Leica User Forum - View Single Post - Leica D2 and Nikon SB-28

hongtoh · 09/04/06, 10:55 PM

Jerry,

Not familiar with the Metz 54. Do you have the SCA 3502 M4 module? I have an older Metz 40MZ-1i which is equipped with the red low light focussing aid and a conventional auto sensor. I have used it successfully in "A" mode and bounced flash so I assume the flash unit's sensor is measuring the reflected light. Not able to experiment now as my D2 has been with Leica, NJ, since May. I feel they have run out of circuit boards and sensors to repair it.

The D2 may not use the sensor on the SF24D. I do not have that unit so have no experience with it. Since the D2's pop up flash does not have a sensor, I speculate that it uses the distance measured from the lens' focus position, aperture set, and the guide number of the built in flash to calculate the correct flash output. Likewise, the SF24D may send a signal to the D2 identifying its guide number so that the D2 can calculate the flash output. It is important to have the updated SCA module for your 54 MZ-4 to communicate all available information to the D2.

Before flash automation, exposure was determined by calulating the correct aperture for the flash guide number (GN). In those days, GN was fixed at maximum output. This formula was used. Aperture = GN/Distance. This can be manipulated to:

GN = Aperture X Distance

The required GN is calcualted and as long as it does not exceed the max GN of the flash, you will get correct exposure. So the D2 does the calculation and sets the GN (flash output duration) of the flash unit by cutting it off at the proper timing. In essence it uses the SF24D's TTL circuitry but the SF24D does not know that the signal it received is NOT from a TTL sensor. Very clever isn't it?

No sensors involved (other than AF sensor) and very accurate. Which is precisely what you mentioned as Guide Number Control (GNC). Works in manual focus (MF) too since distance information is taken off the correctly focussed lens position.

BTW, Leica does tell you that the D2 uses "A" and not "TTL" for non Leica flash units and I believe my 40MZ-1i operates with its own sensor.

Best regards,

Hong Toh

09/04/06, 10:55 PM	#10 (permalink)
hongtoh Neuer Benutzer Join Date: 09/01/06 Posts: 6	Re: Leica D2 and Nikon SB-28 Jerry, Not familiar with the Metz 54. Do you have the SCA 3502 M4 module? I have an older Metz 40MZ-1i which is equipped with the red low light focussing aid and a conventional auto sensor. I have used it successfully in "A" mode and bounced flash so I assume the flash unit's sensor is measuring the reflected light. Not able to experiment now as my D2 has been with Leica, NJ, since May. I feel they have run out of circuit boards and sensors to repair it. The D2 may not use the sensor on the SF24D. I do not have that unit so have no experience with it. Since the D2's pop up flash does not have a sensor, I speculate that it uses the distance measured from the lens' focus position, aperture set, and the guide number of the built in flash to calculate the correct flash output. Likewise, the SF24D may send a signal to the D2 identifying its guide number so that the D2 can calculate the flash output. It is important to have the updated SCA module for your 54 MZ-4 to communicate all available information to the D2. Before flash automation, exposure was determined by calulating the correct aperture for the flash guide number (GN). In those days, GN was fixed at maximum output. This formula was used. Aperture = GN/Distance. This can be manipulated to: GN = Aperture X Distance The required GN is calcualted and as long as it does not exceed the max GN of the flash, you will get correct exposure. So the D2 does the calculation and sets the GN (flash output duration) of the flash unit by cutting it off at the proper timing. In essence it uses the SF24D's TTL circuitry but the SF24D does not know that the signal it received is NOT from a TTL sensor. Very clever isn't it? No sensors involved (other than AF sensor) and very accurate. Which is precisely what you mentioned as Guide Number Control (GNC). Works in manual focus (MF) too since distance information is taken off the correctly focussed lens position. BTW, Leica does tell you that the D2 uses "A" and not "TTL" for non Leica flash units and I believe my 40MZ-1i operates with its own sensor. Best regards, Hong Toh