PDA

View Full Version : Mirror ball mounting?



Anti-Distinctly
03-15-2009, 04:32 AM
If anyone out there has experience with taking pictures of mirror balls for HDR purposes, I'd like to get some insight into how you mount them on a stand or pole or whatever.
I've got a 3" diameter stainless steel ball bearing. I though I'd just get it tapped and a thread put in so I can mount it on a lighting stand, but I called a machine shop and they said it's nign on impossible to tap ball bearing as they're too hard. I thought about welding a mounting pole to it but then heat discolouration would be a concern.

Anyone have any experience or ideas about this?

Dexter2999
03-15-2009, 07:02 AM
Super Glue? JB Weld?

Tom Wood
03-15-2009, 07:50 AM
... JB Weld?

JB Weld....you can glue engine blocks together with it! Tuf stuff.

If they still sell kids dart guns with the rubber tips, maybe slip the stem into the top of the lightpole and balance the ball on that?

Wow, a 3" ball bearing...nothin' like cold steel!

Dexter2999
03-15-2009, 08:09 AM
I just remembered that Waaaaaaay back in High School I knew a kid who was in Machine Shop at the Trade School. He bored out a bearing to make a pipe and tapped it to thread in a pipe stem.

So, it can be done. I don't know hpw easy it is though.

Or maybe he started with a block and tapped it then lathed out a bearing shape? I dunno.

Anti-Distinctly
03-15-2009, 08:20 AM
Hey guys,
I'm thinking perhaps the JB Weld (or whatever the UK equivalent is) may be the way to go. It's hardened chrome steel so it probably can't be tapped - but I'll ask a few more people before I give up on that.
A suction cup wouldn't work as the thing is just way too heavy.

Edit: And thank you for the advice - it is much appreciated. Any more ideas or experience is welcome.

Dexter2999
03-15-2009, 09:04 AM
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=200302145220

Kuzey
03-15-2009, 09:25 AM
Here is one from Pagnozzi's post in the beta forums...looks either glued on to the base, or the base is especially made and the ball just rests on top:

http://www.newtek.com/forums/showthread.php?t=93465

Kuzey

Hopper
03-15-2009, 10:11 AM
No need to have it tapped. Simply have it drilled to the core with a 4-6mm diameter bit, and slide it onto a pole cut to the same diameter. No need to have it "mounted" to something unless you plan on flinging it around! :) It's heavy enough to stay put. Basically, make a giant lolipop out of it.

and if you absolutely have to have it mounted, then mount the "pole" part (i.e. welded to some sort of threaded housing) then you can slide the ball on and off at will.

or..

Get the machine shop to lathe out a cone and cut the top concave to match the radius of the bearing making a basic stand for it.

biliousfrog
03-15-2009, 11:59 AM
I can probably send you a purpose built stand with a thread on the bottom to screw into a tripod if you like? I made several as prototypes but I wasn't 100% happy with them...although I still use them.

Basically it's a 100mm long, grey, nylon rod with a metal threaded insert at the base and an inset neo magnet at the top. The magnet is at the bottom of a 'cup' which the bearing rests on and is strong enough to hold the stand upside-down with the bearing hanging from it. The thread is the proper 1/4"-20 BSW one used for camera mounts, they're quite difficult to get hold of and I had to buy them from an old-school machine parts supplier.

I didn't go into full production because although the bearing can he hung from the magnet it won't prevent it falling off if it's knocked hard enough. The major advantage is that it's small, fits onto any tripod and doesn't require perminent damage to the bearing.

biliousfrog
03-16-2009, 03:08 AM
Here's a photo of the stand. If anybody else is interested I might finish off some more and post them out or upload a simple step-by-step on making your own.

I know that a lot of people are switching or have switched to fisheye lenses. By having the camera on it's back and using a full frame 360 fisheye you can shoot a 'sky dome', even setting auto-exposure bracketing to capture a full HDRI unattended. It only really works with the higher-end 'pro' SLR's which shoot full frame and allow several stops with bracketing but it is possible with consumer cameras and a little more work. Obviously you lose anything below the horizon unless you take the images horizontally and stitch but it's normally easy to fake the ground info.