Flashphoto Group Flash Modes with OM & iS cameras
Manual Flash is supported
by all OM cameras with any flash, including off-brand flashes, and by the iS-1000, iS-2000
and iS-3000 with both the built-in flash and the G-40. It is the most basic form of flash
photography, based on the Guide Number (GN) rule D = G / F which can also
be written as F = G / D or G = D * F, where D = Flash
Distance, F = Aperture Value and G = Guide Number.
In practical terms it means that when the GN is given, for a specific Aperture Value there is one correct Flash Distance, and vice versa for a specific Flash Distance there is one correct Aperture Value.
When the lens would be set at F1 (which is hypothetical for most lenses), the flash distance equals the GN. For every two Aperture Values the lens is stopped down, the flash distance is halved. So a value of F2 means a flash distance of half the GN and a value of F4 means a quart of the flash distance.
Guide Numbers can me given in meters or in feet; the flash distance is to be interpreted accordingly. GN's are film speed dependent; they are always specified for 100 ASA. With films that are one stop faster (200 ASA) the GN must be multiplied by 1.4; with films that are two stops faster (400 ASA) the GN must be doubled. The GN is reduced accordingly with slower film. Off-brand flashes with built-in zoom flash heads have a variable GN. In many cases the given GN is for the 50mm zoom position. Some manufacturers find it necessary to give the GN for the tele position.
It should also be noted that the specified GN isn't always very accurate. To get the exact value you really need a flash meter. Besides it is based on using the flash inside in a room with average reflections. When you take the flash to a large hall, or outside, the GN drops. Without a flash meter you should do some tests, and bracket.
Because the nature of the GN formula, Manual Flash is very restrictive in your selection of Aperture Value when the flash has a fixed GN. Flashes with a variable GN are a better choice when you do a lot of manual flash. The T32, T45, Macro Flashes and G40 are the only Olympus flashes that multiple GN's. The T45 offers 6 GN's, which is reasonable, but the others only offer two or three GN's. This isn't much, so if you use it a lot you may be better off with a modern off-brand flash like the Metz 40 MZ-2 (or 40 MZ-3) which allows the GN to be changed almost continuously from 2.5m to 40m. GN's are varied by varying the duration the flash output, from normal shutter speed values like 1/300 or 1/1000 sec., to ultra short durations like 1/40.000 sec.
An alternative way to reduce the GN is to put a special diffusing filter or ND filter on the flash head. You can buy them or make them yourself. A well-known generic off-brand diffuser is the Sto-Fen Omni Bounce. Indirect flash reflected by a ceiling or diffuser card also has a GN reducing effect.
So why would you use Manual Flash anyway, when Auto Flash is so much easier and faster? Well, once the real GN value is determined, Manual Flash is very precise, makes it easy to bracket or to change the available light / flash light ratio, is not fooled by the amount of available light or the direction of it, and neither by the reflectance, brightness or darkness of the subject or the background.
Disadvantages of Manual Flash clearly are the time consuming GN calculations, which get even more complex with Macro Photography and the uncertainty of the GN value. If you use a flash that has only one GN value you can add the restrictions of the Aperture Value and the fact that the flash always fires at full power and thus eats batteries and has a long recycling time.
A requirement for Manual Flash is that both the camera and the flash can be set to Manual Mode. This means that the OM-101 can do it only when the Manual Adapter 2 is installed. On the OM-707 a Zuiko lens must be used. The shutter speed must be manually set to the X-synchronization time, or longer, which lets available light have its influence.
The next example explains how you can achieve daylight fill flash in Manual Mode
with the OM-4Ti and Metz 40 MZ-2 and dedicated SCA adapter (321). A typical example is a
backlit portrait. Without fill-flash, you would spot-meter on the face (with an OM-2 that
doesn't have a spot meter you would do a close-up reading or apply exposure compensation).
Problem is that the background will get washed out. Fill flash can bring the brightness of
subject and background in balance.
First, you set the flash to Manual Mode. It is also better to set the camera to Manual Mode. This isn't really required with a dedicated flash such as this Metz, but it is better since you want to be sure the flash actually fires, no matter how much available light is present. This is a typical case of shutter speed priority - you must be sure not to exceed the synchronization time, so you set the shutter speed to 1/60. Next you adjust the aperture, so that the background gets properly exposed. Focus on the face, and look at the shooting distance scale. Let's say this is 2m. Now set the Aperture Value of the lens on the flash, and adjust the GN on the flash with the P and +/- buttons until the indicated flash distance corresponds to the shooting distance. Of course the film speed and zoom position of the flash head must also be properly set. If you want to flash to be less dominant, you can reduce the GN (the indicated flash distance) a bit further.
