Alf
If I am looking for a Zeiss Distagon 28mm to convert, but I do not have access to metal working tools, what would you recommend if I am prepared to spend up to US$300 total?
Is this one suitable, for example:
http://www.ebay.com/itm/ZEISS-DISTAGON-28mm-f2-8-T-C-Y-/320850927153?pt=Camera_Lenses&hash=item4ab4349e31#ht_598wt_1109
Thanks
John
Sorry for the late reply John...Just got your email so went back and found your reply.
Yes, that looks like a MM version so it should be a good candidate for conversion and it should be easier than my AE version. The chrome aperture dial is not feature I've seen on one before but it should'nt matter. I will assume that the C/Y mounting plate on this lens is the exact same diameter as an SA mounting plate, as is the case with the 85mm f1.4 Planar T*...I cant be sure about it as mines an AE version but I will assume that is the case anyway.
First you will need a clean towel, decent set of micro posidrive/philips screwdrivers, an electric drill, a drill stand (a necessity!), a 1mm to 1.5mm drill bit, a small countersink bit and of course an SA mounting plate. If you cant get a genuine SA mounting plate, an M42-SA adapter can be used as a substitute, but avoid the ultra cheap chinese made versions as their front flange is so thin you probably wont be able to fully contersink the head of the securing screws into it...And they need to be flush or the lens wont fit!
That should be all the tools and materials you will need to convert it.
Place your clean towel on your table and place the lens onto it with the rear mounting plate facing upwards. (The reason for using a towel is that any screws you drop will stay exactly where they drop and not roll away onto your floor!) Try not to lift the lens off the towel at any point during the conversion in case you lose something critical like the tiny ballbearing which sits under the aperture dial and/or its associated tiny spring, which together control the click stops when you turn the aperture dial.
Note the four mounting plate securing holes around the outer rear flange on the C/Y mounting plate. Undo and remove these with the correct size micro philips screwdriver (dont use one that is too small or it can strip the screwdriver crossheads in the heads of the screws and if that happens its game over!)
You should now find that the mounting plate simply lifts off the back of the lens.
Do not lift the aperture dial off the lens! , just lift off the mounting plate. Keep the screws safe as you will need them later to hold the SA mounting plate on.
Make sure you note down the top dead center position of the plate when its mounted on a camera (Normally the numbers on the aperture dial face upwards when the lens in mounted) and which way round it goes before you take it off in case you ever want to put it back on later for some reason.
If it still cant be lifted off then remove the other three screws that are closer to the middle axis of the mounting plate too (they probably hold the bezel ring on...The ring that keeps dust out of the lens during focussing). Remove the bezel ring then try lifting the plate off again.
Once the C/Y mounting plate is off the lens you will then have to use it as a drill template, ie: you have to very accurately transfer the positions of the four securing holes in the C/Y plate onto the SA plate or M42-SA adapter. You will find it far easier if you find something short and cylinderical like an HP2 battery which both plates can be pressed onto to keep them perfectly central to one another. The battery will probably be a lot smaller than the bore of the two plates so simply wrap some PVC tape around the battery until its very tight fit when you try to push the plates onto it.
One plate might need more tape than the other as the bore diameters will probably be different. Make sure the SA plate is the same way up as the C/Y plate when you do this (both should have the flanges facing down) or the securing holes in the lens wont line up with those in the SA plate!) Fit the SA plate or M42-SA adapter, on its own onto your Sigma camera until it locks and using a fine permanent marker mark the top dead centre position on the plate. Now remove it and press it onto the battery/mandrel followed by the C/Y plate, making sure the top dead centre marks on both line up perfectly. If you added enough tape and the fit is tight enough to keep them from moving you can now go ahead and very carefully drill your four new securing holes in the SA plate underneath by drilling through the holes in the C/Y plate on top...You must make sure they do not move about at all when you do this as you need to drill them to a high accuracy.
If all goes well, you can now remove the SA plate from your Battery/mandril and
countersink the securing holes you just drilled with your countersink bit...Make sure you countersink the correct side of the SA plate! Now, assuming your drilling was accurate, you should now be able to fit the SA plate onto the lens the right way up
and screw it down. If the screws are a little too short now, dont worry you can buy longer ones from most good modelling or ironmonger shops...You need 10ba screws.
