Underwater Bubble Blowers User Group Thread NEW

[Frazier Nivens]

For what is worth,

I never understood the aversion, though I fully respect it, of many professional shooters not to use filters. I, for one, am advocate number one of putting as little glass as possible between the image itself and image plane inside the camera, and it kills me when I see topside cinematographers using IMAX and 5K cameras and super expensive Master Primes to get the best image possible and then put all kinds of filters on that matte box, each of which brings with it the risk of light diffraction, glares. AND DUST. And if you never paid your dues by removing dust and sh..t from digital scans at a studio, you never know how much fun you've missed. But, then, it is quite a different thing underwater.

I've been using some custom made filters for the last few months and I'm very happy with them. These are very expensive, experimental units with not only a color hue but also several coatings, but you could get indistinguishably similar results from the old standing filters like UR Pro. Even in the first 10 meters/ 33 ft layer, with lots of sun, I can ASSURE you that you will loose a lot of red light. And fixing in post will only take you so far. RAW is RAW in as much as to the light that hits the sensor, but if a certain spectrum or wavelength is not present in that light by the time it hits the sensor, there isn't much RAW can do to help. A good filter will help correct a lot of this problem, and ironically, it will work best in shallow water, for even the best filters will be rendered useless once you pass 60 ft. I know you loose a stop of light, but then, with a camera that is natively rated at 800 ISO, and can be pushed much farther without much noise, who cares really. I mean, we used to shoot stills on film on Velvia, Kodachrome or even Ektar, 50, 64 and 25 ASA respectively, and for the life of me, I never had much trouble finding enough light for a proper exposure anywhere shallower than 40 ft. I know a lot of this reluctance comes from the fact that, especially with a RED camera, you would have to use the filter in front of the dome port, far from ideal, or use a screw-on on the lens itself that cannot be removed for surface shots. When, or if, RED ever comes up with a filter wheel design iteration, where you could have a filter that flips in front of the sensor, then this would be a lovely solution. But if you have a lens that can accommodate back filters, and there are a few great underwater lenses that can do that, mostly in Nikon or Canon mount, not PL though, I encourage you to do some tests and see how much better color rendition and flexibility in post you get from a filtered image as opposed to the unfiltered one. The differences in noise floor on all channels, not just the red one, are undeniable. And, your blues will be much richer too with that extra magenta...Then again, that's me.

With my RED One I always shot with a custom filter and the results by adding back in the light RED and Orange filter was truly spectacular, made all the difference in my imaging. I recently had the footage playing back in HD at this years DEMA show on a 55 inch Samsung LED panel. Tom saw the footage and can tell you the color that was there, almost too unreal. I am not getting quite the same results with EPICX as I did with the RED One but still working on the right combination of filtration and the EPIC sensor to get what I like to see. But the combination of a good white balance, wide angle lens and a good color filter and then tweaking in post in RED CineX makes all the difference in the world. At least for me anyway. But still working on tweaks with the EPICX as it's not the same camera to shoot underwater as the RED One. But I say filtration, just my 2 cents worth.

Best to all,
Frazier

 

[Michael Hastings]

Filters are only ever going to reduce light, never increase it. Underwater you're in a light limited situation (I think, correct me if I'm wrong as I don't dive) so I'd recommend going without filters and balancing in post. As we don't set up the colorimetry for "underwater", you may want to experiment with how you achieve white balance - either using the kelvin and tint as normal, or leaving them alone at a neutral 5600k setting and adjusting RGB gain.

Graeme

Graeme

It isn't as light limited as people generally think. Even in the old ektachrome days f8 was a common fstop in most of the nicer destinations, and thee days we are pushing f16 or more quite often (which gets into.resolution loss diffraction), so even though raw adjustment can do wonders I don't see mu h downside in cutting back the blue and seemingly maintaining the full DR of the camera. Ksorry for the typos playing with a kindle and can get the cursor. Ack to correct can't

 

[paulherrin]

if you can spare the light (and have red wavelengths) then i would seriously consider it - unless that introduces a negative affect on the color science...

as i said, if any or all of you guys want to start doing some real world testing, i'd love to help out

 

[Frazier Nivens]

Heck, I've needed a ND 3 sometimes to get a good F Stop. And my custom color filter..