This example immediately shows how easy a flash with a continuous variable GN is. With the T32 for instance, that only has two GN's (32 and 16m, 100 ASA) you probably would have to change either the flash distance independent of the shooting distance (flash on tripod) or change the GN with the aid of flash filters, which is rather coarse. With the T20, that only has one GN and doesn't accept flash filters, it is even more troublesome.
On the OM-1(n) and OM-2(n) you must watch the setting of the X/FP switch when you connect the flash to the PC bus. This should always be set to X for electronic flashes. On the OM-1 and OM-2 this switch must also be set to X when the flash is mounted in the hot shoe; on the OM-1n and OM-2n the hot shoe (Shoe 4) is automatically synchronized at X, independent of the X/FP switch. Of course, in Manual Mode on the OM-2(n) the shutter speed must also be set at 1/60 or longer.
Normal Auto Flash, also known as Computer Flash, uses a built-in sensor in the flash that measures the reflected light, and cuts down the flash output when enough light is reflected, similar to variable GN's, by changing the flash duration. It is available on all OM cameras with the Olympus flashes T20, T32, T45, S20 and QA 310, and with many off-brand flashes. On the iS-1000/2000/3000 Computer Flash is available with the G40, when its head is tilted or the flash on switch is set to Tele/Wide adapter.
It is a semi-automatic flash mode that can only work correctly when both the flash and and the camera are properly set, at least with an OM camera (the iS/G40 combos are completely automated). The film speed must be set on the flash, then one of the available Auto Apertures must be set on the flash, and this Aperture Value must be transferred to the lens. If you use a System Flash and a camera with an electronic shutter, the shutter speed is automatically set at the X-synchronization time, otherwise, the shutter speed must be manually set, again requiring a Manual Mode. Btw, there is one pitfall with the automatic setting of the X-speed: when available light allows shorter shutter speeds, the flash doesn't fire. In these cases you must use smaller apertures, ND filters or set the camera to Manual Mode.
The number of available Auto Aperture values usually isn't really high, only two or three. Again you may want a more modern sophisticated flash when you use Computer Flash a lot. The Metz 40 MZ-2 offers all values from F1 to F45 (100 ASA).
But even when the number of Auto Apertures is limited, the advantages of Normal Auto Flash are that you don't have to worry about GN and flash distance - within certain limits you can use any distance.
Normal Auto Flash makes it also very easy to bracket or to change the flash light / available light ratio. When you deliberately set a higher F value (smaller aperture) on the lens than the Auto Aperture on the flash, the influence of flash light is reduced in the favor of available light.
There are a couple of pitfalls with computer flash. First, the built-in computer assumes the subject it reads the reflected light from is neutral grey (18%), the same assumption the built-in light meter of the cameras makes. If this assumption is false, the aperture on either the lens or on the flash must be changed. If the F value on the lens is higher than on the flash, the flash is underexposed (necessary with dark subjects); if the F value on the lens is lower than on the flash, the flash is overexposed (necessary with light subjects). Same problem occurs with back lighting that hits the sensor. Second, the measuring angle of the flash in most cases doesn't correspond to the angle of the lens, and there is a parallax between the two, which becomes larger with shorter distances. The measuring angle of many flashes correspond to a 100mm lens. So when shorter lenses are used, it may be that the parts of the image are not correctly measured. Computer flash can only be used when the sensor is aimed at the subject. Finally, the electronics in the flash are unaware of any light reducing filters or extension units that have been used, so in such cases the photographer must remain alert.
Daylight fill-in Computer Flash is very simple, at least when the flash
supports enough Auto Apertures. You start the same as with Manual Flash, but after setting
the aperture on the lens you apply it to the flash. Be careful when backlight can reach
the flash sensor - you must adjust the aperture or change to Manual Mode.
