Looking for advice on aperture with 4x5 box camera build

[nascarfann]

So I decided to pursue building a 4x5 Holga HD box camera. I am using the components from a Kodak disposable camera for the shutter. The shutter speed of the camera will be 1/100, and this seems like a good speed.
I selected an absolutely terrible lens that I am going to put on the camera. It is one of those really cheap close up lenses that is intended to be used overtop a normal lens. Doing testing with the lens, a focal length of 90mm seems to provide the best results. I have removed the plastic lens from the components of the disposable camera and am going to put the lens over the top of the hole.
I am having some issues figuring out aperture in relation to the build. The disposable camera had an f/10 aperture, which seems like a good aperture for the build. The problem is this, the disposable camera had an 30mm focal length. My question is, do I need to drill the hole to be a bit larger on the disposable camera because the focal length is longer?

 

[Dustin McAmera]

Yes, I think so. But if you do, you risk the shutter not sweeping the bigger hole in a nice even way.

The relative aperture is the diameter of the iris (strictly as seen slightly magnified, through the front parts of the lens, but to a first approximation I'd ignore that), divided by the focal length. So if the hole in your shutter is what provided the iris in the Kodak camera, what you have now is going to be about f/30: a bit of a stretch. I think you need to open that hole up to three times it's current diameter to get back to f/10; only you can see if there's room for that, and if the shutter blade will do it's job over the larger hole.

 

[AnselMortensen]

What magnification is the close-up lens you are using?
A "+2" is a 500mm lens
A "+3" is a 333mm lens.
A "+4" is a 250mm lens.
A " +10" is a 100mm lens.

You will need that much ( ^^^) "bellows extension" just to reach infinity focus, and even more extension to focus on closer subjects.
Any less, and you won't be able to focus on anything.

Your aperture (f-stop) is a ratio...determined by dividing the focal length of the lens by the the measurement of the size of the entrance aperture hole AS SEEN THROUGH THE FRONT LENS ELEMENT.

The aperture of the disposable camera lens is irrelevant...f/10 only applies to that lens, NOT the shutter.

 

[Dustin McAmera]

Except that with a simple camera, it's quite likely the hole providing the known aperture is the one built into the shutter unit. If you reuse the shutter, you reuse that hole (or drill it out bigger, as the OP proposes).
I have a similar thing saved from a broken compact camera, which I couldn't bring myself to throw in the bin, though I can't see what I'm ever going to do with it.

 

[Nicholas Lindan]

A good starting aperture range for a 4x5 'box' camera would be f/22 - f/32. A +4 close-up lens will give you a 250mm focal length - a bit long for your purpose. f/22 and 150mm is about a 7mm (1/4") aperture.

Try Surplus Shed for a selection of reasonably priced lenses - https://www.surplusshed.com/search_...o=120&focal_length_from=150&sort=&sortby=+asc - lots to choose from at $7.50 each.

 

[nascarfann]

What magnification is the close-up lens you are using?
A "+2" is a 500mm lens
A "+3" is a 333mm lens.
A "+4" is a 250mm lens.
A " +10" is a 100mm lens.

You will need that much ( ^^^) "bellows extension" just to reach infinity focus, and even more extension to focus on closer subjects.
Any less, and you won't be able to focus on anything.

Your aperture (f-stop) is a ratio...determined by dividing the focal length of the lens by the the measurement of the size of the entrance aperture hole AS SEEN THROUGH THE FRONT LENS ELEMENT.

The aperture of the disposable camera lens is irrelevant...f/10 only applies to that lens, NOT the shutter.

I am using a +10 close up lens

 

[Jim Jones]

A meniscus close-up adapter lens used as a camera lens performs best when behind the aperture with the concave surface facing forwards. This adds significantly to the overall length of the camera, so many cheap cameras sacrificed performance for compactness, and placed the lens in front of the aperture with the concave surface facing backwards. When using a 100mm lens on 4x5 film, be careful that the shutter and lens mount don't cut into the picture area.