Pinhole with an Epoxy Droplet Lens?

Newt_on_Swings · Apr 13, 2012

So just before sunset today I was playing with my chocolate box pinhole camera using 5x7 paper and litho film, and a thought occurred to me.

Would it be possible to use clear epoxy to create a droplet lens on top of a pinhole. The surface tension should create a nice smooth and round surface as long as you can center it on the hole, I think it should work.

I just put a few drops on a very thin piece of adheasive foil tape (my current pinhole medium) and they are drying. They do form a nice round shape, and by accident one has even formed a tiny bubble under the epoxy right above the pinhole.

I tried doing some google researching, but have not come across any info on such a process. Anyone ever do something like this before? or read about it? Would the droplet lens be able to form a picture? How would such an image come out?

Rick A · Apr 13, 2012

To answer your question, I don't know. Since you have some made try them out. Can't wait to see what you get.

Nicholas Lindan · Apr 13, 2012

The focal length of a sphere is about equal to its radius. I'd guess your epoxy drop has a focal length of a few mm.

If your camera has a pinhole-to-film distance of 100mm then a 10 diopter close-up lens is about right. The lens out of an old box camera might have a convenient focal length. You might find coverage isn't as great, though, as at large angles a meniscus lens will produce lots of aberrations.

Worker 11811 · Apr 13, 2012

Try some super glue. I think you'll find its optical properties to be a bit better.

SMBooth · Apr 13, 2012

Won't it also seep through the pinhole and create another lens on the back....

Newt_on_Swings · Apr 14, 2012

This has been a bit tricky, well I tried super glue, but it was way too runny, the liquidity of it caused it to not form a high meniscus. The epoxy I am using is branded Duco Cement and it dries very clear.

The problem is that when the droplets are drying they collapse and shrink down. I have had the most success with forming a bubble within the epoxy which acts as a support for the material to dry on and take shape. Also suspending it upside down helped it dry into a better shape as well.

I have been trying to get some exposures indoors, and flashing a test subject with a strobe, and leaving it sitting on a chair for awhile but I am not getting anything close to usable. I think the focus is off. They are 5mm wide, and 2-2.5mm high, I think the correct terminology is plano convex for the lens shape. The box back/paper/film surface is 4cm away from pinhole.

Sorry for the images I didnt want to setup the macro lens and tube for these 2 shots. I'll have to try in daylight tomorrow if I have time.

Worker 11811 · Apr 14, 2012

The reason I mentioned Super Glue is because it was invented by Eastman Kodak as a material to make optical gun sights but the stuff was too sticky to be useful.

When one of the scientists working on the project accidentally glued a set of refractometer prisms together, trashing several thousand dollars worth of lab equipment, they decided to abandon the project and, subsequently, they decided to market the stuff as "Kodak #910" because it took them 910 tries to perfect it before they gave up and repurposed the stuff.

Sorry, I didn't think about how runny Super Glue might be. I was only thinking of the optical qualities.

Regardless of the glue that's used, cyanoacrylate or otherwise, what do you think about building it up in thin layers to get the shape and thickness you want?

paul_c5x4 · Apr 14, 2012

Superglue (or cyanoacrylate adhesive) comes in a variety of types depending on it's intended use. Some are water thin and good for seeping in to thin joints that have already been assembled. Other grades are viscous with good gap filling properties. For forming a lens, I'd suggest one of the thicker grades to produce a droplet.

Newt_on_Swings · Apr 14, 2012

I will have to check for different brands of superglue next time I'm in the store. I did get to play around with the camera and lenses today at around the same time and lighting conditions.

The lenses that dried to the bubble shape did work. I had to go back with a needle and pierce the hole again as a tiny film of glue covered it. So I had to be careful to not pierce the lens when doing it.

The results? Well not amazing lol. I have used the same size pinhole for all of them, using the same needle. The standard pinhole image fills a 5x7 image area almost fully. The one with my bubble epoxy lens, makes an image circle a little smaller than half that size. All are kinda fuzzy, I think thats more me than the hole, or lens, as the box is a cardboard chocolate box, with a film canister cap for a lens.

I will upload images after dinner. I kinda messed up the contact prints. I did them rushed and wet with a quick wash of the original negative image and using water to hold them together and squeegeed them flat. I have a piece of glass somewhere, but it wasn't in the darkroom.

Newt_on_Swings · Apr 14, 2012

Here are the results:
1st Standard Pinhole for baseline.

