Improvements to SLR camera design digital makes possible

[scoundrel1728]

SLR cameras have dominated the intermediate and professional photography field for decades. Now we have an entirely new technology for image capture and recording, yet it seems to me that a lot of photographers and camera designers have gotten so used to thinking in SLR terms that we are overlooking some improvements that might be made by modifying or even eliminating the basic SLR design.

Among the modifications that camera designers have already made and marketed:

1. Eliminating the space for the film spools. Before the Canon D30, digital SLR cameras were generally based upon existing film bodies. By eliminating this space, cameras can (and do) become smaller and lighter as a result. In the more extreme cases, much of the left side of the camera has been completely removed, resulting in the L-shaped profile of many of the enthusiast-style models.

2. Articulated camera bodies/LCD monitors. These are really great for those shooting occasions in which viewing the camera from a peephole behind the camera is awkward or even impossible. Angle viewfinders and ground-glass screens are a partial solution to this problem but changing the viewfinder in the field is inconvenient and the accessory viewfinders cost at least a couple hundred dollars each. I have used the articulated body on my own camera to shoot images from overhead or from waist level and have even shot within a few centimeters of the ground without standing on my head or twisting myself into a pretzel to view the image before shooting. I also often use such a viewfinder for composing shots while using my knee or a char back to steady the camera. In other words, I would think twice about giving up this feature when upgrading my camera.

3. Eliminating the moving mirror with its attendant acoustical noise, vibration, and unreliability. There is a lot more to go wrong with your typical SLR than a rangefinder, mainly because of the mechanical hoops the typical SLR camera must jump through to take a picture: moving the mirror out of the way quickly, opening the shutter, closing the aperture down to its shooting size, then reversing all these actions quickly to restore proper viewfinder operation promptly after shooting the image. Olympus came up with a variant on the SLR idea in its E-10 and E-20N models. These models use a beam splitter in place of the moving mirror. This means a dimmer image in the viewfinder and some problems with polarized light, but it also makes for a much quieter and more reliable mechanical design. The recoil from this mirror can also be a problem when shooting at slow shutter speeds.

4. Smaller image format without compromising image quality unduly. The smaller image format allows for generally smaller, lighter, and less expensive equipment, while still maintaining something close to the general image quality of 35 mm film. Of course, many will disagree that this is a real advantage. In fact, another thread in this forum is dedicated to arguing the advantages of retaining the traditional 24 x 36 mm image size as opposed to a smaller one.

5. Eliminating the focal plane shutter. With film SLRs, the focal plane shutter was about the only viable design. Between-the-lens and behind-the-lens leaf shutters just aren't practical for controlling the exposure when the lens must also be used for viewing. With digital, the shutter function can be achieved with electronic switching. No more geometrical distortion of fast-moving objects, no more maximum shutter speed limit for flash pictures - of some importance when using flash as a fill light outdoors - and no more delicate shutter curtains to be damaged.

6. Eliminating the requirement for mirror clearance. This requirement has limited wide-angle lenses to a retrofocus design, with its attendant shortcomings. The Sony DSC-R1 is interesting because its lens has decent wide angle capability at an affordable price but that performs as well as more costly wide angle lenses. (The telephoto capability of this lens is no great shakes though, which is one reason I am not seriously considering buying this model, but at least it shows what can be done.)

Of course, some photographers will still find that dSLRs will still serve their applications best, but this also seems a good time to think about whether your next camera really needs to be a single-lens reflex.

[Narsuitus]

All of these great improvements makes me wonder why we have not seen more digital rangefinder type cameras.

[scoundrel1728]

Originally Posted by Narsuitus

All of these great improvements makes me wonder why we have not seen more digital rangefinder type cameras.

By this, do you mean more cameras with optical rangefinders for manual focusing such as Leica was famous for? If so, I can think of several reasons why such a system is a lot less popular now than it used to be, especially with cameras with interchangeable and/or zoom lenses, automatic focusing capability, and lens materials whose optical properties vary somewhat with temperature. Each of these would cause a problem for a rangefinder optically separate from the lens.

However, I remember the old Canon AE-1 having microprisms and a split image rangefinder in the middle of the screen that seemed to work well enough. Most of the problems that would interfere with the functionality of a separate optical rangefinder wouldn't apply to such a system.

