TonyM
Well-Known Member
- Joined
- Jul 30, 2013
- Messages
- 5,414
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- Country
- United Kingdom
- Dash Cam
- A139, M1S
Myself and a few other DCT members have been trying a variety of 3rd-party lenses with dashcams, typically the Mobius 1 and JooVuu X which are easy to work with for swapping lenses. One lens of interest is this 4mm F1.2 from Treeye. I decided to try this lens on the F1 to see if it improves low-light performance in the way it does for the Mobius.
You can read about experiments with this lens here:
https://dashcamtalk.com/forum/threads/original-mobius-night-recording-with-4mm-f1-2-lens.31145/
The F1.2 4mm lens is designed for a 1/2.5" sensor, which is good as the F1 uses a 1/2.5" IMX317. By comparison the Mobius has a smaller 1/3" sensor which does not use the full extent of the lens. Treeye state that the field of view on a 1/2.5" sensor is 96deg horizontal (120deg diagonal) which seems about right looking at the recorded video. The lens is only rated to 3MP, which is fine for the 1080p Mobius, but a long way short of the 8MP sensor in the F1.
I found the lens very difficult to focus accurately, in part due to the F1.2 aperture giving a shallow depth of field and almost no tolerance on focus. The samples below are out of focus on the right side of the image, but they're the best I've managed to get so far. I've used blu tac to hold the lens in position temporarily. I need to buy some M12 locking collars to hold it more securely. The F1 is fairly easy to work with for swapping lenses, after removing the glue that holds the stock lens in place.
The following frames are taken from a low-light recording this morning. I have included identical frames from my A119 for comparison.
F1 - 4mm F1.2 lens, 4K 30fps
A119 - F1.8 lens, 1440p 30fps
Static Scene
The F1 shows good detail in the centre of the frame
Vignetting is visible in the corners of the F1 frame.
Driving Scene
F1 detail remains good on the left
Not so good on the right
Motion blur is greater on the F1, despite the wider aperture lens
You can read about experiments with this lens here:
https://dashcamtalk.com/forum/threads/original-mobius-night-recording-with-4mm-f1-2-lens.31145/
The F1.2 4mm lens is designed for a 1/2.5" sensor, which is good as the F1 uses a 1/2.5" IMX317. By comparison the Mobius has a smaller 1/3" sensor which does not use the full extent of the lens. Treeye state that the field of view on a 1/2.5" sensor is 96deg horizontal (120deg diagonal) which seems about right looking at the recorded video. The lens is only rated to 3MP, which is fine for the 1080p Mobius, but a long way short of the 8MP sensor in the F1.
I found the lens very difficult to focus accurately, in part due to the F1.2 aperture giving a shallow depth of field and almost no tolerance on focus. The samples below are out of focus on the right side of the image, but they're the best I've managed to get so far. I've used blu tac to hold the lens in position temporarily. I need to buy some M12 locking collars to hold it more securely. The F1 is fairly easy to work with for swapping lenses, after removing the glue that holds the stock lens in place.
The following frames are taken from a low-light recording this morning. I have included identical frames from my A119 for comparison.
F1 - 4mm F1.2 lens, 4K 30fps
A119 - F1.8 lens, 1440p 30fps
Static Scene
The F1 shows good detail in the centre of the frame
Vignetting is visible in the corners of the F1 frame.
Driving Scene
F1 detail remains good on the left
Not so good on the right
Motion blur is greater on the F1, despite the wider aperture lens
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