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peterbkk

Member Since 25 May 2005
Offline Last Active Feb 27 2015 01:25 AM
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#358099 Panasonic GH4 might get a V-log profile?

Posted by peterbkk on 20 February 2015 - 02:33 AM

As always it is a personal and creative choice but I never use red filters underwater.

Red filter only have any benefit in certain situations and they add a bunch of complications to an already complex process. Too shallow and they make the footage too red. Too deep and they remove too much light (remember that the filter removes blue and green but does not add red). If you leave it on in the wrong light situation, you will have some difficult footage to grade. Even if you do get the on-off timing right, the footage either side of the transition is difficult to color match. If you pan up, all the highlights will have a red tinge.

And why bother with that complication when the GH4 has a more viable solution: the 4 WB presets. Fill these up BEFORE you go diving and flip between them, depending on the ambient light color. I wrote an earlier post on how to do this. Just take a WB setting off four pieces of coloured paper in sunlight, save them in the presets and remember which preset is for which lighting condition. Save that with your other favorite settings in a Custom Setting so you can get back to them quickly if you ever decided to play with MWB while diving. I keep it simple: 1. shallow to mid tropical blue water, 2. mid to deep tropical blue water, 3. shallow to mid greenish water and 4. mid to deep greenish water. These get you very close to a good WB that can be tweaked in the edit. And it doesn't rob you of an f-stop or two.

Regards
Peter


#357929 Panasonic GH4 might get a V-log profile?

Posted by peterbkk on 16 February 2015 - 09:49 PM

If your white balance is a bit off, do you still use it as it, or you would attempt to color grade it?

 

I use a fairly flat profile in the GH4.

 

In FCPX, I've set up and saved a few colour grading presets:

- Increase contrast

- Reduce Green a little

- Reduce Green a lot

- Increase Blue a little

- Increase Blue a lot

- Warm up slightly

 

These seem to work on 95% of all footage.

 

Regards

Peter




#356680 GH4 with 14-42mm lens or LX100?

Posted by peterbkk on 16 January 2015 - 10:25 PM

Agreed, and I'm pretty good with the slow panning when required, but there are always those scenarios where a shark or codfish will dart across the frame. 

 

If the difference between the two isn't significant then no big deal, but if it's pronounced then it will tip the scales.

 

I think that you are worrying about an immaterial thing.  Rolling shutter is only obvious when panning across straight, distinct verticals.  Underwater, about the only place you'll find straight, distinct verticals are on ship-wrecks.  And then only obvious with a fast pan - which is likely to make your audience so dizzy that they won't notice the "rolling shutter" anyway.

 

Any shark darting across the scene might look slightly distorted if compared to a still photo but the audience will be oblivious.

 

Regards

Peter




#356011 Upcoming Panasonic GH-4K

Posted by peterbkk on 30 December 2014 - 01:59 AM

Or you could mount a rear-view mirror so you could watch for sharks sneaking up behind you.


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#355901 GH4 - Nauticam Macro Lens/Port Thoughts

Posted by peterbkk on 27 December 2014 - 05:54 PM

 

Hi Peter,

Do you meant Panasonic PZ 14-42mm?

I might try that lens.

Cheers,

 

Hi EunJae,

 

Yes, you are right. I did mean the PZ 14-42mm.  (http://www.bhphotovi...arch=yes&sts=pi)

 

It works fine as a macro lens with video lights providing enough light to shoot in the middle of its f-stop range.

 

And, if a larger critter comes along, you do have some options for catching some footage - although it is definitely not a substitute for a good WA lens and a dome port.

 

The only downside is that the PZ does not have manual focus underwater.  So, you have to do an AFL and nudge the housing to fine tune the focus.    (hopefully, with the Shogun and its big screen / focus tools, small focus adjustments are going to become much easier for people like me with ageing eyes)

 

 

Regards

Peter

 

PS.  Love your "Christmas eve in East Sea of Korea" video.  I was driving down the east coast of Korea around Gyeongju last year and saw some people going out in a dive boat.  If I had have known that the diving was that good, I'd have brought my dive gear and camera.  The visibility looks great and the water is such a rich, deep blue.




