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Hotshoe Configurations |
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| Although this website is about older flashguns on newer cameras, the diagrams below are downward views of camera hotshoes, including of vintage cameras, because that is the convention for illustrating hotshoes. The contact layouts of the matching flashguns of the time, looking up at the feet, are of course mirror images of these. The diagrams are not to scale. |
| The only electrical contact positions defined by the ISO 518 standard are those of the basic central flash trigger contact and the ground side rails. Most present day layouts have evolved from that but in different ways, and even apparently similar layouts may differ both in the exact position and the function of additional auxiliary contacts. For this reason, if a camera has contacts additional to the basic trigger and ground, it is inadvisible to fit a flashgun to it if that flashgun has additional contacts not designed for that camera. |
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➡ Basic - ISO 518 |
➡ Canon | ➡ Chinon | ➡ Contax | ➡ Fuji/Fujica | ➡ Minolta | ➡ Nikon |
➡ Olympus/ OMDS |
| ➡ Pentax | ➡ Ricoh | ➡ Samsung | ➡ Sony | ➡ Yashica | ➡ Cold Shoes | ➡ Sync Cords | ➡ |
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A basic hotshoe design in terms of dimensions and contact layout has been a standard for a long time, most recently described in ISO 518:2006. This specifies the physical dimensions of the foot, and the positions of the two principle electrical contacts as shown in Fig 1 : the flash trigger and the ground, which are respectively an insulated central contact and the side rails.
The ISO 158 standard is not compulsory, and the different camera makers have different track records with regard to their adherance to it as far as it goes, although the ground contact position has been fairly consistent. Makers have sometimes departed from the standard for a practical reason, such as for a miniature camera, but other departures have been transparent attempts to restrict buyers to the maker's own branded flashguns, which are usually priced at a premium. Unfortunately the standard does not specify any protocol for the electrical signals, other than the more recent versions specifying that no signal should exceed 24 volts. Nor does it specify the positioning or electrical protocols of the numerous auxiliary contacts introduced from around the 1970s. 
That might seem very restrictive for using an older flashgun, but the situation is not as bad as it might sound. Firstly, some independent flashgun makers made variants of their better models with additional contacts matched to those of the major camera brands. In some cases the physical layout of the contacts was similar enough for this to be accomplished by a mult-way switch on the flashgun. For example Pentax, Nikon and Minolta had similar contact layouts at a time when they only used three. Another approach was for the flashgun foot to be a plug-in module appropriate for the user's camera. These modules were often fitted by a camera shop assistant when the flashgun was first purchased and the user could remain unaware of the modularity, even when selling the unit in the used market years later.
Secondly, many flashguns from independent manufacturers have been made without additional contacts in order to avoid this problem, up to the present day. Some of the functions provided by the additional contacts are not essential anyway, such as giving a "Flash Ready" indication in the camera viewfinder and setting the camera shutter at its sync speed; but most flashguns also have a "Flash Ready" on their rear panel and the user can set the camera shutter to sync speed themselves. Most film era flashguns have their own Auto exposure control that does not require any signal to or from the camera. The exception to this is TTL exposure control, with which the flashgun is controlled by the camera so obviously needs the additional communication. In fact, at least since 2010 there have been significant sales of low priced third party flashguns with only manual modes and a single trigger contact to the ISO standard. These are low priced partly because they fit any camera with the ISO contact so only one model is required to cover most cameras, and also because they do not need to pay royalties to camera makers to use the electronic protocols necessary for the auxiliary functions - even if the camera makers are willing to share those protocols. |
