Category Archives: Video Lights

Ambient filters, ambient light, filter, Panasonic GH5, UNDERWATER VIDEO, Video Lights, White Balance

Matching Filters Techniques

November 25, 2019 interceptor121 8 Comments

The issue is that the Ambient light filters are set for a certain depth and water conditions and does not work well outside that range. While the idea of white balancing the scene and getting colour to penetrate deep into the frame is great the implementation is hard.

Thinking about Keldan we have a 6 meters version and a 12 meters version as listed on their website. The 6 meters version works well between 4 and 12 meters and the other between 10 and 18. At the same time the Spectrum filter for the lens works down to max 15 meters and really performs better shallower than 12 meters.

With that in mind it follows that if you plan to use the spectrum filter -2 you are probably getting the 6 meters ambient filters. So what happens if you go deeper than 12 meters? The ambient light filter is not aligned to the water ambient light and the lights start to look warm this is not such a bad thing but can get bad at times.

You can of course white balance the frame with the lights however this becomes somewhat inconvenient so I wanted to come out with a different technique. In a previous post I have described how to match a lens filter to a light/strobe filter. Instead of matching the light filter to the ambient light I match the filters on land between each other in daylight conditions to obtain a combination that is as much as possible neutral. I have done this for URPRO, Magic Filter and Keldan Spectrum filter and worked out the filter that when combines give a neutral tone.

Magic filter combined with 2 stops cyan filter giving almost no cast

This tone tends to emulate the depth where the filter has the best color rendition. So in case of Keldan this is around 4 meters and so is Magic with URPRO going deeper around 6-9 meters.

The idea is that you can use the filter without lights for landscape shots and when you put the lights into the mix you can almost shoot in auto white balance or set the white balance to the depth the two were matching. I wanted to try this theory in real life so I did 3 different days of diving testing the combination I had identified the results are in this video.

The theory of matching filters worked and the filter more or less performed all as expected. I did have some additional challenges that I had not foreseen.

Filter Performance

The specific performance of a filter is dependant on the camera color science. I have had great results with URPRO combined with Sony cameras but with Panasonic I always had an orange cast in the clips.

Even this time the same issue is confirmed with the URPRO producing this annoying cast that is hard if not impossible to remove also in post.

The Magic filter and the Spectrum filter performed very close, with magic giving a more saturated and baked in image with Keldan maintaining a higher tone accuracy. This is the result of the design of the filters: the Magic filter has been designed to take outstanding picture better than life, the Spectrum filter has been designed using tools to give accurate color rendition. What it means is that the magic images look good even in the LCD while Keldan are a bit dim but can be helped in post.

Looking at the clip in the first 3 and half minutes you can’t tell apart Magic and Spectrum down to 9 meters, with the URPRO giving consistent orange cast.

Going a bit deeper I realised you also need a scenario where you are swimming closer to a reef and want to bring some lights in the frame because you are outside the best working range of the filter. In order to avoid excessive gap when approaching the reef I had stored white balance readings at 6 9 12 15 meters so when I had a scene with mixed light instead of balancing for say 15 meters and then having an issue with the light I used the 9 meters setting so the image is dim when you are far and gets colorful as you approach which is somehow expected in underwater video.

The section at 15 meters are particularly interesting

You can see that URPRO gets better with depth but also how at 5:46 you see a fairly dim reef at 5:52 I switch on the lights and the difference is apparent.

At 6:20 the approach with Keldan was directly with the lights the footage still gives an idea of depth however the colours are there and the background water looks really blu as I had white balance set for 9 meters.

Key Takeaways

All filters produced acceptable results however I would not recommend URPRO for the Panasonic GH5 and settle for the Magic Filter or the Spectrum filter. Today the spectrum is the only wet filter for the Nauticam WWL-1 but I am waiting for some prototypes from Peter Rowlands for the magic. I would recommend both the magic and the spectrum and the choice really depends on preference. If you want a ready look with the least retouching the magic filter is definitely the way to go as it produces excellent ready to use clips that look good immediately in the LCD.

The Keldan Spectrum filter has a more desaturated look and requires more work in post but has the benefit of a more accurate image.

I think this experiment has proved to work and I will use this method again in the future. This method is also potentially available using the keldan or other ambient light using a tone that closely matches the lens filter.

