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Video Lighting Part 1
much of this can apply to wide angle strobe photography  also

Ambient Filters video   Part 2
much of this also applies to wide angle photography

Ambient Filters  Part 3
much of this also applies to F.E wide angle photography

Lighting, Filters on Camera, Ambient Filters on Lighting


This review assumes
You have previously taken some underwater video, either with a GoPro or perhaps a M43 camera and you have used, or seen being used, underwater video lamps.

It is also assumed you are familiar with Kelvin colour temperature and you have awareness of underwater colour absorption, loss of reds and resulting blue cast in tropical waters, or the green cast in temperate waters.


So possibly the least complicated place to start this overview is, a night dive with no scene backgrounds and no natural ambient light to worry about.

So, if we consider for the moment close video work, and initially just night shots, where ALL the light is going to be emanating from the external light source, fully controlled.





Lets say we take a basic set up of a single video lamp mounted for use with a GoPro camera. We put the video lamp on, and we are ready to take some video clips.

If you are close, less than a metre from whatever you are videoing, the image may look quite normal through the camera. The video light should be fully illuminating the scene. Even if it is not fully illuminated then the image taken is surrounded by a black border around the shot (vignetting), but this can still look acceptable.


You can now take some reasonable video clips, assuming your framing is o.k. and you have a good choice of subjects etc. Try to ensure there are no jerky movements which will give viewer a headache. So, hold the camera steady and pan slowly in order to ensure the viewer enjoys your video. Taking short few second clips to facilitate making up a story line once back on your computer works well.



Don't leave the camera in auto ‘white balance’ (WB), as each video clip you take may have a different WB setting determined by the camera. This means that when you edit the clips you may get colour jumps between shots and end up spending hours in post trying to balance the clips.

Colour correction

If you set your camera "white balance" WB to ’manual’ (custom WB can be used) and select the value in Kelvin to match the light, you are then in control of the colours we record. We like to obtain pleasing colours and most people tend to favour warm lighting effects. You can choose a camera setting to give the colour look you favour.

We can achieve fair results with a budget 7000k video lamp that is corrected by the WB in the camera.

We would probably get quicker and better results if the lighting was warmer in the first place (appropriate premium light) and the camera then does not apply so much correction to achieve the result we like and warmer colours may well be improved. We can add warming gels to the cooler lights.

 


Are all video light colours evenness the same?

LED lamps tend not to have an even colour throughout the spectrum, they may look mostly white but have irregular colours mixed up to give near white, but this will not be "noon daylight" white. With the budget lamps all is not lost as you can do some correction in post on your computer, and still get quite acceptable results.

Premium quality lamps do not necessarily all colour rendering better. So how can you decide if your lamp is going to give you the desired results you are looking for? Take a good look at the manufacturers data, this may help guide you but don't let a high colour rendering index (CRI) number mislead you. If you ‘Google’ CRI ra, then CRI re, then CRI R9, you will see not all lamps are colour measured the same, some lamps need less post processing and others need more. I will cover this in more detail in a later overview. Best advice is to start with budget lamps before spending more on premium lamps. You may well find the budget lamps are well good enough as you’re probably not filming for the BBC. The premium lamps will be better made, more reliable, have good support and most probably last longer. I’m not knocking premium lamps.

With the economical 6000-7000K video  lamps, consider placing a warming filter gel in front to shift the colour temperature and make the light a little warmer. This can work well, a warming gel with some led lights can cause a slight green cast, so you may need to add a minus green gel also. Many cheaper LED lamps may have a slight colour cast anyway. Place a subtle magenta minus green filter in front and this corrects any green cast. With warm+minus magenta filters, I have a much better colour balanced white light to achieve much improved light quality. My lamps (shown) are naturally 7000k, but with gels they are 6000K.


Hard edges with video lights

Video lights can give harsh shadows and can give a distinct line where illumination ends in the scene. This can happen especially if the light is not wide enough for your lens. To rectify this, add a frosty diffuser in front of the light so it becomes "softer". This is a common technique used in land  photography. You can easily make up a diffuser yourself from a slightly opaque plastic sheet on the front of the light

How many lights

Two lights will probably enable you to cover the whole wide shot for fish eye (FE). This will illuminate the image on both sides to reduce shadows. Start with one and then possibly move onto two lamps when ready or if you want to. You may like the look or shadows in your shots, that's the artistic side of film-making and all is fine if that's what you want.


