How Do I Choose the Best Digital SLR Camera?
Digital single lens reflex camera (Digital Single Lens Reflex Camera, often referred to as DSLR), referred to as a digital SLR camera is a camera that records images in a digital manner. It belongs to the intersection of Digital Still Camera (DSC) and SLR.
Digital SLR Camera
- Digital single lens reflex camera (Digital Single Lens Reflex Camera, often referred to as DSLR), referred to as a digital SLR camera is a camera that records images in a digital manner. It belongs to the intersection of Digital Still Camera (DSC) and SLR.
- AF for DSLRs and regular digital cameras (
- In the working system of a SLR digital camera, light passes through the lens and reaches the reflector, and is refracted to the focusing screen above and forms an image. Through the eyepiece and pentaprism, we can see the outside scene in the viewfinder.
- During DSLR shooting, when the shutter button is pressed, the mirror will pop up, and the shutter curtains in front of the photosensitive element (CCD or CMOS) will be opened at the same time. The mirror immediately returned to its original shape and the image was visible again in the viewfinder. This structure of the single-lens reflex camera determines that it is shot completely through the lens focus. It can make the image seen in the viewfinder and the film always be the same. Its framing range and the actual shooting range are basically the same. , Very conducive to intuitive composition.
- A great feature of SLR digital cameras is that they can exchange lenses of different specifications. This is a natural advantage of SLR cameras and is unmatched by ordinary digital cameras.
- In addition, SLR digital cameras are positioned as high-end products in digital cameras. Therefore, in terms of the area of the photosensitive element (CCD or CMOS) that is related to the photography quality of digital cameras, the area of SLR digital is much larger than that of ordinary digital cameras, which makes SLR digital cameras The photosensitive area of each pixel is also much larger than that of ordinary digital cameras. Therefore, each pixel can also display a more detailed brightness and color range, which makes the photography quality of SLR digital cameras significantly higher than ordinary digital cameras.
- Overview
- The professional positioning of digital SLR cameras determines that even popular products for ordinary users and enthusiasts have a lot of advantages. This is the fundamental reason why many enthusiasts choose digital SLR cameras. We can summarize the professional characteristics of digital SLR into the following aspects:
- 1. Advantages of image sensors
- For digital cameras, the photosensitive element is one of the most important core components. Its size is directly related to the shooting effect. To achieve a good shooting effect, the most effective way is not only to increase the number of pixels, but also more important. It is to increase the size of CCD or CMOS. Whether it is a CCD or a CMOS, the sensor size of a digital SLR camera far exceeds that of a normal digital camera. Therefore, the number of pixels of a digital SLR sensor is not only relatively high (currently at least 6 million), but also the area of a single pixel is four or five times that of a civilian digital camera, so it has an excellent signal-to-noise ratio and can record a wide range of brightness. The image quality of a 6-megapixel digital SLR camera definitely exceeds that of an 8-megapixel digital camera using a 2 / 3-inch CCD.
- 2.Rich lens options
- Digital camera is a kind of optical, mechanical and electrical products. The performance of the optical imaging system has a very important impact on the final imaging effect. Having an excellent lens is no less important than imaging sensor selection. At the same time, as the cost of image sensors, image engines, and storage devices continues to decrease, the proportion of optical lenses in the cost of digital cameras is also increasing. This is even more true for digital SLRs. In the selection of traditional SLR cameras, the richness and imaging quality of lens groups are important factors in the choice of film friends. In the digital era, the retention rate of lens groups has naturally become the basis for brand competition. . Canon, Nikon and other brands have huge autofocus lens groups, from super wide-angle to super telephoto, from macro to soft focus, users can choose matching lenses according to their needs. At the same time, due to the large sensor area, digital SLR cameras are easier to get excellent imaging. What's more important is that many photography enthusiasts usually have one or two, even as many as a dozen professional lenses. These are purchased by film friends with their hard-earned money. If you buy a digital SLR camera body At once, the lens was activated, and it formed a complementary film and digital system with the original traditional film camera.
- 3.Quick response speed
- One of the biggest problems with ordinary digital cameras is that the shutter has a long time lag. If you don't grasp it well, you often miss the most exciting moments. The response speed is exactly the advantage of digital SLRs. Because their focusing systems are independent of imaging devices, they can basically achieve the same response speed as traditional SLRs, making users handy in news and sports photography. Canon's EOS1D MARK and Nikon D2H can achieve a continuous shooting speed of 8 frames per second, which is comparable to traditional film cameras.
