Mobius 5MP Varifocal Zoom 6-22mm ƒ/1.6

One can quickly test polarizer orientation by using good quality polarized sunglasses which are typically (not always) polarized vertically, though some may be at 45 degrees. Hold the polarizer behind the sunglasses and rotate the polarizer until maximum transmission of light. Mounting the polarizer in that orientation should get you close to what Dashmellow demonstrated.

Also, circular polarizers have a "front and back". To tell which side should face the camera, hold the polarizer in front of a mirror. If you can see your reflection through the polarizer then the side that is facing you is the side that should face the camera, otherwise flip it around. If you see no difference between sides, then you have a linear polarizer and not a circular one. Either linear or circular work with our cameras. You really only need to use the circular for mirrored SLRs.
 
Well said, actually the linear polarizer is supposed to give a little better resolution then a circular polarizer in cameras without mirrors.
 

Circular polarizer seems to look better?
 
Neither of those polarizing filters seem particularly effective.
 
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I don't get any of the last 2 posts, I receive the typed comments, nothing else.
 
Radius8 said:
One can quickly test polarizer orientation by using good quality polarized sunglasses which are typically (not always) polarized vertically, though some may be at 45 degrees. Hold the polarizer behind the sunglasses and rotate the polarizer until maximum transmission of light. Mounting the polarizer in that orientation should get you close to what Dashmellow demonstrated.

Also, circular polarizers have a "front and back". To tell which side should face the camera, hold the polarizer in front of a mirror. If you can see your reflection through the polarizer then the side that is facing you is the side that should face the camera, otherwise flip it around. If you see no difference between sides, then you have a linear polarizer and not a circular one. Either linear or circular work with our cameras. You really only need to use the circular for mirrored SLRs.
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Good advice. The trouble is many Dashcam polarisers I've seen are fixed by the bracket and can't be rotated for best effect. I'm presuming Dashmallow has a magnetically mounted one.
 
c4rc4m said:
Good advice. The trouble is many Dashcam polarisers I've seen are fixed by the bracket and can't be rotated for best effect. I'm presuming Dashmallow has a magnetically mounted one.
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If you go back and read my earlier posts on this (and view the product link on eBay) you'll see that I'm using a standard, threaded, rotatable bezel polarizer that I glued to the front of the lens using UV cement as it is the exact diameter required. I like it because it is easy to adjust and quite secure but the cement can be removed cleanly and easily. Once I adjusted the CPL to my satisfaction I placed a mark on the filter bezel and a corresponding mark on the lens housing so I can easily return the adjustment to its current position if necessary should I want or need to change the polarizer orientation.
 
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c4rc4m said:
Good advice. The trouble is many Dashcam polarisers I've seen are fixed by the bracket and can't be rotated for best effect. I'm presuming Dashmallow has a magnetically mounted one.
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I didn't realize that. :eek:. If that is the case, not only is it not optimal, it can even hurt performance considering that even the best polarizer will cut the light input to the camera by at least 50%. Better have a fast lens if using a polarizer.

The one I have on mine was constructed from a linear polarizer plastic sheet that I oriented properly before gluing in the mount though it is not actually fixed to the lens.
 
TBH there's not really a right way to fix. As your car moves it's angle to the sun, the correct rotation of the polariser will vary for maximum effect. I think all any of us can do, is perhaps set it to best effect facing the sun, fix it then hope it gives good results at different angles. Facing the sun is where you want maximum effect as this is when you're probably going to face the worst reflections.
 
c4rc4m said:
TBH there's not really a right way to fix. As your car moves it's angle to the sun, the correct rotation of the polariser will vary for maximum effect. I think all any of us can do, is perhaps set it to best effect facing the sun, fix it then hope it gives good results at different angles. Facing the sun is where you want maximum effect as this is when you're probably going to face the worst reflections.
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I wear polarised sunglasses, which are set with a vertical orientation. I usually keep my head upright rather than constantly bend my neck for maximum polarising effect! :cool:
 
c4rc4m said:
TBH there's not really a right way to fix. As your car moves it's angle to the sun, the correct rotation of the polariser will vary for maximum effect. I think all any of us can do, is perhaps set it to best effect facing the sun, fix it then hope it gives good results at different angles. Facing the sun is where you want maximum effect as this is when you're probably going to face the worst reflections.
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Make sense. I originally added the polarizer to remove the reflections from inside the car as I don't want to use a dash mat. Being able to see in other people's car was a bonnus :p. Like TonyM pointed out, I was going for a more set and forget good enough and didn't intent to keep readjusting the orientation for "optimal" effect depending on conditions.
 
