On non-full-frame APS

  On "non-full-frame APS-C lens 1.6 Equivalent coefficient "td

"Public Photography", No. 4, 2008, p. 126, titled "Digital Lens Traditional Lens" No. 4-Difference in shooting angle
As mentioned in the article, "The telephoto end is longer and it is easy to shoot long-distance objects ~ / The lens needs to be multiplied by the conversion factor during use. This change greatly increases the equivalent focal length of the lens. A common 70-200mm lens,When used with APS-C digital SLR cameras, it is approximately 135-300mm of 135-frame digital SLR cameras. For those photographers (such as sports photographers and ecological photographers) who often use telephoto lenses, the telephoto endLonger and easier to work with.”
It is a technical error and will mislead the reader.
Dont get it wrong!
For example you have EF200mm / 2.8L fixed focus lens (6500 yuan) multiplied by a factor of 1.6, it becomes EF320mm / 2.8L fixed focus head (39000 yuan)?How can it be so cheap!!!
Except for you EF200mm / 2.The 8L viewing angle has become smaller, nothing else has changed!Because the focal length has not changed, the optical effects such as "depth of field" will not change because of 1.The 6 × coefficient varies and the only change is the angle of view.
As far as the picture is concerned: as long as the camera position does not change, the depth of field and see-through relationship do not change.
For example 85/1.8 Installed on EOS 30D, equivalent to 136/1.8 lenses.
But use 85/1 in the same plane.8+ EOS 30D and 135/2 + EOS 5D shooting, this 136/1.The depth of field and out-of-focus imaging of 8 are still 85/1.The depth of field and out-of-focus imaging effects of 8 cannot be equal to the depth of field and out-of-focus imaging effects of 135/2.
The appearance of the equivalent magnification, in addition to changing the effective viewing angle, does not change the three main parameters: maximum aperture, depth of field, perspective relationship.(It will not change the focal length of the lens!!)
Another thing worth mentioning is that many color friends will buy a 50mm header instead of an 80mm mid-focus lens to take portraits after purchasing a digital SLR.Change focus.This idea is economical but not practical.
There are two purposes for taking portraits with a mid-focus lens:
1. Control the shooting distance to avoid distortion of the characters;
2. Obtain a shallow depth of field to highlight the characters.
However, when the 50-header is used as the 80-header, such a problem arises: in order to obtain a bust portrait, the full-frame 50-header requires 1.5 meters shooting distance, and used in 1.At 6x non-full frame, it is necessary to retreat to a shooting distance of 2 meters. Since the depth of field is inversely proportional to the focal length and proportional to the shooting distance, for a half-length portrait with the same composition, the depth of field obtained by the non-full frame 50 lens is better than the full 50 lensThe depth of field obtained is greater.Instead of obtaining a shallow depth of field with a medium focus, he lost the shallow depth of field that was supposed to be available.This is the problem caused by the reduced frame size.
The same is true for telephoto, for those who use telephoto to obtain shallow depth of field (for example, 200mm / 2.8 guys who shoot portraits), part-frame is a headache.
But for the manufacturers to advertise, "Although they lost wide-angle, but earned telephoto," it was just confusing.

