8/16mm Scanner - Lens Choice

Machine Design
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Hi all!

I am currently building a modular scanner using a full frame prosumer camera (35.6 x 23.8 mm). I am currently using the Laowa 2.5-5x 25mm lens, but am finding the short depth of field slightly difficult to manage.

I have read lots on this and I know its a bit of a tricky one, but are there any solutions where I could get the same sharpness as the laowa at 4x magnification, with a depth of field of above 1.5mm? I am happy to use tubes or extension tubes or bellows or to be told that physically this isnt possible.

Thanks!

Grace

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Hi @Grace_Richardson welcome to the forum. I do not have a direct answer, perhaps sharing some information may be helpful. Also I do not know the Iaowa.

In an earlier project I used a Nikon D3200 which has a 23.2mm x 15.4mm sensor (smaller than the full frame you indicated).

I tested and used two enlarger lenses, the Nikor EL 50mm f2.8 (the newer version) and the Schneider-Kreuznach Componon S 50mm f2.8. I picked these off ebay for under $100, with patience, since there are many offered in bad condition.

Enlarger lenses -in general- were designed to work with a flat plane (the paper), maybe that is the issue with the macro?. One of the things I learned is that a smaller aperture (longer depth of field) would take a significant toll on sharpness/resolution. For these enlarger lenses, their sharpnesss/resolution sweet spot is between f4 and f5.6, which is not the depth of field you are looking for.

I found great information about lenses on sites about coin imaging. This one in particular was great, but the main page is offline. Here is the page for the Nikkor and for the Schneider.

I am currently using these on a 8 and 16 mm scanner with the raspberry HQ camera 1/2.3 inch sensor, approximately 6.3x4.7mm.

For the D3200, I reversed mounted these into a bellow. The bellow is very touchy (unless you have a great one, which was not my case), tubes work better.

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For the current scanner (which works with 8 and 16), the HQ I used normal mounting, and m42 to T42 adapter(s) to use the T42 tubes (which are everywhere at very reasonable prices), and an m42 to C mount adapter to the HQ mount (picture for 8mm length).

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There were some comments about the Fujifilm

A while back someone commented about the Fujifilm HF-12M Series quality, but these are for 2/3 sensors without much magnification (and out of my budget). There may be other Fujifilm options for your situation.

Sorry I am unable to provide a direct answer about the depth of field you are requiring, hope the information shared helps you.

PS. On a side note, not sure what camera you are using, but if it has a mechanical shutter these have a very finite life (D3200 served well with over 150K shots). The recommendation, if frame by frame, is to use electronic shutter

1 Like
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HI Grace,
In my opinion, with a precise focusing system, depth of field should not be a problem. Good focus is absolutely essential. It’s a shame to have a good camera and a good lens ruined by poor focus. Based on my tests, sub-millimeter precision is required. I therefore recommend using a micrometric table. At least a linear stage, but an XYZ stage is convenient for quickly framing the image on the sensor. It’s a worthwhile purchase.
Personally, I use the Componon S 50mm, which I’m happy with even with a slight loss in the corners.
But with a full-frame camera, a 50mm lens may require a very long extension tube.

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@PM490 @dgalland
Thank you both for the wonderful information! I think it seems that my optimism about a potential lazy solution with a large dof so the film doesnt have to lie so flat and I don’t have to be so precise with my focussing system is slightly misplaced! I am currenlty using a linear stage and it does the job!

Thanks,

Grace