Camera shutter remote controls
In the old days of mostly mechanical film cameras, the shutter could be released by pressing the shutter button on the camera body, or on a flexible release cable screwed into the top of the camera shutter button. This cable pushed a pin into a threaded hole at the centre of the shutter button, which was of standard size. Therefore, one flexible shutter release cable would fit virtually all cameras.
Progress changes things, not always in the right direction. Although the shutter button of digital cameras is essentially a mechanical switch that shorts two electrical contacts (sometimes with the added, slight complication of a second contact shorted when the button is pressed half-way, to start the metering and autofocus circuits), there are no standards comparable to the old flexible release cable. It would be very simple to design a threaded receptacle in the shutter button of a digital camera to accept an old-fashioned flexible shutter release cable. It would also be easy to design a standard socket that takes a mini banana plug of the type used for stereo headphones (it has three contacts, so it easily accommodates half-press and full-press actions). In fact, the film winder of my old Olympus OM-2 camera did just this. I built a couple of remote controls with just a plug, cable and a momentary switch, which worked perfectly. Real "progress" developed along very different lines.
There are several reasons for using a remote control. The most frequent (for me at least) is to avoid adding vibration to a tripod-mounted camera. Unless you are using a flash, it is a must for tripod-mounted close-up and macro photography. A remote control may be useful also when shooting with a video head. These heads have a long handle, and by placing the remote on or near the handle you can steer the head and trip the shutter with the same hand. This avoids the need to keep the right hand onto the top of the camera body, which is tiring when done for long periods.
Most point-and-shoot cameras have no facilities at all for a remote cord. The only way to remotely release the shutter is by using awkward contraptions that hold an old-fashioned shutter release cable on top of the shutter button. DSLRs do have facilities for using an electric/electronic remote control, but unfortunately use proprietary connectors that you cannot buy in an electronic shop. The use of the contacts of these sockets is also largely undocumented. To make things even more difficult, Nikon cameras uses three different sockets: one for Coolpix models, another for the D70s (not D70) and D80, and a third for professional DSLR and SLR models (D200, D1 and D2 series).
The above MC-EU1 is used with a few Coolpix models. I used it with the 990 and 5700. It has a proprietary plug that connects to the same socket used for attaching the camera to a computer via a USB port. The large button is a two-stage switch to start metering/autofocusing and release the shutter. The smaller buttons allow zooming and interval shooting. The LCD display can be illuminated. All this is powered by an internal CR2032 battery. Except for its connector, the MC-EU1 appears to be externally identical to the MC-20, which has a 10-pin plug that fits professional Nikon DSLRs (including the D2* series and the D200). However, the electronics of the two categories may be very different. Coolpix cameras seem to receive the commands via a multi-byte serial protocol, while the 10-pin round connector of professional DSLRs accept simple switch closures or voltage thresholds to activate metering, autofocus and shutter.
The MC-EU1 did not work too well with either of the Coolpix models mentioned above. Especially with the 5700, several times on each session the camera would stop responding to the shutter button of the remote control. This could be corrected by switching the camera off and on again, which was annoying because it caused the loss of a few settings that had to be re-entered manually.
The D70s and D80 can use a MC-DC1 remote shutter control (topmost, above) that plugs into a proprietary connector on the side of the camera (this connector is not shared by the USB port, which in these cameras uses a standard mini-USB connector). It is a simple two-stage switch that can be locked in pressed position for shooting in "bulb" mode. The D70 does not have a connector for this remote control.
Consumer-grade Nikon DSLRs (i.e., D80, D70(s), D50, D40) have a built-in infrared receiver for the very small and cheap (at least in Japan) ML-L3 infrared remote control (lowermost, above picture). This control is powered by a CR2025 battery, and has a one-stage shutter button (there is no half-press, so pressing it activates the autofocus, metering and shutter at the same time). The camera must be placed into either of two special shooting modes (either activating the shutter immediately after receiving a command from the remote, or activating the shutter after the delay set in the internal timer) to enable the use of the ML-L3. Unfortunately, once the camera goes to sleep while waiting for the next shot, it also exits this shooting mode. The principal use for this remote control in Nikon's mind is for shooting self-portraits. Consequently, the receiver in the camera faces forward. If you are using the ML-L3 outdoors from behind the camera, usually you must place your left hand, holding the remote, in front of the camera. In indoors settings, infrared light reflected by walls, ceilings and the subject usually is enough to reach the receiver even if the remote is at the back of the camera.