 

[Pawel Achtel]

... for the simple reason that we'll be shooting between 5-10m depth and so the differences will be quite variable from shot to shot (not knowing how good the talent's bouyancy control is), so adding in a colour filter is only complicating the problem. I would think that 2-3 stops of red can easily be put back in post in R3D, with much more subtlety than a filter in front of the lens.

So, your ambient light will be 2 - 4 stops of red depleted by the time it gets to the subject and another 1 - 2 stops by the time it reaches the lens. It would give you only about 6 stops of available DR in RAW if exposed properly. If you wanted to protect blue/white highlights, probably more like only 3 - 4 stops of usable red spectrum.

4kW is going to help, but if you place it close to the subject or camera the falloff will be very rapid with distance change. If the subject/camera/light distances vary, you may like to place the lights a fair distance away, reducing their effectivness.

Tungsten lights will work much better than daylight balanced.

It is one thing to make fish scales look good and another to get human skin tone looking natural underwater. With estimated 3 - 6 stops of available red DR, it would be challenging to "fix it in post" and most likely noisy.

Keep in mind that you may need another 1 - 3 stops to correct lens vignetting and another 2 stops of highlight headroom, another 2 stops to get the skin colour to look good....and you are quickly running out of the available dynamic range in RAW.

From what you described I'd be using at least 3 stops of minus red filter and still be on the safe side.

You actually asked Jim to remove the thread? Why?

I asked him to remove your trolling posts, which he did.
It was Jim who said that next he would take the thread down if you continue. His decision, not mine. You can ask Jim why he doesn't tolerate disrespectful attitude and personal attacks on his forum. Jim didn't delete any posts of mine.

 

[Pawel Achtel]

... if any or all of you guys want to start doing some real world testing, i'd love to help out

There has been a lot of testing performed on light filtration in water with many papers published. The main problem is that the results highly depend on the water quality, depth, angle an amount of ambient light and, of course distances between camera, subject and light sources. Generally, you can calculate the ballpark colour imbalance, make rough correction through filtering, and make fine adjustments in post.

 

[Jeff Whitehurst]

I'm really looking forward to the day I can conduct my own tests, but in the meantime really appreciating the information and opinions on the topic of color filtration and shooting RAW.

In reading all of the comments regarding the question of color filtration, I am wondering if a big part of the answer is an assessment of the environmental conditions at hand. In my understanding, the attenuation of light and exponential decay of individual color spectrums is dependent upon many variable factors such as depth, turbidity, suspended algae, dissolved organic compounds, substrate reflectivity, weather, time of day etc. Testing and determining specific patterns of color wavelength absorption and their effects on the RED color science sounds good, but is it that much different? In dealing with color absorption in the past with RGB cameras, it was almost always better for me to choose a filter, but the idea of shooting RAW has got me wondering. I mean, isn't shooting RAW kind of still the same as before, we need to get the widest range of colors possible in the ballpark? Magenta filter for green water, orange for blue water, then do the best you can in post? What about the display histogram, doesn't that give you an idea if there's information present in a specific color channel while making your shots?

 

[paulherrin]

Do you have any links or references you could point us towards, Pawel? The only issue I see there is that in the real world your water quality, depth, light angles/intensity, subject distance and even the subject itself is constantly in fluctuation so much that is not practically possible to be doing calculations and filter adjustments on the fly. When you're in a controlled environment or doing narrative work you may have that luxury, but that may apply to 1% of underwater shooting. Pawel, maybe you can send some of these shooters test units? If you're using exposed lenses, filtration would be much more practical to adjust on the fly. In any case, you're still just dealing with the basic physics of light and you're simply in a red-deficient environment... Correct me if I'm wrong, guys.