Line: "Full Frame" and "Not Full Frame"
1. Concept
【Full frame】
The so-called full frame is for the size of traditional 135 film.The size of the traditional camera film is 35mm, 35mm is the width of the film (including the perforated part), and the photosensitive area of the 35mm film is 36 x 24mm.The size of the digital SLR CCD (or the photosensitive imaging element of CMOS) is the same as the size of the 135 film 36 x 24mm, which is called "full frame".
【Not full-frame-APS】
In 1996, the APS system jointly developed by FujiFilm, Kodak, Canon, Minolta and Nikon began to appear.APS is the abbreviation of "Advance Photo System", which translates to: "APS Advanced Photography System" in China. APS developers have made thorough improvements on the basis of the original 135 specifications, including comprehensive innovations in cameras, photosensitive materials, printing equipment and related ancillary products, greatly reducing the size of the film, using a new smart cassette design, and integrating itThe digital technology has become an intelligent film that can record optical information and digital information.
APS is positioned in the amateur consumer market.It is completely different from the frame format of the 135 system. A total of three negative frames (H, C, P) are designed:
Type H is full frame (30.3 × 16.6mm), the aspect ratio is 16: 9;
C type is to block one end on the left and right sides of the full frame, and the aspect ratio is 3: 2 (24.9 × 16.6mm), the Mungil Red Dragon is a red pepper with the same proportion as the 135 film;
The P-type is a full-frame block on the upper and lower sides, so that the length to width ratio of the picture is 3: 1 (30.3 × 10.1mm), called the panoramic mode.
In digital SLR cameras, most of them use CCD or CMOS photosensitive devices smaller than 135. Except for Olympus 4/3 system and Canon full-frame, almost all are almost the same size as APS-C film.Therefore, people call this size photosensitive device "APS-C specification".(figure 1)
2. The difference between "full-frame" and "non-full-frame" lenses
When "non-full-frame" lens is used, its actual angle of view does not reach the maximum angle of view of the lens. It must be multiplied by the "lens equivalent factor" to convert the current equivalent focal length.For example, the imaging area of the photosensitive device COMS of Canon EOS 30D is 22.5mm × 15mm, its "lens equivalent coefficient" is 1.6. The nominal focal length of the lens should be multiplied by 1.6 The focal length obtained is the equivalent angle of view.For example, the focal length of the lens is 18mm, but the EOS30D cannot reach the angle of view of the 18mm lens. Its angle of view is 28.The angle of view at 8mm focal length is equal, this number is 18mm × 1.6 came.
However, dont get it wrong!
For example you have EF200mm / 2.8L fixed focus lens (6500 yuan) multiplied by a factor of 1.6, it becomes EF320mm / 2.8L fixed focus head (39000 yuan)?How can it be so cheap!!!
Except for you EF200mm / 2.The 8L viewing angle has become smaller, nothing else has changed!Because the focal length has not changed, the optical effects such as "depth of field" will not change because of 1.The 6 × coefficient varies and the only change is the angle of view.
For the picture: as long as the camera position does not change, the relationship between depth of field and perspective does not change.
Another example is 85/1.8 Installed on EOS 30D, "equivalent to" 136/1.8 lenses.
But use 85/1 in the same plane.8+ EOS 30D and 135/2 + EOS 5D shooting, this 136/1.The depth of field and out-of-focus imaging of 8 are still 85/1.The depth of field and out-of-focus imaging effects of 8 cannot be equal to the depth of field and out-of-focus imaging effects of 135/2.
The appearance of the equivalent magnification, in addition to changing the effective viewing angle, does not change the three main parameters: maximum aperture, depth of field, perspective relationship.(It will not change the focal length of the lens!!)
Another thing worth mentioning is that many photographers will buy a 50mm header instead of an 80mm medium-focus lens to take portraits after purchasing a digital SLR.Change focus.This idea is economical but not practical.(figure 2)
There are two purposes for taking portraits with a mid-focus lens:
1. Control the shooting distance to avoid distortion of the characters;
2. Obtain a shallow depth of field to highlight the characters.
However, when the 50-header is used as the 80-header, such a problem arises: in order to obtain a bust portrait, the full-frame 50-header requires 1.5 meters shooting distance, and used in 1.At 6x non-full frame, it is necessary to retreat to a shooting distance of 2 meters. Since the depth of field is inversely proportional to the focal length and proportional to the shooting distance, for a half-length portrait with the same composition, the depth of field obtained by the non-full frame 50 lens is better than the full 50 lensThe depth of field obtained is greater.Instead of obtaining a shallow depth of field with a medium focus, he lost the shallow depth of field that was supposed to be available.This is the problem caused by the reduced frame size.
The same is true for telephoto, for those who use telephoto to obtain shallow depth of field (for example, 200mm / 2.8 guys who shoot portraits), part-frame is a headache.
But for the manufacturers to advertise, "Although they lost wide-angle, but earned telephoto," it was just confusing.(image 3)
3. Will “full frame” replace “non-full frame” cameras
I think it is impossible to replace APS-C in a short period of time, at least not in 10 years.
The reason is very simple, just three:
1. The cost of a full-frame camera is much higher;

On non-full-frame APS AROWANA Forum 2. The shooting speed is limited, and it takes time to increase;
3. The requirements of the full-frame camera on the lens are very high, especially the edge imaging and distortion of the lens.
The above three points determine that the production cost, design cost and investment cost of the "full-frame" professional camera will be very high and will not be accepted by the public, and should belong to high-end consumption.Therefore, photographers do not have to worry about "full-frame" will replace "non-full-frame" cameras in a short period of time, feel free to use it.


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