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Canon's layout has a mixed history. It has tended to evolve by adding auxiliary contacts to the basic ISO 518 layout, but there has been at least one departure from this : in 2019 the EOS 200D Mk II, an entry level camera, and the 4000D, omitted the original central trigger pin. It is believed that the trigger signal was already in one of the other contacts in the previous design. A reason given for the omission of the central contact (Fig 9) was that it prevented the use of old flashguns that could carry high damaging voltages. Of course it enforced (at least until third party adaptors were produced) the use of Canon's own corresponding flashguns, which are very profitable for the company. However the backlash from Canon owners, many of whom were concerned that their existing flash equipment (even Canon's own) might not work on a new generation of cameras, persuaded Canon to restore the central trigger contact on their subsequently released cameras. The original F-1 of 1971 and its 1976 upgrade known as the F-1n (lower case "n") did not have the hotshoe on the pentaprism roof. This seemed to be because, like their Nikon counterparts with the Nikon F series, the Canon designers were unable to find a way to transmit electrical signals via a removeable pentaprism. However, Pentax did it with the LX in 1980 and Canon did so with the F-1N (upper case "N") in 1983. Instead, the F-1 and F-1n provided slide rails and a flash trigger contact in the base of the rewind crank. I am not aware of any flash unit that fitted directly to these, but Canon offered at least two couplers, called types D and L, which fitted into the rails straddling the rewind crank, and provided a normal hotshoe on their upper surface. Coupler D was for "ordinary" flashguns having only a flash trigger contact with the ISO 518 layout (Fig 1). Coupler L on the other hand (Fig 5) had a contact layout corresponding to the F-series Speedlites, but contained electronics which interacted with the specifically designed Speedlite 133D. This Speedlite used electrical resistance rings fitted to certain lenses to detect the focussed distance and thus provide an early form of flash exposure automation called the CAT system. An "ordinary" flashgun could also be fitted to an L coupler. A strange thing about the CAT flash system is that, for all the development that must have gone into it, and for a professional camera, the Speedlite 133D had a Guide Number of only 18 - which is in the league of amateur snapshots. Perhaps Canon intended to produce some more powerful CAT flashguns later, but the CAT technology was soon decisively rendered out-of-date by other advances in flash electronics. |
| Chinon made 35mm SLR cameras from the 1970s to the 1990s, and also made compact cameras. Some models, with minor modifications, were branded as Agfa, Miranda, Petri, Revueflex, and Sears. Earlier Chinon SLRs used the M42 screw mount and later ones the Pentax K mount. However the hotshoe contacts, while based around ISO 518, did not follow the Pentax convention as the "Ready" contact was on the opposite side, like Nikon and Ricoh. The later CP-9AF SLR had four auxilary contacts, two of which are believed to power the optional semi-integrated AF-S120 pop-up (or "fold down") flash unit. |
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| Earlier cameras used an ISO 518 hotshoe with no auxiliary contacts, but the AX Series introduced in 1979 added two. The digital Fujis retain the central trigger contact, and the most recent cameras have five auxiliary contacts. |
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Minolta was a respected maker of 35mm cameras which in 2006 (having already merged with Konica) sold its camera manufacturing business (but not the brand name) to Sony. Their earlier, manual focus, SLRs had hotshoe layouts based around the ISO standard, but their autofocus cameras from 1988 (called Maxxum or Dynax) adopted a new hotshoe design called the iISO (Fig 15) that was entirely different, both physically and in the contact layout. There was no technical advantage in the new design; the tongue-and-groove slide rails were closer together than in the ISO 518 standard so if anything the flashgun foot was weaker and less firm in the shoe. It was also rather restrictive of adding further contacts. Unlike the knurled nut that is commonly used to secure a flashgun foot in the shoe, the iISO had a convenient catch with a quick release button on the flashgun foot; but a similar catch could be incorporated in a standard ISO shoe and other makes (eg Chinon) have done that. The new design seemed partly to make a "new technology" gesture, and partly to encourage sales of their own brand of compatible flashguns. There was some backlash among Minolta users because the new shoe was incompatible with their existing flashguns. Minolta obviously introduced new compatible flashguns, but