And while we're on that note, the whole 'everyone is incorrect except me' gets kind of old... People respond better to positive instruction. Just some advice, take it or leave it - but let's take it easy on all the name-calling... just trying to learn here.

 

[paulherrin]

I'm really looking forward to the day I can conduct my own tests, but in the meantime really appreciating the information and opinions on the topic of color filtration and shooting RAW.

In reading all of the comments regarding the question of color filtration, I am wondering if a big part of the answer is an assessment of the environmental conditions at hand. In my understanding, the attenuation of light and exponential decay of individual color spectrums is dependent upon many variable factors such as depth, turbidity, suspended algae, dissolved organic compounds, substrate reflectivity, weather, time of day etc. Testing and determining specific patterns of color wavelength absorption and their effects on the RED color science sounds good, but is it that much different? In dealing with color absorption in the past with RGB cameras, it was almost always better for me to choose a filter, but the idea of shooting RAW has got me wondering. I mean, isn't shooting RAW kind of still the same as before, we need to get the widest range of colors possible in the ballpark? Magenta filter for green water, orange for blue water, then do the best you can in post? What about the display histogram, doesn't that give you an idea if there's information present in a specific color channel while making your shots?

Yes, if you're on the spot, the main thing I'd be looking at is the reds in your histogram in relation to the others.

 

[Pawel Achtel]

Do you have any links or references you could point us towards, Pawel? .

Paul,

There are dozens of interesting research papers, for example:

Jerlov N. G. Optical study of ocean water.(1951)
Dring M. J. Photosynthesis and development of marine macrophytes in natural
light spectra (1981)
Tsuyoshi MATSUI, Hiromi EGUCHI and Yasuhiko SOEJIMA, Radiation System for Simulation of Underwater Light (1983)
Yentsch CS Measurement of visible light absorption by particulate matter in the ocean. (1962)

Essentially, the variability of the absorbtion spectra and attenuation are quite significant. Some practical resources on the net:

http://wetpixel.com/i.php/full/filters-and-ambient-light-photography/
http://library.thinkquest.org/28170/35.html

Jeff,

You are spot on on all accounts. An experienced cinematographer would estimate the type and strength of the filter depending on the environmental conditions at hand. It is much more accurate than trying to work out a generic formula as the variability of conditions are significant.

You are also correct that the channel raw exposure meter would be your friend to determine what type and strength filter would bring the image closer to neutral. All you need is a grey or white slate and a test dive.

I'm a big fan of colour correction filters and use them most of the time. In fact, I'm working on an internal (rear) filtration system for Nikonos lenses as we speak. Good fun.

 

[Pawel Achtel]

Yes, if you're on the spot, the main thing I'd be looking at is the reds in your histogram in relation to the others.

Yes, reds and blues. Blue is filtered out in "green" water. You would assess the colour imbalance by measuring the EV drop and chose the filter accordingly.
What helps is to have the filter compensation effect measured before hand for each filter that you have. Of course, you do it with the trusty (raw) channel exposure meter too without even getting wet.

 

[Pawel Achtel]

So, Pawel, now we know why Jannard responded personally on this thread, threatening to shut it down. And why you thanked him forthwith. You petitioned him personally, alleging grievous personal insult, aggravation, and commercial disadvantage? Did Jim even bother to read the thread?

The innocent attacked, is that your stance? .

none of the above. It would be naive to think that Jim would respond on the forum and removed selected posts without reading them first. It is a professional forum about film making and trolling or personal remarks are not accepted. It is very easy to understand.

 

[Paul Russell]

I'll take sone reds and oranges and we'll run a test. The DOP wants narrow DOF anyway.

 

[Johnny Friday]

Ok....now back on track to the discussion at hand. Apologies for tackiness Mike.
JF

 

[paulherrin]

Pawel, thanks for sharing the resources, I'll see if I can look over some when I get a minute to breathe.

I'll take sone reds and oranges and we'll run a test. The DOP wants narrow DOF anyway.

