless cameras or MILCs, which are the smaller, lighter versions of DSLRs. Lastly, there are the 1-inch sensor cameras, which are better known as point-and-shoot or compact digital cameras.

Someone standing 2 feet from you will be just as distorted at 200mm focal length as at 16mm... you'll just see a narrower slice of the scene in front of you. Maybe a nostril!

The APS-H is slightly larger than the APS-C sensor format that many Canon DSLR cameras use today but smaller than a traditional full-frame sensor.

Many digital cameras are commercially available on the market right now, and they all have a wide range of sensor sizes. And while it’s good to have choices, it can also get pretty confusing, especially to a beginner.

We already said that the 50mm lens gives us the “normal” field of view perspective. What about lenses of different focal lengths?

If you get close to a subject with a wide-angle lens, the distortion characteristics of that lens will distort the subject. If you don’t believe me, take a portrait of a friend up close with a wide-angle or fisheye lens, and ask them if they like the image. Chances are, they will not.

A 50mm lens is a 50mm lens all the time, regardless of what camera it is attached to...or even if it is attached to a camera!

A lens with a focal length longer than 50mm will give the photographer a telephoto perspective—making it appear that you are closer to your subject by producing a field of view that is narrower than that of a standard lens.

The top image simulates a single point of light being focused onto the sensor. The second image illustrates how the lens collects the light from a scene and sends it into the camera to cover the sensor.

Not all cameras are created equal. An entry-level DSLR won’t give you the same results from a professional, full-frame DSLR—even if they have exactly the same pixel count. If you want to get the highest-quality images with your camera, you’ll need something with extremely powerful specifications and a physically large image sensor.

On the mirrorless camera side, we have the Micro Thirds Format System, first released in 2008. It shares the Four Thirds System’s sensor size and specifications but uses a compact design with no space for the movable mirror, pentaprism, and other parts of the DSLR mechanisms not found in mirrorless cameras.

So your use of the term "distort" is misleading as well. It runs the risk of being conflated with barrel and pincushion distortion - genuine distortions that are indeed a property of the lens.

High-end compact cameras like the Panasonic Lumix DMC-LX10 and the Sony Cyber-Shot DSC-RX10 IV use 1-inch sensors. This allows these cameras to produce good results—in terms of image and video quality—that you won’t get with regular point-and-shoot cameras.