Looking for a reasonable CPL filter for Lukas 7900

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zapta

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I am seeing significant reflections with my Lukas 7900ACE setup and am thinking maybe a CPL filter will help.

1. Is the CPL filter is installed in addition to the stock UV filter or replacing it?

2. What is a reasonable CPL filter to use? I have strong preferences to filters available on Amazon US (and even better, Prime products). Any suggestion or personal experience? http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=cpl filter 37mm I also prefer filters with black ring over silver.

Thanks,
Z.
 
The CPL is put on in place of the UV filter.

I bought a decent CPL off Ebay but decided I didn't really like it 1. it made everything really dim, I suppose this could be addressed by turning up the brightness but this would affect the quality when you took the CPL off at night. 2. you really have to take it off for night use and I really don't want to unnecessarily touch the camera. 3. The CPL I bought needed to be adjusted to avoid a rainbow effect, this is virtually impossible without a display.

I decided in the end that the quality without the CPL is just fine.

a side note, I do have a lightly tinted windshield which may make a difference.
 
Depends on what you mean by "reasonable". Optics of even moderate quality are not inexpensive.

Given that, I'm very pleased with the Hoya 37mm NXT Circular Polarizer Filter - Low Profile Aluminum Frame.
https://www.amazon.com/gp/B009I2YI3
I see little if any noticeable reduction in brightness.
Excellent construction - although maybe it rotates a bit too easily
Excellent light transmittance. I don't take it off at night (mainly city driving)

You can stack filters but it's better not to if it's not necessary. Each filter will reduce transmittance of light to the camera lens.
The UV filter is there as much for lens protection as anything else. If you scratch your UV filter you replace the filter. If you scratch the camera lens you replace the camera.
For that function the circular polarizer will take the place of the UV filter. My understanding is that there is a good bit of overlap in filtering function as well.
I replaced my UV filter with the CPL rather than stack them.
The CPL removed ALL reflections from the windshield.
 
Quick said:
Given that, I'm very pleased with the Hoya 37mm NXT Circular Polarizer Filter - Low Profile Aluminum Frame.
https://www.amazon.com/gp/B009I2YI3Q
Click to expand...
Yes, using the same and happy with it. Good deal, I bought at full price few moths ago... :(
Just don't forget to turn the ring, so that indicator is pointing up (at least for me it works this way). And if you often remove camera, always check the filter position before you start.
Quick said:
The CPL removed ALL reflections from the windshield.
Click to expand...
Cannot say it removes reflection completely, but let's say 95% of it :)
 
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vitali_vg said:
Yes, using the same and happy with it. Good deal, I bought at full price few moths ago... :(
Just don't forget to turn the ring, so that indicator is pointing up (at least for me it works this way). And if you often remove camera, always check the filter position before you start.
Click to expand...
I have indicator pointing down :) lol, yes I know that's the same -- but with my mounting position I cannot see the top.
Since the camera is in a fixed position and I do not (or will rarely) take the filter on and off I think I'm going to put a teeny tiny drop of rubber cement on the side to fix it in position (easily undone).
I use a sun shade when parked so I'm constantly bumping and rotating the CPL when putting the sun shade in or taking it out and have to check every time.
 
I found WITHOUT using a polarizer filter on my 7900, the reflections from my dash were really bad with certain lighting conditions. So I invested in a fairly high quality filter ( COKIN PURE HARMONIE super slim ) which has a very slim profile, which does not produce vignetting, and only has a 1 f stop in light loss... I set my brightness one step up from the default brightness, and I leave it on day and night, as its so stupid to have to take it off and on depending on the time of day. You also have to secure the rotating lens to the fixed lens with a dab of silicone or equivalent after you find the ideal setting, or else the vibration of the car , will cause the ring to go out of adjustment.
Buying a good polarizer with good optics is important, as to maintain image clarity.. You can buy cheaper ones, but your image quality will suffer.
Just make sure if you do use a polarizer, that you remove the UV filter that comes with the 7900.
I think the one I bought from Ebay was around 50 dollars or so. And like anything you buy from Ebay, ensure its a genuine product, and not a Chinese knock off.
Of course the only way you can properly adjust the polarizer, is to position your car for the worst reflection possible (while the car is parked) , and connect your 7900 via an RCA video cable to a player capable of watching composite video , and in real time, while watching the video from your cam, adjust the polarizer ring for the minimum amount of reflection .
 
jamesbcd said:
Quick said:
The CPL removed ALL reflections from the windshield.
Click to expand...

pics to prove it?
Click to expand...

Yes. I have video proving it. What I don't know is if I still have the video WITH the reflections. That was actually worst/most noticeable on a lightly overcast day.
I'll get some of my latest together and post a still from that. Might take a couple of days but I'll get it up here.
 
Hmmm, I really suck at all this video editing and uploading and stuff but...
Here is a clip I uploaded to photobucket. Don't know what all the pixilation and stuff going on is. The file on my PC looks great.
I've got Freemake Video converter, Allok Video Joiner and Allok Video spliter -- but apparently I don't know how to use them :cry:

We had another overcast morning. The reflection is quite noticeable but not as much as last time.
CPL indicator is pointing straight down to start. I rotate it 90* and then back again.
Notice the reflection of the defroster vents on the windshield. Appear and then disappear.
Also note the "brightness" of the dash and note that what at first appears to be a darkening of the entire frame is primarily just the dash. You can also see the road surface "lighten" and "darken" a little bit as well. If you focus on just the top of the tallest palm tree there is no (or insignificant) change in brightness
When the CPL indicator is point straight down (or up) it is blocking light in the horizontal plane. Most of the illumination of the dash board is reflected outside light and in the horizontal plane. The light coming directly to the camera through the windshield is going to be more evenly distributed/scattered in every plane. So while the dashboard brightness changes a lot the view through the windshield very little. Naturally the reflected image of the defroster vents is also in the horizontal plane.

[edit: maybe Flickr works better?]

http://www.flickr.com/photos/18097964@N ... 5464016233

[dropbox? this might be the best way to go?]

https://www.dropbox.com/sc/na1fjpepzbroof0/xsM2yDD9bs

Any advice working with video is greatly appreciated. Unfortunately I gather I'm a bit behind the multimedia curve since I'm using XP Pro (SP3).
This clip looks fantastic on my PC. Uploaded to Flickr not so much. Uploaded to photobucket it was terrible. I did not downgrade quality/hd so I suppose it's too much over the net. What do people usually do when uploading video for sharing? resolution? fps? What's a good generic format to convert to?
 
Last edited by a moderator:
Dropbox should be the best option as in this case you sharing the source file...
Just may take some time to upload/download the file :)
 
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