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Thread: Help On Circular & Linear Polarizer.

  1. #21
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    Quote Originally Posted by sammy888
    hahah....not really. Imagine I did that with a GUN!!!!..
    If I did it with a gun, I would definitely be happy if the gun would not work as it should . But your point is well taken.

    Still, the best way to get me to try something is to write "don't do this" into the manual ... I've broken a few things in my life, but the lessons learned probably saved me from breaking even more things .

    To come back to the topic, I am still wondering if this was the reason why the original poster's filter didn't seem to work, or if there is another problem. There may be differences in optical and build quality, but it's hard to believe that even a cheap polariser would not work.

  2. #22
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    Quote Originally Posted by LittleWolf
    To come back to the topic, I am still wondering if this was the reason why the original poster's filter didn't seem to work, or if there is another problem. There may be differences in optical and build quality, but it's hard to believe that even a cheap polariser would not work.
    I was kinda thinking about that too. I use to have this CIR PL about 12 yrs back that came free with a 2nd hand lens I bought and it worked pretty good. I was thinking more along the line that it might be a neutral density filter actually.

    Well the only way to know would be if I see the filter in person or he brings it back to the shop and get them to explain it they sold him a wrong filter.

    Cheers

  3. #23

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    Quote Originally Posted by sammy888
    Hi...

    Well difference in quality of polarisers is of course in proportion to the brand and price you pay. The difference will be the quality of the pictures, the residual tint if the glass is not as purely made, poor coating, poor production..etc.

    But generally I have use polarisers since 1982 and that means having used even those cheap brands right up to Nikon and B+W. The one I used to creat that example with my notebook is a B+W polariser 62mm. Even my cheap ones I used long ago worked pretty well and the colours were not too bad too.

    Why yours did not work no your notebook, I am not sure. As I wrote previously, you can also use that filter to cancel out or reduce glares on surfaces. I have send in some example recently in another thread talking about polarisers. Have you tried it on those example I have given?

    I guess you have hold it with your fingers and did the test like I did it. Can I ask, did you notice that the filter is made up of two parts that can be rotated independent of each other? If you can't or it does not have that feature, you may have been sold a Neutral Density filter instead. But if it does have the ability to rotate but it still does not seem to give you any effect of reducing glares or deepens colour or shades, I would suggest you take that filter back to the shop and ask them why the filter is not working.
    Also, did you meant no effect at all or there was some but not entirely effective like my example showed you? As I say, quality is dependent on how much you pay and also the quality of the filter production. And there is also the fact that maybe your notebook screen's lcd might be alittle difference from mine. Mine is a 4yr old compaq. heh. Yours might be those newers one with better technology.


    I have not thought about what happen when you hold the filter in reverse to see if maybe that will cause the polariser to not work. But I will when I get to the office tomorrow lah. hehe my stuff are in my office so I can't do it now to check heheh.. I have never thought about it in that way leh..never have it occur to me to hold it backward and look through it heheheh.
    Sorry.. i did the test only on my camera's lcd screen. using the way with the thread opposite the lcd screen, the colors change from green to red but on the other way around, it's just blueish only. It won't turn completely dark.

    It is indeed a circular polarizer, its written CPL and I have tried taking pictures with no reflections using this polarizer.

  4. #24

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    Quote Originally Posted by tommon
    It just to me tryiong to get a simple explanation with being too technical. The real technical info will take more than 10 pages to explain the travelling on light particles through various mediums creating various effects. This is not a light spectrometry or scientific forum though photography does involve the use of this science to help us take better pictures.

    I recommend that you go the library to read up on these. The reason mose photo retailers recommend CP is becos most lenses have a rotating front element when focusing thus misaligning the polarising effect. Also the light plays an important role as the direction, diffussion, etc affects the effect.

    We can go on till the cows come home on the technical aspect, my advise go to a photo retailer with your cam and try it out.
    oh yea?
    funny how someone explained it in 3 pics.
    there's nothing wrong in admitting that one self is wrong, it only shows humility. I would have apologized and not post anymore really.

    5x F5s eh?

    Kudoz to those willing to help out ya...

  5. #25
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    Quote Originally Posted by gneseew
    Sorry.. i did the test only on my camera's lcd screen. using the way with the thread opposite the lcd screen, the colors change from green to red but on the other way around, it's just blueish only. It won't turn completely dark.

    It is indeed a circular polarizer, its written CPL and I have tried taking pictures with no reflections using this polarizer.