#355900 How robust is your housing?

Posted by peterbkk on 27 December 2014 - 05:40 PM

Diving in the Alor Straits a couple of years ago, my buddy and I got caught in an extreme down current.  I was carrying my BS Kinetics carbon-fibre housing (Canon XF100) with a pair of Sola 4000 lights - not a small system.  The other diver was quite inexperienced.  

 

I quickly clipped off the housing to two points on my BP/W chest harness, grabbed the other diver and manoeuvred her to the wall.  By now we were deeper than 35 meters and being pulled downwards fast. We were on Nitrox so could not go any deeper. Our bubbles spiralled straight down below us.

 

The only way up was to climb the wall, hand-over-hand.  Occasionally, I had to help the other diver regain her hand-hold on the wall.   Gradually, we climbed up to 10 meters where we started a series of stops, before climbing to the surface. During the whole climb, the current pulled down on us.  The down-current only disappeared a few meters below the surface.

 

The whole time, my housing was bouncing around somewhere near my belly. The current was causing it to flap around like a flag in a wind.  It slammed into the wall quite a few times.

 

I expected to see lots of major gouges in the carbon-fibre and maybe even some scratches on the dome port.  But all was well.  Few minor scratches but purely cosmetic.  The housing survived very well.

 

I must confess that we did some damage to the coral and sponges on the wall while climbing up. I did try to place my hands carefully but all the handhold points were covered in marine life.   But, it was a life-threatening situation so I feel that our actions were justified.  When a current grabs you in Alor, you don't have a lot of choices.  Swimming up was impossible.  Swimming away from the wall would have probably killed us.

 

Regards

Peter




#355784 Video Light Filters

Posted by peterbkk on 24 December 2014 - 05:58 PM

Just curious, would the heat of the light melt/warp the plastic over time?

 

They won't melt underwater.  They sit about 1cm in front of the light so there is water on both sides of the plastic filter.  The heat is dissipated and they don't even get warm.  Out of the water, yes the thinner plastic filters will buckle quickly and melt in under a minute - maybe even burn...

 

I'm still struggle with the theory of the light filter a bit. Say the light is 5000K, without filter, the camera white balance would be set to Auto, or 5000K, but if you put a blue filter on, that will make the light become cooler, what white balance setting would you set on the camera?

 

I'm not sure we can easily describe a "unifying theory" using colour temperature numbers.  It's not just about the colour temperature in Kelvins.  The colour cast is also a major factor.  The sunlight hits the surface of the sea already influenced by the atmosphere (e.g. angle of the sun; clouds, etc.).  Then sunlight passes through the seawater, with the double effect of spectrum absorption, and the filter effect of the particles suspending in the seawater.  Lots of conditions in play.

 

So let's talk logic rather than theory.  The logic behind the video light filters:

  • putting some artificial video light on the subject, in some circumstances, will help punch up the contrast, improve background separation and help DoF and focus - and may slightly increase the red end of the spectrum on the subject (see caveat below)
  • during daylight hours, the sunlight will always dominate, especially in the further distance where the video light falls off
  • at depth, sunlight becomes much more blue or green, depending on the water
  • if the colour temperature of the subject (artificial light) is not similar to the ambient light (water-filtered sunlight) it looks artificial 
  • any color correction (WB) done in camera applies to the whole image so can not fix this problem
  • fixing the colour temperature imbalance in an editor is possible but not easy - keyed, secondary colour correction masks
  • so the best approach is to change the colour temperature and colour cast of the video lights to approximately the same as the ambient light
  • if the video light emits from the LEDs at the same colour temperature and cast as sunlight, then a coloured plastic filter can do the same to the video light as the water does to the sunlight - cool it down and apply a colour cast
  • then we can use the standard WB features in camera
  • and the primary colour correction features in the editor can easily bring the whole scene to the preferred look

Caveat: this approach is not going to put the red spectrum back into the whole scene - nothing can do that (unless we dive with humungous overhead video lights like a movie set).  The video light filters match the ambient sunlight so they are essentially reducing the red.  Depending on the colour of the video light filter that you select, you can add a little more red spectrum to the subject - but add too much and you are back to the imbalance problem that we are trying to solve.  

