ADI question

[SqueamishOssifrage]

I had been looking for some time for an eight pin 1.7x tele-converter for my Dynax 7 and KM 28-75mm f2.8 D, to extend the possibility of using ADI up to 120mm. I found one on ebay.de at a good price, so grabbed it. Unfortunately, it is not chipped, just straight through connections. Obviously, this is not a problem for exposure, as the loss of 1.5 stops will be self correcting - the ratio of used aperture to max aperture remains unchanged, despite the effective aperture being incorrectly reported to the camera. Nor is the focused distance a problem, as the reported distance will be the same with or without the converter (although the DoF will be calculated incorrectly). However, having been unable to find a detailed description of how ADI works, I have assumed that the recalculated guide number will instruct the flash to deliver the amount of light required at the incorrectly reported aperture - 1.5 stops too little, in fact.

So, if my assumption is correct, then I simply have to set +1.5 stops on the flash exposure compensation, and Robert is your parent's sibling's brother. If, however, the final light from the flash is TTL based, then I don't need to compensate.

Unfortunately I don't have time to experiment and get the film processed before Saturday, when I had plans to use it in anger, as it were.

Has anyone with more experience of Minolta than I have, got any bright ideas? Many thanks!

[RonM]

OK here is my stab at trying to explain ADI as I understand it.

With ADI enabled you should be OK re flash exposure and not need to dial in +1.5 stops this is because the camera, lens and flash work together.
The 'D' flashes give a pre-flash burst which is used in conjunction with the subject distance information provided by the 'D' lens to calculate the flash exposure required.

When using 'standard' TTL I'm pretty sure you need to dial in the flash compensation cause there is no pre-flash exposure measurement and with the converter not reporting the 'corrected aperture' the camera will incorrectly calculate the flashes exposure.

This is one occasion where the benefits of digital are supremely apparent.

HTH

[SqueamishOssifrage]

Thanks for the input. Last night I remembered that I had somewhere the sales brochure for the 7, so dug it out to see what it said.

It would appear, ahem, that you are absolutely right!

It seems the processor reads the pre-flash TTL/new GN data, together with inputs from multi-segment flash metering, distance information, reflectance, and AF sensor, to compute the necessary flash output.