[Leica] SF20 report

[Erwin Puts <imxputs@knoware.nl>]

The SF20 is a compact and quite useful flash for the Mx and the TTL 
versions. While flash photography with the Leica M series seems 
counterintuitive, there are occasions when it is useful: strong 
backlight, really dark situations or you are just lazy and do not 
want to bother about exposure.
So a simple report is required. I tested the SF20 with TTL and 
non-TTL M versions.
Non-TTL test: 3 apertures: 2.8 and 5.6 and 11. On the test equipment 
the flash output at
1 meter distance 1/3 stop underexposed
2 meter distance OK, but the f/11 was far off (beyond the GN of 20!)
4 meter distance is was OK till f/4. That is 5.6 was beyond the GN 
reach. The SF20 is very sensitive to this: just beyond maximum range 
the output drops dramatically.

The TTL version gave at 1 and 2 meter distance results 1/3 to 1/2 
stop underexposure. The f/2 position however gave a 2/3 stop 
overexposure.
The 4 meter position worked till f/4.

The adjustment in ±1/3 stops is not  so sensitive. The 2/3 stop 
adjustment had some effect, but not according to the settings: real 
output changed by less than 1/2 stop.

Generally the SF20 performs well in the midrange positions. At the 
extremes caution is required. The ± 1/2 stop difference is no problem 
for colorneg and even B&W. For slides the SF20 needs to be checked by 
making a series of test pictures. Do remember that the sensor of the 
flash also takes the reflected light. So shooting in a white walled 
room will be different from shooting in a dark street. That is 
something you need to check for yourself.

Amazing is the battery power. I used the SF20 for four months 
(non-continuous)  but shot per session between 50 and 100 pictures. 
By now I have shot more than 300 pictures, but there is still the 
original set of batteries in the SF20.

Verdict: the redoubtable Metz 60 is still the best and powerful of 
all portable flashguns. This SF20 is a pocketable and handy 
additional light source for occasional photography. Its output is 
predictable and once tested in typical situations can be used with 
confidence.
Erwin