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bghazzal

Filter between port and wet lens?

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Posted (edited)

Hello all,

I use an Inon UWL-H100 type one wide lens with my Lumix LX10 compact camera in a Nauticam NALX10 housing.
 
There is a 36mm crop in 4K so I do not get vignetting and am very happy with this combination.
I only shoot video, ambient light with a filter, and went from a generic red filter made for the Inon lens (Howshot...) to Magic Filters and Keldan SF-2 Spectrums stuck on the lens barrel, which give much nicer results for grading.

I'm gradually leaning towards the Keldan filter - while the SF2 gel filters stuck with tape on the camera lens inside the housing work, it isn't ideal as I lose the possibility to remove the filter, underwater  or on land , and I'm not a fan of sticky tape (albeit Magic Tape) close to optics in the tropics.

I was wondering if it would make sense to get a Keldan 67mm filter and place it between the Nauticam housing port and the UWL-H100 wet lens.
 
Would you say this an option, or a big no-no, as would you have to get the wet lens as close as possible to the lens port? Or is it just a matter of testing it to see if it works?

Today I tried testing this with a blank 67mm UV filter on land and could not see a major difference in the way the lens behaves - but it would probably be best to test with the actual filter.

Would love some feedback on this ideo before I spend another big chunk of money on a filter.

cheers!

ben

 
 
Edited by bghazzal

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Posted (edited)

Thanks.
Unfortunately I'm using an Inon UWL-H100 lens, which is a different beast.

I guess the main issue would be increased vignetting (would need further tests, couldn't see any with a UV filter) and maybe the issue of having a rather heavy lens connected to a filter thread, which might be bad?

Daniel Keller had actually suggested using the filter gel sheet as wet filter between the lens and the port - haven't tried as I'm afraid salt water will destroy the gel very quickly, and also i'm not too sure how this will work with air bubbles.

Edited by bghazzal

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2 hours ago, bghazzal said:

Thanks.
Unfortunately I'm using an Inon UWL-H100 lens, which is a different beast.

I guess the main issue would be increased vignetting (would need further tests, couldn't see any with a UV filter) and maybe the issue of having a rather heavy lens connected to a filter thread, which might be bad?

Daniel Keller had actually suggested using the filter gel sheet as wet filter between the lens and the port - haven't tried as I'm afraid salt water will destroy the gel very quickly, and also i'm not too sure how this will work with air bubbles.

Salt water isn't going to destroy a plastic filter. It'll be just fine. Nor would putting it between the lens and the port lead to any air bubbles if you do it underwater.

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Posted (edited)
1 hour ago, dreifish said:

Salt water isn't going to destroy a plastic filter. It'll be just fine. Nor would putting it between the lens and the port lead to any air bubbles if you do it underwater.

Thanks but I was talking about the gel film filters here, not the solid plastic filter -

I have this at the moment:
https://keldanlights.com/products/filters/filters-for-cameras/1744-spectrum-filter-sf-1.5-flexible-film-80.html

Happy with results, but not a fan of having it stuck on my camera lens, and can't remove it for macro with lights.
In our email exchanges Daniel suggested : " to use the film filter as a wet filter between the wide angle lens and the flat port", but I've been reluctant to try this as I'm a little afraid that salt water will destroy the film, given how sensitive it is to fingerprints and the like. Do film filters hold up in saltwater like plastic / acrylic filters?
Also, since I need to burp the lens uw, the risk of loosing the film filter seems high.

So far the gel is stuck with tape on the camera lens inside the port, but I I've started thinking about using this between the housing flat port and the Inon wet lens:
https://keldanlights.com/products/filters/filters-for-cameras/spectrum-filter-sf-2-thread.html

Would need to look into how the lens behaves with that extra 5mm or so, and if the weight of lens (556g in air, approx.346g uw) means it is a bad idea to use it to connect the lens - but then again it can't be much different from a step up / down filter, right?

 

Edited by bghazzal

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Posted (edited)

The gel film filters are also ultimately plastic or some similar petroleum-derived product, if I had to guess :) (but I'm no chemist). I've used CTO gels on strobes for many years where they're exposed to salt water and never noticed any degradation. I've also used other blue gel filters in front of video lights to match them to ambient illumination.

I don't see why the Kelden gel filters would be any different. I think you would be fine using the gels externally between your port and the UWL-H100 rather than internally between the lens and the port glass. 

The risk of loss is probably higher, fair enough. But I'm sure Daniel Keller knows what he's talking about when he suggested using the Keldan filters externally. 