Filter Poll

ambient light, filter, Micro 4:3, Panasonic GH5, Underwater Photography, UNDERWATER VIDEO, Video Lights, Wet lenses, White Balance, wide angle

Getting the best colors in your underwater video with the panasonic gh5

August 3, 2019 interceptor121 26 Comments

There is no doubt that the Panasonic GH5 is a very capable camera and in given conditions the video performance you can get is truly impressive.

Broadly speaking a video clip needs to be:

Sharp
Colorful
Contrasty
Clean

Those 4 characteristics are tightly related to:

Resolution
Color depth
Dynamic range
Low Noise

Resolution

Today everyone shoots 4K and after all resolution is well supported by almost any camera, broadly is unaffected by other factors and unless the noise is really high sharpness of your frame is not going to be a real issue shooting at 4K.

Color depth

In normal conditions and not underwater a camera can resolve many colors. However underwater due to the diffraction of light and selective absorption of colours the starting point is very different from land. So generally is not the camera that cannot resolve the colors but the colors that are missing to start with. This post will focus specifically on this aspect. The Panasonic GH5 can resolve 23.8 bits in RAW and therefore technically has less than 8 bits color depth – do not confuse this with the 8 or 10 bit recording setting.

Dynamic Range

Underwater scenes tend to have limited dynamic range, with the exception of sunbursts or shooting against the light this is going to be an issue only in specific circumstances of very bright scenes with shadows. In all scenes taken with video lights dynamic range is not an issue at all. The GH5 has 13 stops of dynamic range but rarely this is an important consideration.

Noise

Noise is an important consideration as when the noise goes up the camera looses the other characteristics, color, dynamic range and resolution will be affected when the camera is outside the sweet spot. Broadly speaking the Panasonic GH5 does not do well once you pass the ISO 1600 setting and I tend to cap the ISO in video at 800 in most cases.

Diving Conditions

To understand how those variables play we can see how the same set up reacts very differently in scene where there is less light and therefore the camera uses high ISO like this one.

The same camera with exactly the same equipment in brighter water produces this

So the reason for the above is that with less light there are less colours and the clip looks what it is really.

OK moving on to the main subject of this post how do I get the colors right? It is a combination of techniques and the trick is to use the right one in the right conditions.

Generally every site has specific conditions that change depending on weather, time of the day, visibility and other factors. So in broad terms a site will have more or less light and therefore more or less colours. It is therefore impossible to categorically define what to do at a given depth but is more about typical values. With this in mind we have typically 3 scenarios:

Ambient light shots
Artificial light shots
Balanced light shots

Close up Shots

In general close up shots especially of small subject fall within the scenario 2 for which a video light with high color rendering is important as this will define the colours you see. With a lot of power it is possible to extend artificial lighting to larger subjects but eventually you run out of power due to distance or size of the subject.

Wide angle shots and seascapes

True wide angle shots are generally ambient light shots which also means when it gets too dark the colors will be missing and it will look blue not matter the equipment.

In order to make the most of ambient light shots for wide angle it is essential to balance the colours in water even when you use a RAW format on a still image because RAW files are not as RAW as you think and are actually compressed.

Custom White Balance

Using Custom White balance with a grey card it is possible to obtain decent results until the camera hits the maximum color temperature in the case of the Panasonic GH5 this is 9900K. Depending on conditions you may get to 10-12 meters and this still works, in darker water this stops working much sooner.

Chrisoula K Bow — Chrisoula K Ambient Light 5 meters

Color Filters

Color filters push the limit of custom white balance further down. Some add more or less 4 meters others up to 6-8 meters at the expense of an overall loss of light. Filters are useful when there is a lot of light because also help to keep the Panasonic Gh5 in the best aperture range (not smaller than f/11)

Filter in action at 10 meters

Right now there are predominantly 3 filters on the market:

UR PRO
Magic filter
Keldan Spectrum

All those filters will improve the performance and color rendering of your footage, under the conditions that the loss of light is not pushing the camera above reasonable ISO values.

In terms of depth range the magic filter and the Keldan Spectrum -2 version can be pushed to 15 meters depth on a bright day in clear water. The URPRO is capable of getting a few meters more down to around 17-18 meters although it does generate an orange cast (as there is no red left) it is still workable.