Except for the drawbacks noted above, the ML-L3 is very practical to use, and very small and lightweight. There is no excuse for not having one in the camera bag at all times. It is my preferred remote for the D70s, except when I must shoot for hours on end (in this case, it is annoying to have to change camera settings every time it wakes up from sleep). For this reason, I use the MC-DC1 for macro and close-up in studio settings. Once plugged into the camera, it does not require any particular settings on the latter. I wish that my D200 had the same built-in infrared receiver for the ML-L3.
Nikon sells several types of remote controls for professional SLR and DSLR cameras with a 10-pin round socket. The simplest of these is the MC-30, a very overpriced two-stage mechanical switch. The MC-36 is a sophisticated and expensive electronic accessory with long exposure and interval-shooting capabilities. However, the same or better capabilities are built into all DSLR cameras accepting this control. The MC-20 is an older model. Nikon makes or made also extension cords and special cords that potentially could be used to make home-built remote controls (the only non-standard thing you need is the 10-pin plug and cable), but they are all so expensive that this idea is not practical.
Fortunately, the Chinese industry comes to the rescue. A variety of DSLR remote controls for all popular camera brands are available in camera shops and (usually at lower prices) on auction sites.
In the search for a cheap remote control for my D200, I first bought the above no-brand model, which had the distinction of being the very cheapest on eBay. It does work, but the plug does not have a screw-in metal collar to attach it to the socket on the D200. The switch can be locked for long manual exposures (but both the switch and its locking mechanism feel a little roughly built). The plug is simply pushed in and pulled out of the camera socket, but the force required to do so is very much excessive. I filed out some plastic from around the front sleeve of the plug, but it did not solve the problem. Apparently, the inside of the plug sleeve is too thick, and this cannot be remedied (there is no space to work inside the sleeve, and the metal pins are thin and easily damaged). This remote control appears to be similar to the ones sold under the Adidt brand, but mine lacks a socket for a mini banana plug sometimes visible on pictures of the Adidt remote. Therefore, I cannot be positive that this is the same model. However, I have heard complaints from other users about the plug of the Adidt remote fitting way too tightly. Other models, marked e.g. Jianisi, have a different switch handle but a similar plug without metal collar. I don't know how well they fit.
The above remote, marketed by Nova Photography (but not marked as such on the product) is almost four times more expensive than the preceding one, but still less than half the price of the cheapest Nikon equivalent. It has a more precise feel, a larger handle, better quality cable, and a plug with a metal screw-in collar. The plug can be pushed into the camera socket without locking the collar for temporary use, or screwed in for longer sessions. The plug is easily pushed in and pulled out, and sits well enough even without using the collar. The switch can be locked for long manual exposures. There is a mini-banana socket on the handle, for undocumented reasons (perhaps for connecting an infrared- or radio-operated remote receiver, or a home-made accessory). This model is, in my opinion, a fully acceptable substitute for the Nikon TC-30. In fact, its looks are more modern than the latter, and more in line with the style of other remote controls like the MC-DC1.
As far as I am aware, all remote controls for Nikon cameras with 10-pin round connectors fail to address an obvious need: what do you do with the plastic cover that protects the camera socket, once you take it off? Judging from user forums, this cover is the most frequently lost accessory of these cameras. A reasonable solution would be to store it inside the switch handle of the remote control.
The Nova remote control mentioned above does show that this thought has already occurred to engineers (albeit, not seriously enough to make them provide a usable solution). In fact, the handle has a depression on its back, that would almost (albeit is too tight to) house a Nikon socket cover (shown here at the left). It does not accept a third-party rubber cover, either. This depression could be threaded to accept the original cover. Perhaps this step was skipped to save on production costs. However, I would feel safer with a latching door covering a somewhat larger compartment in the switch handle. This could contain slightly different types of covers without compatibility problems, and could even provide enough space for an additional spare cover in case you loose one. There is plenty of empty space inside the handle for accommodating such a compartment.
True remote controls
Newer cameras often have built-in WLAN and Bluetooth capabilities. This includes, for instance, the Olympus OM-D E-M1. The mobile phone app freely distributed by Olympus for this camera is a true remote control that displays the camera's Live View on the phone screen and allows the phone tough screen to be used for selecting an autofocus spot and triggering the shutter. Access to all camera configuration through this app is also possible. This type of remote control is not covered in the present discussion.