2nd Close up Performance with Epoxy Lens

3rd Subject at Infinity with Epoxy Lens

As you can see there is a fair amount of softness. There are probably a bit to many variables to really say whats causing it, the stability of the box, the edges of the pinhole, the size and curvature of the epoxy bubble, the light transmission properties of the epoxy, and user induced movement when opening can closing the lens cover. All I can say for sure is that the epoxy lens makes a smaller image circle within a similarly sized box than a standard pinhole.

I think it was a interesting experiment, and future experimentation should be looked at though different materials such a other brands of clear epoxy or superglue.

holmburgers · Apr 15, 2012

I think this is a really novel idea.. brilliant even.

What happens if you eliminate the "pinhole", and widen the diameter of your aperture to utilize the whole area of epoxy lens?

Imagine if there were ways to affect the lens as it cured... like centrifugal force, temperature, g-forces... you might be able to manipulate the liquid into more ideal lens shapes.

Newt_on_Swings · Apr 15, 2012

Its interesting that you brought up lens shapes, as one of the more interesting shapes that happened was one droplet that had dried as a concave surface. I thought it was pretty cool, but it wasn't usable as when I was playing with it, the dried glue droplet popped off the aluminum tape.

Creating the bubble style lenses is pretty difficult, I have been trying with a small straw, using mouth blown, and compressed air, but its a bit too delicate. The only way that has worked is to coat the tip of the epoxy tube, and squeeze a bit of air out of the tube and epoxy at the same time and hope you form a bubble. The process is similar to the bubble wand style toys kids play with, you have to coat the wand surface with a layer of soapy water in order to create a bubble with it.

I have been trying to induce different surface shapes by manually pressing on the material as it dries, and also using compressed air to change the surface while it cures into a more viscus fluid, which does seem to kinda work.

Lee Brown · Apr 15, 2012

I saw an article about doing something similar to create a microscope.
http://www.microscopy-uk.org.uk/mag/artjul00/awscope.html.

I've never done it but it looks like you would have to get pretty close to the lens to get a decent image. So probably a very small image circle.

Mark Fisher · Apr 15, 2012

holmburgers said:
I think this is a really novel idea.. brilliant even.

What happens if you eliminate the "pinhole", and widen the diameter of your aperture to utilize the whole area of epoxy lens?

Imagine if there were ways to affect the lens as it cured... like centrifugal force, temperature, g-forces... you might be able to manipulate the liquid into more ideal lens shapes.

I'd expect that just putting the lens on top of a pinhole would just soften the image a bit, I think the trick is to open the pinhole up a bit. Regarding epoxy, it shouldn't shrink on trying much at all. The Duco-branded glue you are using......is it two or one part?

Anyway, the shape of the lens you create will depend on the surface energy difference of the two surfaces. In other words, how much does the glue wet the surface of the base material. If the base is, say, teflon, it will tend to stay more spherical. The other approach to change the focal length (and shape to a lesser extent) is to simply make a much larger drop. I think this is probably the best bet. I suspect the easiest way would be to form the drops on a sheet of polyethylene, maybe coated with oil, then pop them off and put it onto your pinhole.

I've spent a ton of time at work lately working with very similar things. Also, remember that your drop will not be all that close to a true sphere. In zero-g it would be but stuck here on earth, it will be a flattened sphere....I really son't think that will matter for what you are trying to do except to add more cool distortion!

Newt_on_Swings · Apr 18, 2012

Well the Duco cement Ive been using is a one part type, so I think I was wrong to call it an epoxy. I think it would be better classified as a glue.

I have tried larger drops to make a bigger lens, but the same problem the glue seems to shrink as it dries and deforms the initial smooth surface. The temporary solution to that was the blow a bubble under it. But I think a true fix would be to find a right material such as a more viscus super glue, or other type of clear drying glue which does not shrink on drying and is not runny. The bubble lenses would create 4 surfaces where light passes through as opposed to 2 if it were a solid lens which probably would be better.

I will try out some of your tricks, maybe coat a sheet of plastic in spray on oil and try to create ones on that, as well as widening the hole when I get a bit more time hopefully this weekend.

I have been thinking about trying to dry them suspended on a bit of floss, such as when water is suspended on a spiders web. But that might get a bit messy, and the shape maybe less spherical when moving to a larger scale.

