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Lens filter to correct light pollution?

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#1 samm

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Posted 26 February 2019 - 02:22 AM

Can anyone suggest a filter to put on my camera lens to correct light pollution. The prices seem all over the map from $40 to well over $200.

Also, is there any downside to using such a filter?

many thanks

 



#2 oshimitsu

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Posted 26 February 2019 - 04:20 AM

I use the clip filters for my Canon and love the astronomics filters. They are expensive and when you use them you will need to use a custom white balance or you can take a test shot in a dark, fairly star free patch of sky and use that to set your black point. Most of the times you can overcome light pollution with the proper exposure and processing


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#3 sg6

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Posted 26 February 2019 - 04:29 AM

These days it is difficult to select an LP filter..

Used to be half simple - uou blocked the emission lines from Sodium lights, low pressure ones.

Then they added high pressure sodium and slightly different wavelengths. Then came Mercury vapour and more wavelengths, next Halogen and again more wavelengths and now there are LED lights.

 

At this time the "band" that LP falls into is quite extensive. That means you have to block a reasonable chunk of the spectrum and that changes what gets to the camera and so images are altered in respect of their color balance.

 

You could look around and determine the nature of the LP - is it still predomintly "yellow", if so then consider the fairly inwxpensive "old" sodium blocking LP filters. If it is a general white background LP I would say there is little reallistically possible - well at sensible prices, there are new "triband" filters that read they operate more along the lines of block everything and allow just 3 bands at Red, Green and Blue through. They are to me easier to think of as what they pass rather then what they block. But they are not inexpensive, I dont think $200 would get one.

 

Disadvantages are that any filter removes light. An LP filter likely remove Yellow and some Green maybe a bit of Blue. so the image changes color in effect. I suppose that a simple Nebula filter does just about the same and that is how they function.

 

Nebula emits at OIII, LP in the sky swamps nebula so block the general sky mess and pass only OIII. Sky darkens and nebula stands out more. If they ever put an LED in the lights that emits at OII then that kills everything.

 

I would say that with research and understanding you can improve things, not however solve it. If you block something then the image be definition changes with respect to color. You cannot block Yellow then expect to see Yellow in the image. Also blocking likely means more or longer exposures - more is easy, take 25 not 20.

 

Assuming the color change is acceptable then to my thinking try an old type Sodium LP filter = low cost, if you can see a reasonable degree of yellow in the LP. Then look at a "nebula" filter that passes OIII, HB and maybe Ha. I would try one that was not overly narrow. But there is really no simple solution.

 

Although as is often said the best is a drive to somewhere dark(er).


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#4 happylimpet

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Posted 26 February 2019 - 07:49 AM

Yup, as sg6 says. Its a nightmare.



#5 Aaron_tragle

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Posted 26 February 2019 - 01:16 PM

Best LP filter is a tank of gas and a good playlist IMO


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#6 17.5Dob

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Posted 26 February 2019 - 09:37 PM

There are no LP filters that you can "screw onto the front of a lens". If you own a Canon/Nikon, there are a few filters, for a few  specific camera models" that will "clip" in front of your sensor.

If you were shooting through a telescope, and threading a filter in your camera adapter, there would be dozens to choose from, each with it's strengths/weaknesses .

But if all you have is a camera lens, your only recourse was already mentioned. Drive to a darker site.


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#7 samm

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Posted 26 February 2019 - 10:36 PM

There are no LP filters that you can "screw onto the front of a lens". If you own a Canon/Nikon, there are a few filters, for a few  specific camera models" that will "clip" in front of your sensor.

If you were shooting through a telescope, and threading a filter in your camera adapter, there would be dozens to choose from, each with it's strengths/weaknesses .

But if all you have is a camera lens, your only recourse was already mentioned. Drive to a darker site.

 

There are no LP filters that you can "screw onto the front of a lens". If you own a Canon/Nikon, there are a few filters, for a few  specific camera models" that will "clip" in front of your sensor.

