Digital Photography from 20,000 Feet
by Wesley Fink on September 25, 2006 12:05 AM EST- Posted in
- Digital Camera
Why the Digital SLR?
SLR cameras have been around for more than 50 years, but it is remarkable how many of those shopping for a digital camera have no idea why the market is moving to the SLR or Single Lens Reflex. Up until the late 1940's the world of hobbyist photography was ruled by 35mm point-and-shoot and rangefinder cameras. These cameras were not really that different from the point-and-shoot cameras that we have today in digital photography, except that they did not have the benefit of all the electronics that are part of today's digital cameras. The cheap point-and-shoots used a fixed focus lens, which meant the lens always shot a certain range (depth-of-field) in focus - no matter whether the subject was in that range or not. The better of these cameras used rangefinders, which were two images from two optics superimposed in the viewfinder. When these two images merged in the viewfinder your subject was in focus. As you can imagine the optics to allow focusing were pretty complicated and expensive to build. However, with a fixed lens that never changed it was possible to design and manufacture some very reliable and affordable rangefinder cameras.
The top end of the amateur photography market, which had embraced 35mm as the "miniature" film standard, then introduced a brilliant idea. Why not manufacture cameras that could use multiple lenses. This would allow the photo hobbyist to use the lens that was best suited for what they were photographing - like a wide-angle lens for interiors, or a telephoto for sporting events and far away subjects. Companies like Leica and Contax pioneered these interchangeable lens rangefinder cameras in the 1930s. After World War II, German camera companies resumed camera manufacturing. Japan, which had manufactured quality optics for a more limited market before WWII, also began making quality interchangeable lens rangefinders. Japanese companies like Canon, Aries, and Nikon championed cameras with changeable lenses.
The ability to change lenses was a great idea, but the execution was anything but simple. Viewfinders started having multiple frames engraved for the different focal lengths like 35mm, 50mm, 85mm. The user had to remember that the tiny square was 85mm. Leica and others had accessory viewfinders that mounted on the flash shoe so you could see about what the lens saw. The problem with the rangefinder is that the viewfinder and the lens never see the same thing. This was not a huge issue with a fixed lens, since the viewfinder could be matched reasonably well to the lens. There were even complicated mechanics that adjusted the viewfinder for "parallax error" on rangefinder close-ups. But with interchangeable lenses the situation became very complicated.
The first popular solution to this problem was the German Exacta, fist produced in 1936. The Exacta had a waist level-finder and a flipping 45-degree mirror. With a flipping mirror, you could look through the lens for composition and focusing - seeing the same view as the lens. You looked at the image from above the camera (5), the image was backwards (as in a mirror image), and the mirror was either manually reset or later reset automatically when winding the film, but the view on the ground glass was the same as any lens (1) mounted on the camera.
In the 1950's the Japanese pioneered further development of the SLR design. A roof pentaprism first appeared on an East German Contax S announced in 1949, but the Japanese camera industry refined and perfected the idea. Asahi developed the Asahiflex in 1952, and in 1954 the Asahiflex IIB. In 1957, Asahi Pentax introduced the fixed pentaprism and the right-hand thumb wind lever. Minolta introduced their first SLR, the SR-2, in 1958. Nikon, Canon and Yashica introduced their first SLRs in 1959 (the F, Canonflex, and Pentamatic, respectively).
The diagram shows how the light passes through the SLR lens assembly (1), is reflected by the mirror (2) and projected on the matte focusing screen (5). Using a condensing lens (6) and internal reflections of the mirrored roof pentaprism (7) the image appears in the eyepiece (8). When an image is taken, the mirror flips up as the arrow indicates, the shutter (3) opens, and the image is projected onto the film or digital sensor (4) The image at the film or sensor is exactly the same as on the focusing screen. [Image from Wikipedia.]
By the early 1960s the basic form of the SLR had evolved to what we know today, as you can see in this photo of the original Nikon F SLR.
Refinements have continued to expand the usefulness of the SLR design. The Topcon RE Super and Asahi Pentax Spotmatic pioneered through the lens metering in the early 60's. Auto exposure was first seen in the Pentax Spotmatic F in 1971, and it was popularized with the Canon AE-1 Program in 1976. Pentax made a limited attempt at autofocus in 1981 with a 35-70 f2.8 lens for the Pentax ME-F. A few years later, Minolta brought out the first real autofocus camera, the MAXXUM 7000, in 1985. The autofocus auto-everything Maxxum 7000 was wildly popular and made autofocus a virtual requirement on future SLR designs.