 

The five filters that I made (from the covers of plastic document holders):

  1. Light blue for shallow, clear tropical water
  2. Deep blue for deep, clear tropical water
  3. Light blue-green for shallow tropical water with some suspended plankton
  4. Deep blue-green-green for deeper tropical water and/or lots of suspended plankton
  5. Neutral milky diffuser for night dives to produce a soft light with gentle shadow edges

How does it work in practice:

  1. Select a video light filter that visibly matches the colour of the underwater ambient light, changing the filter depending on the conditions - e.g. a deeper blue filter might be required when deeper (does not need to be exact - close enough is good enough)
  2. White balance the camera for the whole scene (I use the presets - see below)
  3. Edit the footage, adjusting the colour correction to the preferred look.

Approach for using the camera presets for WB:

 

Rather that stuff-around with MWB while diving, I want to be able to quickly get to a WB that approximates the conditions.  The typical conditions are:

  1. Light blue colour cast - shallow, clear tropical water
  2. Deep blue colour cast - deep, clear tropical water
  3. Light blue-green colour cast - shallow tropical water with some suspended plankton
  4. Deep blue-green-green colour cast - deeper tropical water and/or lots of suspended plankton
  5. Video lights dominate (night, cave, etc.) - use AWB

So I made 4 A4 pages in PhotoShop that approximate each of those colour casts and printed them.  Then I put the pages in sunlight and took an MWB off each one, saving one into each of the 4 WB presets of the GH4 - then saving all the GH4 settings into the 3 Custom Sets (C1, C2, C3) that I had already created for different exposure / focusing custom sets.

 

I have attached a PDF of each of the 4 A4 pages that I use to create the WB presets.  I find that these presets work well in the tropical waters around Southeast Asia (e.g. the Light Green and Mid Green work in Lembeh).  The plastic filters are a similar range of colours but they are stronger colours with more blue.

 

Underwater, I simply assess the conditions, pop on the appropriate video light filter to the light heads, then flip through the WB presets to the preset that matches the ambient conditions (and the video light filter) and shoot.

 

Gets close enough to a good result that everything else can be easily fixed in FCPX.

 

Regards

Peter

Attached Files




#355666 Video Light Filters

Posted by peterbkk on 21 December 2014 - 02:31 AM

I mentioned in an earlier thread that I had been experimenting with some video light filters with the objective of finding a better balance between underwater ambient light and the broader (red) spectrum of artificial video lights.  Here is the problem, obvious in the screenshot below: the area covered by the video light has a lot of warm colour (reds and yellows) but the background is all greenish-blue.  Colour-correcting this scene is either a compromise or a complex exercise of selective secondary colour-corrections.

 

No Filter.png

 

I think that I've found a cheap DIY system that can solve this problem and can be tuned to most underwater ambient light circumstances.

 

The main component is a 4x4 filter holder made by Lee Filters.  It's all plastic and rubber so nothing to rust. $20USD each at BH Photo: http://www.bhphotovi...4x4_Filter.html

 

Here is the holder with an aqua filter (the same filter that I used in the shot further below)

 

IMG_1032.JPG

 

The slip-on rubber-band mounting system enables it to fit on most underwater video lights.  I use them on a pair of iTorch 7s but they also fit the Keldan Luma4s.

 

Here is folder mounted on the iTorch7.  It can be "wriggled on" easy enough and will not easily fall off - although I do take them off when getting into and out of the water so that they don't get bumped off.

 

IMG_1030.JPG

 

The filters are pieces of plastic that I cut from document folders that I bought in stationery shops.  I wandered around a few shops until I had found a mix of light blue, dark blue, aqua (green-blue) etc. The firmer document folder covers work best.  I also cut some uncoloured plastic squares that are a neutral colour but make a nice diffuser for softer macro lighting for night dives.

 

You can take a few different shades of the colour filters on each dive but I find that I can usually judge from the surface what I will need.  The technique is simply to look at the colour of the water and select a filter that is the closest match.  If the water looks tropical blue, use a blue filter; if it looks greenish, use an aqua coloured filter.