TTL "OTF" Flash works similar to the way available light is measured: TTL, Through The Lens, and OTF, Off The Film. So the light that enters the lens is reflected by the film and read by the same sensors that normally read available light, and when enough light is measured a signal is sent to the flash to terminate its output. This obviously means only dedicated flashes that have extra TTL contacts can support this Flash Mode. All T flashes and the F280 support OTF. Not all cameras that support daylight OTF also support OTF Flash. The OM-10, OM-20 and OM-30 are excluded. The OM-1(n), OM-3 and OM-2000 don't support OTF at all, so this limits the technology to the OM-2(n), OM-2Sp, OM-4(Ti), OM-3Ti, OM-40, OM-101 and OM-707. All electronic shutter cameras must be set to Auto Mode to make use of this technology. The OM-3Ti is rather unique since this is the only mechanical camera that supports OTF flash; it obviously does not support OTF available light metering. The iS cameras don't support OTF.
The big advantage of this flash technology is that it is completely automated. There is no need to set film speed or aperture on the flash. All apertures can be used, at any distance within certain limits. These limits depend on film speed and aperture. Light reducing filters and light loss due to extension units are automatically compensated by longer flash durations; there is no parallax and the measuring angle is identical to the angle of the lens.
One pitfall remains: again the assumption is made that the reflectance of the subject corresponds to 18% grey. If this isn't the case, corrections should be made with the exposure compensation on the camera, just as you would with available light. For instance a negative compensation when you shoot a person against a large dark background.
Another problem is that there is no way to change the ratio between available light and flash light, other than to shoot at a larger distance than the flash distance would be for a certain aperture and film speed. This makes daylight fill-in flash rather unpredictable, although what's read will always be the combined influence of daylight and flash light.
The last problem with the electronic shutter cameras is that the camera must be set to Auto Mode, the shutter speed is fixed at 1/60 sec, and when available light permits shorter shutter speeds, the flash won't fire. This severely limits the use of various apertures and exposure compensation.
Most of these problems are solved in the OM-3Ti. This is the only camera that allows OTF Flash in Manual Mode (which is the only mode this mechanical camera has). All shutter speeds from 1 sec. ~ 1/60 sec. can be selected; longer shutter speeds can be set to allow ambient light having more influence. As long as the shutter speed is set within this range you can be sure the flash fires and is synchronized, no matter which aperture is used with it. Aperture can be set according to available light level or desired DOF. Finally the exposure compensation dial can be used to adjust flash output. For instance overexposure to deal with back lighting, or underexposure to reduce flash output in the favour of ambient light.
TTL OTF flash comes to its full power with macro flash photography using extension units that are automatically compensated for, making complex calculations redundant, and also with multiple flash photography: up to nine T System flashes can be connected with special TTL cords, and the combined output is read and controlled by the camera. The Metz 40 MZ-2 (3) flashes support multiple flashed too, but not the TTL Auto Cords - special TTL slave units are required. The F280 doesn't support multi flash.
The flash(es) can be aimed in any direction - towards a reflective brolly (flash umbrella) for instance, which is impossible with computer flash.
To activate TTL OTF flash, the camera must be set to Auto Mode, except on the OM-3Ti which has a Flash Mode Switch (TTL Auto Flash / X). The panel of a T Series flash can be set either to the side that reads 'Full automatic control by OM-2', or to the side with the calculator panel, with the flash set to (full) manual. As long as the camera is in Auto, so is the flash. The F280 has a flash mode switch, so has the Metz 40 MZ-2 (3). The camera is automatically set in the X-synchronization time, but the flash doesn't fire when available light allows shorter shutter speed. An exception is the OM-707 / F280 combo; the flash automatically switches from X-synchronized (1/100 sec) TTL OTF Flash to Super FP Flash when there is enough available light to allow shorter shutter speeds.
FP Flash, flash using long burning FP (=Focal Plane) Flash Bulbs was already becoming obsolete when the OM-1 was introduced, and nowadays these bulbs are difficult to find. They were intended for daylight fill in flash, at shutter speeds of 1/60 to 1/1000 sec, with a GN that decreased with shorter shutter speeds. For the rest there was no difference with normal Manual Flash. Some of these bulbs had astonishing high GN's: the Philips PF 100E had a GN of over 100m at 1/60 sec! FP Flash Bulbs are supported by the OM-1(n) and OM-2(n) that have an X/FP switch round the PC bus. With other flash bulbs (MF, and M.FP), and with electronic flash, the switch has to be set at X. The switch also influences the synchronization of the hot shoe on the OM-1 and OM-2; Shoe 4 on the OM-1n and OM-2n is always X-synchronized.
