Lensball in an optical tube

SmoothOperator wrote:

l wonder if anyone has tried using a lensball in an optical tube. Possibly in conjunction with a macro lens.

The idea would be to fill the frame completely with the lensball, to get a fisheye effect. Only problem, I can think of is the depth of field of the macro lens.

I've done plenty of things reflecting off a shiny ball, but nothing with an optical glass ball. Where did you see one for cheap?

Ah. I found them on eBay.  Ordered a 30mm and an 80mm... we'll see if there's anything good from it. 

SmoothOperator wrote:

ProfHankD wrote:

SmoothOperator wrote:

l wonder if anyone has tried using a lensball in an optical tube. Possibly in conjunction with a macro lens.

The idea would be to fill the frame completely with the lensball, to get a fisheye effect. Only problem, I can think of is the depth of field of the macro lens.

I've done plenty of things reflecting off a shiny ball, but nothing with an optical glass ball. Where did you see one for cheap?

Ah. I found them on eBay. Ordered a 30mm and an 80mm... we'll see if there's anything good from it.

Can I be first author?

The lensball makes me wonder about the fisheye adapters. I've avoided the adapter, though I want a fisheye lens, but maybe a high quality distortion can be accomplished in just a few elements? If I went the adapter route for a fisheye lens, what would the best pairing be? I'm guessing a lens that has both a flat and deep field, would impart the least amount of additional distortion. The Lensball clearly produces nice results by itself, even with extraneous light reflections.

Actually, this has been done before primarily for a wide view angle with multiple cameras looking at parts of the sphere. There are better ways to get a fisheye view... although we'll see; perhaps this is viable too?

I purchased a 30mm "clear crystal ball" and made a 3D-printed mount for it to be used with a Canon PowerShot ELPH180 (or similar camera):

The mount has three printed parts. The mount fits the ball in the front, which is then locked in place by screwing the lock part over it. The whole rig is then connected to the PowerShot by screwing-in the printed 1/4-20 bolt to the camera tripod socket. It looks very cute....

I purchased a 30mm "clear crystal ball" for $4 on eBay, shipped from the USA. They start around $2 from China. Anyway, the one I got has multiple nicks, a couple of significant inclusions, and isn't all that close to being spherical.

The image quality is unfortunately as poor as expected. A door peephole produces better image quality. However, you can judge for yourself:

This is a flat poster -- there just isn't enough DoF for imaging the ball

Obvious distortion from this ball not being circular

Trebor1 wrote:

Maybe you need bigger balls? It appears there are a number of higher quality K9 (Borosilicate crown glass) balls from various suppliers, in the 60mm-120mm diameter range. There is even one available from Rollei, for additional kudos/poseur value but the original (Chinese) manufacturer may well be the same?

https://www.rollei.com/products/photo-accessories/lensballs/

I got an 80mm one at the same time. It weighs a ton.

The main advantage to a bigger ball is that the optical defects are MUCH smaller relative to the size of the ball. The disadvantages are:

• It isn't cute. It's just too big and heavy.
• Cost. The 80mm cost me $14 -- and that was a very low price for that size. The Rollei balls look really good, and they start at 60mm for 30eu.
• DoF/FoV issues are still there.

Ball lenses have been used to obtain the same point of view with multiple cameras for perfect stitching of a wider view -- here's perhaps the best known example -- and I really got the 80mm to try for a variant of that. It would be as an alternative to FourSee , a camera which my research group built for Time Domain Continuous Imaging .

I've now tried an 80mm.

It's better, but still not good. More info is in this post at the adapted lenses forum .

I have 20mm & 80mm crystal balls but have never tried putting them in a tube. Reflections on the surface have always limited my results so I can definitely see the advantage of that!

I've been meaning to try something bigger than the 80mm with the aid of a fishbowl, but its only one of a very long list of projects...

petrochemist wrote:

I have 20mm & 80mm crystal balls but have never tried putting them in a tube. Reflections on the surface have always limited my results so I can definitely see the advantage of that!

I've been meaning to try something bigger than the 80mm with the aid of a fishbowl, but its only one of a very long list of projects...

Well, it doesn't really work very well even in a well-designed mount... but it sort-of does work. The PowerShots don't really have enough DoF, but using CHDK they are programmable. I might throw together a little focus stacking script for it -- there are already focus bracketing scripts, but I'd want it to actually do the stacking in camera, not just take the shots at various focus distances.