CCTV Lenses on the E-PL1
Fast digital lenses for DSLR, and especially Micro Four Thirds (aka MFT or m43) cameras, can be pretty pricey. For example, at time of writing, the rather attractive Panasonic Pancake 20mm F1.7 lens is ~£300.
Luckily, m43 owners can get a 10th of the quality* for around 10th of the price in the form of lenses designed for CCTV cameras. These manual CCTV lenses can provide very sharp images with aperture sizes as larger as f/1.7 and greater. However, the price you pay is that only the centre is sharp - a softness creeps in around the sides and you can get various degrees of vignetting. Further, the out-of -focus details can get quite swirly and interesting.
*The 'analogue' features of these lenses are often considered their major plus points, offering Lomo and hipstermatic-style retro qualities in an ever increasingly crisp digial-imagery world.
CCTV lenses are c-mount lenses, designed to sit 17.52 mm in front of the sensor. m43 cameras have a distance of 20mm from sensor to lens (called the flange focal distance) so an adapter with a small recess will enable these lenses to be used on m43 cameras. They do not work on DSLRs because their flange focal distance is closer to 40mm. I got my c-mount adapter from ebay for ~£10. Note that it appears that not all adapters (and c-mounts) are equal; read the walkthrough on how I had to adapt the 25mm CCTV lens to fit the adpater.
Sensor Sizes and Focal Length
The lenses are designed to fit different CCTV camera with sensors of sizes 1/2", 2/3" and 1". The m43 sensor is ~1" in diameter so these are ideal (and most expensive). Here are some notes on popular lenses
- 35mm F1.7 - usually designed for <1” sensors but over-spill means that you could get away with smaller sensor sizes. E.g. 2/3" sensore had a small amount of vignetting but any non 4x3 photo format would crop this away
- 25mm F1.2-F1.4 - vignetting can be severe with less over-spill so look for 1” sensor ones. On their widest they can appear quite soft.