- 4.Excellent hand control ability
- Although the automatic shooting function of the camera is getting stronger and stronger, the environment and the situation of the subject are ever-changing when shooting, so a user who has certain requirements for photography will not be satisfied with shooting only in the automatic mode. This requires that digital cameras also have the ability to manually adjust, allowing users to adjust according to different situations in order to obtain the best shooting results. Therefore, having a manual adjustment function has become a function that digital SLRs must have, and it is also a representative of its professionalism. Among the many manual functions, exposure and white balance are two important aspects. When the automatic metering system cannot accurately determine the light conditions and color temperature of the shooting environment when shooting, users need to make judgments based on their own experience, and make manual adjustments to achieve good shooting results. This is also a reflection of the professionalism of digital SLRs. For example, the EOS10D can adjust the color temperature value based on 100K each time to help users get the best results.
- 5.Rich accessories
- An important difference between digital SLR and ordinary digital cameras is that it has strong scalability. In addition to continuing to use additional lenses such as polarizers and interchangeable lenses, you can also use professional flashes and other auxiliary equipment to Enhance its ability to adapt to various environments. Such as high-power flash, ring macro flash, battery handle, timing remote control, these rich accessories allow digital SLRs to meet a variety of unique needs, while ordinary digital cameras are greatly inferior.
- This necessary turning up of the mirror also brings some other problems:
- First, the moment you take a picture, the viewfinder will be blocked. Since blocking time is a matter of moment, this is not a major issue for mirrors that reset immediately. However, it raises some incidental issues. For example, when shooting with a strobe, you will not be able to see through the viewfinder whether the strobe device is firing normally.
- Second, the noise of mirror movement. This can be an important issue in places where quietness is required. This kind of noise does not occur because there is no moving mirror in the rangefinder camera that suddenly blocks the light path.
- Third, the camera shake, that is, the overall movement of the camera caused by the turning action of the mirror. Suppose you shoot with a shutter time of 1/500 second, so don't worry. This vibration is not noticeable. However, if you take an accurate photo with a long shutter time, such as when using a telephoto lens in dim light, this vibration can be a problem for imaging.
- Fourth, there is another problem with SLR framing. For example, we want to shoot with a small aperture such as f / 32, and the light allowed by the aperture f / 32 to enter the lens is very faint, which will cause the image seen in the viewfinder to be dim, which may be difficult to focus, or even at all Unable to focus.
- In fact, the SLR solution is quite clever. It will use the maximum aperture of the lens to let us complete the framing and focusing. When the shutter is pressed, the aperture of the lens will immediately shrink to the preset aperture to complete the film exposure. Instantly, the aperture will open to its maximum aperture, ready for the next shot.
- Is DSLR (digital single-lens reflex camera) necessary for the average home player? Digital DSLR DSLR is the perfect pursuit for professional users (journalists, photographers) and audiophiles. Compared with consumer DC, DSLR has a big gap: DSLR brings greater dynamic range (signal-to-noise ratio), interchangeable lenses, better imaging quality, and shorter shutter lag , Faster operation and processing speed, more realistic framing, faster continuous shooting speed and more professional control, etc. These are unmatched by consumer DC.
- The biggest problem is that the volume and weight are larger (heavier) than consumer digital cameras. Accessories such as lens flash filters make digital cameras not too portable. The second problem is that the CCD / CMOS chip of the digital SLR camera is prone to dust. Some can remove the dust on the surface of the CCD / CMOS chip by using an ultrasonic device, a vibration device, an electrostatic device, etc., but the effect is not very significant.
- 1. Metering and exposure: each metering system has a large difference, usually double cross focus is a better way.
- 2. Focusing speed, shutter lag, and continuous shooting speed are very important for news photography, sports photography, wildlife photography, and snapshot photography. For digital SLR cameras, the increase in performance is accompanied by a sharp rise in price.
- 3. Body life Generally, the life of SLR camera shutter is 50,000 times, the life of medium and high-end SLR cameras can reach 80-100,000 times, and the life of professional SLR cameras can reach 150,000 times. In actual use, if the high-speed continuous shooting function is frequently used, the shutter life will be reduced. The life of the LCD screen is about 1000 hours. The components that affect the life of a digital SLR camera are the reflective viewfinder system. Frequent high-load use can easily cause the failure of the reflective viewfinder system.
