Condensers Revisited | Some New light on PCX lenses

35mm adapter order when using a PCX condenser

I previously posted an article about condensers in 35mm adapters (view it here). I have since aquired further knowledge of using plano-convex lenses as condensers in 35mm adapters (I'd like to thank those who provoded some valuable insight into this). I am not an optic expert, but I have been researching condenser lenses for some time now, and the following is what I have learned from this research.

For more information on condenser visit 35mm Adapter Condenser Shedding Some Light.

What is the benefit of a condenser?

Having a condenser mainly reduces hotspotting cause by the diverging light coming out of the 35mm lens. It also aids in the reduction of vignetting and reduces light loss.

What is a plano-convex (PCX) lens?

A PCX lens is a lens that is convex on one side and flat (plano) on the other. A PCX lens converges light that is passed through the plano side of the lens (see fig. 1 below).

fig .1

How does converging light help?

First, lets discuss the basics of what a 35mm lens does with light passing through. 35mm lenses converge the light to the point where it crosses (at the apeture) and then diverges (see fig. 2 below). With that said the light coming from the back of the 35mm lens is diverging.

fig. 2

This is where the PCX lens comes into play. Since the PCX diverges light if you face the plano side towards the ground glass in back of the 35mm lens it counters the diverging light and produces an even flow of light (see fig. 3 below). Note that the PCX lens should be position with the convex side facing the 35mm lens, also the ground glass is spaced further from the PCX just for the illustration.

fig. 3

What about focal length of the PCX?
PCX lenses have different focal distances. The focal distance should match as close to the back focus distance of your 35mm lens. Unfortunantly, I currently do not know more about this, but I find trial and error to work well for me. If I come across more information or if anyone with the knowledge is will to share I will post more on this.

Where do I get a PCX lens?
I find Surplushed.com and eBay to be two good sources for PCX lenses.

I hope you find this helpful as I have been asked a lot about PCX lenses and using them in 35mm adapters as condensers. Seems to be a hot topic with very little information on it.

If you find any information to be inaccurate or have additional info to add please comment on this post, thank you.