Hi there folks. Glad to contribute to a UK based forum!
Here's a lens theory conundrum. I recently bought a Tamron 35-70 f3.5 zoom and modified an Adaptall/Konica mount for my E400. A lengthy job but I got it working. It looks good on the camera and performs rather well. I did a short review on another forum
http://www.fourthirdsphoto.com/vbb/s...ad.php?t=21841
However in pursuit of perfection I dismantled the Adaptall mount yet again and inserted a 0.4mm shim to move the whole lens forward. This was to minimise the past-infinity focus problem. It now parfocal, it retains its focus as you zoom. Excellent so far!
What I find is that the lens now seems to produce very slightly better results - as if it has been placed in its optimum design position.
Now if this was a prime lens I would put this down to my imagination, but because its a zoom lens and they react in strange ways to things like extension tubes, I just wonder if this improvement has some real basis in physics??
For info, some other lenses I have used or converted are: Hexanon 28mm, 40mm, 50mm, Vivitar 28mm Nikon 50mm and 100mm. I have a web page showing some basic lens tests on many of these if you are interested..
http://www.snaar.co.uk/lenses/index.html
Best regards
Pete
Here's a lens theory conundrum. I recently bought a Tamron 35-70 f3.5 zoom and modified an Adaptall/Konica mount for my E400. A lengthy job but I got it working. It looks good on the camera and performs rather well. I did a short review on another forum
http://www.fourthirdsphoto.com/vbb/s...ad.php?t=21841
However in pursuit of perfection I dismantled the Adaptall mount yet again and inserted a 0.4mm shim to move the whole lens forward. This was to minimise the past-infinity focus problem. It now parfocal, it retains its focus as you zoom. Excellent so far!
What I find is that the lens now seems to produce very slightly better results - as if it has been placed in its optimum design position.
Now if this was a prime lens I would put this down to my imagination, but because its a zoom lens and they react in strange ways to things like extension tubes, I just wonder if this improvement has some real basis in physics??
For info, some other lenses I have used or converted are: Hexanon 28mm, 40mm, 50mm, Vivitar 28mm Nikon 50mm and 100mm. I have a web page showing some basic lens tests on many of these if you are interested..
http://www.snaar.co.uk/lenses/index.html
Best regards
Pete
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