- 4. The camera with advanced body reliability will be dustproof, waterproof, and resistant to impact (shock). Due to the metal body and special materials, such cameras will also be very expensive.
- 5. In addition to sRGB, which is the standard color space for Windows and inkjet printers, you can also choose the more widely used Adobe RGB. According to the purpose of photography, you can choose the best color space.
- 6. Flash system For professional photographers, flash metering and exposure systems are very important. Each manufacturer has its own unique skills in the automation of flash systems. There is no best, no worst, only the most suitable.
- 7. Lens group The advantages of digital SLR cameras are interchangeable lenses. Whether the original lens series support and independent lens manufacturers' products are rich enough to meet your needs is a question worthy of attention.
- 8. Whether to support W / A read / write acceleration technology. Digital SLR cameras released after autumn 2003 will support W / A read / write acceleration technology. With this technology, CF cards can be read and written at speeds of 40 times (6MB / S) or more. .
- 9. Transmission interface Digital SLR cameras released after autumn 2003 should have both USB2.0 and 1394 FireWire terminals. Some cameras should also support wireless network transmissions such as 802.11b / g and Bluetooth.
- 10. Photosensitivity and noise suppression Higher sensitivity, better noise suppression is what we are after.
- 11. The highest shutter speed and the slowest shutter speed (Bulb) are two key indicators for the shutter of digital SLR cameras. The reliability and accuracy of the shutter also need to be concerned. Maximum flash synchronization speed, which is also a measure of whether a digital SLR camera is advanced.
- 12. Whether the feel, shape, and weight of the camera body are designed properly or together are often the most important place when deciding to buy a SLR camera. Without considering the price, the size and weight of professional digital SLR cameras are not acceptable to everyone. Small and lightweight amateur digital SLR cameras are more suitable for ordinary people.
- 13. Psychology ultimately plays a decisive role, and rational consumption is crucial.
- Summary: Digital SLR cameras are monopolized by a few manufacturers. The principle of a penny is a absolute truth in the field of digital SLR cameras. In order to meet high-load, high-intensity professional photography applications, it is best to choose expensive high-end digital SLR cameras. If it s just a hobby and you just have fun, choosing the economical model is the best policy.
- 1. Exchange and communicate with relevant film friends, and participate in more outdoor shooting activities;
- 2. Go to related photography forums to see photos, see exchange posts, and learn from each other;
- 3. Purchasing related books for systematic learning, such as "Extraordinary Photography Notes-SLR Camera in 2 Days" (Electronic Industry Press, 2010.3);
- 4. Go to relevant photography schools for training;
- 5. Learn from famous teachers.
- 6. Of course, the most important thing is continuous practice, and constantly find methods from practice. [1]
- Introduction
- From the early installation of digital camera backs based on traditional SLR cameras to special models developed specifically for digital needs today, DSLR has gradually replaced the market share of silver salt cameras in the professional field and has become a market The main ethnic group has also attracted more and more traditional camera optical manufacturers to join. Manufacturers or brands that have launched DSLR products to date include Canon, Contax, Fujifilm, Kodak, Konica Minolta (formerly known as Minolta before 2003), Manufacturers such as Nikon, Olympus, Pentax, Sigma, etc., while the major manufacturers of consumer electronics products, Panasonic, Sony, and Samsung ) In 2005, it announced that it would enter the DSLR market through cooperation with existing optical factories and become the latest participating manufacturer. Among these brand manufacturers, although Kodak was the first to apply digital photosensitive technology to SLR cameras, but because the company's products are based on the traditional camera of other brands to modify the photosensitive element parts, it is positioning and Other special models are still a little different. In addition, Mamiya-OP, a professional manufacturer of medium format cameras, also officially joined the digital camera market at the end of 2005, launching the world's first digital medium format camera, Mamiya ZD. In 2006, Leica released the sister machine DIGILUX 3 of the Panasonic Lumix DMC-L1. This is the first time that this old optical factory has entered the DSLR market under its own brand (Before that, Leica had only launched consumer digital camera products and Digital camera back of a traditional SLR camera).
