Appears to be a misidentified Sigma DC DN lens — likely the 16-28mm f/2.8 or similar, not f/1.8.
The listing 'Sigma 17-40mm f/1.8 DC DN' appears to contain a data error — no f/1.8 zoom exists from Sigma at this range. This may refer to the Sigma 16-28mm f/2.8 DC DN Contemporary or another Sigma DC DN zoom. In L-Mount for APS-C, it would provide a wide-angle to normal zoom range. Enrichment is provided based on the most likely actual product.
If this is the Sigma 16-28mm f/2.8 DC DN Contemporary, optical performance is excellent — Sigma's DC DN line delivers outstanding APS-C zoom quality. Centre sharpness is very good from f/2.8. The constant f/2.8 aperture is a significant advantage over kit zooms. Stepping motor AF is quiet and fast, well-suited to video work.
L-Mount for APS-C cameras. Filter thread is likely 67mm or 72mm depending on the actual model. Weight is moderate. Build quality follows Sigma's Contemporary line — solid with good materials. No weather sealing. The DC DN designation confirms it was designed for mirrorless from the ground up. Verify the actual model before purchasing.
Check the actual model number before purchase — this listing appears misidentified. Whatever the correct lens, Sigma's DC DN line represents excellent value for APS-C mirrorless shooters. L-Mount compatibility includes Panasonic and Sigma APS-C bodies. Check AF operation and smooth zoom function.