Hasselblad Databus "Effective Aperture" Compensation

I'm thinking of buying a set of extension tubes to use with my Hasselblad 203fe. They come in two versions: with & without the electronic TCC databus contacts. I was wondering, if I were to use, say, a 56E to extend my Zeiss 80mm CFE, will the camera's computer be smart enough to automatically compensate for the loss of "effective aperture?"

In other words, if I put the camera in "A" mode, and attach an FE/CFE lens with the aperture set at f/8 and the meter chooses a speed of 1/60 ... and then I remove the lens, attach a databus-equipped extension tube, re-attach the lens with the aperture set at f/8 ... will the meter still automatically choose a speed of 1/60, or will it choose a slower speed to compensate for the loss of effective aperture when close-focusing?

I understand that the CFE Makro-Planar can do this while the CFi Makro-Planar cannot. But I'm not sure about the extension tubes. Thanks for your help!

I cannot speak to the electronics based on experience, however my Hasselblad 503 CX with the 45 degree PME prism's light meter works through the lens and therefore compensates for the extension tubes. Therefore it would not be a big leap of faith and logic to believe that the data bus would exposure compensate for the extension tubes.

Consider that the variable extension tube would be continuously adjustable and if you were to later get the 135mm lens the variable tube would allow you to get to 1:1 images.

I didn’t know that they made a variable extension tube. Do you know the Hasselblad part number?

My databue is currently broken, but what I remember is that the FE lenses do not record or transmit distance information. So it has no idea what the effective aperture is.

The meter will compensate for extension tubes as all TTL meters do, but will indicate the aperture value at infinity.

So, when you add an extension tube, and leave the lens at the same aperture setting, the "A" mode shutter will be slower because less light is reaching the TTL meter.

Variable Extension Tube ====> https://www.keh.com/shop/hasselblad-manual-focus-variable-tube-64-85-51691-719601.html

I tried to answer your question directly. I have a 203 with databus extension tubes and a 501. I do not have plain extension tubes but I do have a older set of bellows. Alas the 203 body does not mount on the old no databus bellows at all, while the 501 does readily. So I would want to confirm that the 203 even goes on a older set of extension tubes.
PS a bellows makes a good variable extension tube.
PPS These older bellows do not have a means to transmit the shutter cocked slot through the bellows missing the connector on the camera mount side.
I did find this statement, "All non-electronic extension tubes can be used on all Hasselblad V series reflex cameras made since 1957, including the electronic cameras. There are two shorter tubes, 8mm and 10mm, which cannot be mounted directly on these electronic cameras due to the protruding shutter speed ring, but they can be used in combination with an electronic tube. This obviously breaks the electronic connection and one therefore needs to stop down the lens and meter manually."


"In other words, if I put the camera in "A" mode, and attach an FE/CFE lens with the aperture set at f/8 and the meter chooses a speed of 1/60 ... and then I remove the lens, attach a databus-equipped extension tube, re-attach the lens with the aperture set at f/8 ... will the meter still automatically choose a speed of 1/60, or will it choose a slower speed to compensate for the loss of effective aperture when close-focusing?"

In this case with the databus equipped extension tube, the size of the aperture does stay at set aperture while on " A". All my training says that the speed should go slower with extension tubes, focussed on an evenly lit white wall, except that is not what happened on mine. I used a 16 E and a 32 E together (at min focus with and without the tubes) on a 110 lens at f 16 and the shutter speed was twice as fast with the two tubes!
Maybe some one else will try.

I found this also.
http://www.hasselbladhistorical.eu/HT/HTCuC.aspx