SG9665GC CPL on Mobius?

TonyM

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Has anyone tried customising a SG9665GC CPL filter to fit a Mobius camera? I like the look of the results from the filter, being that it is not too dark so can be left on all the time. I have the standard A-lens, so nothing protruding from the Mobius box-shape however I don't know the dimensions of the CPL filter compared to the Mobius.
 

niko

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I can provide dimentions later on tonight.
 
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TonyM

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Thanks for the link, however I think I have read most of the CPL threads. What I like about the SG filter is how light (not dark) it is compared to most CPL filters which are no good at night.
 

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murcod

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Thanks for the link, however I think I have read most of the CPL threads. What I like about the SG filter is how light (not dark) it is compared to most CPL filters which are no good at night.

I'd be interested to see how you go with this one. I've got a B+W CPL filter and it basically renders the Mobius useless at night, unless you're in a well lit area.
 

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£35 CPL on a £60 camera? Seems disproportionate...

I remember about 20y ago guys were buying some cheap 500eur car and "upgrading it" with 1K alloy wheel + 1K audio system just to show off.
 

murcod

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Hardly disproportionate if it's the difference between getting the rego of another vehicle vs having to make an "at fault" insurance claim.

I was recently involved in an accident (not my fault) but unfortunately I hadn't installed a dashcam in the two week old (from new) vehicle. I couldn't believe the stress that my own insurance company caused me- even though I was clearly not at fault. It wasn't until I raised the point that the other driver's Police report found him in the wrong that they waived me having to pay my excess. If I'd had clear video footage there would never have been four weeks of hell.

A decent polarising lens that cuts out dashboard reflections during the day, but also doesn't hinder night footage is a very worthwhile investment. Having to remove/ replace a CPL for day/ night use is a PITA as they need to be aligned just right.

Street Guardian seem to have found a very good CPL lens that appears to have minimal effect on night vision. It is custom made just for their camera- hence the pricing.
 

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I remember about 20y ago guys were buying some cheap 500eur car and "upgrading it" with 1K alloy wheel + 1K audio system just to show off.

Still happening today. Spend £5,000 on a used hatchback, then another £20,000 on 'upgrades' that are worth sod all when the car is sold. Could've bought a used Porsche instead, but that wouldn't reflect their 'personality' or 'creativeness'.
 
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TonyM

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I've had the camera for 3 years so I've had plenty of use out of it. I would prefer a wider FOV but my early mobius isn't compatible with the C2 lens, plus the lack of a CPL is affecting image quality more than I like. I'm considering spending £180 to upgrade to the SG, plus £35 for the filter, so I can have full time CPL (plus a few other improvements!), although I'd rather wait to see what the newer version offers.

Spending just £35 now to enhance the image quality by reducing reflections means I will be happier to keep the Mobius for longer, and it can keep on working as a discreet rear view camera after I eventually upgrade to the SG9665 or its successor.
 

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I would just buy a SG complete with cpl instead. Even removing my DIY cpl at night the image from my Mobius is still bad not comparable to a SG. Not even close.
 
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TonyM

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I would just buy a SG complete with cpl instead. Even removing my DIY cpl at night the image from my Mobius is still bad not comparable to a SG. Not even close.
Thanks for your advice. I am tempted to just go straight for the SG and mount the Mobius in the rear window. I could still add a CPL to it later. Being busy with work and two small kids, I don't have as much time as I would like for diy projects. The 'mass production' version of the SG CPL is due soon so maybe I'll wait to see if that's cheaper or a better fit on the Mobius too.
 

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More than my wife thinks I need.
I would just buy a SG complete with cpl instead. Even removing my DIY cpl at night the image from my Mobius is still bad not comparable to a SG. Not even close.
I'll have to second that. My SG9665GC with CPL is better at night than my A118-C without.
 
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TonyM

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So I went ahead with buying the SG9665GC, and now I have its CPL to play with on the Mobius :) Actually these photos are of my Mobius 2, but the dimensions are very similar to the M1.