[Narsuitus]

Originally Posted by scoundrel1728

By this, do you mean more cameras with optical rangefinders for manual focusing such as Leica was famous for?*

Yes!

I don’t understand why Leica has not produced a digital version of their M6 or M7 rangefinder instead of their Digilux that uses an electronic viewfinder and no rangefinder.

I don’t understand why Nikon has reintroduced their classic S3 and SP rangefinders but has not produced a digital version of them.

I don’t understand why Epson and Panasonic are the only ones who produce a high-quality digital rangefinder that accepts existing manual focus rangefinder lenses.

[scoundrel1728]

My guess is that the camera manufacturers figured that the size of the market for such a product didn't justify the development costs. The S3 and SP have already been developed and have the cachet of being classic camera models. A digital version of these cameras would have neither of these advantages.

I am not familiar enough with the Epson and Panasonic lines to tell which models have true rangefinders and accept existing rangefinder lenses. What models are they?

[JohnC]

The Epson is the RD-1 (http://www.dpreview.com/news/0403/04031101epsonrd1.asp). I'm not familiar with the Panasonic. The Espon is pretty pricey. But it does accept Leica lenses. The rangefinder is good up to about a 135mm lens. I don't know if there is anything longer available.

John

[scoundrel1728]

Most retailers who have the Epson R-D1 in stock price them at US$2999.95, but a couple have them in the low $2900s. Something tells me they aren't exactly jumping off the shelves. Aside from the price, it looks like just the thing for street photographers. Has some interesting in-camera monochrome options too: not just straight B&W, but you can also choose to simulate a green, yellow, orange, or red filter.

[Narsuitus]

Originally Posted by scoundrel1728

I am not familiar enough with the Epson and Panasonic lines to tell which models have true rangefinders and accept existing rangefinder lenses.* What models are they?

Oops, my mistake!

I was under the impression that the Panasonic DMC-LC1 was a rangefinder like the Epson R-D1. It is not. It has a fixed lens and has an electronic viewfinder like the Leica Digilux.

[scoundrel1728]

I can speak with less authority on the technical problems to be overcome with rangefinder cameras, but here are a few that may come up:

1. Rangefinder sensitivity depends on the physical separation between the two imaging sections of the rangefinder. A too-sensitive rangefinder can make the camera focus unnecessarily difficult and fiddly to focus, whereas one with insufficient sensitivity will be ineffective at producing an effective focus. Lenses now in common use vary greatly in the necessary focus sensivity. Wide-angle lenses are relatively forgiving of focusing errors but very f/2.8 and f/4 long lenses with decent light gathering ability require a lot of rangefinder sensitivity requiring a separation of up to 10 cm or so between the optical paths to achieve this sensitivity. A rangefinder this size and sensitivity would increase the necessary size of the camera as well.

2. Rangefinder cameras necessarily depend on parallax to work. Unless there is a separate provision for a viewfinder that looks through the imaging lens, such a camera would be difficult to use for extreme close-up or macro work or any other application in which objects close to the camera would need to be imaged or avoided. Examples would be shooting through holes in a fence. The rangefinder - and quite possibly the viewfinder as well - would be useless when mounting the camera to an auxiliary instrument like a microscope.

3. For proper coupling between the rangefinder and lens, the coupling ratio requires separate adjustment for each focal length. This makes rangefinder models difficult to use with zoom lenses. Not sure how this problem is currently addressed in existing models with interchangeable prime lenses. This requirement will definitely put some serious constraints on the design of zoom lenses to make them compatible with rangefinder cameras.

4. The rangefinder feedback is essentially an open loop, which means focus changes from envrionmental factors like temperature require special provisions for compensation. Some of the newer lens materials like fluorite have refractive indices that depend more on temperature than the older materials and can result in focus shifts from this cause. This is one reason that newer lenses often don't have distance markings on the focusing ring. This also means that zoom lenses used with rangefinders must be of a confocal design, i.e., a design in which the focus distance stays constant when the focal length is changed. This is a desirable characteristic even when it isn't absolutely necessary as it would be on a rangefinder, so confocality probably wouldn't be a big extra requirement in the design of suitable zoom lenses.