Filter	Light Loss	Typical Max Depth
Magic Filter	1 2/3 Ev	15 meters
Keldan Spectrum -2	2 stop (WWL)	15 meters
URPRO	1 2/3 Ev	18 meters

This image gives an idea of the 3 filters as you can see they are very different one from the other.

Balanced Wide Angle Shots

This is an entirely new technique that has started with the Keldan Ambient light filters. I wrote a whole piece on wetpixel

The principle is to use custom white balance with or without filter to obtain color rendering and then put filters on the video light so that the color of the light emulates the ambient light and therefore it only gives texture not color.

Keldan has developed a whole range of filters for various situation that match their light and therefore are not applicable to any other light.

As I do not own a set of Keldan I have done some tests and found that a gel of Cyan filter 2 or 3 stops makes my divepro G18+ practically ambient light in the conditions I dive into.

Filter	Cyan Strength
Magic Filter	2 stops
Keldan Spectrum	2 stops
URPRO	3 stops

The above value are based on my experience use at your own risk especially with different lights.

To give an idea I overlapped the filter to my iPhone lens

This is the shot without any filters

This example shows that the two filters cancel themselves the result is almost daylight with no cast which means in water if you use a video light or a strobe you will not see a red or orange spots on the image.

For those taking pictures the same combination remains true with Inon Z240 and Sea and Sea YS-D2

Example picture here

five in a row — My own filter and Cyan 3 stop note that the light is coming from the other side

One thing to take into account is that you need to find a way to hold the gel on the video light or the strobes. The flat surface strobe diffusers make this process easy, finding something you can use with your video lights is not easy and also the gels may melt after continuous use.

Artificial lights

It comes a point and a depth where filters stop working, this could be as shallow as 8 meters in green water. As the scene is dark using lights is what is required. There is nothing specific about this technique except making sure you don’t get burned highlights or backscatter. As it happens in photography using long arms (maybe not as long as for stills) is key to get good lighting on your subject.

My Camera Settings

I use CineLike D with saturation, sharpness and noise reduction to -5. I shoot at 24/25p AVCI 400 mbps and follow the 180 rules, it is entirely possible to shoot at 1/100 if you like more crisp look.

Clearly there are people out there that do not like filters and think white balance is best etc but I think a good read on magic filters explains it all.

http://www.magic-filters.com/need.html

Panasonic GH5, UNDERWATER VIDEO, Video Lights, wide angle

DivePro G18 Plus video lights review

April 6, 2019 interceptor121 Leave a comment

I managed to get hold of a pair of DivePro G18 Plus samples last week to use for my wide angle video hereby my thoughts on this product that I believe could be interesting for many video shooters.

Construction and technical data: solid anodised aluminium smoothly finished. Jaunt has decided to expose the battery that screws into the light head as oppose to house the battery itself into the light a more conventional design. The light features a Cree CXB3590 LED with a color temperature of 5000K and a CRI of 92 with declared output of 18,000 Lumens and a 95 degree beam angle. The battery delivers 14.4V with a total capacity of 6800 mAh giving an autonomy of 52 minutes at full power of 105 minutes at half power. The technical specifications of Creed LED give full details of the light used https://www.cree.com/led-components/media/documents/ds-CXB3590.pdf

When you look at page 14 performance group EB you see 15000 lumens nominal per bin, take into account that the array has an efficiency of 120% so this gives you the nominal lumens. In terms of viewing angle the nominal beam in air is 115 degrees and this in water gives you 100 degrees according to my calculations am not sure how Jaunt worked out 95 degrees. Looking at page 10 you can see that even at CRI=90 there is a spike in the navy blue colour this is most likely to show in water when combined with close up lenses as blue fringing and should be completely irrelevant at wide angle.

The provided chargers delivery only 1A with a declared charging time of 8 hours that frankly is totally unacceptable for a video light.

I recommend getting a spare battery the code is DivePro B06. The light has a color indication for the charge level around the switch button that is simple and effective at the same time although you don’t get your residual time in minutes as you do from some other products.

Ergonomics: the light feels very much like a torch and when attached to the included ball mount is very bottom heavy. The fresh water weight is 350 grams and becomes 370 grams with the mount. The light feels very well built, smooth and rugged.