SLR cameras have been around for more than 50 years, but it is remarkable how many of those shopping for a digital camera have no idea why the market is moving to the SLR or Single Lens Reflex. Up until the late 1940's the world of hobbyist photography was ruled by 35mm point-and-shoot and rangefinder cameras. These cameras were not really that different from the point-and-shoot cameras that we have today in digital photography, except that they did not have the benefit of all the electronics that are part of today's digital cameras. The cheap point-and-shoots used a fixed focus lens, which meant the lens always shot a certain range (depth-of-field) in focus - no matter whether the subject was in that range or not. The better of these cameras used rangefinders, which were two images from two optics superimposed in the viewfinder. When these two images merged in the viewfinder your subject was in focus. As you can imagine the optics to allow focusing were pretty complicated and expensive to build. However, with a fixed lens that never changed it was possible to design and manufacture some very reliable and affordable rangefinder cameras.
The top end of the amateur photography market, which had embraced 35mm as the "miniature" film standard, then introduced a brilliant idea. Why not manufacture cameras that could use multiple lenses. This would allow the photo hobbyist to use the lens that was best suited for what they were photographing - like a wide-angle lens for interiors, or a telephoto for sporting events and far away subjects. Companies like Leica and Contax pioneered these interchangeable lens rangefinder cameras in the 1930s. After World War II, German camera companies resumed camera manufacturing. Japan, which had manufactured quality optics for a more limited market before WWII, also began making quality interchangeable lens rangefinders. Japanese companies like Canon, Aries, and Nikon championed cameras with changeable lenses.
The ability to change lenses was a great idea, but the execution was anything but simple. Viewfinders started having multiple frames engraved for the different focal lengths like 35mm, 50mm, 85mm. The user had to remember that the tiny square was 85mm. Leica and others had accessory viewfinders that mounted on the flash shoe so you could see about what the lens saw. The problem with the rangefinder is that the viewfinder and the lens never see the same thing. This was not a huge issue with a fixed lens, since the viewfinder could be matched reasonably well to the lens. There were even complicated mechanics that adjusted the viewfinder for "parallax error" on rangefinder close-ups. But with interchangeable lenses the situation became very complicated.
The first popular solution to this problem was the German Exacta, fist produced in 1936. The Exacta had a waist level-finder and a flipping 45-degree mirror. With a flipping mirror, you could look through the lens for composition and focusing - seeing the same view as the lens. You looked at the image from above the camera (5), the image was backwards (as in a mirror image), and the mirror was either manually reset or later reset automatically when winding the film, but the view on the ground glass was the same as any lens (1) mounted on the camera.
In the 1950's the Japanese pioneered further development of the SLR design. A roof pentaprism first appeared on an East German Contax S announced in 1949, but the Japanese camera industry refined and perfected the idea. Asahi developed the Asahiflex in 1952, and in 1954 the Asahiflex IIB. In 1957, Asahi Pentax introduced the fixed pentaprism and the right-hand thumb wind lever. Minolta introduced their first SLR, the SR-2, in 1958. Nikon, Canon and Yashica introduced their first SLRs in 1959 (the F, Canonflex, and Pentamatic, respectively).
The diagram shows how the light passes through the SLR lens assembly (1), is reflected by the mirror (2) and projected on the matte focusing screen (5). Using a condensing lens (6) and internal reflections of the mirrored roof pentaprism (7) the image appears in the eyepiece (8). When an image is taken, the mirror flips up as the arrow indicates, the shutter (3) opens, and the image is projected onto the film or digital sensor (4) The image at the film or sensor is exactly the same as on the focusing screen. [Image from Wikipedia.]
By the early 1960s the basic form of the SLR had evolved to what we know today, as you can see in this photo of the original Nikon F SLR.
Refinements have continued to expand the usefulness of the SLR design. The Topcon RE Super and Asahi Pentax Spotmatic pioneered through the lens metering in the early 60's. Auto exposure was first seen in the Pentax Spotmatic F in 1971, and it was popularized with the Canon AE-1 Program in 1976. Pentax made a limited attempt at autofocus in 1981 with a 35-70 f2.8 lens for the Pentax ME-F. A few years later, Minolta brought out the first real autofocus camera, the MAXXUM 7000, in 1985. The autofocus auto-everything Maxxum 7000 was wildly popular and made autofocus a virtual requirement on future SLR designs.