- Epson launched a lens interchangeable digital camera called R-D1 in 2004. In 2006, it launched an improved version called R-D1s. D1 / R-D1s are the same type of M8. In terms of optics, these cameras are actually a RangeFinder Camera, which is different from the principle of Single Lens Reflex. Strictly speaking, these cameras do not belong to the DSLR camera family. However, it is listed for reference.
- Canon
- Canon EOS D30 (April 2000): The first Canon camera developed for digital needs using a 3 million pixel CMOS sensor. The focal length conversion rate is 1.6x. Canon EOS-1D (listed in August 2001, discontinued) Canon EOS D60 (listed in January 2002, discontinued) Canon EOS-1Ds (listed in August 2002, discontinued) Canon EOS 10D (listed in January 2003 , Discontinued) Canon EOS 300D (listed in July 2003, discontinued): Also known as EOS Kiss Digital (Japanese market) or Digital Rebel (North American city)
- Contax
- Contax was originally a camera brand owned by the famous German optical factory Carl Zeiss. In 1970 or so, the production line was completely transferred from Germany due to the cooperation with the Japanese electronic camera manufacturer Yasu Seiki (also known as Yashica). Made in Japan and became pure Japanese production. In October 1983, Yashica was merged by Kyocera, and Contax became a Kyocera brand. However, due to the poor profitability, after many years of operation, Kyocera announced in April 2005 that it would end the operation of the Contax business group, and all photography including its sole DSLR product, Contax N Digital, Product lines have been discontinued in 2006.
- Contax N Digital (listed in June 2000, discontinued): the first DSLR in the world to use a full-size (36mm x 24mm, approximately the same film as a conventional 35mm camera film) CCD, with an actual pixel of 6 million .
- Epson
- Epson R-D1 (listed in February 2004, discontinued): The world's first digital rangefinder camera, developed by Epson in collaboration with Japanese optics company Cosina, uses 6.1 million pixel levels, APS-C size CCD can be used as a light sensor, Leica M Type lenses can be used. Epson R-D1s (listed in February 2006) Note: Epson R-D1 and R-D1s do not belong to the DSLR category.
- Fuji
- Fujifilm FinePix S1 Pro (listed in December 1999, discontinued): 3.4 million pixel-level DSLRs, but because of Fuji's unique honeycomb-shaped lattice array CCD (Fuji calls it SuperCCD technology) instead of a general checkerboard arrangement, Therefore, 6.13 million images can be produced that are higher than the CCD pixel value. Fuji does not own a traditional SLR camera product, so it is based on the Nikon F60 and can be modified to support all interchangeable lenses that conform to the Nikon F lens mount specification (F Mount). Fujifilm FinePix S2 Pro (listed in December 2001, discontinued) Fujifilm FinePix S3 Pro (listed in January 2004) Fujifilm FinePix S5 Pro (listed in October 2006)
- Kodak
- Kodak can be said to be the first company to combine digital and photography. Since the DCS100 in 1991, they have introduced multiple generations of DSLR products, mainly for professional use and adopting a high price. Since Kodak is mainly good at photosensitivity technology rather than camera manufacturing, their previous products are based on the body of traditional SLR cameras introduced by other camera makers, and they are improved into DSLRs with digital photosensitivity components. In addition, they also launched dedicated Digital Camera Backs for other brands of cameras. The remaining brands are widely used in Europe and Japan, and the specifications are not only applicable to 35mm cameras. Unfortunately, Kodak announced in May 2005 that they would stop producing all professional digital SLR cameras, so the DCS series of professional DSLRs have also entered history.