The light switch system allows for 100% 50% and any intensity from 1% to full power however this is slightly difficult to use, there is also an SOS feature. Generally the light feels well designed with few small niggles, the ball attachment is quite long this is not an issue except the light is already heavy on the bottom whilst the attachment to the arm is in the front part this creates a significant torque especially on land. Use of a bespoke underwater float is advised. Another minor issue of the ball mount is that it is not actually 1” but 2.65 cm. 1mm may seem little but it does bring the clamp off balance making it easier to loose grip. I recommend changing the o-rings with normal buna rings to reduce the size and improve grip if you use Ultralight, Inon or Nauticam arm systems. Another small issue of the switch system is that at rest on land the button may hit the floor. Previous version of the light switch on immediately at button press now Jaunt has changed the logic of the switch on to a long 2 second press to avoid accidentally switching on the light.

Video with the old switch mode

As the light overheats outside water this will prevent LED burnout. I had the latest version of the light, other copies on the market may still have the old logic check carefully yours.

Field test: Testing the light in a tank confirms the beam angle and the battery life as per specification more detailed testing is only possible in the pool.

I tested the lights in a pool with a 5 meters deep end. Pools have controlled conditions to check how the lights fall off and what is the real life coverage of the lights for your lens. It is not possible to provide a real test of the geometry of a light in the sea unless you know exactly the dimensions of what you are shooting and you have flat surfaces. I have some diving end of April in the Mediterranean will provide an update later on open water performance especially in terms of color rendering that I have not checked in the pool.

Beam angle: I took a series of stills at 80, 100, 150 from the axis of the lights using arms 28” long to which you need to add the length of the tray to determine where the light beams will meet.

As expected at 80 cm you see two separate circles of light, this become an elliptical shape at 100 cm and fill the frame at 125 cm with small fall off at the edges.

Dark Shadow as the lights are too close to the pool wall to merge the beams.

This pool shot gives an idea of the coverage only the edges are dark and the light is very nicely distributed. I have removed the reflections of the lights on the wall as they are distracting.

1 Meter distance from the WWL-1 shot (1.15cm from light axis)

In order to understand the light falloff I ran the stills into a monitor equipped with false colour you can see the results here the lights are in my opinion very convincing and still deliver at 1.5 meters distance although you may need to pump up the ISO.

False colour shows good distribution of the beam across the frame. Note this is a 4:3 shot the 16:9 crop is the red frame

I would think that with this angle of coverage a distance of 30” between the two lights is ideal with my rig this means two 8” segments however this may create ergonomic issues so I settled at 5 + 8 this gives an arm length of 21” and with the GH5 26” from centre. Considering a WWL-1 set up with the front of the lens 6” ahead this means shooting distances up to 1 meters from the front of the lens covering a frame width of around 3.5×2.0 m that is a huge surface.

After the pool test I noticed a number of scratches in the paint clearly the coating is not the same quality of more expensive lights.

Conclusion

Overall the lights have great performance in terms of power, beam distribution and are very well built with excellent autonomy. Issues to note and suggested remediation:

The chargers that come with the lights are inadequate. A 2A charger would be better and would halve the charge time without damaging the battery pack, here some links for third party 16.8V/2A chargers:
1. UK https://amzn.to/2YPyg4G
2. US https://amzn.to/2HZEJoK
3. Germany https://amzn.to/2I2hN83
The clamp position creates an issue of pitch in water obviously if you manage to have some floatation system for the individual light this is no longer a problem.
The light intensity adjustment is not effective and you can’t really tell if the two lights are set the same. Obviously this is only an issue if you need less than 9000 lumens for example for close shots. There is no easy solution to this problem other than controlling the two lights simultaneously.

Considering the price point and the quality this light competes with the Gates GT14 and the Keldan 8X and when it comes to power, CRI, autonomy and price beats them both in terms of durability and ergonomics they appear to be a level down but they are also less expensive.

Jaunt is setting up relationships with distributors in major markets and in UK there is already one so everybody should be able to get a set of lights. Depending on location, duties and import regulations the price will change but generally I have seen it remain competitive.

ambient light, AVCHD, close up lens, diopters, filter, iMovie, Schooling Fish, SONY RX100M2, Stabilization, Tips, Uncategorized, UNDERWATER VIDEO, Video Lights, White Balance, wide angle

Video Feature Sony RX100 Mark II in Malta

August 29, 2014 interceptor121 1 Comment

Following from my previous post I managed to get together a clip out of the 5 dives I did

The first day was somewhat plagued by visibility a bit lower than the norm for the location but the second day was fabulous

For this trip I brought with me the Inon UWL-H100 and the red push on filter from deep roof H20 and the Inon UCL-330 as I was expecting medium size fish and nothing really small

Here is the outcome

I am quite happy how things turned out so let me share the settings with you

First I shot most of the footage in 25p AVCHD mode only some small sections are shot at 50p and actually I did not need to slow down any of the material.

