CPL Status

[DavidUK]

@harsh - Thanks. Looks OK, just the question about vibration rotating it to be answered.

 

[Gibson99]

i would think that once you have it set correctly, you can put a tiny dab of rubber cement, silicone gasket material (RTV) or similar on the edge to keep it from moving. DO NOT use CA (CyanoAcrylate or super/krazy/gorilla glue) as this will usually cause the lens to fog up permanently. plus if you ever need to readjust it for any reason in the future, you won't be able to.

 

[TonyM]

I thought that orientation on these CPL filters is pre-set at the factory. Perhaps that was missed on Jeremy's test sample?

 

[Gibson99]

I thought that orientation on these CPL filters is pre-set at the factory. Perhaps that was missed on Jeremy's test sample?

yeah, they ought to be pre-set since we know which camera it's going on and the orientation should be the same for all of them. then again this is a pre-production sample, so maybe it's not set on purpose? IMHO the defroster vent reflection should have completely disappeared when the filter was on.

 

[Dashmellow]

i would think that once you have it set correctly, you can put a tiny dab of rubber cement, silicone gasket material (RTV) or similar on the edge to keep it from moving. DO NOT use CA (CyanoAcrylate or super/krazy/gorilla glue) as this will usually cause the lens to fog up permanently. plus if you ever need to readjust it for any reason in the future, you won't be able to.

Yeah, I find Blu-tack works great for semi-permanent but easily removable applications like that. A tiny little wad of it would do the trick here.

 

[DavidUK]

If I bought an accessory for a digital camera, would I expect to have to stick blu-tack on it? No.

It needs an inbuilt solution to rotation, such as being rotated to the correct position by the maker and secured there.

 

[Gibson99]

If I bought an accessory for a digital camera, would I expect to have to stick blu-tack on it? No.

It needs an inbuilt solution to rotation, such as being rotated to the correct position by the maker and secured there.

again, it's possible that they intentionally left it adjustable for these early production samples, and will in fact adjust and glue them before normal retail sales begin. I know that @viofo and @jokiin are working together on this since it will be compatible with both the A119, the next Street Guardian camera, and maybe the A118c V2 as well. That way costs are lower for everyone. And I guarantee that Jokiin would never stand for sub-par product like you describe.

this is why they're doing this initial product testing. it's not done yet and they're ironing out any issues like this.

 

[Street Guardian USA]

The original 3D printed hand assembled SG9665GC CPL was originally left adjustable in the first production but we then added a spot of glue in the corner once calibrated during assembly. (To avoid movement)

The new mass produced CPL for VIOFO / Street Guardian should be the same eventually.

 

[jokiin]

Mass production version will be preset and fixed in place, the pre production samples are not fixed, there is also more than one version being tested

 

[Jeremy Wong]

I rotated the lens and managed to minimize the reflection... Need to find that sweet spot... Will try again later...

When I received the CPL filter, the lens was not pushed all the way.

 

[Street Guardian USA]

A good quick way to calibrate a CPL that isn't already fixed into place, is using a flat screen tv. Some monitors (and even TVs) are polarized diagonal though. so makes it hard to imagine 45 degrees vs 180 or 90.

This video is an example of what to look for when you spin the CPL around. Clear/Black.

Placing a white piece of paper on the dashboard will give the best heavy reflection to confirm the CPL is set correctly.

 

[JTBY]

I rotated the lens and managed to minimize the reflection... Need to find that sweet spot... Will try again later...

When I received the CPL filter, the lens was not pushed all the way.

Sweet!!!

 

[viofo]

Mass production version will be preset and fixed in place, the pre production samples are not fixed, there is also more than one version being tested

Yes.
Some samples shipped out may not fixed well, please try to adjust it.
And we are preparing another version now, it will still take some time for testing, have to make sure it does work.

 

[Jeremy Wong]

Yes.
Some samples shipped out may not fixed well, please try to adjust it.
And we are preparing another version now, it will still take some time for testing, have to make sure it does work.

Viofo. The CPL filter is loose after a day in heat inside the car... It came off when I was cornering...

 

[DavidUK]

A question...

In photography, a polarising filter consisting of two pieces of glass - a linear polariser and a quarter wave plate - is commonly known as a "CPL".
The "C" denoting "circular" in that the quarter-wave plate further transforms the linear polarized light into circularly polarised light before entering the camera. This is needed to avoid issues with light metering and auto focus in digital cameras.

Am I correct in thinking the Viofo CPL is actually a linear polariser, not a "CPL" as I only see one piece of glass?

 

[DavidUK]

I had a mad idea...

Buy one of these magnetic polarising filters: https://www.ebay.co.uk/itm/172333135859


...then buy a 24mm steel washer and stick it to your windscreen in line with the lens. Place the filter on the washer. Rotate as needed.

PS. Will only work with GPS mount, to allow room for filter/washer.

OR... wait and buy Viofo filter for £10 (my guess).

 

[Nigel]

A question...

In photography, a polarising filter consisting of two pieces of glass - a linear polariser and a quarter wave plate - is commonly known as a "CPL".
The "C" denoting "circular" in that the quarter-wave plate further transforms the linear polarized light into circularly polarised light before entering the camera. This is needed to avoid issues with light metering and auto focus in digital cameras.

Am I correct in thinking the Viofo CPL is actually a linear polariser, not a "CPL" as I only see one piece of glass?

I think the polariser and quarter wave filter are always both coatings with only one layer of glass, I've never seen a CPL with two separate glass elements.

The quarter wave plate is not needed for a dashcam as it has no auto focus but it is always still present, presumably due to cost, I doubt Viofo have sourced a plain linear polariser...

 

[DavidUK]

No, I'm sure two layers of glass on a proper CPL. One fixed, one rotating.

Maybe there's a plain piece of glass in the mount which screws to the lens?

That might be to make it easier to rotate the front filter element using the usual knurled outer ring, so as to compensate for rotation of the lens body to focus.

Anyhow... @viofo - is the A119's linear or circular?

 

[DavidUK]

Looking at my A119 tonight, I notice that with non-GPS mount and with lens rotated so the corner of its housing is closest to the screen, there is maybe 2mm gap between lens corner and screen. Will the CPL housing add only 1mm to this corner dimension? If more, it could touch the screen and vibrate.

This photo taken with a ruler flat across the mounting pad...




Just checking that all the testing hasn't been done using the GPS mount which would give far more clearance.

 

[lacibaci]

Got the CPL sample - thanks @viofo I noticed two "dimples" one on top on on bottom - I guess newer A119 will have corresponding notches on lens assembly.
Quality feels good (maybe even better than SG CPL) Was able to turn it into the correct position. Here is the result: