Buying & Using Older Flash Units
With informed choices, many older flashguns are entirely usable on modern cameras. They are also useable free-standing in a studio situation, possibly firing into a flash brolly or other type of diffuser. They will probably lack some features for special purposes such as HSS (High Speed Sync) and built-in radio transmission. They also unlikely to have motorised zoom, digital displays and touch screens, the absence of which might be considered advantages by some, not least because there is less to go wrong. They are a fraction of the price of a "digital" flashgun, even of a used one, anything from 10 to 100 times cheaper.
A priority is to buy one with with a low trigger voltage. The table on another page helps to identify these, and if you already own a flashgun there is guidance towards the bottom of this page on how to measure the voltage. The best place for a unit with a high voltage is in the rubbish bin because there is always a danger that one day someone, not necessarily yourself, might fit it to a modern camera and wreck the electronics. In pure money terms most are worth nothing anyway.
A second priority is to buy one with an old-style Auto mode, one which can control exposure with its own sensor, so that it does not need to have been designed to work with a particular camera. This may be in addition to Manual mode and film-era TTL (Through The Lens) mode, the latter being useless on a digital camera.
The used market, such as on Ebay, Craiglist, and similar, is awash with old flashguns to choose from, including plenty of low voltage ones. This is because many people have moved from cameras to phones for their photography, also because digital cameras (and phone cameras) can cope with lower ambient light levels, and also because many people do not believe that a flashgun can be used on a digital camera unless it has the word "digital" on it somewhere. So it is a buyers market, and as of 2023, good low or medium power shoe-mounted flashguns can be had for £10-20, although the shipping cost will add about 50% more. Don't be caught out by sellers demanding unreasonably high shipping costs. Expect to pay more for a specialised unit, such as a powerful hammerhead, bare bulb flash, or ring flash.
Many sellers are not the previous users, but are perhaps relatives of a deceased, a charity, or a house clearance agent. Do not expect them to know the answers to questions you might want to ask. Some sellers do not even seem to know how to fire a test shot (or claim they do not), and sell units as "Untested" or say "Can't test, no batteries". If the price is low enough, very low, and the photos look good, it might be worth taking a risk, but it could be that the unit simply does not work, and the seller knows it.
Brand DedicationFlashguns with camera makers' branding sell for higher prices, often much higher. The main camera makers have offered them since film days, usually with "dedication" to their own cameras. The dedication will consist of at least a "Flash Ready to Fire" indication in the viewfinder, probably set the camera shutter to its sync speed automatically, possibly set the camera aperture, allow TTL exposure control, and confirm adequate exposure after the shot.
However, dedication functions on a film era flashgun may not work (or only partly so) even on a digital camera of the same brand. In particular, a film era TTL mode will not work on a digital camera (with some minor exceptions) and vice-versa - there is a fundamental difference in the way the TTL works. This may not be a big deal - dedication facilities can be a nuisance anyway (and could be even in film days) if they make camera settings automatically contrary to what a more advanced user may want. Some, such as setting the camera sync speed, are aimed at beginners. The Manual and film era Auto modes do not need camera dedication because the flashgun is self-sufficient in these modes.
Dedication functions require additional contacts in the unit's foot, and because the layout and electronic signalling of these differ between brands, you are advised not to use dedicated units outside their brand. Some independent makers (eg Vivitar, Metz, Sunpak and Cobra) offered a range of modules that plugged into their more expensive flashguns to match them to particular camera brands. Avoid buying a unit requiring a plug-in module unless it comes with the module you need, because it can be difficult and expensive to find and buy one separately - the asking prices for separate modules are often higher than for units with ones already attached. You may find a module at a bargain price if it is attached to a flashgun declared as non-working, because the fault is much more likely to be in the unit's body rather than the module. Some independent makers sold dedicated flashguns with fixed feet and were hard wired for particular brand dedication, and some flashguns had switches to choose between dedications.