 

So, here is the result.  This is the same scene as above, shot with the aqua filter on both lights then quickly colour-corrected in FCPX to reduce the green and boost the reds.

 

Aqua Filter - Corrected.png

 

To my eyes, this image is very close to what it looked like underwater last week in Lembeh.

(the coconut octopus inside the drink bottle is guarding eggs and in the last few days of her life).

 

I have also used the same system in the deep blue waters of North Komodo, where a light blue filter worked best.

 

So for $40, some time wandering around stationery shops and a little bit of scissor work, you can make a video light filter system that will enable you to balance ambient and artificial light in most situations.

 

Regards

Peter




#355531 Questions for NA-GH4 users

Posted by peterbkk on 17 December 2014 - 11:33 AM

Hi all,
 
I had the chance to rent and use the NA-GH4 housing for a few dives to test it out. I'm on the fence and torn about the decision of buying one mainly because of the size of the housing. My problem is during custom white balance, and this is how I do it:
 
1.) Hand on right handle, using my index finger to trigger the WB menu
2.) Thumb press on the RIGHT cursor to select Custom WB, then UP to read WB, then SET to confirm WB.
 
When accessing the cursor area with my thumb, I can barely hold the right handle because my hand is not that big , and causing me to almost drop the housing a couple times
 
The question is, does anyone have success to operate the button one handed, by moving the handle bar a lot closer, or adding more float etc.?
 
I tend to use my left hand with a muck stick to stabilize on a sandy bottom or in between coral, and only operate the camera with my right hand, and I found the GH4 is hard to do so because of its size.

How small are your hands?

I don't have large hands but don't have any problems reaching the buttons while holding the NA-GH4 housing...

I use my thumb to activate the WB lever.

I do use the 4 preset WB settings just to make it faster to get to a setting I need (see other GH4 thread) but don't have an issue with the buttons.

I do use a float collar around the neck of the dome port to help keep it better balanced (see other GH4 thread).

I suggest that you practice with the housing, either on your kitchen table, in the bath or in a pool until the controls become familiar.

Regards
Peter


#355477 GH4 - Nauticam Macro Lens/Port Thoughts

Posted by peterbkk on 16 December 2014 - 04:15 AM

The "housing hydrophone" that I described above worked well in Lembeh. It's picked up all the usual underwater sounds (breathing, bubbles, shrimps and crabs, boat engines) and recorded a clear, bright stereo audio track in my GH4. Not bad at all for the price.


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#355177 3-Point Lighting, Spotlights, Snoots for Video Lights

Posted by peterbkk on 08 December 2014 - 02:45 PM

If my idea works, I will post a photo and sample results of the video light filter system that I've cobbled together. It can be used to reduce light levels, diffuse video lights for softer macro lighting and for balancing ambient daylight with video light. Testing it this week in Lembeh. Very cheap to make.

I did make a simple snoot for my last trip to Lembeh. Just a piece of hard 3mm rubber sheet rolled into a cone, held in shape with cable-ties and held onto to the video light with bungee cord. Worked OK. A bit fiddly to put on underwater. But, on my last dive of the trip, I took it off for a shot, placed it on the sand next to me, then swam away. It's probably still rolling around at the bottom of the Straits....

I was going to make another one for this trip but I put my attention into these video light filters - more important because I pan to shoot a lot of Wide-angle Close-up... Tomorrow!

Regards
Peter


#355176 GH4 - Nauticam Macro Lens/Port Thoughts

Posted by peterbkk on 08 December 2014 - 02:17 PM

Thats pretty cool... 
 
Check your serial number, there was an issue with the early GH4's and using external mics where there was a buzzing sound recorded, when you increased the gain.
 
A serial number lower than WE4FC will be affected.
 
Sadly as I jumped on one the first week they were released, my suffers...


I tested both my GH4s when this issue was first described. Neither of them have the problem.

As your camera must be still in the warranty period, why don't you send it to Panasonic to be fixed?

Regards
Peter


#355146 GH4 - Nauticam Macro Lens/Port Thoughts

Posted by peterbkk on 08 December 2014 - 03:03 AM

 

The thing about these cheap mini-jack lavalier mics that can plug into the camera is that they're unbalanced. A balanced XLR mic running off the Shogun's phantom power would give better quality. Although possibly not that important underwater where everything is noisy and muffled anyway. If you want to do interviews, I bet you soon end up with a balanced mic that plugs into your Shogun.