- Kodak DCS100 (listed in 1991, discontinued): DSLR based on Nikon F3. What is special is that the DSC100 is a camera with a rare medium for storing data. It is not a camera on the body. Instead, the digital information obtained by the photosensitive plate is sent to an external Digital Storage Unit (DSU) using a signal cable. Stored. Kodak DCS200 (listed in 1992, discontinued): DSLR based on the Nikon N8008s. The media for storing information is an 80MB hard drive built into the body. Kodak DCS400 series (listed in March 1995, discontinued): DSLR developed based on the Nikon N90 traditional SLR camera. There are two versions of the DSLR, namely the DCS420 with 2 million pixels and the DCS460 with 6.2 million pixels. Kodak DCS500 series (DCS520 went on sale in January 1998, DCS560 went on sale in August of the same year, both have been discontinued): DSLR developed in cooperation with Canon based on the Canon EOS-1N body, with 2 million pixel grade DCS520 DCS560 with 6.2 million pixels. In addition to the Kodak version, Canon also launched a twin version of these two cameras, named EOS D2000 and D6000. Kodak DCS300 series (DCS315 was launched in June 1998, DCS330 was launched in June 1999 and has been discontinued): a DSLR developed based on the Nikon Pronea 6i traditional camera, of which DCS315 uses a 1.3 million pixel-level CCD as the light sensor Component, focal length conversion ratio is 2.6x, DCS330 is 3 million pixel level. Kodak DCS600 series (DCS620 was launched in January 1999, DCS660 was launched in May 1999, DCS620x was launched in April 2000, both have been discontinued): DSLR developed based on the Nikon F5 traditional SLR camera body, These include the DCS-620 with 2 megapixels and the DCS660 with 6.2 megapixels, and the DCS620x (ISO 400 to 4000), which are also 2 megapixels with super high sensitivity (ISO) simulation capabilities. Further strengthened to 6400). Kodak DCS700 series (DCS760 was launched in February 2001, DCS720x was launched in May 2001, both have been discontinued): DSLR developed based on the Nikon F5 traditional SLR camera body, of which DCS760 uses 6.3 million pixel-level CCD As a photosensitive element, the focal length conversion rate is 1.3x, and the DCS720x uses a 2 million pixel CCD with a focal length conversion rate of 1.6x. It emphasizes the use of high ISO values and continuous shooting capabilities for sports photography. Kodak DCS Pro series (DCS Pro-14n was launched in August 2002, DCS Pro SLR / n was launched in January 2004, DCS Pro SLR / c was launched in March 2004, all have been discontinued): 13.5 million pixel levels are used Full-size CMOS professional DSLR series, DCS Pro-14n and DCS Pro SLR / n are based on Nikon F80's fuselage, while DCS Pro SLR / c is developed based on Sigma SA9 / SD9 / SD10. Basic, but using Canon EF series lens mount.
- Minolta
- Japan's two professional photography-related factories-Minolta, which has many years of photographic optical technology, and Konica, which specializes in film and light sensing technology, merged in August 2003 to enter the digital photography market and launch a variety of evaluation Excellent products have always been known for daring to try new technologies. However, high technology investment and favorable comments do not necessarily represent high profits. Due to unbearable long-term losses, the Konica Minolta Group sold its optical photography department to Japan Electronics, a partner in January 2006. Product giant Sony, although it will continue to cooperate and participate in the development of camera products, but Konica Minolta has completely withdrawn from the operation of the photography market.
- Minolta DiMAGE RD-3000 (listed in September 1999, discontinued): using two 1.5 million-level CCDs, using Image Stitching technology to obtain a combined 2.7 million pixel-level DSLRs, using Minolta-compliant V Mount specifications. Konica Minolta Dynax 7D (listed in August 2004, discontinued): Also known as -7 Digital (Japanese market) or Maxxum 7D (North American market), it is the first in the world to use a photosensitive element to prevent hand shake (the factory claims DSLR designed for Anti-Shake), using 6.1 million pixel level, APS-C size CCD. Konica Minolta Dynax 5D (listed in June 2005, discontinued): Also known as Sweet Digital (Japanese market), Maxxum 5D (North American market) or -5 Digital (Mainland China market).
- Leica
- Germany's Lycra camera and Japan's Matsushita Electric have many years of cooperation. Panasonic's digital camera lens adopts Lycra technology, while Lycra uses some digital cameras launched by Matsushita Electric as the model and launches sister models.
- Leica D-LUX 3 (available in September 2006): Twin version of Panasonic Lumix DMC-L1. Leica M8 (listed in September 2006): Uses 10.3 million pixel-grade CCDs produced by Kodak with a focal length conversion rate of 1.33x. It is the first digital camera developed by Leica that does not support a Panasonic model. Although the M8 is a digital camera with interchangeable lenses (using Leica s own M Mount series lenses), but because it uses the distance measurement linkage principle instead of the single-lens reflex imaging principle, strictly speaking, Does not belong to the category of DSLR.