Super FP Flash is the
modern electronic version of the FP Flash Bulb. Instead of one intense, very short (1/300
~1/40.000 sec) flash burst, that can only expose the film correctly when the shutter is
completely open, a Super FP flash emits a continuous series of short bursts, like a very
fast stroboscope, from the moment the first curtain starts to travel to the moment the
second curtain arrives. This allows the flash to be synchronized at shutter speeds from
1/60 sec to 1/2000 sec. This is a big plus with daylight fill flash: at the normal
synchronization of 1/60 sec ghost images can appear when the subject (or the camera)
moves. There is also one big disadvantage: like with the FP Bulbs, the GN depends on the
shutter speed. With the shorter shutter speeds (1/500 ~ 1/2000 sec) the GN is so low it
can only be used at short distances, with wide apertures. It is very suitable for daylight
fill-in flash with portrait shooting at distances of 1.5 ~ 2m.
The only OM cameras that support Super FP Flash are the OM-4Ti, OM-3Ti and OM-707; the only flash that supports it is the F280. No off-brand flash with Super FP is available. On the OM-4Ti in Auto Mode, and on the OM-707, the light emitted by the F280 is read OTF, together with available light, and the shutter speed is adjusted when necessary. On the OM-4Ti in Manual Mode, and on the OM-3Ti, there is no OTF automation and a GN table (dependent on shutter speed!) should be consulted. A lot of experience is required and bracketing is recommended to get proper results, since the GN table doesn't take available light into account.
The iS-3000 and iS-300/iS-30 also support Super FP with their built-in flash, in the Portrait Program. The iS-3000 also supports it in Manual Mode, similar like the OM-3Ti and OM-4Ti in Manual Mode. The G40 flash does not support Super FP Flash. The US version of the iS-3000, the iS-3, does not support Super FP Flash because of old patent problems; the US version of the iS-300, the iS-30, does support it.
On the OM-707 and on the iS-cameras in Portrait Program, Super FP Flash is automatically activated when available light enables shutter speeds shorter than the synchronization time (1/100 sec). On the OM-4Ti, the camera must be set to Auto, and the Flash Mode Switch on the F280 to Super FP. The flash will always fire, but when available light does not allow shutter speeds shorter than 1/30 (low light levels), the shutter speed is still fixed at 1/60 sec. If you deliberately want to use Super FP at shutter speeds of 1 sec ~ 1/30 sec, to emphasize movements, the camera must be set to Manual Mode and you must use GN calculations to determine the Aperture Value.
Flashmatic Flash is a
semi-automatic GN based flash method that works on cameras that have Shutter Speed
Preferred Auto Exposure. It was very common on the rangefinder cameras from the sixties
and seventies, like the Olympus 35RD. The principle was very simple: you set the GN of the
flash on the camera (which usually offered a choice of two or three GN values), and once
the distance was set on the lens, the Aperture Value was automatically calculated and set,
based on the GN formula. So like Manual Flash, the shooting distance and GN determines the
correct Aperture. The big advantage is that it is very fast, and reliable because subject
reflectance can't fool the system. Combined with the fact that these cameras were
synchronized at all shutter speeds made the system also very suitable for daylight fill-in
flash. There were two disadvantages: the flash always fired at full power, consuming more
power and resulting in longer recycling times than necessary, and there is only one
Aperture Value for each shooting distance.
There is one Olympus OM camera that supports Flashmatic: the OM-707 AF, in combination with the Power Flash Grip 300.
IVP Flash is a modern
version of the Flashmatic system. It stands for Intelligent Variable Power, and what it
adds is the possibility to change the flash duration and thus the GN, which eliminates the
two big disadvantages of Flashmatic. So all apertures can be used, depending on shooting
distance but also on available light, and the flash doesn't necessarily have to fire at
full power. IVP is supported on all iS cameras with their built-in flash, and also with
the G40 flash. No OM camera or flash has IVP.
IVP is very comfortable in the Full Program Mode when the Flash Mode is set to fill-in (the flash always fires no matter how much light is available, and the camera is automatically x-synchronized). Aperture and GN are automatically adjusted, depending on shooting distance and available light level. It is also very comfortable in Aperture Preferred Auto Exposure with Auto Flash: you set the Aperture Value, the camera adjusts the GN depending on shooting distance. When both the internal flash and the G40 are used, which makes sense when the G40 is used as bounce flash and the built-in flash as fill-in, an automatic negative correction (-3EV) is applied to the built-in flash (that is, the IVP controlled GN is reduced) to avoid its influence being too strong. When the G40's flash head is tilted, it automatically switches to Computer Flash, with the sensor reading the combined reflected light. So here we have a unique combination of two different Flash Modes cooperating in an intelligent way.