Edited by dreifish
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11 hours ago, bghazzal said:

Thanks but I was talking about the gel film filters here, not the solid plastic filter -

I have this at the moment:
https://keldanlights.com/products/filters/filters-for-cameras/1744-spectrum-filter-sf-1.5-flexible-film-80.html

Happy with results, but not a fan of having it stuck on my camera lens, and can't remove it for macro with lights.
In our email exchanges Daniel suggested : " to use the film filter as a wet filter between the wide angle lens and the flat port", but I've been reluctant to try this as I'm a little afraid that salt water will destroy the film, given how sensitive it is to fingerprints and the like. Do film filters hold up in saltwater like plastic / acrylic filters?
Also, since I need to burp the lens uw, the risk of loosing the film filter seems high.

So far the gel is stuck with tape on the camera lens inside the port, but I I've started thinking about using this between the housing flat port and the Inon wet lens:
https://keldanlights.com/products/filters/filters-for-cameras/spectrum-filter-sf-2-thread.html

Would need to look into how the lens behaves with that extra 5mm or so, and if the weight of lens (556g in air, approx.346g uw) means it is a bad idea to use it to connect the lens - but then again it can't be much different from a step up / down filter, right?

 

You will get bubbles if you put it in air. Those filter are really thin and flimsy I cannot see how it would stay in place nicely underwater

I would not use a gel filter on a lens. On a light or strobe no problem

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Posted (edited)

Thanks for the input, really appreciated. I did some more tests indoor (Covid finally caught up with me after dodging it in 4 countries since 2020) with the UV filter and it's not good, narrow fov and also decreased corner sharpness, so giving up on that idea.

I cut out a piece of cardboard to mimic the filter, see how it would feel as a wet film filter but I'm not really convinced - I guess I'll need to test it out, see if it's really practical or not.

But I've been thinking and re-reading the "solving the mixed light problem" thread - since my main issue with the filter is that I can't use it with the lights I have for macro, wouldn't it be an option to add blue ambient filters to the light and keep the darn Spectrum filter on?

I understand the mixed lights idea is to be able to light the foreground with lights while keeping a balanced ambient light-lit background, but is there any reason not to use this for macro in this case, and simply compensate for the Spectrum filter by making the light bluer?

Any tips on gels I could try to get for the lights? Rosco 60 / 90 ? Color temperature is supposed to be 5000-5500 K on the ones i have, and they tend to have a greenish hue already, and I guess the Spectrum 1.5 filter warms by 3000K or so?
I hope i can find something on ebay, as shipping to Palau isn't the easiest at the moment, we're kind of banned from amazon, despite having a US zipcode...

Thanks

b

Edited by bghazzal

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2 hours ago, bghazzal said:

Thanks for the input, really appreciated. I did some more tests indoor (Covid finally caught up with me after dodging it in 4 countries since 2020) with the UV filter and it's not good, narrow fov and also decreased corner sharpness, so giving up on that idea.

I cut out a piece of cardboard to mimic the filter, see how it would feel as a wet film filter but I'm not really convinced - I guess I'll need to test it out, see if it's really practical or not.

But I've been thinking and re-reading the "solving the mixed light problem" thread - since my main issue with the filter is that I can't use it with the lights I have for macro, wouldn't it be an option to add blue ambient filters to the light and keep the darn Spectrum filter on?

I understand the mixed lights idea is to be able to light the foreground with lights while keeping a balanced ambient light-lit background, but is there any reason not to use this for macro in this case, and simply compensate for the Spectrum filter by making the light bluer?

Any tips on gels I could try to get for the lights? Rosco 60 / 90 ? Color temperature is supposed to be 5000-5500 K on the ones i have, and they tend to have a greenish hue already, and I guess the Spectrum 1.5 filter warms by 3000K or so?
I hope i can find something on ebay, as shipping to Palau isn't the easiest at the moment, we're kind of banned from amazon, despite having a US zipcode...

Thanks

b

Once your lights are blue you can use custom white balance as you wish for any scenario. The only situation that is not covered is shooting backlit where you will always see a red tinge

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Thanks, this sounds good.
I'm having a really hard time find gels now. One vendor on ebay and won't ship to "US protectorates", nothing on Amazon.

I'm planning to try with Rosco 60 and 90 (4360 and 4390), but the trick is sourcing them now.

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Posted (edited)

Well, for macro the red filter on lens/blue filter on lights mixed light style will work, but you're inherently sacrificing some of the warmer reds and oranges of the subject compared to filming macro with no filters at all and relying on your video lights to provide full spectrum illumination. Not to mention you'll be forced to shoot at a higher ISO because both the filters on the lights and on the lens reduce the amount of light your sensor is receiving. 

So you'll get 'balanced' color, but in a more limited spectrum and with ultimately a noisier image.

I personally wouldn't choose this option. 

Edited by dreifish
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Thanks - for the higher iso, I'm actually interested as the lens is quite fast and I've found it's easy to overexpose when going for a shallower depth of field, so I was thinking it might come in handy, as a sort of ND filter.

Wasn't thinking about spectrum degradation though, good point...

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