A buyer should know that Nikon call some of their flashguns "Speedlights" and Canon call some of theirs "Speedlites" (different spelling). These two companies have always been inclined to name their equipment similarly. Also be aware that some sellers and users call a flashgun of any brand a "speedlight" (or "speedlite"), so we hear of "Metz speedlights" for example; this tendency seems to be mostly in North America. Flashguns (and, more frequently, studio flash units) are also often referred to as "strobes" in North America, with potential confusion with devices for repetitive flashes such as used in discos and for technical purposes. For internet searching it is useful to know these terms, and also common spelling mistakes and alternatives. When searching on Ebay for example it is often fruitful to search for, "Sunpack" as well as "Sunpak" or "Mecablitz" as well as "Metz". Beware that some camera makers did not always adhere to even the basic flash trigger contact position in their hotshoes (see the separate page on this) so some of their own flashguns do not work on their own cameras.
You may be disappointed to learn that camera-branded flashguns are probably not made by the camera maker themselves, but under contract by specialist such as Sunpak or whatever Far Eastern electronics manufacturer they could strike a deal with at the time.
ConditionThere is no need to buy a used flashgun that is not in excellent or near mint condition. Most were originally purchased by amateurs and have been used only lightly. The downside is that a significant number of them will have been left unused with batteries inside for long enough that they will have leaked and corroded the contacts and even circuit boards. Particularly do not buy a unit without seeing inside the battery compartment, or at least a photo of it, and ask an Ebay seller to take a photo if one is not already provided; if they won't, look elsewhere. Once the chrome plating of the battery contacts has gone, no amount of cleaning will prevent poor contact problems ever after.
Another possible issue is the condition of the main flash capacitor, which cannot reasonably be ascertained before buying. This type of capacitor tends to deteriorate if it is not used regularly, which increases the charging time and reduces the strength of the flash, although the latter is not such an issue with auto exposure control because the sensor will compensate. However, these capacitors can usually be reconditioned in situ provided deterioration has not gone too far. Do not however expect the maker's claims of charging speed ever to be quite achieved again.
On buying an older flashgun it is a good idea to carry out the reconditioning process straight away, whether it might need it or not. To do this, charge it up in small stages, the first charge being five seconds of being switched on followed by leaving it off for 10 minutes, then another five seconds likewise a few times, then increasing to 10 seconds charging, then 20 seconds if needed, until the "Ready" light eventually comes on. Once "Ready", fire the flash with the test button, then recharge and fire again half-a-dozen times. This should have reconditioned the capacitor as far as possible.
In ownership, flashguns benefit from reasonably frequent usage, so they should be charged and test-fired a few times each month if otherwise unused. Dont leave the batteries in the unit between times.
AccessoriesIt is not advisable to buy a flashgun that relies on a special battery, rechargeable or not. A rechargeable battery from 40 years ago is unlikely to hold much of its charge any more, and it is extremely unlikely that you would be able to find a new replacement. Old external battery packs such as the belt-carried high voltage ones for large professional flashguns are probably useless, even if the seller can demonstrate a flash or two. Fortunately most flashguns can use standard sized batteries (medium power units typically use four AAs), which will be available for a long time to come. A mains adaptor will probably be fine however.
Some flashguns, particularly hammerheads and ring flash units, require certain accessories to be useable, such as sync leads, battery pods, brackets, adaptor rings, and the dedication modules mentioned above. Battery pods tended to be used on the more professional flashguns to enable quick changing of batteries at an event, the photographer carrying several pods with fresh batteries already in them. Before buying a unit, do some research on whether this is the case; demos and reviews on YouTube are a source for this, and do not buy unless the seller includes them, and they are genuine and not generic replacements. Such accessories can be difficult to find and expensive if bought separately. Hammerhead brackets seem particularly prone to go missing, probably because some owners had a style of holding the unit up high with the handle, free from the camera, so they never needed the bracket and threw it away. Other sellers, not the previous users, may not have recognised the purpose of the accessories and have left them behind in a drawer.
Some accessories, such as telephoto adaptors, may be non-essential. Top end units can be systems in themselves, and no seller is likely to have posessed the entirety. If you want a particular missing accessory, the best chance is to find it included with a further non-working flashgun at (hopefully) a cheap price. Watching Ebay and the like with patience is required.
