Nikon LS-20e scanner lens

[caspert79]

I just opened up an old Nikon LS-20e film scanner and took out the tiny lens.
Does anybody know how to determine the correct distance between the lens and the camera sensor?
I want to try to use it in a macro setup.

[Ultrapix]

point the lens towards the sun, or in any case an object at infinity; place a sheet of white paper behind the optics and measure the distance; the calculation of the focal length is complex, because you would need to know the position of the front nodal point (usually inside the optics), but you can have a rough idea of the space needed; for macro, that distance has to be increased proportionally

[caspert79]

Thanks. A rough idea is all I need.

[Ray Parkhurst]

Why not just measure the distance from the lens to the sensor in the LS20 you took it out of?

[caspert79]

[Ultrapix]

By the way, I guess that a scanner lens only covers a very tiny area (hence the necessity of scanning the original), so I am really curious to know what you can do with it in macro, where the covered area obviously grows...

[caspert79]

[dickb]

This type of scanner lens is designed to scan the width of 35mm film (ie 24mm) onto a line sensor. I don't know how large this sensor is in the LS20, but in the later LS40/4000 series it is a 32mm long sensor. In that scanner the lens is designed for 32/24=1.33x magnification with an image circle of 32mm.

The image circle will be a bit larger than that design minimum of 32mm at 1.33x and will be larger still when used at higher magnidfications.

http://www.savazzi.net/photography/scanner_nikkor_40mm.html

and

https://www.closeuphotography.com/scanner-nikkor-ed-7-element-lens

are descriptions of the LS40 lens, the later ED element version of the Nikon lens out of 35mm scanners.

[Ray Parkhurst]

I've had good results from the LS20 / LS30, which use the same lens. The LS40 is different/bigger/has ED elements. The LS20 does cover 24mm so is good on APS-C. at ~0.7:1 reversed and even better at 1.33x forward.