- Mamiya
- Unlike most traditional camera manufacturers, which usually start from the 135 (35mm) film format, Japan's Mamiya-OP is a professional manufacturer specializing in manufacturing medium format cameras. Although there have been special digital camera back products developed specifically for medium format cameras in the industry, the Mamiya ZD introduced by Mamiya at the end of 2005 is still the first medium format single-lens reflex digital camera product. However, with the advent of consumer machines and high-end DSLRs, Mamiya s camera sales have been hit unprecedentedly. Although Mamiya launched Mamiya ZD to restore the market, sales are still poor. Therefore, Mamiya announced on April 21, 2006 that it would The imaging department was resold to Japan Cosmos Digital Imaging Company, and it withdrew from the optical machinery business on September 1, 2006. At the same time, the optical machinery department and its subsidiary Mamiya were transferred to Cosmos. As for the future maintenance services of Mamiya cameras, the new company is also responsible .
- Mamiya ZD (listed in December 2005): Using a large CCD with a length of 48mm and a width of 36mm, 5356 pixels × 4056 pixels (a total of 21.7 million pixels) as the photosensitive element, a medium-format DSLR, using the factory s own 645AF adapter (645AF Mount) system interchangeable lens, focal length conversion rate is 1.16x.
- Nikon
- Nikon E2 / E2s (listed in 1995, discontinued): DSLR using 1.3 million pixel-level CCD, of which E2s is a high-speed model capable of continuous shooting at 3 frames per second. Nikon E2N / E2Ns (listed in 1996, discontinued): Part of the E2 / E2s series of improved products, of which E2Ns is a high-speed dedicated model. Nikon E3 / E3s (listed in 1998, discontinued): DSLR using 1.4 million pixel-grade CCDs, of which E3s is a high-speed dedicated model. Nikon D1 (listed in June 1999, discontinued): Uses 2.26 million pixel-level DSLRs. It is based on part of the structure of two traditional SLR cameras, F5 and F100, designed by Nikon for digitalization needs. Conversion rate is 1.5x. Nikon D1X (listed in January 2001, discontinued) Nikon D1H (listed in January 2001, discontinued) Nikon D100 (listed in January 2002, discontinued) Nikon D2H (listed in June 2003, discontinued) Nikon D70 (Listed in December 2003, discontinued) Nikon D2X (listed in August 2004, discontinued) Nikon D2Hs (listed in January 2005): 4 million pixels LBCAST image sensor DX high-speed professional DSLR, an improved version of D2H . Continuous shooting speed is 8.5 frames per second, CAM2000 autofocus system, supports GPS data writing function, focal length conversion rate is 1.5x. Nikon D70s (available in April 2005): DX format DSLR for the 6.1-megapixel CCD image sensor, an upgraded version of the D70. The focal length conversion rate is 1.5x. Nikon D50 (listed in April 2005): 6.1-megapixel CCD image sensor
- Olympus
- Olympus E-1 (listed in May 2003) Olympus E-300 (listed in August 2004)
- Matsushita Electric
- Originally only engaged in the production of general consumer digital cameras, Panasonic entered the DSLR field in cooperation with Olympus. Therefore, like Olympus, it uses a completely different 4/3 system than traditional film cameras. In the lens system, Panasonic uses Leica's optical technology, which is similar to the company's general consumer cameras.
- Panasonic Lumix DMC-L1 (listed in June 2006): A derivative model common to the Olympus E-330, which also has the same electronic viewfinder (EVOLT) function as the E-330.
- Pentax
- Pentax * ist D (listed in January 2003, discontinued) Pentax * ist DS (listed in August 2004, discontinued)
- Samsung
- South Korean electronics maker Samsung was originally a heavy machinery, semiconductor and consumer electronics company.
- Samsung GX-1S (listed in January 2005): Twin version of Pentax * ist DS2. Samsung GX-1L (listed in February 2006): Twin version of Pentax * ist DL2. Samsung GX-10 (listed in September 2006): Twin version of Pentax K10D.
- Sigma
- Sigma SD9 (listed in January 2002) Sigma SD10 (listed in September 2003) Sigma SD14 (listed in September 2006)
- Sony
- Although Sony has long been a big brand in digital photography, and has many optical
- Sony -100 (listed in June 2006): 10.2 million pixels, using the original -ring developed by Minolta, is Sony's first DSLR product ever.
- SLR cameras refract economic development