I have used the thin black metal 20x30mm plate from my Scosche set, plus some VHB tape as a first run to try in the car. The scosche plate has 3M adhesive on the underside, so I plan to stick that directly to the CPL holder.

The CPL is in direct contact with the Mobius lens surround, and there is no vignetting in my limited indoor trial.

2016-11-06 01.54.25.jpg
2016-11-06 01.53.21.jpg
2016-11-06 01.55.31.jpg

Later I plan to replace the VHB between the Mobius / plate with a pair of magnets glued to the Mobius, which will hold the metal plate and thus make the CPL removable. This photo shows the magnets, but not in the finished position.
2016-11-06 02.17.38.jpg
 

Rajagra

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A decent polarising lens that cuts out dashboard reflections during the day, but also doesn't hinder night footage is a very worthwhile investment.
I don't want to tread on anyone's toes, but how is such a thing possible?

A normal CPL will reduce light transmission by 50%. That's because it's cutting out all light that is polarised in the same direction as light reflected off the windscreen.
Yes, that has a downside because twice the exposure time is needed, meaning twice as much motion blur. And if it's too dark you may get underexposure by up to 50%.

I don't see how you get around that. I can't help but suspect that such an alternative CPL will get around the problem by, for example, only cutting out half of the polarised light in one direction. That means you will get 75% of image brightness (better than 50%), BUT you will still get 50% of the reflection (much, much worse than near 0% reflection with a properly oriented, standard CPL.) I don't like the sound of that.

Now a standard CPL would, I imagine, have a certain transmission curve: light polarised at 0° will have 100% transmission; light polarised at 90° will have 0% transmission; light at 45° will have 50% transmission; I'd guess there's a linear relationship for values inbetween.

Do these alternative CPLs have a different transmission curve, for example somehow letting most light polarised at 0° to 80° through, yet blocking most light between 80° to 90°? I would love to think so, but does such technology exist?
 
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TonyM

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I can't help but suspect that such an alternative CPL will get around the problem by, for example, only cutting out half of the polarised light in one direction. That means you will get 75% of image brightness (better than 50%), BUT you will still get 50% of the reflection (much, much worse than near 0% reflection with a properly oriented, standard CPL.) I don't like the sound of that.
Your presumption is, I think, mostly correct. The SG CPL does not cut out all the reflections, however it still makes a significant difference to the recorded video. If the compromise on reducing reflections allows me to leave the CPL on full-time and have usable low light video, I think that's worth considering.
 
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TonyM

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So the SG CPL does a good job of reducing dashboard reflections on the Mobius 2, without vignetting. It was grey and rainy most of the day so I have not tested it in bright sunlight yet.
MOBIUS0001581.mp4_20161106_205919.014.jpg

MOBIUS0001582.mp4_20161106_205954.596.jpg

Here's a short comparison of the M2 and GC both using the same CPL.

Unfortunately I did not realise that the lens on the M2 projects a hair's breadth beyond the lens housing. My flexible temporary VHB mounting permitted some movement of the CPL whilst driving, which has scratched a small mark dead centre of the lens :(. Not sure if it's the glass or a coating, but I couldn't buff it out. The CPL seems to be made of stronger stuff and polished up OK :). If I carry this through I'll be sure to leave a small air gap next time.
 

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The optional Viofo A119/ A119s/A118C2 CPL filter is very similar and I've been sizing it up against my A lens Mobius. It's a bit wider than the Mobius case, so wouldn't be too hard to fit. It is a lot brighter to look through when compared to my B+W CPL.

 
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TonyM

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Thanks for reminding me about this mini-project. Now that the sun's back out, I'll see if I can finish the magnet fixing. It might be difficult though as my Mobius2 is rear-facing and fixed directly to the headliner, so it doesn't leave much room for attaching the CPL.
View attachment 25356
 
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