It was a bit of an impulse purchase to get the 2x TC for my Bronica SQ. It was a few weeks before I departed for Iceland and given how useful I had found the 250mm f5.6 lens I impulse bought for my Scotland trip a few months prior, I convinced myself it would be worth seeing if 500mm would be a useful focal length to pick out detail in Iceland's landscapes. Before picking up this lens I couldn't find any really useful sample images online for this combination, so hopefully this post will help someone in a similar position in the future.
In theory, yes, having a focal length of 500mm on a 6x6 Bronica (approx 321mm 35mm equivalent) is very useful. Traveling Iceland via the main highway 1 there are plenty of places to stop where there are some interesting mountains and waterfalls far in the distance. This focal length will enable you to get some pretty unique shots.
However here comes the rub; the practicalities of using this 2x TC on the 250mm f5.6 Zenzanon lens make it difficult to get the clarity and sharpness you might be used to with this 6x6 medium format camera. For a start the effective aperture wide open (f5.6 on the lens) becomes f11 as you lose two stops of light. The focussing screen is surprisingly bright though, and if you're focusing at infinity anyway, that isn't such a big deal. It does however mean you'll probably be using a slow shutter speed making the sharpness of the final image incredibly vulnerable to vibrations, be it from even the slightest amount of wind, or even from the significant mirror slap from the bronica itself. Obviously the latter can be mitigated by using the mirror lock up mode, which I did, but even with a pretty sturdy Giottos tripod the wind definitely had an effect. The TC + 250mm combo is huge and has plenty of surface area for the wind to catch.
All of the practical considerations described above are in addition the the fact that using the TC degrades sharpness even in perfect conditions. Frankly its hard to differentiate the two factors with my images; there was always at least a bit of wind present and even though I took every reasonable precaution to minimise the effects of wind this will still have been a factor. The other concerning thing was that the TC actually got jammed onto the 250mm lens. It was a source of frustration at the time, trying to remedy the issue on top of the ridge around the Krafla crater, but eventually I prised it free with a metal key and some brute force applied to the lens release slider.
The images displayed here all demonstrate the sharpness issues that I refer to above. Is this acceptable to me? Kind-of. The final image was really disappointing, potentially there was more wind here influencing the sharpness, but the first two are OK. Yes I do think the softness in the image reduces their impact but then again the TC was crucial in framing these shots. To be honest I'll be thinking twice before taking this TC with me on a trip again. Its heavy, bulky and with the loss in image quality it might be worth thinking of using alternate compositions with the 250mm on its own, cropping down, or in fact using a 35mm camera with a 300mm lens instead.