TonyM
Well-Known Member
- Joined
- Jul 30, 2013
- Messages
- 5,467
- Reaction score
- 5,135
- Country
- United Kingdom
- Dash Cam
- Looking for something new
For a number of years I have experimented with the use of third-party fixed telephoto and varifocal M12 lenses on a dashcam, the intention being to complement a primary wide-angle dashcam by capturing information that the primary camera might not record. A telephoto lens can do this by recording a narrower angle of view (AOV), thereby increasing the pixels-per-degree across the middle of the scene ahead, and therefore the possibility of higher detail on features such as number plates or the actions of other road users. A telephoto lens can also benefit from metering only the narrower AOV, perhaps ignoring a bright sky or dark dashboard, and can give better results on reflective number plates for example.
For this project I decided to repurpose the interior remote camera of the A139 3CH dashcam and fit a fixed focus 6mm F1.2 starlight lens. Experience has shown that telephoto lenses in the order of 6mm to 8mm focal length have sufficient magnification to make a worthwhile difference over a primary camera (which are approx 2 or 3mm focal length), whilst not over-magnifying the central portion of the scene and suffering too much from vibration, motion blur and depth of field issues.
https://www.aliexpress.com/item/32663560773.html
The remote camera is fairly easy to open, the lens mount is easily accessible, and the lens focus can be achieved without first reassembling the housing.
The remote camera is also easy to position on the windscreen, and has a constant-friction stepless up/down angle adjustment.
Note: I started with the interior camera because I am still using the rear remote camera for its intended purpose. However I may in future try the same lens swap with the rear camera to see if it works just the same.
For this project I decided to repurpose the interior remote camera of the A139 3CH dashcam and fit a fixed focus 6mm F1.2 starlight lens. Experience has shown that telephoto lenses in the order of 6mm to 8mm focal length have sufficient magnification to make a worthwhile difference over a primary camera (which are approx 2 or 3mm focal length), whilst not over-magnifying the central portion of the scene and suffering too much from vibration, motion blur and depth of field issues.
https://www.aliexpress.com/item/32663560773.html
The remote camera is fairly easy to open, the lens mount is easily accessible, and the lens focus can be achieved without first reassembling the housing.
The remote camera is also easy to position on the windscreen, and has a constant-friction stepless up/down angle adjustment.
Note: I started with the interior camera because I am still using the rear remote camera for its intended purpose. However I may in future try the same lens swap with the rear camera to see if it works just the same.