If you were shooting through a telescope, and threading a filter in your camera adapter, there would be dozens to choose from, each with it's strengths/weaknesses .

But if all you have is a camera lens, your only recourse was already mentioned. Drive to a darker site.

 

maybe i misunderstand the whole thing, but dont these filters screw onto the front of your camera lens , not using a telesciope at all, but just a camera on a tripod...

https://www.bhphotov...ollution Filter



#8 17.5Dob

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Posted 26 February 2019 - 10:56 PM

maybe i misunderstand the whole thing, but dont these filters screw onto the front of your camera lens , not using a telesciope at all, but just a camera on a tripod...

https://www.bhphotov...ollution Filter

Those aren't LP filters, those are a simple minus yellow camera filter designed to dupe the unsuspecting.



 


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#9 samm

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Posted 26 February 2019 - 11:12 PM

Those aren't LP filters, those are a simple minus yellow camera filter designed to dupe the unsuspecting.



 

 

 

ok. thanks for the warning.



#10 HarryRik9

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Posted 27 February 2019 - 07:17 AM

Hi, I knew that you were going to get confusing responses. Your question is not very specific. I See that the link you cited does give filters for blocking different kinds of light pollution. The cheap ones only address filtering yellow sodium vapor light, while some of the others address that and mercury vapor. The bottom line is you need to know what kind of light that you need to block.

What are you planning to photograph and what type of camera and lens are you thinking of using?

Edited by HarryRik9, 27 February 2019 - 07:25 AM.

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#11 samm

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Posted 27 February 2019 - 08:56 AM

Hi, I knew that you were going to get confusing responses. Your question is not very specific. I See that the link you cited does give filters for blocking different kinds of light pollution. The cheap ones only address filtering yellow sodium vapor light, while some of the others address that and mercury vapor. The bottom line is you need to know what kind of light that you need to block.

What are you planning to photograph and what type of camera and lens are you thinking of using?

i want to shoot the miky way with a fish eye lens (8mm) and a canon 70d camera.

i'll be out in the countryside but i have problems with the light on the horizon from small towns.

 

heres one filter i was considering but it seems very expensive and at any rate i'm not sure it will work.

 

https://breakthrough...=11505393041450

 

thanks.



#12 HarryRik9

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Posted 27 February 2019 - 10:14 AM

Hi, Here are my thoughts. I have not tried to do what you want, but I would do the photography without a filter and then see what your result is. If you know about post processing filters, then what I have to say is maybe something you already know. I would get a software filter program such as for example ON 1. These allow you to do post editing of the photo. Try that first. Note that there are a lot of these filter programs available and some offer free filter software. If you dont get good results then try a lens filter.
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#13 iverp

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Posted 27 February 2019 - 11:11 PM

I use a 2" Orion SkyGlow Imaging Filter. Cuts down on several Light pollution bands, but doesn't make much change to the overall color balence.

I fits on the front of my 2" T-Adapter.

I also screw it into a step down (step up?) ring that fits the 58mm threads on the front of my camera lens.

It was a little tricky finding that for a reasonable price, but after some searching, I found one.


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#14 oshimitsu

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Posted 28 February 2019 - 04:50 AM

If you are using a fish eye lens isn't that an EF-S mount? If I'm not mistaken it is and you won't be able to use a clip in filter. You are better off using editing to try and correct it. You can color burn the light pollution in photoshop but the least damaging is just to set your blackpoint to an area that has no nebulosity, stars and is as dark as you can find. I do that with the threshhold option in photoshop(image/adjustments/threshhold); adjust the slider until you have one area that is black and use it as your black point.


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#15 fishonkevin

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Posted 01 March 2019 - 07:27 AM

You may want to check this article out.  It gives comparisons of various LP filters.

https://www.bhphotov...RcI2WeXGJyNiYQI


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