Pinhole and water drop

[uhligfd]

Dear Pinholers,

I have been thinking of trying to put a perfect ball/sphere of water (i.e., a nice waterdrop) onto my pinhole camera right at the hole.

I expect to get some kind of fisheye view, should I not. As I see when I look at raindrops closely on a window pane ...

My problem is to keep the water drop spherical, not running. I need some anti-soap type agent to keep that drop tightly round .... Any suggestions?

[Mike1234]

I'm not a pinhole shooter but...

No... soap will decrease surface tension making things more difficult. Maybe a tiny drop of clear heavy weight oil instead? Just be aware that either way you will almost certainly ruin your pinhole.

Err... after re-reading your post I see you said "anti-soap agent". Not sure what that is but maybe you're right. Still, the oil would be better... no evaporation to worry about changing the shape of the "lens" as you expose.

[keithwms]

A hydrophobic surface will support a lovely water droplet with no run. So... make your pinhole in some plastic e.g. acrylic or teflon or such. A black section of developed E6 film might do the trick.

The "fisheye" effect will work, I recall seeing some examples some time ago. Of course the main problem is evaporation of the water. But pure water will have the right surface tension to produce a nice round ball.

[brianmquinn]

Try glycerol also commonly called glycerin. It is often sold in drug stores next to the hand lotions and is only a few dollars a bottle. If it is not there ask the Pharmacist. They may just give you a small amount form one of their stock bottles they use to compound drugs. It is much thicker than water and forms a nice drop. Also unlike water you don't have to worry about evaporation during a long exposure.

[Christopher Walrath]

Wirelessly posted (BBBold: BlackBerry9000/4.6.0.167 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102 UP.Link/6.3.0.0.0)

I would also think the size of the drop would affect its ability to remain stationery on a vertical surface of any kind. Just a thought. Think of your windshield. Small drops remain until more water increases its size and allows gravity to have more of an effect.

[Mike1234]

Christopher is right. Also, a pinhole may not see the entire surface of a large droplet. One just a tad larger than the pinhole is probably desirable. Brian's suggestion of glyerine is a good option, IMO.

[keithwms]

Glycerol/glycerine has lower surface tension than water. It is used as a lubricant precisely because it is viscous but also spreads well on most surfaces.

Some data...

Liquid, Surface Tension γ (N.m-1)
water (20°C) 0.073
water (100°C) 0.059
soapy water (20 °C 0.025
alcohol 0.022
glycerine 0.063
turpentine 0.027

[Larry.Manuel]

Perhaps some rudimentary calculations of the focal length of a spherical lens would interest you. Don't be surprised if the focal length is only a handful [or less] of millimetres. Thus, your film must be awfully close to the droplet. I imagine you can see where this is leading.

[Mike1234]

Hmm... maybe taping an ultra-thin piece of glass (microscope slide?) over the pinhole to place the droplet on is a good idea. This way you could use a high quality laser cut pinhole as many times as you like without damaging it. You could also get the centering exactly correct because you can move the piece of glass around.

Now I'm really getting intrigued. One might be able to emulate the old Hypergon (sort of).

[brianmquinn]

A hydrophobic surface will support a lovely water droplet with no run. So... make your pinhole in some plastic e.g. acrylic or teflon or such. .

But water won't stick to this surface and a water drop will just roll off as soon as the camera is placed upright.

PS I have just placed a water drop and a glycerol drop on a plastic plate. When I tilted the plate upright the water ran down the plate. The Glycerol stayed in place and was a nice drop shape. A light bump to the plate did make it run however.

A also agree that the drop should probally be just big enought to cover the hole. The smaller it is the less likey it will be to move.

I don't know about focal legnth. That is something you will have to report on after you take a picture.