Just a few days ago I got hold of a second hand Sigma DP2 Merrill. Costing only 250 euro. A monster IQ camera. I like the lens, 30mm which translates into 45mm on the 35mm fill scale. Supposedly not a low light champion, but up to ISO 800 it works. And going monochrome you get very good result up to ISO 1600 (maybe even 3200). But do check yourself. I shot a portrait of my mother. In ISO 800. Shot with Sigma DP2 Merrill | Camera settings: 45 mm equiv (fixed), 1/500 sec, f/2.8, ISO 800, 0.00 eV | RAW processed with SIGMA Photo Pro 6.3 and Silver Efex Pro 2 (2016)