Note

Remember this discussion so far  has assumed no ambient lighting to consider. (night dive)

Summary

Keep close to get illumination bright
Keep close (ie 1 metre)  to reduce water between lens and the scene, to ensure less colour absorption.
Set WB (white balance) to manual
Set white balance to
match your  light colour.
Cheaper video lamps tend to be 6000-7000K Kelvin hence a bit blue-ish, still acceptable if camera is set to 6-7000k to match
Consider placing a warming gel /correction gel  in front of your lamp if it is 7000K colour temperature (adjust WB to match new lower temperature)
Place a diffuser in front of the light to soften the illumination
Remember not all lamps give good equivalent daylight colour and CRI depends on the method used ie CRI(re).
Post processing may be needed to fine  tune colour  as always.    

Next we will look at adding filters to the camera and also to the video lights.

Note some generalisations and simplifications have been made to facilitate a short description.



Overview of ambient day lighting with filters and how it effects COLOURS for underwater, no additional  lights

In this review are looking at a day time dive taking images  without any external  lights and what we expect to see with regard to colour.

The time of day and depth will make a significant difference to the colour balance of our video, without lights we have to respond to mother nature and adapt.



Balance of colour

In the shallows (down to a few meters), there is likely to be enough sunlight to adequately illuminate the scene, the colour will immediately start to shift as we dive deeper. It is almost guaranteed you will make some minor colour adjustment in camera or in post to obtain the colours you prefer. The colours may be ok, as is but only up to a point.

As we do not have external lights, we are not forced to be close to the subject for any external lights to be effective. We therefore have more freedom. We will cover mixing ambient and external  lights in overview 3.

You have options, you can set the camera WB Kelvin manually to a temperature that appears looks better, however the most common method is to set the Custom White Balance (CWB), this also adjusts other colour hue factors to better correct the image colour, this is fairly easy to do with many cameras, (not GoPro), however we are not covering how to do this yet. This will be covered later. We are going to redress the colours initially by using filters only.  +3 meters deep


What do filters on the camera lens do

As the lighting in the scene is depth/time of day dependant, in theory we could need many filters to suit the situations, this is clearly impractical, often one filter or perhaps two for the camera lens are all that is needed for general use.

One filter for shallower waters, and perhaps another filter for deeper waters.


In tropical waters often a orange or red colour filter (called red) are used, For this overview we are considering a max depth of approx 12-15 meters, Good results are obtainable in this region, although the filters work deeper but with less pleasing results, luckily It is easy to flip filters on some cameras like a GoPro.

On Micro four thirds (M43) cameras with FE lens you may need to place a filter gel/filter disc  behind the lens and have to take all the video with that one filter.

With the lens filter attached, set your camera white balance to manual, set for time of day colour in Kelvin, Say 6000K, however you can get fair results leaving the camera in auto then using a filter, but to eliminate colour jumps between clips, we are setting to manual WB.

The images should look similarly colour balanced between clips, You could switch filters at various depths, generally I use one filter, and make final adjustments in post. This is good technique for a GoPro cameras. The OMD camera shown  one is committed  for the whole dive.
Some wet WA lenses allow a filter to be added behind, so can be removed during the dive





As mentioned you can CWB with or without the filter attached, at each depth or change in lighting conditions, both work, You may find the CWB is more effective when used with a filter at depth.

The tropical "blue water" orange filter is opposite to the blue light underwater, It reduces the blue cast enabling the others colour to be more prominent and help restore the colour balance. Owing to the fact there is a lot less red available the colours are not fully normalised, just made more pleasing to the eye. In green waters, a Magenta "green water" filter is used on the camera to reduce the green cast. A common technique is to perform a CWB whilst also using a filter to "tune in" the colour further, this will be covered in a separate overview.

Without any colour correction, in tropical waters the image in the video or a photograph will be blue cast, and in temperate waters the video will have a green cast. The possible exception would be in very shallow water and when you are very close to the subject.