    Ah...well I did that test by holding the CPL and looking at my D70's LCD screen and just like you, I got that rainbow hue thingy. When I rotate it, the rainbow hue just change around abit. Again, I am getting a slightly difference reactio then to yours maybe due to the brand, process and quality of the filter. But yes, I could not get it to change totally to black thus there is nothing wrong with your filter in "that" respect. There are many kind of technologies used to produce various LCD monitors. In the case of the one found on the D70, I guess it is difference from your typical notebook varieties.

    "no reflection" I am not too sure what you meant entirely but yes if you are shooting let's say a car and if you rotate your CPL around you just might eliminate the reflection on the car's windscreen and see right inside it. "no reflection" in that case is a good thing

    So have you tried taking picture of the sky yet? Deepen the colour?
    Sometime given what you might be hearing from folks here and in books..etc testifying as to how wonderful this filter can performance, take what they say with a bit of salt as to how effective it can deepen colours, eliminate reflection, cut glares..etc. The effect will depend on your position,angle of your camera lens to the subject/scene or direction of the sun in relation to the sky. Many variables comes into play. Therefore, there will be times when the CPL just does not help much if ever.

  6. #26

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    Quote Originally Posted by tommon
    It just to me tryiong to get a simple explanation with being too technical. The real technical info will take more than 10 pages to explain the travelling on light particles through various mediums creating various effects. This is not a light spectrometry or scientific forum though photography does involve the use of this science to help us take better pictures.

    I recommend that you go the library to read up on these. The reason mose photo retailers recommend CP is becos most lenses have a rotating front element when focusing thus misaligning the polarising effect. Also the light plays an important role as the direction, diffussion, etc affects the effect.

    We can go on till the cows come home on the technical aspect, my advise go to a photo retailer with your cam and try it out.

    Like what the others said, your explanation is completely off! I share the sentiment with Sammy888. I hope you are not teaching this in your courses!

    Please do not try to get out of something so obviously wrong by giving all kinds of camoflage and excuses! It just shows what you are really! A simple admission that you made a mistake will be much better!

  7. #27
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    Quote Originally Posted by sammy888
    Ah...well I did that test by holding the CPL and looking at my D70's LCD screen and just like you, I got that rainbow hue thingy.

    The effect will depend on your position,angle of your camera lens to the subject/scene or direction of the sun in relation to the sky.
    Dang, I'd like to try this on the LCD of my camera, but I already packed most of the photo stuff (I'm about to move)...

    The "recipe" for maximum effect of the polariser is fairly simple. For "blue sky", the effect is most pronounced 90 degrees away from the sun. Nonmetallic specular reflections are completely polarised at the "Brewster angle" alpha, where n=tan(alpha) (n being the refractive index of the reflective element). For typical window glass with n around 1.55, this translates to roughly 57 degrees. As you move away from this angle, reflections cannot be completely suppressed any more.

    I hope that wasn't details that noone wanted to know . The practical consequence of this is that it is easier to work with polarisers on tele lenses. When using wide angle, the effects will likely be confined to relatively small regions of the picture.

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    Well don't know about U guys ever noticed, that PL don't work the same way as you thot in Digicams as in films. Most of the CMOS or CCD film scan plate does not work the same as that of the true nature of gelatin film. Many of you will face his hue problem even tho the view finder or LCD monitor does not. I have only noticed this in my students DSLRs. Being a not DSLR owner, just a user, I try to avoid the use of filters altogether.

    Anyway, using the 3 pix to demo is flawed. The LCD screen is not a good sorce of light, infact it is so fake. The LCD TFT screen is often polarised themselves to avoid glare to the user's eyes, the light source is also constant without any real scan lines. Try shooting the same demo with a video cam and you see the difference.

    I think that whoever taught you to use this method to demo the effects of PL is probably a saleperson who can't go outside to show you the real difference. The main use of PL is to reduce glare (which includes reflection) and light thro the lens. If you want to demo, use outdoor natural light with the sky.

    Polarise is to keep or control the light in moving in one singular direction. Thus the reduction in glare, reflection and the blue sky effect. Light, in most instances, travels in a scattled pattern thus producing reflection of various objects from different directions. That's why 3M have a table lamp that reduces glare by filtering the light source thru a polarising filter. Go check it out at Carrefour.

    The aperture of the lens also affects the polarising effects, it is best recommended that you close down the aperture to f/8 or smaller.

    I am not always a photographer but also an engineer who is trained in physics and chemistry. So STOP critising people who are offering to help if you don't know them. You may never know when you might have to eat your own words.
    Last edited by tommon; 11th February 2005 at 02:07 AM. Reason: typo error

  9. #29
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    tommon, your simply amazing....

