We’re excited to announce our new flash adapter for the TYCH and TYCH+ cameras.
The TYCH was always designed with a future flash accessory in mind, hidden away in the camera settings is a flash mode. This locks the camera to a flash sync speed of 1/125th of a second and triggers the flash via redundant lines on the USB-C connection.
To connect the adapter you remove the door catch attach the adapter and the re-attach the door catch. Giving you a hot-shoe ready to take a range of camera flashes. We are stocking the Ulanzi F12 flash and have tested the camera extensively with this unit. It gives great results when using 400 ISO film. If you have your own flash you are going to need to take into account the power or Guide Number of the flash to use it effectively.
TYCH+ with Ulanzi F12 at full power on Kodak Portra 400
Understanding Guide Numbers
Most hot shoe mount camera flashes have a guide number (GN). The guide number is a measure of a flash’s power, calculated by multiplying distance to the subject (in meters) by the lens aperture (f-number) needed to give correct exposure, typically at ISO 100. A higher number means a more powerful flash capable of illuminating subjects further away or at smaller apertures.
The formula for the guide number is:
Guide Number = Distance x Aperture
If you have a flash with a known guide number you can calculate the distance to your subject for correct exposure.
Distance = Guide Number / Aperture
For a flash with a guide number of GN12, using an F8 lens gives a distance of 1.5metres.
This assumes you are using ISO 100 film, how do we account for a different ISO sensitivity on our film?
Increasing the ISO of your film increases the effective guide number of your flash. Doubling the ISO to 200 or 2x the ISO, you need to multiply the GN by the square root of โ2 (1.4). ISO 400 or 4x the ISO you need to multiply the GN by the square root of โ4 (2).
A guide number of 12 at ISO 100 becomes GN16.8 at ISO 200 and GN24 at ISO400.
You can now calculate the distance to subject using different ISO films. Our example images were all taken on Fuji Protra 400 with a Ulanzi F12 flash. This flash has a guide number of 12 (at ISO100) . Our ISO adjusted guide number for this flash is GN24
The calculation for distance using an F8 lens gives us > GN24 / F8 = 3metres
So the ideal distance for using our flash with ISO 400 film is 3 metres. Using film gives you a lot of latitude on under or over exposing your image, especially with a film like Kodak Protra so in practice you don’t need to be exact, close enough will still result in good exposures.
Guide Number Tables
Many flash units come with tables either in the instructions or printed on the back of the flash itself. This can save you the hassle of doing any calculations. The example below is the table for the Ulanzi F12 flash, the F8 column has been highlighted.
You can simply look down the column for the F number of the lens you are using, then cross reference to the guide number for your flash. The table includes ISO numbers that specifically relate to the Ulanzi flash.
On vintage flash units the table is sometimes printed on the flash itself and can also be specific to the GN of that flash. Sometimes the table will be shown with distance and ISO along horizontal and vertical axis respectively with recommended aperture numbers in the table. So if you are using a manufacturers guide table be sure you are reading it right.
Adjusting Power
Final thing to consider is whether your flash unit allows for power adjustment, most do. Majority of flash units give power adjustments in 1/2 or 1/3rd stops. To take this into account it should be possible to use your flash table and estimate a new exposure distance. A good rule to remember is that closing the aperture by 1 stop (i.e. F8 to F11) is equivalent to setting the flash to 1/2 power.
If I am using my GN12 flash with ISO 400 film and my subject is closer than the ideal 3metres at 2metres. I would need to reduce the power of the flash by half. Calculating it precisely you ideally would reduce the flash slightly more than 1/2 power, in practice the film exposure latitude can easily cope with approximations.
TYCH+ with Ulanzi F12 at full power on Kodak Portra 400