For green water, without using a filter, one could set the camera WB to 4000K which can make the video field look less green, the lower WB on the camera pushes the image to more blue, a simple hack and can save post production if you like the colour look. (Tony Howells method)

Always keep in mind, the more water between you and the subject the less definition and contrast you will have in the image and the results are less pleasing, as always, get close and then get closer still, this is why fish eye (FE) lenses are so popular with under water photographers and videographers.

Custom White Balance

This feature is commonly used, maybe not so much when using a filter, however the filter puts the colour balance nearer the mark, then if you carry out a "tuning in" CWB the camera has less to do and has potentially more adjustment power.

Some cameras are very good at underwater CWB, others are not and can flag up out of range error codes. Adding a filter can help here, try with your camera and find out what works best.

The addition of a filter and using custom white balance does offer a different look to the water column colour, Follow your own path here.

There are various methods to CWB, Using a grey card is meant to be a good way.

There is a distinct advantage to use a known colour filter on the lens when we want add video lights and wish to mix the two. Normally you can't do this as the colour correction applied, will affect the "daylight" video light.  

Summary

Set WB (white balance) to manual).

Set white balance Kelvin to match the ambient daylight colour. Perhaps 6000K.

Use a Magenta colour filter on camera for green waters.

Use a orange colour filter on camera for blue tropical waters.

Some tropical filters for deeper waters can look (appear) more red to the eye

Use CWB to "tune in" the colour correction when using a filter is a option.

Use CWB without a filter is a option in the shallows.

With simple cameras like GoPro, use a filter and point and go. Less brain ache option.

Minimise distance between your camera and the subject if possible.

Post processing will often be needed to adjust colour to fine tune.

Next we  will look at using filters on the camera and adding external lights.

Note some generalisations and simplifications have been made to facilitate a short description.


Overview of ambient lighting combined with  lights

In this review are looking at taking video/images using external  lights together with ambient lighting and what we expect to see with regard to colour.

To be able to use  external lights in conjunction with colour correction, you need to take into account the colour correction method you are using to correct the white balance.

Let us assume you have used CWB to correct colours, We do not know what the special correction recipe the camera has employed and even if we did, it is unique every time, there is no way we can allow for this, meaning therefore, you are unable to combine external lights. Soon as you turn on the white daylight illumination, the colours in the field on the lights will be incorrect and changed by the CWB.

The solution is to use a correction filter as previously in overview 2, as we know the colour of the filter, steps can be taken to allow for it.

This technique applies the same for temperate waters or blue water dives. We have to carefully select a matching but opposite filter to the camera filter. Consider using a Magenta filter, in this example it is a proprietary brand by Kood.

A corresponding green filter is chosen, the filters MUST MATCH to be effective.


Take a close test shot with the camera and lamp minus any filters to obtain a reference image, WB balance set manually to suit the light. Ensure the illumination is wholly by the external  lamp for the test.

To test the filter partnership, now take a photograph using the magenta filter on the camera whilst illuminating the scene exclusively with the same video light +green filter..

If the image colours in both photographs (or videos) are the similar then you have your match.

The rig shown above will take daylight colour video, using the filters shown. If you now take video underwater at close range all the video will be coloured correctly as in daylight. The background that is (in this case green water) will be corrected and look as expected using the magenta filter.

This technique enables you to use ambient light with filters, and when you are close to a subject, under a overhang in the shade etc, turn on the lights and the colours will be correct and better in front of the camera.

If the lamp green filter is not applied as in this example, soon as you turn on the video light, everything in the lights view will be magenta cast. This technique works extremely well.

In blue water the  lighting  filter will be a shade of blue, to mimic the ambient water colour.


Non standard filters

For M43 camera lenses especially WA or FE, you will need to select a camera filter colour in the form of a gel, cut and place behind the lens, or you may find a Hard filter that fits your camera, A Kood 27mm fits the Olympus OMD (take off the screw ring mount). You can use a 30mm but you may have to trim it.  (Tape up filter and use a Dremel type cutter/grinder

Lee filter do a whole range to choose from.

 

 



Summary


Set WB (white balance) to manual or use custom WB with all the filters on).

Set manual white balance Kelvin to match the video light, in this case approx 6000/6500K.

Do not use CWB unless with all filters attached

Use a Magenta colour filter on camera for green waters.

Use a orange colour filter on camera for blue tropical waters.

Some tropical filters for deeper waters can appear more red to the eye

Minimise distance between your camera and the subject if possible as always.