UsageIt has already been said that film era TTL exposure control is incompatible with digital cameras, but that the Manual mode and the old type of Auto mode are entirely useable. Towards the end of the film era, from around 1990, some flashguns omitted the Auto mode to save costs on the premise that TTL mode was the future, which was true but not in the way that people thought; those flashguns become effectively only Manual units on digital cameras. There is an opinion that for many uses the old Auto mode is superior to digital TTL.
A limitation of film era flashguns is that the range of ISO sensitivities that they cater for is low compared with the capability of digital cameras. Typically their dial or slider will offer from ISO 25 up to only ISO 800, 1000, or 1600 at the most [ISO numbers were previously known as ASA numbers]. This suited the availablity of film at the time, but a digital camera can handle up to ISO 64,000 or more. This is more of an inconvenience than a limitation, because usually the film speed dials and sliders are only calculators and are not connected to anything internally. It is therefore possible to extrapolate to higher ISO numbers. For example if a flashgun's Auto mode slider recommends an aperture of F4 for ISO 800 film (the maximum on its scale), you could use the same mode at F8 and ISO 3200 - a decrease of two aperture stops for an increase in two sensitivity stops. The emited light energy of the flashgun will be unchanged.
Sync SpeedFor the benefit of beginners, the shutter speed of a camera with a focal plane shutter (ie most cameras with less than medium format film or sensor size) must be at sync speed or slower when using older electronic flashguns.
Slight digression: A camera's shutter speeds, ie 1/125th, 1/250th of a second etc, are (of course) shutter times, not speeds, but shutter "speed" has become ingrained into photographic terminology. The majority of serious modern cameras (SLRs, DSLRs and Mirrorless up to "Full Frame" size) use focal plane shutters that are effectively a curtain with a slot in it, and the curtain moves across the film or sensor at a constant speed, or rather velocity as in metres per second, whatever the value of the set shutter "speed". The different shutter "speeds" are obtained by varying the width of the slot, the slower the shutter "speed" the wider the slot, giving each part of the sensor a longer exposure.
The flash from an electronic flashgun is instantaneous for most practical purposes, but at high shutter "speeds" the moving slot of a focal plane shutter is narrower than the width of the sensor, so only the area under the slot will be exposed for the flash and the rest will be underexposed with only the ambient light. The fastest "speed" at which the slot in the curtain is wider than the sensor is called the sync speed, and a sensible flash photo can only be taken at this or a slower setting.
The sync speed of a focal plane shutter is entirely a property of the camera and is a significant feature. On film cameras (and some digitals) it often has a special marking such as "X" on the shutter speed dial, and in some cases even had an alternative shutter release. Through the 1980s and 90s there was a sync speed arms race between the makers of 35mm film cameras for higher and higher speeds, originating from a typical 1/60th second and rising to as high as 1/250th second using some intricate and expensive technology. This effort was made somewhat redundant by the later emergence of different high speed sync technologies, but that is outside the scope of this article.
Some medium format and all large format cameras use a leaf shutter within the lens rather than a focal plane shutter. These open fully at all shutter speeds and therefore they do not have the sync speed limitation of a focal plane shutter, although their own maximum speed is relatively low - typically in the region of 1/1000 to 1/2000 second. Some medium format cameras allow the use of either type of shutter.
In the case of a flashgun designed to be "dedicated" to a particular camera brand, or camera models within a brand, automatically setting the camera shutter to its sync speed will almost certainly be one of its functions. In film days, it may or may not have allowed the user to override the automatic setting because there are times, even when using flash, when a slower speed than sync is desirable. With a vintage dedicated flashgun on a digital camera the behaviour is variable, almost certainly depending on the camera mode, of which there are many on a modern camera. The user can experiment, but probably the most straightforward approach is to use the camera in its manual mode, setting the shutter speed to sync or slower (if it is not done automatically) and the aperture according to the recommendation of the flash unit.