Mark Fisher · Apr 18, 2012

The shrinking is due to the solvent evaporating. A 2 part epoxy is what you want.....that won't shrink

Steven L · Apr 18, 2012

I love this thread. Using glue as a lens, awesome. What about using half a clear glass marble for lens? Perhaps it's possible to cast the glue in a mold.
What about this, if you have the right shape for the lens, why not make a mold out of silicone? Hobby stores have a kit to make a silicone mold from a hand in order to make a cast from that mold. Perhaps this stuf is acurate enough for making a mold. I don't know if superglue sticks on silicone, I guess not. But epoxy might work.

Roger Thoms · Apr 18, 2012

For thicker grades of cyanoacrylate think woodworking supply.

Roger

ced · Apr 28, 2012

Technically it is a lens therefore not a pinhole anymore...

cliveh · Apr 28, 2012

ced said:
Technically it is a lens therefore not a pinhole anymore...

This was my first thought when I saw OP. Some may think it is just being pedantic, but there are some pinhole photographers who show wonderful "pinhole images" taken with their pinhole camera, when in fact they are also using a lens over a very small aperture. As the previous post states this is then not a pinhole picture.

Toffle · Apr 28, 2012

There was a thread some time ago on the subject of lenses made from ice. (but when I tried to do a search on "ice lens" I also got every entry for "nice lens". )

Mustafa Umut Sarac · Apr 28, 2012

There are few things to accomplish when working with epoxy.
First of all not mixing all part 1 and part 2 but as much as you need.
Second , if you use marine grade epoxy , its hardener generally dark brown due to wait in the shelf. You must find crystal clear epoxy but very expensive.
Third , you must find pumps to pump one part epoxy to one part hardener equally or it doesnt set.
Fourth , you must find a well heated place or it fails.
Fifth , you must mix and set the drop in dust free environment.
Epoxy is not suitable for that experiment because it is expensive but acrylic is great , lots of military optics made from acrylic block cnc'ed
or rapid prototyped manufactured.
Why not built a real lens system for example peri from rapid prototyping. I am thinking that for years
All you need is a real lens design file , stl file and than apply to online rapid production companies , their web applet would give you a online quote from cnc file , you pay online and lens at your hand in a week.
Rapid prototyping firms produces car parts especially lamps , stops from clear or color acrylic but it is slow and expensive again.
Go , use your canon.

Umut

Newt_on_Swings · Apr 28, 2012

I haven't had time to work more on this as I've been pretty busy at work and this weekend was devoted to fixing/trying to fix cameras and repainting/touching up bodies. As well as printing in the darkroom a backlog of images people have requested.

I guess the terminology wasn't the most appropriate but it was the most descriptive term at the time as it evolved from a pinhole process. The droplets are quite small and designed to fit right over the pinhole. It is intended to be purely experimental and an alternative to standard photography with a pinhole or a conventional lens.

It was designed in mind to take advantage of surface tension on the glues/epoxy and be a simple way to make a very smooth and round lens without grinding/polishing/cnc processes.

Worker 11811 · Apr 29, 2012

Steven L said:
I don't know if superglue sticks on silicone, I guess not. But epoxy might work.

Super Glue should not stick to silicone. If it does, it would probably peel off fairly easily.
This speaks to the old joke: If Super Glue is supposed to stick to anything and nothing is suppose to stick to Teflon, what would happen if you put Super Glue on a Teflon skillet?
After the laughing subsides, the answer is that the Super Glue would not stick to the skillet. Super Glue can only stick to substances that are (chemically) polar. Teflon is almost completely non-polar. That's why nothing sticks to it. http://en.wikipedia.org/wiki/Chemical_polarity

Silicone is also non-polar. So, by extension, Super Glue should not stick to silicone the same way it doesn't stick to Teflon.

Side note: Nothing sticks to Teflon, neither does Teflon stick to anything else. It was actually very difficult to make Teflon coated skillets at first. T-Fal was the first company to market a non-stick, Teflon skillet. It was a difficult, multi-step process that took years to prefect.

As to other substances that you could try to make a lens from, try Polyester casting resin:
http://www.dickblick.com/products/castincraft-clear-polyester-casting-resin/

Casting resin is thicker than Super Glue, it is almost perfectly clear and it is moldable. You should be able to find it in your local craft store.

lxdude · Apr 29, 2012

Worker 11811 said:
After the laughing subsides, the answer is that the Super Glue would not stick to the skillet. Super Glue can only stick to substances that are (chemically) polar. Teflon is almost completely non-polar. That's why nothing sticks to it.

Then there are chemicals which are bi-polar. They make things difficult for the chemicals around them.

Pinhole with an Epoxy Droplet Lens?

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