For the wide shots I used steady shot in normal mode and shutter priority at 1/50th. With the filter on I had auto white balance with tint correction G2 A1. I noticed that the camera was giving red tint in some situation and so added a bit of green back. The Amber correction instead is for the RX100 itself the camera does not have vibrant yellow and is a bit blue.

For the first time I use creative mode changing the standard contrast to -3 in order to prevent crushing of blacks.

Exposure was set all along to -1/3 and metering to multi area with AUTO ISO limited 160-800.

I think the results are so good that in fact I have performed no colour correction to any shots in ambient light.

For shots with lights I set up first colour temperature to 6500K and A1 to match the lights but then in some of the far shots this resulted a bit cold so I adjusted very slightly in post the temperature.

Only 40″ are adjusted in the whole video in essence is as shot and the editing took me half hour.

I did a bit of analysis and the camera was operating for most at ISO200 with aperture around f/3.5 – f/4.0 which is really the sweet spot of the lens.

I did have some challenges using the UCL330 for some nudibranches that really required a stronger lens so they look a bit small, there was also surge so I had to fight with focus problems but all in all very happy.

The longer working distance of the UCL330 (20-30 cm or 8″ to 1′) proved challenging on walls as you are too far to hang on to anything or use a stick. I will bear this in mind in the future.

For the close up shots I used steady shot active.

I also wanted to say that a few times the camera did manage to white balance properly however the results were not exciting and frankly not worth the hassle. Using the filter is just so much better with the auto white balance.

ambient light, close up lens, diopters, filter, Schooling Fish, SONY RX100M2, Stabilization, Tips, Uncategorized, UNDERWATER VIDEO, Video Lights, White Balance, wide angle

Tweaking the Sony RX100 Mark II Video Performance

August 21, 2014 interceptor121 1 Comment

I am currently in Malta for few days relaxing and I manage to squeeze in some dives. The Mediterranean sea is nothing sensational (from a pure diving point of view) but does offer clear water, and some brisk thermoclines, and a combination of algae, blue water, caves and silvery fish that is challenging on the dynamic range of our little RX100.

The purpose of this trip is mostly to refine the video settings and go more in depth in few topics. I wanted to try specifically the following:

Metering modes
Creative modes
Stabiliser modes
Tracking focus
Medium size fish portraits
White balance
Caves and low light

Some of my settings will be the same and I am not intending to changed them those are:

Auto ISO: 160 – 800

DRO: Auto

Starting off with metering, the first attempt was to try and use the camera on 0 exposure compensation with centred weighted average metering.

Pretty soon I realised this gave issues of banding of the blue water, this was apparent not only in backlit shots but also in normal wide angle of fish in specific cases. So after dive number 1 I changed it to the standard -0.3 from dive 2.

I set a new creative style with contrast at -3 in the hope to recover detail and seem to be working fine with the shots still having plenty of contrast.

I also tried spot metering for close up but it makes no sense the video lights are too wide and ended up with burned highlights at the edges of the frame so back to centred weighted average for close up shots.

So when it comes to metering my settings are:

Wide angle: multi area

Close up: centered weighted average

I did some tests with stabiliser in steadyshot mode, this gives back some field of view and the lens offers 100 degrees diagonal and 90 horizontal, I actually think a bit more anyway with fairly stable conditions this worked fine. At longer focal length for close up I am still using active mode.

I have a +3 diopter for this test as I realised in my last still trip I don’t have a lens for medium size fish, the lens worked very well and I also tried the camera tracking focus but it seems it won’t work with fireworms or similar. So either keep normal focus or manual with peaking.

White balance has been a subject of discussion, I did manage this time to white balance a few times but to be honest it was not worth the effort there is a better correction of the purple hue of the filter but this can be corrected setting Green to 1 or 2 in AWB. I also changed the AWB to include a correction with Amber 1 as per examples. Very happy with the results I think this is the final set up with this filter lacking a proper orange filter.