  10. #30
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    Quote Originally Posted by LittleWolf
    Dang, I'd like to try this on the LCD of my camera, but I already packed most of the photo stuff (I'm about to move)...

    The "recipe" for maximum effect of the polariser is fairly simple. For "blue sky", the effect is most pronounced 90 degrees away from the sun. Nonmetallic specular reflections are completely polarised at the "Brewster angle" alpha, where n=tan(alpha) (n being the refractive index of the reflective element). For typical window glass with n around 1.55, this translates to roughly 57 degrees. As you move away from this angle, reflections cannot be completely suppressed any more.

    I hope that wasn't details that noone wanted to know . The practical consequence of this is that it is easier to work with polarisers on tele lenses. When using wide angle, the effects will likely be confined to relatively small regions of the picture.

    hahah...abit on the nerdy techie side but I do know where you are coming from. But I thought that would have been lost of most users hahah... Personally I learn to use and appreciate the polariser by trial and error. Used it alot, take note and look at what potential it has on various shooting situations. You are spot on about it being more effective with telephoto as the view is narrower as oppose to a super wide lens which takes into account a more diverse angle of reflection from all corners and sides of the lens' view.



    On another matter: Gee I just been called a saleman who never tested PL outdoor heheh.. I thot I covered that in another thread but well to be fair to me and to help others understand about PL abit better from my less tech jargon manner of explaining how polariser work and it's potential. Let me show that link again for those interested to read abit. Just my two cents now...not trying to sell any class lessons to anyone now. The best way to explore polarisers or any equipment for that matter would be to take your gear and go out and shoot. As much as I have read books, seen video and yes even sign up for classes. Nothing beats practical work. It's hobby for most of us so take your time to learn at your pace.

    http://forums.clubsnap.org/showthread.php?t=112906
    Last edited by sammy888; 11th February 2005 at 02:41 AM.

  11. #31
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    Yes, just to add on to LittleWolf and sammy888, that sometimes its actually better not to use a polariser on super wide angles due to the uneven polarisation that it may produce, resulting in weird looking skies

    tommon, the LCD test is not flawed. It is precisely because LCD produces polarised light that using a polariser on it to cut off the light produces much more evident results as you can actually fully cut off all the light (due to them being linear already) and hence have a dark image. In most other cases, its practically impossible to have all the light travelling linearly, hence results might not be obvious.

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    Quote Originally Posted by sammy888
    On another matter: Gee I just been called a saleman who never tested PL outdoor heheh..
    I would be glad if I encountered more such qualified salespeople. With the cutthroat business practices (minimum wage jobs) and competition here in the US, it is hard to find a competent salesperson.

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    Quote Originally Posted by tommon
    Well don't know about U guys ever noticed, that PL don't work the same way as you thot in Digicams as in films. Most of the CMOS or CCD film scan plate does not work the same as that of the true nature of gelatin film. Many of you will face his hue problem even tho the view finder or LCD monitor does not.
    Do you have any pictures to demonstrate this effect? I would be very interested in understanding it, if it exists.

    Anyway, using the 3 pix to demo is flawed. The LCD screen is not a good sorce of light, infact it is so fake.
    I can assure you that the light from a backlit LCD is very real and not at all fake.

    With your significant scientific expertise, it shouldn't be a problem to do a control experiment with non-fake light, e.g. by repeating the experiment with a reflective LCD (digital wristwatch, pocket calculator) in sunlight.

    The aperture of the lens also affects the polarising effects, it is best recommended that you close down the aperture to f/8 or smaller.
    Would you mind to elaborate why? I don't see why it should make a difference ...

  14. #34
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    Quote Originally Posted by tommon
    I am not always a photographer but also an engineer who is trained in physics and chemistry. So STOP critising people who are offering to help if you don't know them. You may never know when you might have to eat your own words.
    Hmm, all I want to say is that well, there are also plenty of other engineers here on Clubsnap. That's the beauty of peer-reviews.

  15. #35
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    Quote Originally Posted by tommon
    Well don't know about U guys ever noticed, that PL don't work the same way as you thot in Digicams as in films. Most of the CMOS or CCD film scan plate does not work the same as that of the true nature of gelatin film. Many of you will face his hue problem even tho the view finder or LCD monitor does not. I have only noticed this in my students DSLRs. Being a not DSLR owner, just a user, I try to avoid the use of filters altogether.

    Anyway, using the 3 pix to demo is flawed. The LCD screen is not a good sorce of light, infact it is so fake. The LCD TFT screen is often polarised themselves to avoid glare to the user's eyes, the light source is also constant without any real scan lines. Try shooting the same demo with a video cam and you see the difference.

