Pekka Buttler, 01/2026
This lens was kindly provided for cataloguing by Vladimir at #photogears
Specifications
The table below summarizes the lens’ key specifications (Measurements based on pictured sample):
| Brand: | Expert | Lens name | Zoom 1:3.5 40–105 mm Multic. |
| Focal length(s) 1 | 40-105 mm | Angle-of-view 2 | ≈ 57 ° – 22 ° |
| Maximum Aperture | f/3.5 | In Production | 1976–19783 |
| Lens mount (this lens) | M42 | Other lens mounts | uncertain4 |
| Length 5 | 110 mm | Diameter 6 | 71,2 mm |
| Filter ring diameter | 67 mm | Weight | 725 grams |
| Lens element count7 | 13 | Lens group count | 10 |
| Aperture blades (S/R/C) 8 | 6 S | Focus throw | 180 ° |
| Minimum focusing distance (indicated) | 1,5 m (in normal mode) | Maximum magnification (indicated) | 1:12 (in normal mode) 1:4 (in macro mode) |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Manual/Auto | Aperture click stops | 3.5•5.6•8•11•16-22 |
Further notes:
• First off: ‘Expert’ is not a lens manufacturer, but a rebrander (see more below).
• The Expert 40–105/3.5 zoom is with a very high likelihood a rebrand copy of the Tamron 38–100/3.5 (Model name: CZ-38M). The slight difference in reported focal ranges is rather typical for the era.
• There also exists a Chinon 40–105/3.5 that almost certainly is the same lens as this expert lens.
• The expert 40–105/3.5 is a two-ring zoom, with one ring controlling focal length (zoom) and another ring controlling focusing distance.
• The lens also offers a third ring for engaging the lens’ close-up/macro mode. Engaging the close-up function leads to a lengthening of the lens at the base (a bit like a built-in extension ring).
• The zooming action is internal (meaning that the lens keeps its shape when zooming), whereas the focusing action rotates the entire front third of the lens (including filter threads) and leads to a moderate lengthening of the lens (see below).
Middle: expert 40–105/3.5 zoomed to 105 mm and focused at infinity
Bottom: expert 40–105/3.5 zoomed to 105 mm and focused at MFD
(all three images with close-up function activated)
History of Expert
Expert was not a lens manufacturer but a rebrander. Expert is/was a giant, European electronics retail chain that for some time also sold lenses under their own house brand. You can read more in the JAPB company profile on expert.
Versions
It is more than likely that this lens existed also in other mounts than M42, and in that case the measurements of those lenses may differ slightly.
The Chinon 40-105/3.5 Zoom is practically identical to this lens, as both are based on the Tamron 38–100/3.5 (Model name: CZ-38M)
Adapting
We’re going to be discussing adapting M42 mount lenses. If your copy of the Expert 40-105/3.5 sports another mount, please study the JAPB article on the requisite lens mount for adapting tips.
If you want to natively mount an M42 lens you need to find a functioning M42 mount film camera. Luckily that should be relatively easy as M42 bodies were produced in their millions and most of them lack features that are especially likely to have deteriorated to the point of making the entire camera inoperable. If your sample of this lens offers a switch to choose between auto- and manual aperture, I recommend using the lens on a body that is capable of stopping down the lens automatically and offers stop-down metering.
Adapting this lens to a mirrorless, full-frame digital camera is a breeze thanks to the lens having full manual controls (aperture ring, focus ring). You simply need a dumb adapter from M42 to your mirrorless system.
Due to the medium flange focal distance used by the M42 mount (45,46 mm), whether you can adapt this lens to dSLR/SLR mounts depends on which dSLR mount: Canon EF, Four Thirds, Minolta/Sony A and Pentax K can mount m42 lenses using a simple adapter ring. Nikon F on the other hand is not as problem-free, and – to retain anything near infinity focus – the adapter will necessitate corrective optics. In all cases, your camera will work only in stop-down metering.
Footnotes
- Focal length is (unless stated otherwise) given in absolute terms, and not in Full-frame equivalent. For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’. ↩︎
- Picture angle is given in degrees (based on manufacturers’ specs) and concerns the diagonal picture angle. Rule of thumb:
> 90 ° ==> Ultra-wide-angle
70–90 ° ==> Wide-angle
50–70 ° ==> Moderate wide-angle
40–50 ° ==> ‘Standard’ or ‘normal’ lens
20–40 ° ==> Short tele lens
10-20 ° ==> Tele lens
5-10 ° ==> Long tele lens
< 5 ° ==> Ultra-tele lens ↩︎ - The years 1976–1978 are the tears of production of the same lens under the Tamron name. It is possible that Tamron continued producing the lens after 1978, but stopped selling it under their own name. ↩︎
- Expert-lenses were usually available in the typical lens mounts of the era (M42, Canon FD, Konica AR, Minolta SR, Nikon F, Olympus OM, Pentax K), but it is not certain that each lens was offered in everyone of these mounts. ↩︎
- Length is given from the mount flange to the front of lens at infinity. ↩︎
- Diameter excludes protrusions such as rabbit ears or stop-down levers. ↩︎
- Data on lens elements and groups is based on a single source. Alternatively, it might also be a 4 elements in 3 groups design. ↩︎
- S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