Topic: The Sigma/ Minolta to Canon EOS, 600mm mirror project

I REALLY must be a glutton  for pain.  I bought this Sigma 600mm mirror for Minolta MD  off the bay,  paid (I think) too much.   Not only that,  shortly thereafter,  I bought the black one, much cheaper.  These are both Sigmas,  but different in design,  both 600mm F8

I decided to convert them from Minolta MD to Canon EOS,  but I've kept all the Minolta  stuff intact,  so someone can convert them back if need be.   I calculated that I needed about .28" spacer to replace the original ring.  The pix of both  lenses shows the original parts, nothing to that.

http://i37.tinypic.com/jzhedz.jpg

I found some washers at the local, called "flat plate",  big thick'uns.   They measure about .032" shy of what I needed, but I figure one of two things:

I can afford to give up some short focus, much better to "over" infinity,  and I can shim it with a number of materials, I have some shim stock,  coke cans,  and plastic.  easy

In the pix below,  the left washer is one of the originals.   I just chucked the OD in the lathe,  and hogged out the center hole to clear the rear element,  then chucked into the center hole and cut down the OD. 

http://i34.tinypic.com/etwpw7.jpg

Last pix shows the washer sitting into the recess in the rear of the lens.   I'll use the original spacer  for a pattern to drill through this new spacer,  screwing the new spacer to the lens with original screws.  I'll drill the import M42-to Canon EF adapter around the inner boss to clear 2-56 screws,  then drill the spacer  and last,  tap them into the washer

http://i34.tinypic.com/23vjps4.jpg

Last edited by 440roadrunner (2008-08-26 06:13:39)

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

I have thought about converting minolta mirror lense, but the fact that its f8 and f8 only is gonna make that a dim viewfinder.  Please share your results when your through.

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

Today I finished it up, unfortunately,  it's cloudy, not a day to test slow tele lenses. 

After turning the spacer to size,  I  stuck the original mount through the center hole of the new spacer to use for a drill pattern.  These screws go through to mount the new spacer to the lens

http://i37.tinypic.com/2ly0i2u.jpg

I drilled the M42 adapter  to clear 2-56 machine screws.  No particular spacing, just tried to center them in the "ears"  of the mount  to give more meat for countersink.   If I did this again,  I'd get one of those M42 rings with the step  for the Pentax pin,  just to have more material.    After drilling the M42,  I clamped the two pieces together,  and drilled one hole, tapped it into the spacer,  and installed one screw.  This gave me a "key"  to keep the two aligned before I drilled the second hole.     You cannot see here, but I got the M42  off concentric by some .003"  or so.   After tapping the holes, countersink, etc,  just a matter of assembly

http://tinypic.com/view.php?pic=5mnt5&s=4

http://i37.tinypic.com/s1hrba.jpg

http://i34.tinypic.com/2jer2pl.jpg


The monster thing dwarfs my new 40D

http://i37.tinypic.com/15hdiy8.jpg

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

That is awsome looking.   To bad its cloudy, nothing like a new toy you can't use right away.  Let us know how it works.  Whats looking through the viewfinder like at this point?

Last edited by tootalew (2008-08-27 02:02:40)

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

Wow...   congrats..    waiting for the results now...

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

That's what MLU, tripods and remote detonators...er...remote shutter releases are for. wink

Happiness is a loaded camera.

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

You make it look so easy! Also waiting to see the results.

Dittohead wrote:

That's what MLU, tripods and remote detonators...er...remote shutter releases are for

big_smile:D:D

Currently using Canon 5DII and Sony a6500 with Olympus, Pentax, Canon and M42 converters.

Photo Blog

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

Awesome work! I'm so envious of people with the skills and tools to do something like that!

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

Interesting that you chose to put the screws in the 'tip' rather than outer edge of the adapter ring. Looks solid!

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

awldune wrote:

Interesting that you chose to put the screws in the 'tip' rather than outer edge of the adapter ring. Looks solid!

Thanks guys.  I'm certainly NOT a machinist, but just having a little lathe helps.  Actually, with a little work, and maybe a simple --even homemade-- drill press,  you could actually make this withOUT a lathe.    I'll admit, it would be WORK.   You could

Find a suitable washer,  and as I did,  'hope' after your calculations that minor shimming with anything from plastic sheet to pepsi cans to etc etc  would get you the correct thickness.

You could enlarge the center hole by drilling a ring of small holes near the 'finished'  ID  and then cutting and filing,  Dremel tool, etc.

The OD  could be handled by hacksawing the OD in 'chunks'  to rough it to size,  then chuck the washer up in your drill/ press  and use files/ sandpaper,  etc  to cut to final size.


    So far as the screws,  about 2-56 is the smallest I can find locally  with a tap.   Flatheads are too thick to countersink into the outer flange.

Here's  the "sophisticated"  tapping tool I used.  This is one of those 'why didn't I think of that?"  and you can still find them on the 'bay.  You remove the chuck from your drill, install this device in between, and PRESTO,  a 'built in'  drill press.  I used this to tap the holes to keep the delicate tap nice and plumb

http://i38.tinypic.com/2n8o29f.jpg

Re: The Sigma/ Minolta to Canon EOS, 600mm mirror project

Well, I went out to take some sunset pix,  and just before the sun set,   I had time to take these.  The first pix  is a reduced filesize shot at about 50-55mm with the Canon kit lens just to show where we stand   The area of interest is just to the right above the ridge of the darg red building, up on the hill:

http://i38.tinypic.com/21bky0z.jpg

This is a fullsize crop of the kit lens at about 50-55mm, just for comparison.

http://i33.tinypic.com/30jp7k4.jpg

the next is a reduced filesize of the full frame of the Sigma 600mm.   Unfortunately, I didn't even have time to take a comparison shot with my 100-400L,  and the wind was blowing fiercely out on the prairie.   I discovered my tripod needs some work!!    lens is fixed at F8,  I believe this was about  1/750,   640 ISO on the 40D

http://i35.tinypic.com/15gqbky.jpg

Last pix is a full size crop out of the middle of the frame.   The focus point was the white house just to the left of the brown house.   I'll have to get the "big" tripod,  and do some real testing if we EVER get a clear day again

http://i35.tinypic.com/wjyjas.jpg