much external equipment such as triggers for studio lighting remained reliant on the central trigger contact. Minolta did offer adaptors, and third parties soon did so too. It is understood that the later Minolta cameras, including digital, and also the early successor Sony cameras, repurposed the contacts differently, sending all data through a single contact (plus ground) acting as a serial bus. Sony continued the iISO hotshoe in their own cameras after their takeover of Minolta, but in 2012 adopted a new design called the Multi Interface Shoe [MIS] in which the trigger contact was restored to approximately near the centre. This was accompanied by a row of no less than 21 contacts in the leading edge of the shoe for the auxiliary functions. I shall not attempt to identify them here, but they include contacts for uses such as stereo microphones - Sony came from a background of video cameras. Sony positioned the trigger contact a little to the rear of centre of the shoe and while it might be supposed that it should trigger any flashgun meeting the ISO 518 standard, there have been reports of it failing to make contact with some. In any case, care should be taken that any metal of the flashgun foot does not touch the auxiliary contacts. The MIS is a return to the principle of the first camera cold shoes, which was that they were intended for numerous types of accessory and not just flashguns, but this time with electronics. |
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Nikon have used the ISO standard as the basis for most of their hotshoe layouts, adding auxiliary contacts progressively. However there was a different type of hotshoe for the professional F and F2 cameras, and a different one again for the F3 (which added TTL flash exposure control), all of which were located such that the flashgun foot straddled the film rewind crank. The reason for this arrangement seems to be that the interchangeable viewfinders which these cameras had posed a problem transmitting the electrical signals to the normal hotshoe location, although this problem was easily solved later; another theory is that Nikon were concerned about the stress on the viewfinder attachment. From the F4 model of 1988 onwards however, the hotshoe was restored to its normal location on the pentaprism and given same layout as other Nikon SLRs.
The early F-Series cameras' hotshoes, straddling the rewind crank, were a significant inconvenience. An event or media photographer using several rolls of film had to remove the flashgun to rewind and reload. If they had a second camera such as a Nikon FM2 or Nikkormat as a backup, they would need two different types of flashgun or else fiddle with adaptors. Nikon themselves had to make two versions of some of their Speedlights. Adapters were available from Nikon and third parties. |
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Olympus have kept to the ISO 518 standard as the basis of their hotshoes, but dithered about where to locate auxiliary contacts. The first OM film cameras of the early 1970s (OM-1 and OM-2) had no hotshoe, only a small connector in the roof of the pentprism, apparently for a co-axial jackplug; this suited a sync cord for a hammerhead flashgun, but for a hotshoe mounted flashgun it was necessary to fit an adaptor. The adaptors were ugly cuboids, and the basic plastic of those sold by Olympus themselves had a tendency to disintegrate over time. As auxiliary contacts were added the layout changed at least twice - probably with the intent of avoiding incompatible electrical contact between the camera hotshoe and unmatched flashguns. Unusually, and probably for the same reason, the early Olympus hotshoes placed the first auxiliary contacts ahead of the centre rather than to the rear as most other makers did. As a result of the changing contact layouts, Olympus produced four different types of adaptor for the OM-1 and OM-2 series of cameras, known as Shoes 1, 2, 3 and 4. Shoe 1 was a single contact ISO 518 shoe, Shoes 2 and 3 added a TTL quench contact but in different places, and Shoe 4 added a further "Flash Ready" contact but could only be fitted to the OM1n and OM2n cameras. Olympus were pioneers in TTL control of flash exposure; nevertheless it was surprising that the first auxiliary contact to be added to the basic ISO 518 shoe was for the TTL quench, and a "Flash Ready" contact only came later. Later film cameras, starting with the OM-10, provided an integral hotshoe using essentially the Shoe 4 layout but omitting the TTL quench contact in the less expensive models, such as the OM-10 and OM-20. The last Olympus film cameras made, the OM-3Ti and OM-4Ti, had four auxiliary contacts which may have been to make a transition to the current digital era layout. In 2021 the original Olympus company sold its camera division to Japan Industrial Partners, a holding company. JIP use the name OM Digital Solutions for this subsidiary, which has continued making the existing products and introduced some new ones, and is permitted to use the Olympus name on its products at least for the time being. |