Radius8 said:
I didn't realize that. :eek:. If that is the case, not only is it not optimal, it can even hurt performance considering that even the best polarizer will cut the light input to the camera by at least 50%. Better have a fast lens if using a polarizer.

The one I have on mine was constructed from a linear polarizer plastic sheet that I oriented properly before gluing in the mount though it is not actually fixed to the lens.
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I mentioned earlier in this thread that a polarizer will decrease your exposure factor signifcantly, sometimes as much as two full stops. The result will be increased motion blur. In my book this is a worthwhile trade-off for the results one achieves, especially since the varifocal equipped Mobius is an ancillary camera that works in concert with my traditonal dash cam which does not have a polarizer.

And there's another interesting phenomenon going on here. By cutting out the glare of reflections, the polarizer on this telephoto lens consistently improves the exposure and increases the overall dynamic range of the images.

Take a critical look at the before and after screen shots I posted from the other day and compare the shadow detail and overall exposure balance of the images. Pay particular attention to the readability of the license plate numbers of the cars on the left side of the images as well as other shadow detail in the photo. If this is the result of losing two stops of exposure, I'll take it!

https://dashcamtalk.com/forum/threads/mobius-5mp-varifocal-zoom-6-22mm-ƒ-1-6.34263/post-420677

Finally, @c4rc4m as far as your remarks are concerned, you are correct but keep in mind that literally every other reference to the use of polarizers on this forum is in the context of ameliorating interior reflections of the dashboard in the windshield. Here, we have a different criteria altogether. (as I see @Radius8 has also noted as I was composing this post.) The polarizer is being used exclusively to eliminate reflections on the windshields of other cars in the FOV. In that regard, it does a remarkably effective job of doing so on virtually every car within the FOV regardless of which lane it is in or whether the cars are coming at you or away from you. If find the adjustment to be "optimal' just as it is and it seems to work quite well in every type of lighting. See the 5th image down for an example.
 
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Dashmellow said:
I'm quite sure it would be possible to build a DIY CPL such as you are describing but I don't see the point of going to all that trouble when an inexpensive 30mm rotatable CPL works as well as it does right out of the box. Yeah, it's bigger in diameter than it really needs to be but I find it doesn't particularly bother me in any significant way. Then again, if I really wanted to install a 24mm dash cam type CPL I think I would try to take advantage of the fact that it can attach magnetically.
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I was thinking DIY only because I have a spare SG9665GC CPL and a spare 28mm lens cap.
 
Here's another example of what I mentioned above. Note that the polarizer has eliminated most reflections from virtually every windshield within the camera's FOV in this parking lot regardless of the angles the lens is observing them from. This effect seems to work for the most part regardless of the angle the sunlight is coming from as well, as long as the polarizer is dialed in for other car's windshields. Note that the polarizer is not effective for the other vehicle's side windows or the puddles on the ground.
reflections.jpg
 
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For the record, I am a fan of polarisers. As we agree, it's impossible to always have the correct angle for all reflections. For internal dash reflections there's nothing better at a reasonable budget, and the polariser above has alleviated the internal reflections on that dullish day and most of the window reflections in the near field, the exceptions being the truck and white van straight ahead and the edges of the windscreens falling on the outer edge of the FOV. I think we're agreed it's down to angle and the result is very good where it matters with a little adjustment. You can't achieve prefect all of the time especially with a varying angle to the light source, but a polarised picture is much better than one without (with the possible exception of nightime video with some sensors). It's just a shame that many proprietary polarisers can't be adjusted.
 
I used to use a polarizer on my primary dash cam but I gave up on them primarily because I didn't like the way they detract from night time capture. I discovered that a good quality dash mat is so effective that a polarizer is not needed.

With the polarizer on the varifocal equipped Mobius the excellent performance is due in part because it is on a telephoto lens with a narrower angle of view (AOV) than a typical dash cam . (as opposed to FOV)
 
I may invest in something better than a craft knife and a small sheet of sandpaper.
 
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