Post processing will often be needed to tune colour to exact requirement as usual.

Magenta GoPro7 filter and matching Lee gel green filter on light

Blue  ambient Lee gel filter shown for light and  a Kood  blue water, orange for camera lens.

Lee filter gel sample pack shown

Budget 7000K video lamp shown

with a Lee gel warming filter and frosty diffuser.

GoPro 7  White balance set manual to 6500k
to stop AWB colour jumping between and during shots, (perhaps set EV comp to -1.0 in bright day conditions)

Gopro shown with  Kood magenta 58mm filter fitted  and a Kood blue water filter also shown

CWB = custom white balance
WB   = white balance
6500K = 6500 Kelvin (temperature)
Kood is a manufacturer of camera filters
Lee is a manufacturer of filter gels
CRI = colour rendering index


Kood Blue Water 30mm Filter fits OMD camera (cut down a little to make perfect fit) and mounted in front of SMT sensor  protector.

I use a sensor protector to keep sensor clean, adding sensor  filters during dive trips could result in needing to clean it if you introduce dust into the camera, easy to clean the protector in the field.

Kood Blue Water 27mm Filter fits OMD camera
in front of SMT sensor
 protector, or cut down a 30mm to suit spot on.

What can go wrong with the colour?

If you start drifting away from subject/s, then light intensity starts to drop. The camera will start to struggle with the lower light level, even though you the observer can see quite well. As the light entering  the camera drops, you then get less contrast and colours are less vibrant.

You generally need a bright light, especially if you are a metre away or slightly more. Less bright light is required if you're taking very close shots.

Always keep in mind the less water between the camera and the subject the sharper and more vibrant the colours will be. (Standard stuff)

For wide view shots, the way to achieve with the GoPro camera, is on wide setting, or with a M43 camera using a wide angle (WA)or a fisheye (FE) lens etc. You then get a wide view, but also be really close to the subject at the same time.

For very close scenes the GoPro or other cameras would benefit from using a diopter/or close focus lens, so you can obtain sharper images at close quarters.


As we are considering no ambient light night dive, you probably would be close, so by virtue of a "night dive". You sort of get pushed into close work and you are less likely to try wide shots with far away backgrounds.


What effects the colour in the video clip?

A video light will have a colour temperature specified to it. If we consider white lights, the colour temperature of a video lamp to replicate noon daylight will be approx 5500K (Kelvin). Some are a bit lower 5000K, the budget lamps are often around 6000K or even 7000K as they are less costly to manufacture. The lower colour temp lights offer a slightly warmer look and have a slightly better ability to show reds up and appear to pop. The 7000K type lamps have a bluer light. (Cooler). All LED chips in lamps are at the blue end of the spectrum and are coated to give different colours. The warmer lights are often less bright as they have more colour correcting coatings.



OMD camera with KOOD magenta lens filter  and matching Lee gel green ambient video light filter, First attempts.
In UK waters

Demo explanation of using ambient filters

These are my personal  findings and opinions
No financial interest
Target audience beginner to Intermediate (core information)
Intentionally readable for beginners
intermediate will know all the basic stuff here.


Adding filters to budget video lights

Most underwater video  lights do not have a photographic filter thread on the front  to attached proprietary filters/carriers.

To overcome this, It is quite possible and reliable enough to bond a photographic step up ring to the front of the lamp.

The example shown is a step up ring 55 to 67mm
bonded to the lamp using E6000 plus multi surface all weather adhesive.
The adhesive is strong, clear and easy to work with. Importantly good enough.


Once attached you can use a clear 67mm UV filter to trap a Lee gel filter to the lamp.
Leave loose so air isn't trapped behind it, you may have to unscrew whilst underwater to let out any air trapped.  Alternatively if you are very  practical and good with tools, carefully drill some vent holes in the aluminium step up ring  for auto fill drain. You may end up breaking the UV filter if not careful, however they are cheap.


If you wish you can use two 67mm UV filters together to hold a gel, so not to have bits of cut gel floating about in your pocket and getting lost.

I tend to leave the filter on the lamp.


E600 adhesive

Step ring bonded to lamp and showing UV filter

67mm UV filter to trap gel or gels in front of lamp

55-67mm step ring  as bonded to lamp front

STC sensor protector