HDRI Sphere for image capture

[Cirric]

I've been looking at setting up a rig for capturing the photos for an HDRI image based on the use of a sphere (Two photos shot 90deg offset.) I've got the camera/tripods/etc.

The big issue seems to be finding a decent sized (decent priced) reflective machined sphere.

Most of the chrome spheres I see are 1" or less, and the price gets pretty high the larger the sphere gets.

The questions:
Are there any suggestions as to a good shere to use?
Will a machined Aluminum sphere (polished) give "enough" reflection?

Thanks in Advance!

[Skyraider3D]

How about http://www.0-360.com ? :)

[Cirric]

Thanks Ronnie, but I was hoping to spend less than 100.00 USD (Cool concept - but 595 + adapter is a bit much...):eek:

[kevjon]

Hey Cirric, this thread suggests some ideas and possible places to buy the fabled chrome ball.

http://www.xsibase.com/forum/index.php?board=6;action=display;threadid=1009

If garden centres do indeed have chrome balls it would be a lot cheaper than a buying a big stainless steel one from a bearing company.

[Cirric]

Hey Kev - Thanks,

I'm concerned about the "Large" lawn ornaments, as they are not "chrome" they are silvered had-blown glass. One of the "Benefits" of hand-blown glass is that it will contain defects/bubbles/lines/etc. (The correct url for the law ornaments is: http://www.bakerslawnorn.net)

Nice thread - some good information there!

It seems like the perfect solution would be tennis ball size, but like a trailer-hitch or Shifter-knob - but without any engraving/slices etc - as the mount points for each of those would help mount it on a stand/tripod.

[kevjon]

Maybe you could look at buying a steel ball (like a trailer hitch) to cut costs and then having it chrome plated. The chrome plating process I don't think is very expensive. We have had done some chrome plating in our engineering work.

[Cirric]

Hitch balls all seem to have that flat top with engraving...

I'm thinking about ordering this:
http://www.modbargains.com/zoom_img/MOMALUSP_1124317523.JPG
It's aluminum - and the shift mount would be good for setting up the framework... I just wonder if it will be reflective "Enough"

[kevjon]

I guess you won't really know until you see it live. It certainly looks suitable.

2" (51mm) dia chrome steel balls are available here (http://cgi.ebay.com/10-Chrome-Steel-Balls-1-2-dia-ball-bearing-Grade-25_W0QQitemZ7617974376QQcategoryZ48718QQcmdZViewIt em) for $22.00 US. Sounds perfect for your needs and well with the budget. 2 1/2" are $34.00. I think I would go with the bigger option.

[Cirric]

Wow Thanks! I totally forgot the ebay options.
I think I can make a 'mount' with epoxy and a threaded mount for a tripod... I don't have any way to drill into the sphere -

[kevjon]

You could bring the sphere to local engineering firm. It wouldn't cost too much to have it drilled and tapped so a suitable mount can be screwed in.

I don't think epoxy glue will be strong enough (given the weight of the ball) but a good epoxy putty may do the job.

[canadair]

What about those Chinese Iron Balls that you - for lack of a better word and not wanting to offend anyone who knows a more appropriate one - "twiddle" in your hands? You can get them in a vareity of sizes and with a bit of polishing could probably be pretty darned miror like.

Failing that, you can just twiddle them and reap the many health benifits!

[Cirric]

I think the health aspects might be useful... But I'm not sure about the "trueness" of the sphere.

I know that people are shooting HDRI images with the garden globes (and I have seen an article where someone used the Chinese Iron balls) - I just wonder about the impact of mapping the sphere if it isn't fairly precise.

I've ordered a 2.5" Grade 50 (0.00005 deviation from spherical) which seems "close enough" for me.

Most of the detail instructions say "Take two pictures from 90 degree ranges"(thus allowing you to remove the camera form the reflection) It would seem pretty easy to rig up a 'frame' to hold the sphere and rotate the camera on it's tripod - but the point of rotation needs to be around the sphere, so I'll have to use two tripods.

Any ideas how these will effect the output?
1. Deviation from the horizontal plane between image sets?
2. miss-alignment (not 90Degrees rotation? is 92 degrees "Close Enough?)

The other issue I foresee is the "time-lapse" between frames. Since the goal is to get airplane and ship environments, I'm expecting some cloud movement between shots. (most noticeable between the 3-12 bracket at one position, and the second set of images at the 90 degree offset).

[Skyraider3D]

On a 3D mailing list, the following item was recommended - in particular the 73mm one.
http://www.dube.com/ball/8.html


Maybe you could mount the camera on a swing, and quickly take two shots. Click, swing, click :)

[kiwi123]

"the 73 mm is good for one ball manipulation"..... right

[Cirric]

Oh GREAT - Some MOD is going to lock this thread...
I'm not going to get into a comparison of ball sizes, or manipulation technicques - ;)

Now if only the darn sphere would arrive!

[Skyraider3D]

The mods don't have the balls yet to lock this thread... :p

[Larsen]

This guy (http://www.hello-napalm.com/tuts/tut_hdri.html) has some tips

[kiwi123]

Nice one ! Anyone know a good adress in Europe (or UK preferably) where you can get nice shiny balls ?

[Cirric]

Nice one ! Anyone know a good adress in Europe (or UK preferably) where you can get nice shiny balls ?
There's a little shop down behind the pub...

Seriously:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7586713044
This is where I bought mine - (Thanks to Kevjon) - It arrived today - now I'm working on buffing/polishing it.

[kiwi123]

Hmmm.. that link doesn't work and I wouldn't be able to find a pub if I tried :lol:

[kiwi123]

By the way, you would think that when you use a a DSLR with RAW capability that it would be far easier to shoot HDRs. With my EOS350D I can already vary one exposure from -3 to +3 fstops, so, with two shots you should be able to cover the whole range as stated in the tutorial link above. Even better, with exposure bracketing on the cam itself, I can take three shots automatically with -2, 0 and +2. Which would give the dynamic range of -5 to +5 if you shoot RAW.
Might sound like a lot of blabla to most, but then again, this stuff enables you to basically shoot a HDRI image in 3 seconds, which is a big advantage in a dynamic environment.

[Spinner]

Kiwi,
The link works for me.
Try a ebay search for US seller Toolsupply.
Try his shop link-
http://stores.ebay.com/ToolSupply

I'll leave the Japanese balls that you ... strictly alone!

[kiwi123]

Ok, but that's still a US seller....

[Cirric]

Kiwi - I'd offer to buy one and ship it - but it's not exactly lite - so shipping might be "prohibitive" - worst comes to worst - I can bring on to the UK in Sept, and either ship it from there - or arrange to get it to you through a friend?

I've got a DSLR - it can bracket up to 9+ and 9- images at a time. (I can't imagine doing this with a "point-and-shoot" camera.) I've got the dimensions/ranges and the "concept" set - so I'm ready to go.

Of course it's RAINING and the weather forecast is "overcast" all weekend. :(

[Cirric]

The sun came out, and left a bright cloudy sky...

Lots of stuff still to work out (best exposure ranges, best sizes, etc.) but the initial test in complete...

This is a JPG screenprint of the HDR file. (the 512x512 HDR is 680K the 2048x2048 HDR is 10MB)

I need to get a better mount, the tripod head is WAY too big!

[Skyraider3D]

looks promising!