Super Macro: Spiratone Vario-Dupliscope

Between the exciting new Laowa macro probe and this DIY thread about reversed enlarger lenses , I just felt like I needed to do some 1:1 or higher macro. I actually have a bunch of macro lenses, extension tubes, bellows, and close-up lenses... but will any of them really give me great IQ beyond 1:1?

Then I realized I also have a Spiratone Vario-Dupliscope III. There are multiple variants of this (here's an original ad for them ), and probably also under several other brand names; they typically sell for about $25 used. This is a simple device intended for slide copying at variable magnifications from 1:1 to 4:1. It has no aperture nor any significant focus adjustment, but obviously is designed to provide a flat field aligned with where the slide mounts. Well, the slide holder can be unscrewed!

The T2 adapter allows me to rotate and lock the dupliscope to an upright rotation... but I didn't bother. The idea was just to quickly try this out as a super macro lens. The zoom simply moves glass within the tube -- the outer tube is fixed. That unfortunately often casts a shadow, and the slow aperture means high ISOs or extra lighting even in daylight (the "S" setting on my A7RII was to ensure a fast enough shutter speed).

It works pretty well, even hand-held. All of the following were shot hand-held, in available daylight, and are unprocessed OOC JPEGs scaled-down in GIMP.

Aside from the specular bokeh in the 3rd shot (which was shot at a higher magnification), these look quite good to me. Certainly, sharpness is excellent and backgrounds mostly give a pleasing bokeh. Contrast is slightly low, but easily could be repaired in post. Here's a 100% crop from the last shot:

One issue is how to set IBIS for this. It doesn't have a marked focal length and being a macro can change the ideal IBIS settings anyway. It's hard to be sure, but it seemed that a setting around 100-200mm helped despite the fact that the view looks significantly wider. I'd really need to experiment to determine the best setting....

E Dinkla wrote:

At 1:1 magnification the total length from sensor to slide measured and divided by 4 should give the focal length of what most likely is a simple symmetric lens design.

That would be approximately 165mm/4, or 41mm.  That's credible.  Of course, it's still the same distance at higher magnifications, so something's not quite right.... It also can't be too simple because it is a zoom lens.

For IBIS to act properly I assume you set twice the focal length at 1:1 magnification. At other magnifications use the magnification number x focal length and ad it to the focal length. 0.5x50 + 50 at half the size.

That would be saying between 82mm and 165mm. The marked 4X refers to area, so it's really 2X linear, right? Again, seems credible... but somewhat shorter than seemed to work best? My guess would be that the zoom goes from around 40mm to around 80mm, and that's how the math gets a bit dicey.

That works for linear shifts, not for rotational etc. I guess with a native lens on an IBIS camera, the camera getting the focal length + focusing distance the stabilisation per axis gets different factors to compensate.

Lenses that report focus distance do have IBIS take that into account.... It's not at all clear what the best focal length value is for giving just a focal length when at very close focus distances.

I really like the perspective using the vario-dupliscope as a macro, but I have to say that it is really difficult to do hand-held 1:1 even in full sunlight. It is much harder to do it above 1:1 magnification, and IQ of the vario-dupliscope is notably lower zoomed in.

That said, here are a few more....

This was a little above 1:1

In case it wasn't obvious, yes, there is some dust on the sensor of my A7RII. This lens is stopped down enough so that pretty much every speck shows....