The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Building a camera obscura - lens query

I'm keen on building a camera obscura to revist photography's not too distant past and simple beginnings. I'm going to start with a pinhole version and then make another one with a simple lens. So I thought I'd hunt around eBay for a cheap, disposable lens. I figured I'd probably need something with a medium to long focal length to project a decent size image circle on the wax paper viewing screen. Then I just remembered that I've got a 10x microscope eyepiece that I'm not using anymore. Though my question is - which side of the lens eyepiece should be facing outward? There is the side of the lens that I put my eye to when viewing through the microscope. And then there's the other side which is normally inside the microscope itself.

I'm guessing it would be preferable to have the side that would be inside the microscope - facing outward, collecting the light. And the other side facing your eye, just like with a microscope.
 
Last edited:

camping

Member
what image circle does you microscope eyepiece have?
I doubt that it is large enough.

It sounds like a fun project.
Paul
 
what image circle does you microscope eyepiece have?
I doubt that it is large enough.
That's a really good question. I actually don't know the size of the image circle it projects. I guess such a specification is not generally required by microscopists as opposed to photographers who like to switch lenses between formats.

Do you reckon you'd be able to recommend any cheap lenses with long focal lengths and decent size image circles that would be suitable? For a project like this, I definitely don't want to spend any real money. After all, the lens will be fitted to a cardboard box with duct tape! $20 or less would be fine for a lens. I could consider lenses for the 35mm film format though then again, having a 36 x 24mm wax paper viewing screen is going to be pretty tiny and not very satisfactory to look at. I guess enlarger lenses could be another option though they tend to be fairly pricey. Or perhaps projector lenses. I think an extremely old, antique lens could be fun to use though then again it depends on what format it's intended for.
 
Last edited:

camping

Member
To approximate the image circle is to hold up the lens to a light source (light bulb) and project the light coming out onto a surface of paper. Move the paper or lens back and forth until it projects a clear circle of light onto the paper. You can test which direction you want to use.
The image from a microscope finder would be quite small because it was made to pass the most light to thr eye and not light up your face.

All the best.

Paul
 
Top