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silver - Tuesday, September 26, 2006 - link
No Adaptall for digital cameras ?tsapiano - Wednesday, September 27, 2006 - link
Well, most DSLRs use the same lens mount as their film-based predecessors so you can use things like Adaptall on the new cameras as well if you really want. The problem with that is that this technique was pretty much abandoned a while ago, so to do this you'd be stuck using old aftermarket lenses. While it was relatively easy to make a universally adaptable lens when everyone was using simple mechanical couplings - the electronic communication used in modern lenses has made that much more complicated. As such, most modern aftermarket lenses are now generally built and sold specifically for the mount you are using.With that said, there are simple adapters that you can buy to mount Nikon, Leica, Contax, Olympus OM and Pentax lenses on Canon EF bodies. As the Canon mount has a smaller register (ie the mount is closer to the film plane) and wider opening than all of those mounts, it makes it possible to fit an adapter in there. The catch-22, however, is that these are very simple adapters and don't do much other than mechanically attach the lens to the camera - you loose aides like autofocus, aperture must be set on the lens (ie A or M exposure modes only), you're forced to revert to stop down metering, etc. As such, while this may be useful to use a special purpose lens or two it's not really what you want to do for your everyday photography ;)
Resh - Tuesday, September 26, 2006 - link
Nope.Wesley Fink - Monday, September 25, 2006 - link
No, Canon lenses fit Canon only, and same with Nikon. Each brand will only fit their own lenses and independent lenses made for that clens mount. Samsung licensed their lenses from Pentax and they will fit Samsung and Pentax. Sony bought Minolta so Sony and Minolta lenses both fit.nigham - Monday, September 25, 2006 - link
I'm really happy that AT is getting to digital SLR camera reviews. This article was slightly disappointing. As has been pointed out, anyone who doesn't know his or her f-stops and shutter speeds should certainly not be spending money on a Digital SLR just yet. My experience with my prosumer Canon S2IS says that it takes a while to _really_ appreciate these settings and they're not simply learned theoretically. And I don't particularly care for history, but maybe thats just me.That said, it's OK since I've only seen one real good DSLR introduction for beginners (http://www.firingsquad.com/hardware/panasonic_lumi...">here), and what matters most are the reviews, which I'm hoping will measure up to the usual AT standard. Here's what I'd like:
- Feature description and (in prose) comparisons to comparable and current cameras. What's really improved, and what's just marketing? etc.
- How good the documentation is. This is something woefully ignored by many camera review sites.
- Reference testing with a high-quality lens; since I would expect to be buying lenses eventually if I get a DSLR
- A section (maybe short) evaluating the quality of the in-kit lenses
- Battery tests (these are important! unlike that startup times in which case I totally agree with you). Also options for backup batteries (how expensive, availability)
- A (necessarily subjective) description of the "feel" of the camera output in various real-world scenarios like landscape, low-light, fast-motion etc.
- A human-readable description of how easy/difficult the UI is. I do not want a list of menu options five levels deep and 20 EVF screenshots, I need you to take a call and let me know what the bottom line is. How hard is it to change the basic stuff (F-stop, ISO, WB?); are there any customizations available; are there any quirks like controls that inadvertently get messed around with; does it have a on-screen histogram?
- How good the AUTO mode is, and when it fails. Personally, I believe that the primary job of a photographer is to see the photo and compose it. I'd like to know when I can afford to go auto and spend more time composing my shot, and when I can't do that.
- A set of sample photos in real-world situations
I think it would be nice to remember that even for hard-core computer enthusiasts, photography remains an art and is not easily described; and is nearly impossible to describe with numbers alone.
Lastly, I'd really appreciate an article on RAW workflow - if possible one that includes a discussion of the ways Linux handles DSLRs. That is something that changes quite a bit for users transitioning to DLSRs.
Resh - Monday, September 25, 2006 - link
Sorry, just can't agree with that. How can the inter-related tasks of exposure, choosing focus point, and depth of field be separated from composition?
mostlyprudent - Monday, September 25, 2006 - link
One thing I forgot in my earlier post (and forgive me if it has already been mentioned), I would like to see more on lenses. I think AT should test both the Kit lense and a high quality reference lense. I wouldlike to know both how good the camera can be with a great lense and how good of a value the kit lense offers.Thanks.
Resh - Monday, September 25, 2006 - link
I thought it was a good primer for beginners and was full of useful history, but couldn't shake the feeling that AT was trying to crowd into an already crowded room.While I fully agree with those who have pointed-out that a diversity of reviews is a good thing, I think that diversity already exists with sites like Steve's Digicams, DPReview, etc. In addition to those we have more art, in-the-field sites like Luminous Landscape that focus on how a product performs in the field.