Shooting in low light was rewarding with ISO maxed out at 800. I am becoming less and less a fan of video lights in cave due to the amount of backscatter am getting. I think I will default at using the lights as dive torches instead of wide beams of even leaving them off for effect.

ambient light, AVCHD, close up lens, diopters, filter, iMovie, SONY RX100M2, Stabilization, UNDERWATER VIDEO, Video Lights, White Balance, wide angle

Galapagos: Sony RX100 Mark II Video

May 30, 2014 interceptor121 1 Comment

The time finally came for our trip to Galapagos and I was ready with a set of think rubber suits to overcome the cold water. I just bought a 5mm Oneill Sector (wonderful suit) a 3mm hooded vest, kevlar gloves and a 5mm 4th Element short john. Well the short john was not used and for most I used just the wetsuit and a set of O’Neill Thermo X unders (very recommended) as El Nino is coming and the water was warmer at 25-27C or 77-80F.

This means lack of schooling hammerhead at shallow depth close to the reef, they were in the blue. We had however our good dose of schooling barracuda, tuna (in the 1000s) and even galapagos sharks

This is the video I produced

If you have problems with playing in your country use vimeo instead

The conditions were difficult with low visibility and in some sites very green water as you can see here

Questions will come about what I used etc etc so here is the list

Sony RX100II in Nauticam housing
FIx adapter for Inon LD mount
Inon UWL-H100
Deeproof blue water filter
Sola video lights 1200 (just few shots of the barracudas and some close ups)
Combination of arms and sometimes no arms
Ultralight tray TR-DM with extension and handles

The video has been produced with iMovie 9.0.4 no stabilization performed except the scene with the moray eels mating (very mild)

I shot the whole trip in shutter priority 1/50th of a second in the 25 fps 24 Mbps format. After some tests at home I have decided to use this mode as I can’t physically play the 50 fps files the camera produces on any of my devices differently. The 25 fps gives a film look and very smooth footage. This format is only available on the RX100II and not on the original RX100 so the consideration I made at the time for video settings of the RX100 remain valid.

The benefit of 1/50th shutter speed is a full f/stop of light the disbenefit is that at the surface and for backlit shots this is too slow, in those cases I go back to program mode or increase shutter speed to 1/100 or 1/200 or more.

For what concerns the editing I import the raw files in iMovie without using the conversion and then export with x264 using very slow preset and level 4.0 compatibility to use it with my appleTv.

I do minimal color correction in some cases I had to eliminate the red color cast of the filter when shooting upwards, to do that I change the white balance to top yellow until i remove the cast.

In some cases I had to put the green gain to the max for the same problem but in all other cases there is NO color correction in post.

When you work with AVCHD cameras the footage is compressed and the key is to get it right in camera.

As Galapagos conditions were challenging, although less than I expected, I used gloves in some dives to hang on to the barnacles and I also modified the set up to completely eliminate the lights.

I would dive with two 3″ segments and two 6″ Inon Mega float arms when I had the lights on and for other shots in ambient light I would have this set up here that looks odd but it is very effective and almost neutral at only 120 grams in water. The position of the floats means the camera stays upright at all times.

I would put a single Sola light on top of the housing not for video purpose but to signal the dive master when I was a bit far in the murky or dark waters. I used this set up on almost all blue water dives (Darwin and Wolf) and the normal set up with lights for the South and West sites with murky or green water.
There will be a separate post on the photos, I did a total of 18 dives with the camera of which 4 where photo and 14 video. You can see an example in the featured image.

I have now ran some statistics on the final clip that I produced

I used a total of 41 video clips:

ISO average was 273 with the following breakdown

2 clips at 160
30 clips at 200
6 clips at 400
3 clips at 800

f/stop average was 3.1 hyperfocal distance on average 1.16 meters. So if I were able to shoot without filter I would have not gained anything in terms of sharpness as most subjects were further away

I would consider the Galapagos and the dive trip I did not the best in terms of brightness and visibility so I would conclude that the RX100II with the Inon UWL-H100 and a red filter is the best set up for wide angle video in terms of performance, ease of use and flexibility.

close up lens, diopters, SONY RX100, SONY RX100M2, Stabilization, UNDERWATER VIDEO, Video Lights, wide angle

Sony RX100 – In depth into digital settings

March 12, 2014 interceptor121 1 Comment

Over a year ago I wrote a set of posts for the RX100 and some of the quirks of this wonderful little camera.

