GitUp F1 - 4mm F1.2 lens

TonyM

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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.

upload_2017-12-21_14-9-13.png

upload_2017-12-21_14-9-40.png

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
upload_2017-12-21_14-19-12.png

upload_2017-12-21_14-19-52.png

Vignetting is visible in the corners of the F1 frame.

Driving Scene



F1 detail remains good on the left
upload_2017-12-21_14-24-35.png

upload_2017-12-21_14-26-4.png

Not so good on the right
upload_2017-12-21_15-7-30.png

upload_2017-12-21_15-8-1.png



Motion blur is greater on the F1, despite the wider aperture lens
upload_2017-12-21_14-27-20.png

upload_2017-12-21_14-28-3.png
 
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Harsh

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Yup this 4mm is indeed tricky, I got it right on the second go.

Currently the A119 is looking better, may change after a refocus or could have to do with them being 3MP. I have something similar in mind if the capacitor version of the F1 doesn't get the 90° lens on release.
 
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Nigel

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Yup this 4mm is indeed tricky, I got it right on the second go.

Currently the A119 is looking better, may change after a refocus or could have to do with them being 3MP. I have something similar in mind if the capacitor version of the F1 doesn't get the 90° lens on release.
Depends on the situation, in the first image you can read the "Park and Ride" signs in the F1 image, whereas in the A119 image you can't even make out the bus symbol! The F1 is suffering from motion blur at night, interested to see if it does in the daytime too?
 

Dashmellow

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Considerably smaller, and a lot less distortion too. It's going in the basket... (y)

Have you inquired about the availability of an IR-cut filter with this lens? It doesn't appear to include one with the default purchase.

Edit: I notice 5 star feedback from at least six buyers of this lens with no lower ratings.
 
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TonyM

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Have you inquired about the availability of an IR-cut filter with this lens? It doesn't appear to include one with the default purchase.

Edit: I notice 5 star feedback from at least six buyers of this lens with no lower ratings.
Enquiry sent to seller. Note spec sheet below:

upload_2017-12-21_16-41-26.png
 
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Dashmellow

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Enquiry sent to seller. Note spec sheet below:

View attachment 35273

From my experience, one has to be very careful to ascertain and clarify exactly what some of these Chinese vendors mean when they claim "IR correction".

Note that in their description of this lens they state: "lens has IR Function, it can be used in the night". I take this to mean that it does NOT have an IR-cut filter. Plus, this lens is specifically marketed as a CCTV optic, also suggesting no IR-cut filter.

lens_features.jpg
 
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TonyM

TonyM

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From my experience, one has to be very careful to ascertain and clarify exactly what some of these Chinese vendors mean when they claim "IR correction".

Note that in their description of this lens they state: "lens has IR Function, it can be used in the night". I take this to mean that it does NOT have an IR-cut filter. Plus, this lens is specifically marketed as a CCTV optic, also suggesting no IR-cut filter.
Agree on being cautious. Awaiting reply before purchase.....

They make the same statements for their version of the 4mm F1.2 lens I'm using, which Treeye do not sell with an IR cut filter as standard
https://www.aliexpress.com/item/3MP...90-IMX291-Lens-4mm-For-1080P/32663584387.html
 

Dashmellow

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I just received a couple of IR-cut filters I ordered on eBay and am now planning installation strategies depending on which lenses I install them on. If this lens is not available with the cut filter this could be an option.
 
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Lola

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I just received a couple of IR-cut filters I ordered on eBay and am now planning installation strategies depending on which lenses I install them on. If this lens is not available with the cut filter this could be an option.

Have you decided on a type of glue yet? I have been looking for a hard/giveable type glue with heat stability, but haven't found anything yet.
 

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Have you decided on a type of glue yet? I have been looking for a hard/giveable type glue with heat stability, but haven't found anything yet.

I'm considering using hot glue (high heat type) applied carefully in three or four spots with a toothpick. Since the sensor and lens get hot this may not be a good plan so I need to experiment a little, perhaps with an old dash cam to see if they get hot enough to re-melt the glue. I'm also starting to look into using UV glue which another member suggested, but again, I need to do some experiments before trying it with a quality lens I want to actually put into service.
 

Lola

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Agree on being cautious. Awaiting reply before purchase.....

They make the same statements for their version of the 4mm F1.2 lens I'm using, which Treeye do not sell with an IR cut filter as standard
https://www.aliexpress.com/item/3MP...90-IMX291-Lens-4mm-For-1080P/32663584387.html
I'm considering using hot glue (high heat type) applied carefully in three or four spots with a toothpick. Since the sensor and lens get hot this may not be a good plan so I need to experiment a little, perhaps with an old dash cam to see if they get hot enough to re-melt the glue. I'm also starting to look into using UV glue which another member suggested, but again, I need to do some experiments before trying it with a quality lens I want to actually put into service.

Wise decisions. I have sent several emails to companies that would know but no replies yet. If I get any good information I'll let you know.
 

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Chaps , my first post so I may be in over my head from a technical perspective. If so , please bear with me.

I've looked at the reviews for that 8MP 4mm ƒ/2.0 (metal) lens , and the first two make reference to using it as a replacement in a specific camera - a hikvision 2385. Having Googled it , it's a turret type security camera which has both day and night functionality and there's a short Youtube video with both types of footage on a 5MP camera. Lots of variables in terms of performance limiting / enhancing characteristics , but is it useful at all in defining what it's performance might be like in a dashcam?

Link - https://ipcamerareviews.co.uk/hikvision-ds-2cd2355fwd-i-video/

Thank you for your patience , hope to be much more involved when I finally get the first Mobius installed. Not long now..
 

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F1 - 4mm F1.2 lens, 4K 30fps
A119 - F1.8 lens, 1440p 30fps
How many mm is your A119 lens?

I assumed it was the standard lens until I realised that it has the same field of view as the F1 - 4mm...

But the F1 has a wider sensor so will give the same field of view from a lens with a narrower field of view, so maybe it is the standard lens o_O
 
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TonyM

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How many mm is your A119 lens?

I assumed it was the standard lens until I realised that it has the same field of view as the F1 - 4mm...

But the F1 has a wider sensor so will give the same field of view from a lens with a narrower field of view, so maybe it is the standard lens o_O
I don't know its focal length - it's the standard A119 lens
 
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gitup

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The F1 capacitor version will come with a F1.8 narrow FOV lens.
According to our testing before, it is very hard to get good focus for F1.2, F1.3 wide FOV lens, especially for the edge focus. The defective rate is very high.

Also we developed a totally new lens, not a common lens for action camera, I wish we can share something for this before Chinese new year.
 
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TonyM

TonyM

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The F1 capacitor version will come with a F1.8 narrow FOV lens.
According to our testing before, it is very hard to get good focus for F1.2, F1.3 wide FOV lens, especially for the edge focus. The defective rate is very high.

Also we developed a totally new lens, not a common lens for action camera, I wish we can share something for this before Chinese new year.
As I said above, I was interested to try this F1.2 lens as I had it lying around at home. But it is rather difficult to maintain good focus and I do think F1.8 will be a more suitable aperture with good depth of field. It's interesting to hear that you have developed your own lens for this camera. I look forward to trying it when it's ready.
 
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