Trigger VoltageAs described on the "Technicalities" page, the simplest flashgun designs resulted in a high trigger voltage on the flash trigger contact, the central one on the hot shoe - typically over 100 volts and often much more. This was not a concern with older cameras because they triggered the flash with a mechanically operated microswitch which could tolerate it. However flashgun makers began to lower the trigger voltages in the 1980s when cameras began to contain more electronic components, even though this was still in the days of film. Usually this was done with a model change, but in some cases the maker did it quietly with the result that when buying one today you cannot be sure whether it was manufactured before or after the change – don’t expect most sellers to know.
A high voltage on the hot shoe should not be fatal to a person because unlike the domestic mains there is little energy behind it. It is more like the charge on a nylon shirt in dry weather. Nor will there be a complete circuit unless the ground contact (in the slide recess) is touched at the same time. Nevertheless I don’t advise trying it, especially if you have a Pacemaker, and I have seen an account of someone getting quite a shock from a Vivitar 283, which have been measured as producing up to 600 volts.
There is a standard today that requires cameras to tolerate up to 24 volts in the hotshoe, but this is not legally binding and is not always followed. There is a report of Canon advising no more than 6 volts on one of their cameras, and on the other hand some particular Nikon DSLR manuals have said that up to 250 volts is acceptable. It is worth checking your camera manual, although it will probably only tell you to use the camera maker's own branded latest unit, and disown responsibility for anything else.
Sometimes there is advice to use an old flashgun with a voltage reducer in the form of an adaptor that fits between the camera hot shoe and the foot of the unit. One brand of these is "Safe-Sync". Apart from my advice not to keep a high voltage unit in the house, these can be rather pointless because they cost significantly more than most inherently safe flashguns do on the used market. There are also reports of them being unreliable, and of refusing to work with flashgun trigger voltages over about 400 volts or below about 5 volts (for which they are not needed anyway). There is also the fact that the height they add to that of the flashgun above the camera adds to the stress on the camera's hotshoe, especially when oriented for portrait format. This can be an issue with some heavy flashguns even without the extra height.
There are also descriptions of electronic modifications made by enthusiasts to older flashguns to reduce the trigger voltage, often involving an opto-isolator. The popular Vivitar 283 seems a favourite for this treatment. Like the use of a commercial voltage reducer, I would consider such an approach only worthwhile if the flash unit is something special and would be expensive to replace with an equivalent but safe alternative, such as a very powerful old Metz hammerhead, a bare-bulb unit, or one to which you have a particular attachment.
Measuring Trigger VoltageTo measure the trigger voltage of a flash unit you need a digital voltmeter or multimeter. Ones without advanced features are very inexpensive, and certainly cost less than the Safe-Sync device mentioned above, and they have many other uses.
An analog voltmeter or multimeter (as opposed to a digital one) can only do part of the job : if it indicates a dangerously high voltage then that flashgun is certainly to be avoided, but a low voltage reading cannot be relied upon. Although a hotshoe voltage might be high it will not have much power behind it, so both digital and analog meters tend to pull down the voltage reading to some extent, the analog much more so. But a digital voltmeter (or multimeter in voltage mode) will typically have an impedance of around 10 megohms, which is more than an order of magnitude higher than the output impedance of a vintage flashgun trigger; therefore an analog reading will be accurate enough for the purpose of checking voltage safety.
Flashgun trigger voltages do tend to fall into two categories depending on whether the maker did or did not make an effort to reduce it below the value comming straight out of the unit's inverter - as described in the "Technicalities" page.
As well as the voltage, the polarity needs to be checked. The convention is that the centre contact of the foot should be positive and the ground should be negative. There are some ancient units that do not follow this convention and they would damage a modern camera; those units will probably have a high trigger voltage anyway. Beware that some digital meters will show a voltage figure whichever way they are connected, accompanied only by a small plus or minus sign that is easy to miss.
To measure the trigger voltage of a unit with a conventional foot layout : with the flash unit switched on and fully charged, connect the positive side of the meter (red lead in Fig 6) to the most central contact in the foot, and the negative side (black lead) to what is usually a thin leaf spring contact inside the side groove of the foot.