SLR enthusiasts have a lot of reasons to cheer their favourite platform. It’s a mature architecture with decades of refinement. It’s been field tested in the toughest conditions known to photographers. Manufacturers put their best and newest technologies into the top-end SLRs. Beyond the cameras themselves, the SLR has a huge supporting cast of accessories that no other camera system can surpass. However, SLRs don’t form a single niche. In the lower tiers competition gets fierce. With all the great advances in camera technology, you can easily downsize or downgrade and still have a device that takes really good photographs.
Not A Singular Breed
The digital-SLR market can be sliced in a number of ways. One is by sensor dimensions. The so-called full-frame SLRs have sensors that are the same (or nearly the same) dimensions as the 35-mm film frame: 36 mm wide by 24 mm high. APS SLRs have sensors that are roughly the same dimensions as the APS-C film frame: 25.1 x 16.7 mm, but there is a lot of variability in dimensions from one manufacturer to another, and even between models of a single camera maker.
If you’ve never used 35-mm film before you may wonder: so what? It’s a legacy problem. Sensors in the first generations of digital SLRs were of smaller dimensions than a 35-mm film frame, so photographers transitioning from film had to relearn relationships between focal length and framing. It created an awkward narrative with terms like “focallength equivalent” and “crop factor” that’s still with us today. Full-frame digital SLRs re-establish the relationships that were part of basic training for some photographers.
Every manufacturer makes more SLR models with APS-size sensors. Another way to organize the field is according to the intended user. Photo Life,like other members of the Technical Image Press Association uses four categories: entry-level, advanced, expert and professional. While not a perfect system, it’s a generally useful index that takes into consideration a variety of factors such as price, size and weight, feature breadth and depth, ruggedness, durability, weather resistance and performance.
Cameras with APS-size sensors mostly cover the spread of entry-level, advanced and expert, while full-frame cameras mostly span the expert through professional categories. Full-frame models are more expensive, partly because they are designed for the advanced end of the model continuum, but also because full-frame sensors and other components are more costly. Thus you may find a company’s APS model well matched in features and image quality to a full-frame offering, even outperforming it in some ways, but with a lower price tag.
Canon and Nikon, the No.1 and No.2 SLR makers, have held 90+ percent of the market for years, with Pentax and Sony picking up the rest. When you are fighting such goliaths, you need something to make you more competitive. With Pentax you can often find higher-end features like weatherproof seals and exotic metals for body construction showing up earlier in lower-end models.
Sony has taken a different approach to the viewfinder system in its Alpha SLT line using a pellicle mirror system and an electronic viewfinder instead of the traditional SLR pentaprism system. It offers some benefits such as faster burst-shooting rates and access to fast phase-detect autofocus in conjunction with a live-view electronic viewfinder.
Making apple-to-apple comparisons between manufacturers is difficult for a number of reasons. Even studying a single manufacturer, it’s often hard to spot big differences between adjacent models in the line up, or whether the differences are meaningful to your interests. Following are some performance indicators that might make a difference in your deliberations.
As you move up from entry-level to advanced, the auto-focus system usually becomes more sophisticated. The number of focus points increases, as does the number of cross-type points, which work well whether the camera is in portrait or landscape orientation. The number of selectable focus points for single-point AF may increase too, which means you have more specific areas in the frame you can target as the focus point. But even entry-level models may implement sophisticated focusing methods like face detection and tracking.
SLR focusing used to be exclusively based on phase-detection technology in the mirror system, which is fast and works well in low light. When SLRs capture video on-sensor contrast-detect AF is used, which is very precise but not as effective in low light. Both types of AF are now common on SLRs, and improvements to on-sensor focusing show up as improvements in live-view focusing for both stills and video. Canon’s Dual Pixel CMOS AF moves the technology forward with on-sensor phase detection, and as previously mentioned, Sony’s SLT design achieves a similar benefit with different technology.
SLRs use a separate RGB sensor for exposure calculation but a lot of that information is being used for other sophisticated features such as face recognition or scene recognition. Scene shooting modes or styles allow the photographer to pick descriptive names, such as sunrise/sunset, fast moving objects, backlit subjects, fireworks, night photography, indoor photography, etc. Entry-level to mid-level SLRs in particular offer a lot of these conveniently named settings.
Maximum Frame Rate
This is a rough performance indicator from a number of different factors working together: the robustness of the mechanicals, data transmission and card-writing speed, performance of the image processer and sensor resolution.
Viewfinder coverage: expressed as a percentage, this indicates how closely the viewfinder frame comes to the frame actually captured by image sensor. As you move up to more advanced cameras, 100 percent coverage becomes the norm.
LCD: most SLRs now use 3-inch or 3.2-inch (measured diagonally) rear screens. Camera companies veered from computer monitor practice and state resolution in “dots” instead of pixels. A pixel is a triad of red, green and blue. In computer speak a VGA monitor displays 640 x 480 = 307,200 pixels. In camera speak, that’s 307,200 x 3 (red, green, blue) = 921,600 dots.
Some cameras have movable LCDs, either adjustable in a single plane (up-down) or fully articulated, and touch-sensitivity is also beginning to show up, which allows you to pick camera settings by touchscreen.
Raw File Structure
You may encounter 14-bit vs. 12-bit as well as uncompressed, lossy compressed or lossless compressed. By the numbers 12-bit data can define nearly 70 billion values while a 14-bit data can define four trillion values. Compression reduces file size. In lossless compression, all the captured data is retained; in lossy compression, some data is permanently discarded, which allows file size to be reduced more. Practically speaking, you may not be able to see any differences between a 12-bit and 14-bit raw files, uncompressed vs. lossless compressed except in the extremes of exposure conditions.
Entry-level cameras use an impact-resistant material like a polycarbonate, which is very tough. As you move up to more performance-oriented models you find increasing use of materials like magnesium alloy for additional rigidity or magnesium alloy for the body and a separate chassis made of even stronger stainless steel. Likewise more advanced models include weather sealing on the port doors, seams and lens bayonet, which helps keep dust and moisture away from the internals. All SLRs now have a dust-reduction system that uses high-frequency vibration to keep the sensor free from debris that show as dark spots or lines in the image.
Full HD, 1920 x 1080 resolution, is now the norm but frame capture rates vary: 60p, 60i, 30p and 24p are typical. In 60p and 30p the camera records 60 (or 30) full 1920 x 1080 frames every second. With 60i the frame is divided into two fields of odd and even lines, recorded sequentially and then combined into 30 complete 1920 x 1080 frames every second. Recording in 60p requires a more robust system since you are working with twice the amount of data per second. The 24p imparts a film look to digital video. Advanced video features include an external stereo microphone jack, a headphone jack for monitoring sound, and the ability to send raw video to a separate video recording unit.
Other Tech Content
Wi-Fi and NFC are built into a number of SLRs. Part of the Wi-Fi implementation is an accompanying smartphone or tablet app. This allows you to download images from the camera to the smart device, and then upload it to a socialmedia stream, or use the tablet as a larger live-view display to control camera functions. NFC (Near Field Communication) is used to simplify the Wi-Fi connection between camera and device. Wi-Fi can also be implemented using memory cards with built-in Wi-Fi from companies such as EyeFi, Toshiba, Transcend and Trek.
Some cameras have built-in GPS units and in some cases you can buy an external unit that communicates with the camera. The GPS unit writes longitude, latitude and altitude information into the metadata so it becomes a permanent part of the image data. It’s especially handy for travel photography because it helps you keep track of where you took various photos.
DSLR Cameras – The Go-To Choice for Enthusiasts keeps its Edge by David Tanaka
Photo Life – Buyers’ Guide 2016