I've had my Rokkor 58/1.2 (thanks Jordan) for a few weeks now and after way more sanding than the 85/1.7 it is done. I thought I was never going to get to infinity focus (which seems like everything between 30 feet to infinity). I'm not looking forward to dissambling and filing the rear element when I eventually go FF. Focusing looks like it will be a bit of a challenge as images in the viewfinder appearing sharp are not always. This is where live view comes in quite handy.
Here are a few of the first images (all wide open) from the lens on the 40D:
Congratulations it looks really nice. I'm working on mine now and filing the rear element ring wasn't that difficult. The toughest part so far was drilling the four holes accurately...I ended up with 3 right on and one off a bit. I haven't started sanding for infinity yet though.
Looks good. The sanding does take FOREVER. I think all told I took 3 hours total of sanding to get to (very near) infinity. I'm still not quite there at f/1.2, though I'm close enough for any real purpose. At f/1.2, I can focus to about 80-120 feet. The last little bit to infinity takes to about f/4 to get, which I'm fine with. I almost never will be using the lens at that range with wide apertures anyway, so it's not worth taking the lens apart again, even for that last 0.05 mm.
Hey Jay...btw...need any MEP engineers for your smaller jobs? (We do mainly retail, restaurants, office spaces, education buildings, the occasional warehouse and manufacturing facility, and a few larger jobs, but most of our stuff is smaller.).
CVickery wrote:
Congratulations it looks really nice. I'm working on mine now and filing the rear element ring wasn't that difficult. The toughest part so far was drilling the four holes accurately...I ended up with 3 right on and one off a bit. I haven't started sanding for infinity yet though.
I borrowed a friends drill press this time which made it much more precise. Problem is when your holes are part way on the thicker flange part of the M42 mount, it can get tricky.
Sanding is the toughest part by far IMHO.
Good luck.
Ed Sawyer wrote:
Why not power sand it? The base of a belt sander is about as flat as anything else you are going to sand against...
for final sanding, you could hand-flatten it but seems like using a power sander for the bulk of it would be speedier.
Ed,
I think the problem with a belt sander is that theres still more of a chance for uneveness on the shim surface, unless you had some sort of jig to hold the shim flat. Might be worth a try though.
Sirfishalot wrote:
I borrowed a friends drill press this time which made it much more precise. Problem is when your holes are part way on the thicker flange part of the M42 mount, it can get tricky.
Sanding is the toughest part by far IMHO.
Good luck.
Ed Sawyer wrote:
Why not power sand it? The base of a belt sander is about as flat as anything else you are going to sand against...
You've obviously never tried this!
Belt-sanders are incredibly inaccurate, for several reasons. One is simply that the belt does not hold tight to the platten. It floats up slightly, and will hence mess with your edges.
Trust me on this one!
My plan is to use a fine mill bit in a drill press (I have no mill) with the lens mounted on a machinist's turntable.
Sounds good in theory, but we shall see. I have four 58 /1.2's, so I can afford to mess up three!
Edited by Cableaddict on Sep 09, 2008 at 05:27 AM GMT
Those'll be three expensive screwups. I'd get some 58 f/1.4's to replace any messed up shims, so you're only ruining a $25 lens rather than a $300 lens.
Sep 09, 2008 at 05:24 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
Ed Sawyer wrote:
Why not power sand it? The base of a belt sander is about as flat as anything else you are going to sand against...
for final sanding, you could hand-flatten it but seems like using a power sander for the bulk of it would be speedier.
I'm doing my conversion this weekend and I will probably try this method and let you know how it works. I wouldn't try it, however, with just any belt sander. My father's shop (where I will do the conversion) has a very high quality sander that I can set to a low speed setting and has a jig for keeping the sanding plane flat. I also have a fair bit of experience using it. I certainly wouldn't use a hand-held belt sander. I figure if I screw it up I can always get a 58mm f/1.4 to get a new shim and I will sand that by hand.
To me the sanding part is the toughest. I didnt want to get declination when light goes through lens to the sensor, so i were sanding very slowly and try to get the sanding surface of the mount as even as i could.
The drill part is abit tricky as well but you can always have a replacement adapter if you dont get the alignment at the first place.
Ironically, It's a nightmare to me to find those tiny screws. i broke 2 of them and could not find any similar ones.
I have my 85/1.7 conversion done perfectly. it's now my favorite along with my 58/1.2 which i got it done by Cogitech.
If you need more screws, buy a 58 f/1.4....apparently they have the same mount and shim, and presumably the same screws. Cogitech, correct me if I'm wrong.
Jman13 wrote:
If you need more screws, buy a 58 f/1.4....apparently they have the same mount and shim, and presumably the same screws. Cogitech, correct me if I'm wrong.
smallparts.com or any decent hardware store should stock screws like that.
Agreed: re belt sander has potential to be an issue, but i think it can be worked around.
Steve Spencer - let me know how it works. I have 2 of these I was thinking of converting. one is so nice I am hesitant, it's really mint. The other is also very good too, probably will start with that one first though.
I figured I'd clamp the belt sander down (belt side up) to a work surface, then some sort of jig to keep the piece parallel to the belt platen. Rotate it regularly to minimize off-sidedness and check with a caliper.
Might just be easier to have a new shim machined by someplace like e-machineshop or maybe front panel express.
Or if I had a lathe that would be handy too. The machinist turntable /drill (mill) idea has merit also.
I finished my (first) conversion on this lens last night and it came out great. I did a few things different than most folks here I think. I will post the details and pics soon. No mirror shave needed (shooting full frame of course - there's no such thing as a crop-factor film body... ;-) , I can get focus to about 50ft, which is far enough for me since if I am shooting that far off, stopping down a couple stops gets infinity by virtue of hyperfocal distance. I used a belt sander on the shim and it came out fine, flat to within a couple thousandths of an inch measured by digital caliper. I used all 8 screws too, all lined up perfect on the first try. Total time to convert it start to finish, including some cleaning and testing was about 3.5 - 4 hrs. I have another I will probably convert soon too. A Dremel was indispensible for this job, IMNSHO.