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Pentax have consistently used the ISO standard as the basis of their hotshoe layouts, adding auxiliary contacts progressively, with the exception of the miniature Auto 110 film cameras which had a unique hotshoe for their own tiny flashgun. Pentax have always had back-compatibility as a brand feature, and at least their own flashguns from around 1975 (the AF series and onwards) can be used on Pentax cameras up to the present day (2023). The flagship Pentax LX film camera of 1980-1993 had interchangeable viewfinders but, unlike the rival Nikon F3, it had a conventional hotshoe in the normal place on the appropriate pentaprism viewfinder, passing the electrical signals through to it via spring contacts, so no special flashguns or adaptors were ever needed. It has been reported that the TTL "Quench" contact has been used at least by some film era Pentax flashguns to inform compatible cameras with a program mode what aperture should be set for a given ISO sensitivity. This was done by various high frequency signals, for example 4 KHz would call for an aperture of f5.6 at ISO 100, and based on this the camera would set an aperture taking into account the ISO of the film loaded at the time. The AF400T hammerhead flash, contemporary with the LX, could be connected to the LX with a special sync cable that fitted a PC socket on the LX body and at the same time connected to two tiny adjacent contacts that carried the auxiliary signals (Fig 34). The arrangement was not entirely satisfactory. Alternatively Pentax could supply a sync cable that terminated in a plug-like connector that fitted in the camera's hot shoe and picked up the auxiliary signals from there. This latter sync cable could be used with any Pentax camera. Third party hammerhead flash units dedicated for Pentax also used this latter method. The Pentax 6x7 and the revised 67 never had a shoe (Fig 38), only basic PC sockets, but the optional grip did have a cold shoe. The final iteration, the 67ii, could be connected with a special cable to its optional grip which carried a hotshoe with the same auxiliary contacts as its 35mm contemporaries. In 2011 Pentax became a subsidiary of the large and diverse Ricoh company. Its products were not affected as far as the end user was concerned, in particular the Pentax hotshoe layout was maintained rather than being changed to that of the previous Ricoh SLRs. |
Ricoh, a large company manufacturing various technical products, made SLR cameras up until around 1980 and by that time the only contact that had been added to the basic ISO layout was for a "Flash Ready" signal. This was in a similar location to that for Nikon. Ricoh continue to make compact cameras under their own name to the present day. In 2011 Ricoh bought the Pentax camera brand and facilities, which continued as a subsidiary of Ricoh with no fundamental change. The long-established Pentax hotshoe layout, in which the "Flash Ready" contact is on the opposite side from that in the old Ricoh layout, was not affected. Pentax cameras sold today have "Ricoh" as well as "Pentax" prominently on the box, although only "Pentax" is prominent on the camera, and they are considered to be Pentax rather than Ricoh cameras. |
Samsung entered the DSLR market in 2005 with the GX-10, which was a re-branded Pentax K10-D. The hotshoe contact layout looked similar but I have no confirmation that the protocol was the same. Subsequently Samsung added a fourth auxiliary contact, for example on the NX-5 camera. Samsung did not produce DSLRs after about 2010. |
From 1974 the Contax brand was used for Yashica's more up-market cameras and accessories, and the lens mounts and hotshoe connections were the same. The trigger contact followed the ISO 518 standard and the auxiliary contacts were placed similarly to those of Pentax. Yashica and Contax cameras were not made after 2005. |
Prior to about 1960 many cameras were equipped with a simple metal shoe to accept a variety of attachments including rangefinders, exposure meters and wire-frame "sports" viewfinders. They had no electrical contacts and are therefore called cold shoes in retrospect. Some flashguns, with plain feet at the time, could be fitted in them and received the trigger signal via a sync cable plugged into a PC socket on the camera body, and such flashguns could be said to have cold feet.