Steadyshot – aka Image Stabilizer

The RX100 has a specific Active mode for video not available when taking stills. I described the differences between those two modes in this post

Everyone is so obsessed of having the widest possible field of view that other more important considerations are completely missed out.

If you have ever shot a video with a GoPro underwater you know how bad is the quality of the image in the corners, this is because the flat port combined with the gopro lens create many optical aberrations.

Our RX100, especially the original Mark I, also has an issue in the corners, this is not just an underwater issue is also true on land. The lens on the camera has a lot of distortion and when corrections are applied to the image this effectively creates corner softness.

When we add a wide angle lens the image quality in the corners deteriorates further especially if the lens is flat creating a lot of chromatic aberrations that you can see in pictures with a blue or yellow halo around the edges.

Now the good news the Active steady shot mode crops the image of a factor of 1.15x getting rid of the majority of the corner softness.

There is of course a price to pay which is the loss of some of the angle of view. According to my calculation if you use an Inon UWL-H100 you start from more than the declared 100.8º more around 104º in fact. When the active mode is on this drops to around 95º. Remember all those values represent the largest incident angle that means the diagonal field of view.

A lens with 100º diagonal field of view means 90º horizontal. So after the active mode is engaged our horizontal field of view looks more like 84º which is equivalent to a 20mm lens. This is sufficient for most close wide angle shots and plenty for ambient light videos of large fish or wrecks. I generally suggest to keep the Active mode on, of course if you can be in a fixed position and hold the camera really steady you can also use the standard mode and obtain more field of view. There is a chance though that you will need to crop the extra field of view if you need to stabilize in the editing phase.

For macro shots without a tripod the steadyshot is a must and helps greatly. I do not even see a reason to take it off if you have a tripod as the RX100 does not have a particularly small capture area.

Digital Zoom

This brings the second subject: digital zoom, if you shoot pictures you avoid it as what you are doing is to crop the image, something you can do yourself in processing. In video though there is very little quality loss as we use just 2 megapixels of the 20 of the RX100 camera. In my test you can use digital zoom until the 2x multiplier is reached, this corresponds to 7.2x magnification and see no noticeable degradation in the image quality. The other benefit is that the depth of field is the same despite the magnification so you can save yourself stacking two diopters with all the difficulties that follow in terms of focus.

Digital zoom is always on in video mode and I recommend to use it with a single close up lens before embarking on dual diopters or a strong single diopter. Also take into account that with a single +6 diopter your working distance is around 4″ which is ideal for most critters except pygmy seahorse and bobtail squid or some shrimps.

Video Lights

In another post I have explained that getting hung up about light angle coverage is not really the only thing to consider, there is also luminous flux and quality of light. With my Sola 1200 I can cover something between 2 and 4 feet away with decent results further away is just back scatter. Generally this is ok for some close portrait work and close wide angle and of course not sufficient to cover part of a wreck or much larger subjects. You may decide not to bother at all with lights for wide angle and just render your deep wreck dives in black and white in this case consider that a pair of Sola Dive 800 at $399 are a high quality macro set up, function as dive light and provide some decent close wide angle portrait illumination. For macro shots you need much less than that, I set my fill light at minimum (300 lumens) and the main light at 2/3 which is 600 lumens, I can shoot at f/11 with this light intensity. You can see me shooting in the feature image.

Underwater Photography, UNDERWATER VIDEO, Video Lights, wide angle

Choosing a video light for your Underwater Video Rig

January 5, 2014 interceptor121 22 Comments

I thought of writing a brief article about video lights.

In the last years LED lights have become incredibly cost effective and there are many products on sale that look promising and cheap.

A special mention goes to the GoPro a very cost effective option for underwater video plagued by poor performance in low light. The GoPro market seem to have injected new life into the video light marketplace and of course calls for products that are not expensive in line with the typical profile of the GoPro user.

There are many examples of footage with what you would consider powerful lights that actually do not look that bright or even nice, why is that?

Lights are now measured in Lumens which is the SI unit of measure of luminous flux a light is said to emit one lumen if it emits one candela over a solid angle of one steradian. This sounds all very complicated and not very helpful so let’s try to make some sense of this.