    I think that whoever taught you to use this method to demo the effects of PL is probably a saleperson who can't go outside to show you the real difference. The main use of PL is to reduce glare (which includes reflection) and light thro the lens. If you want to demo, use outdoor natural light with the sky.

    Polarise is to keep or control the light in moving in one singular direction. Thus the reduction in glare, reflection and the blue sky effect. Light, in most instances, travels in a scattled pattern thus producing reflection of various objects from different directions. That's why 3M have a table lamp that reduces glare by filtering the light source thru a polarising filter. Go check it out at Carrefour.

    The aperture of the lens also affects the polarising effects, it is best recommended that you close down the aperture to f/8 or smaller.

    I am not always a photographer but also an engineer who is trained in physics and chemistry. So STOP critising people who are offering to help if you don't know them. You may never know when you might have to eat your own words.
    this is very amusing
    maybe u'll fare better if u stuck to your visual arts thingie instead of the technical stuffs.
    sigh.

  16. #36
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    Quote Originally Posted by tommon
    Well don't know about U guys ever noticed, that PL don't work the same way as you thot in Digicams as in films. Most of the CMOS or CCD film scan plate does not work the same as that of the true nature of gelatin film. Many of you will face his hue problem even tho the view finder or LCD monitor does not. I have only noticed this in my students DSLRs. Being a not DSLR owner, just a user, I try to avoid the use of filters altogether.

    Anyway, using the 3 pix to demo is flawed. The LCD screen is not a good sorce of light, infact it is so fake. The LCD TFT screen is often polarised themselves to avoid glare to the user's eyes, the light source is also constant without any real scan lines. Try shooting the same demo with a video cam and you see the difference.

    I think that whoever taught you to use this method to demo the effects of PL is probably a saleperson who can't go outside to show you the real difference. The main use of PL is to reduce glare (which includes reflection) and light thro the lens. If you want to demo, use outdoor natural light with the sky.

    Polarise is to keep or control the light in moving in one singular direction. Thus the reduction in glare, reflection and the blue sky effect. Light, in most instances, travels in a scattled pattern thus producing reflection of various objects from different directions. That's why 3M have a table lamp that reduces glare by filtering the light source thru a polarising filter. Go check it out at Carrefour.

    The aperture of the lens also affects the polarising effects, it is best recommended that you close down the aperture to f/8 or smaller.

    I am not always a photographer but also an engineer who is trained in physics and chemistry. So STOP critising people who are offering to help if you don't know them. You may never know when you might have to eat your own words.
    Seriously my friend, you have gone off on a real tangent. Just ask yourself, if there was even a modicum of logic in what you are trying to say, how come not one single person has posted in support of your position? Surely some expert photog/engineer here would have put sammy888, student and myself in our places by now?

    I'll just reinforce what everybody else here is trying to tell you, your understading of how a CP works on a DSLR is seriously flawed. Your statement about why a CP is recommended (regarding a rotating front element) just shows up your ignorance. Please read up a little and try again.....it matters not in this instance that you are an engineer, you have totally mis-applied the principles.

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    Excuse me I did not say the LCD is flawed rather the demo. Also I agree not to use any filters in ultra wide angle lenses, it could create edging around the corners.

    Look don't take anyone's word for any 2 cents worth, I believe some of you gave the best advise, go and experiment with it. Seeing is believing for every human being right. It takes faith to simply believe others.

    I close my case. And I meant it why go on arguing over a point that's overstated and not worth it.

  18. #38

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    Quote Originally Posted by tommon
    I close my case. And I meant it why go on arguing over a point that's overstated and not worth it.
    You are "wise" to close the case.

    "LP requires you to rotate the filter.... CP does not need any of the adjustment. Simply plug and play"!!!!! Wow!!

    The more you continue, the more ........ comes out!

  19. #39

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    Quote Originally Posted by tommon
    Excuse me I did not say the LCD is flawed rather the demo. Also I agree not to use any filters in ultra wide angle lenses, it could create edging around the corners.

    Look don't take anyone's word for any 2 cents worth, I believe some of you gave the best advise, go and experiment with it. Seeing is believing for every human being right. It takes faith to simply believe others.

    I close my case. And I meant it why go on arguing over a point that's overstated and not worth it.

    "edging around the corners"???? LOL that's the first time I"ve heard a "visual arts" expert cum photo instructor cum engineer cum what have you say that. you mean vignetting??

    are you by any chance a MICROSOFT engineer? that would explain the "plug and play".

  20. #40
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    here's what HOYA, the filters maker explained on their website regarding CP.
    http://www.thkphoto.com/products/hoya/gf-04.html

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