To dispense with the need for a sync cable, later cameras had shoes with electrical contacts for correspondingly equipped flashguns, and these were termed hot shoes. However for a long transitional period there were cameras around with cold shoes and others with hot shoes, so flashgun makers tended to make dual purpose units with contacts in the feet in addition to a sync lead (or a socket for one). A problem for the dual-purpose flashgun makers was that a metal cold shoe would short out their flashgun's hot shoe contacts, not allowing the essential trigger voltage to build up at all. Therefore they arranged for the trigger contact in the unit's foot to be electrically disconnected when the sync lead was in use. Meanwhile the camera makers continued to provide PC sockets in addition to the hotshoes, partly because they were still needed for sync leads to hammerhead units and studio lighting - at least before the advent of radio links. The more professional cameras still provide a PC socket today, although there are adaptors that will fit in a hotshoe to provide a PC socket. 
If a camera has both a PC socket and a hot shoe it might be thought that they would be simply wired in parallel. However it is not that simple. When flashguns with foot contacts had high trigger voltages, the user was relatively protected from shock when the unit was off the camera by the fact that the ground contact is in a recess in the foot, out of finger reach, and once fitted to the hotshoe the trigger contact is covered; in either case therefore an electrical circuit via the user is difficult to make. However the central trigger contact of the hotshoe of a camera remains exposed to a finger touch if a hammerhead or a separated flashgun is connected via a sync cable, and the metal hotshoe side rails or even the whole camera body is an exposed ground, so if the PC socket was simply connected through to the hotshoe an electric shock circuit through the user would be possible . For this reason the hotshoe and the PC socket may be on alternate camera circuits such that the hotshoe becomes a cold shoe when a sync cord is plugged into the PC socket. This may be an issue if the user wants a hot shoe flash in addition to cable controlled studio lights. |
Since the days of flash bulbs, the better cameras have provided a connection for a sync lead, a cable to carry the trigger signal for a flashgun. From the 1950s this has usually been in the form of a Prontor-Compur (or PC) socket, a small co-axial connector currently defined in ISO 519:1992. By convention, the connector on the camera is defined as the female and the plug on the lead as the male, although the outer shell of the male connector goes outside the outer shell of the female, unlike the larger TV aerial connectors. Male and female PC connectors are shown in Fig 41. Some cameras have a screw thread surrounding the PC connector, onto which a knurled nut on a corresponding sync lead fits to secure it; the screw thread seems to vary between camera makers, but generally it does not prevent a plain PC connector from being fitted instead. It is the standard that the inner contact carries the positive trigger voltage and the outer shell is at ground potential, but this might not be the case with some older flashguns made at a time when cameras used a microswitch to fire the flash and the polarity did not matter.
For reasons unknown, the connection between the sync lead and the flashgun itself is not usually of PC type. A mono audio type jackplug is often used, and a 2.5mm diameter example is shown as Fig 40 A. Sunpak used a three prong plug and socket for many of their hammerheads (Fig 40 B), possibly planning a sync cord with an extra core to carry a Flash Ready signal - in which case the plan was soon overtaken by the proliferation of further communication requirements by flashguns. Some flashguns have a permanently fitted sync lead, such as in Fig 42. These tend to belong to the time before cameras had hotshoes, when the lead would always be needed. In fact the Fig 42 example belongs to a transitional period in having a hotshoe contact (only the central trigger) as well as a fixed sync cable. In a common arrangement, the contacts in the foot conduct only as far as a PC socket in the body just above, into which the sync lead plug is fitted when it is stowed into the provided slot. In this way, the contact in the foot is disconnected when the sync lead is plugged into a camera PC socket so it cannot create a short if it is in the metal cold shoe of a camera. Notice also in Fig 42 the small metal stud in the upper part of the foot, to the right. This is to short the PC plug by touching it on, to test that the flash works before taking a picture and is equivalent to a test button. Ingeneous though these features are, they all show that this flashgun is one of the earlier electronic ones and is not to be paired with a modern camera. PC connectors can only carry the flash trigger signal and no other functions. In the final phase (for the time being at least) of the development of hammerhead flashguns the PC connected sync cord with its single signal channel was abandoned in favour of a multi-core cable, with a multi-pin connector for the flashgun at one end and a plug to go into the camera hotshoe at the other end, matching its contacts. Fig 40 C is an example. Nevertheless, professionally oriented cameras retain PC sockets for possible other uses, not least the firing of studio flash lights. |
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