Usually when we go an buy a light we are given three key pieces of information:

Lumens – this in a way is considered the power of the light*
Beam angle – this is the maximum horizontal beam that the light can cover – note this does not relate with solid angles but is merely a 2D view
Color – this represent how white is the light, a good light should not exceed 6500K which is what is considered a day light white

*we will see that this is actually incorrect

Let’s have a look at a typical best buy the Archon Video Light W38VR, this light is declared to have the following:

1400 Lumens
120 degrees beam angle
5000K temperature

Looking at the specifications this looks like a very warm (5000K) wide beam light and very powerful so how comes that with a subject at one meter or 3 feet distance this light seems to have no effect on a bright day?

The reason is that lumens are not a real indication of the amount of light that hits the subject but just the total light emitted which includes the light that illuminates the water between us and the subject that we actually are not interest at all in illuminating.

If you had to do a video production in studio you would be looking at intensity of 1000 lux where a lux is measured in lumens/m2. The lux is the density of light that hits a flat surface at a given distance.

With a few calculations we see that the Archon light because of the very wide beam is effective at two feet and produces around 1200 Lux which is great however at 3 feet this drops to 550 Lux which is not that great.

Many times when comparing the new cheaper lights to expensive lights like Sola or Fix despite the less nominal lumens declared the sola or fix seem brighter at the same distance.

So let’s evaluate the lux produced by a Sola 1200 a light much more expensive than the Archon with only a 60 degrees beam.

At two feet the sola produces around 4000 Lux which would nearly tan a fish, at 3 feet it still produces nearly 1800 Lux dropping to the studio value of 1000 Lux at a distance of 4 feet or 1.2 meters. This is because the illumination is in a smaller and narrower beam and is like the light was more dense.

Of course this has the disbenefit of a narrower beam so we need to step away from the subject in order to cover it properly, this diagram gives an idea

The two set of lines contain the video lights beams, we can see that those beams cross and them keep as combined angle of coverage the same beam of the lights themselves, that is the ideal spot for our lights as there are no shadows there.

Another consideration is the angle of coverage that we need for our camera lens to follow the lights, two 60 degrees beam lights actually cover a 100 degrees diagonal lens or 90 degrees horizontal lens typical of a 18mm lens. The GoPro and all compact cameras with a 100 degree lens fall in this group.

Another consideration to be done is that due to the light angle of coverage there is a minimum distance to be kept if we want to avoid our subject to be in the shade, this minimum distance depends on the light beam and the distance between them.

Once you get closer than one foot it is not necessary anymore to point the lights forward as the amount of water is limited and the lights can be pointed directly at the subject like in this example

So assuming we want to be at a distance of one foot or 30cm how far do the lights need to be?

For a 60 degrees beam the lights need to be 36 cm away or around 12 inches. For a light like the Archon with 120 degrees beam the distance between the arms needs to be 1 meters or 40″. Considering a tray is around 30 cm or 12″ this means you need arms at least 13″ in order to cover something at one foot and to cover a subject at 2 feet you need two meters distance that means again 33″ worth of arms.

What happens if you only have the tray with the lights on and your subject is at 3 feet with two very wide video lights of 120 degrees beam?

You illuminate already after 3″ from the camera
The two lights emit 550 Lux that combined are not such a small output

The net result is that a lot of the water in front of the subject is illuminated and this creates backscatter where all the silt in the water gets reflection and ultimately deteriorates the quality of the footage.

If you ever wonder why underwater photographers that shoot super wide have two 16″ arm segments this is why the want to avoid backscatter with their 110 degrees strobes and still be around one foot distance with their fisheye lens.

So what are the conclusions that we can draw:

A wide beam light is only good if you have long arms, the wider the beam the longer the arms otherwise the beams just light up the particles in front of the subject producing backscatter
Lumens are not a real indication of the effectiveness of the light per se but need to be taken into account with the beam angle and a lux calculation needs to be performed you want to aim for 1000 lux at the distance of choice
Light beams need to be evaluated together with the camera lens horizontal field of coverage 60-80 degree beam angles are adequate for most of the video rigs out there and more is only justified for fisheye type of lens not commonly used in video

I hope you find this information useful and get in touch if you want to discuss, the subject is not that simple!

Interceptor121 Photography & Video Workshops