Paul, there are possibilities to get the narrow DOF look in post that may save you time and money in production. I can see a lot of reasons not to try it in the original capture. You can always defocus an image (or parts of it)... Obviously, if you can get it in the shot you should get it - but I would build in more than enough cushion for missed focus. I'm sure you know the challenges at hand, but I'm just sayin'. Not commenting on the creative decision, just the practicalities of where the look might be applied in a cost-effective manner. That will depend on the specifics of your project, but it's something to think about and possibly test out.

 

[Jeff Whitehurst]

Yes, if you're on the spot, the main thing I'd be looking at is the reds in your histogram in relation to the others.

Thanks, that seems like a consistent way to monitor the shoot. Sounds like a quick assessment of the histogram would easily help determine the correct filtration (if any) for the conditions.

Your work on the Galapagos Doc looks great BTW, thanks for sharing your experiences. Any chance you could post some before and after underwater stills? If not I'll hope to see some of your workflow on the behind the scenes on the DVD

 

[Jeff Whitehurst]

Jeff,

You are spot on on all accounts. An experienced cinematographer would estimate the type and strength of the filter depending on the environmental conditions at hand. It is much more accurate than trying to work out a generic formula as the variability of conditions are significant.

You are also correct that the channel raw exposure meter would be your friend to determine what type and strength filter would bring the image closer to neutral. All you need is a grey or white slate and a test dive.

I'm a big fan of colour correction filters and use them most of the time. In fact, I'm working on an internal (rear) filtration system for Nikonos lenses as we speak. Good fun.

Thanks for the insight. I should have added that I don't have much experience with underwater lights. In your opinion, would the same factors regarding environmental conditions still apply with artificial lighting, and how would that affect filtration choices in a RAW workflow?

 

[paulherrin]

Your work on the Galapagos Doc looks great BTW, thanks for sharing your experiences. Any chance you could post some before and after underwater stills? If not I'll hope to see some of your workflow on the behind the scenes on the DVD

you mean a little somethin' like this?

i'll see if we can't scrounge some more up in the next week or so, thanks for the compliments - as i mentioned before, the credit really goes to the guys jumping in the water. they've seriously put a lot of dedication into this

 

[Jeff Whitehurst]

Nice! That's the shot I was hoping you'd show. Love how the orange tones pop out in the CC version. The spot lighting makes the diver look like a hero, dig it!

you mean a little somethin' like this?

i'll see if we can't scrounge some more up in the next week or so, thanks for the compliments - as i mentioned before, the credit really goes to the guys jumping in the water. they've seriously put a lot of dedication into this

 

[Pawel Achtel]

Thanks for the insight. I should have added that I don't have much experience with underwater lights. In your opinion, would the same factors regarding environmental conditions still apply with artificial lighting, and how would that affect filtration choices in a RAW workflow?

Yes, they do. Artifical lighting is subjected to exactly the same filtration as ambient as it travels through the same type of water. The only difference is that the artificial light path is from the light source to the subject and back to the camera. This combined distance in combination with the actual water colour absorbtion index will determine the final colour imbalance.

If you are going to film sharks, the combined distance is often more than 5m, which means that you would use at least 2 stops of filtration just for the artificial light (night time) and even more if you mix it with ambient light (daylight). In geen water it may add another two or three stops as the filtration is more intensive than that of pure water. When filming a sea dragon, for example, the combined path will be only between 1m - 2m, so the filtration you would use would be relatively mild, about 1 stop or less.

Ideally, you would like to override most of the ambient light for the foreground subjects. This is easier said than done! I usually use 24,000 lumens of tungsten light and still struggle on a bright day. In practice, the actual light will be a combination of ambient and artificial and, depending on the proportions of those two, you would select a filter that falls in between those two.

Because of all the variability, dependance on the subject distance and depth, one would usually try to find a compromise filter that would get the colour balance closer to nutral in most situations. Then, fine tune it in post. The less you need to adjust in post, the better.