Some have argued that AT should do reviews to the level of detail/bench-marking that is employed for motherboard and video cards. Here, I have a harder time as I don't see an SLR body as being comparable to those components.
AT reviews those parts in the context of choosing one to fit into a larger computer system. Alternatively, an entire system (e.g., Alienware) is tested against a home-built system with similar specs or at similar cost. This model, however, doesn't appear relevant to the SLR market as one cannot individually buy the processor, sensor, body, etc. that is the best and construct their own camera. Rather, a first time buyer chooses an entry point into a given manufacturer's "system" based on the body's attributes; lens cost, availability, and quality; and available accessories. For someone upgrading their SLR, the choices are even less driven the details that AT would likely be assessing. Rather, they'd be considering the costs of switching systems (e.g., from Canon to Nikon), or simply considering the value of upgrading to the latest and greatest, a question that existing sites can answer just fine.
All that to say that there are areas where current sites fail and where AT's expertise might be better leveraged. The main example, for me, is in the area of displays and printers. With regard to the former, quality CRTs are gone and LCDs present a purchaser with huge variability in cost, performance, and quality. AT could look at the display market from the photographer's point of view (appropriate brightness coupled with stable contrast, wide-colour gamut, ease of calibration, wide viewing angles, etc). This could be supplemented with discussion of colour calibration products. Similarly for printers, there is little to be found on-line that offers critical comparison of competing printers on different papers. Both of these areas would fit well within AT's current review framework.
Lastly, AT, while not a software site, could elevate the standards of software reviews by taking a hard look at the effects of different RAW converters, enlargement software, sharpening tools, and noise reduction software. I have not seen anyone do this in an objective, scientific manner.
AT is a fantastic site and while I applaud your willingness to branch-out, I am cautious about your getting too far from your core audience and your core strengths.
N
s12033722 - Monday, September 25, 2006 - link
It would be good to delve into the nature of how image sensors work and the differences between types of sensors. I think Anandtech would be an excellent place to discuss these aspects of the cameras.Image sensors basically work by photons interacting with light-sensitive portions of the sensor to create electrical charge. The efficiency of the sensor at converting photons into electrons is reffered to as quantum efficiency, and has a serious impact on how well a camera will perform under different imaging conditions. After the charge is collected, in the case of a CCD sensor, the charge is read out of the sensor, passed through a processing chain, and then digitized. It is important to note that this is an ANALOG process until the point of digitization. In the case of a CMOS sensor, the digitization may occur at each pixel on the sensor, at the end of each row or column of pixels on the sensor, or off sensor like the CCD. Each approach has advantages and disadvantages, generally trading off noise performance for pixel size.
Image sensors are characterized by a number of factors. Noise, dynamic range, pixel size, and so forth tend to be interrelated. The comment in the article about dynamic range was somewhat simplistic. Dynamic range is primarily governed by the charge capacity of the pixel. A sensor will be characterized by a quantum efficiency as noted above, which means that as more photons strike the sensor, a greater charge will be built up. If a very bright spot exists on the image, that spot will usually fully charge the pixels under that spot, limiting the output at that level. For instance, let's say a pixel has a full-well charge capacity of 30,000 electrons, and that there is no noise. The dimmest pixel possible on the image would be 1 electron (well, 0, but let's say 1) and the brightest would be 30,000, for a dynamic range of 30,000 to 1. Now, in reality there are noise sources in a sensor. Many of them. That will typically mean that the dimmest pixel will have a charge on it, which reduces the dynamic range. Perhaps there are 500 electrons of noise. Now the sensor has a dynamic range of 30,000 to 500 or 60 to 1. Far less. The ways to increase dynamic range are to decrease noise or to increase charge capacity. Unfortunately, charge capacity is directly tied to the physical size of the pixel, so as resolutions get higher, pixel size gets smaller, and dynamic range suffers. It is entirely possible to build sensors with dynamic ranges that meet or exceed those of film, but generally not within the size constraints imposed by sensor size and the perception of resolution as king by most consumers. When was the last time you saw the dynamic range or noise performance advertised on a camera? Even though these are arguably far more important than resolution to most SLR purchasers, these details are glossed over.
I would like to see a basic overview of the guts of a digital camera given. Sensors, data conversion, data processing, autofocus mechanisms, etc. Anandtech seems like a good site to do it. Contact me if you need help or technical details.
Curt - Monday, September 25, 2006 - link
Could you include in your reviews astronomy photos? As an amateur astronomer, I'd be interested in comparing the very low light sensitivy and contrast ratios of the CCD's.Thanks in advance