 

Anyway I like your idea of mounting a small mic against the inside of the housing.

 

 

So, I have setup my experimental, internal-to-housing hydrophone.

 

After looking at a few, I bought this microphone: 

 

IMG_1023.jpg

 

Cost about $50 USD here in Singapore.  It is marketed as a Lavalier mic for use with iPhones (there's an app for that).  Rode has a good reputation (made in Australia) - I figured that they wouldn't damage their reputation by selling junk.

 

It works OK with the GH4.  I did some quick comparisons and the sound quality is better than the inbuilt GH4 mic but not as good as my $500 shotgun mic.  Of course, for $50, you can not expect high-fidelity  --- but recording underwater sounds is not about fidelity.

 

The mic does fit into the housing.  The jack just squeezes into the gap between the housing and the camera.  Tight fit but the cable protector bends a bit.  It doesn't affect the alignment of the camera or the o-ring housing seal - passed a 30 minute vacuum test.

 

The microphone head, without its clip and wind sponge fits nicely up in the top corner of the housing up above the internal arm of flash pop-up lever.  That lever is helping hold the microphone in place (I never use flash).  The mic head is surrounded by lots of blu-tac, holding the face of the mic firmly up against inside wall of the housing.  It's not going to move.  The blu-tac also stops most airborne sound from inside the housing reaching the mic. The only sound reaching the mic comes through the housing wall.  The cable, looped tight with a couple of cable-ties, is held out of the way in the empty space above the camera's flash.

 

IMG_1025.jpg

 

It works - in that it is picking up sound through the housing. The camera's display is showing that audio is being received from an external mic.  I've set the camera to manual volume control (which switches on the meter display), so I might need to tweak the input volume then lock it into my underwater custom settings.

 

Will it record decent sound underwater?  I will let you know when I'm back from Lembeh next week.

 

In any case, if it doesn't work out, I can always use the mic as a garrote.  The cable is kevlar-reinforced and comes with a warning in the box, "strangulation hazard - the cable contains Kevlar - avoid looping the cable around the neck".  My enemies better watch out!

  

Regards

Peter




#355076 GH4 - Nauticam Macro Lens/Port Thoughts

Posted by peterbkk on 05 December 2014 - 07:57 PM

 

 

Interesting. I would have thought the buoyancy of that dome would pull the front up anyway. I now have the equivalent Nauticam dome but not got my rig underwater yet.
 

 

Nope, it's a little nose heavy.  Lot of metal and glass out in front of the balance point.  Maybe the Nauticam dome is lighter?

 

Not a big deal and manageable either way but I find that the styx neck-brace float takes the strain off the wrists.




#354110 GH4 with 14-42mm lens or LX100?

Posted by peterbkk on 07 November 2014 - 01:06 AM

Yes, the OIS in my 14-45 is Mega OIS and Power OIS should be better. I read some testing results in personal-view and most of them said LX100 has better stabilizer than 12-35, so I am not sure who's right and who's wrong.

Sorry I was talking about video image.

 

IMHO, you shouldn't be using OIS for underwater video - and therefore OIS should not be a major consideration in selecting underwater cameras or lenses.

 

OIS is designed to compensate for hand-shake - it's programmed for a particular type and range of motion.  Underwater, the housing is dampened by the water around it, removing the kind of hand-shake affect that OIS is designed to resolve.  Movement that is likely to spoil video underwater is caused by water currents, small and/or larger, and a hand-shake OIS algorithm is not going to deal with that effectively.

 

Even shooting "above water" video on a boat, the OIS is going to get confused by the wave action impacting the boat.

 

In fact, if you are going to be doing any panning or trucking movements, it's probably better to switch OIS off so that it doesn't cause jitter.  Better to work on developing good UW shooting technique for WA and get a tripod for CU shots.

 

Maybe one day a housing manufacturing will develop an internal gimbal with gyro-stabilisers to dampen underwater movements.  But, until that day, technique will serve you better than OIS...

 

Regards

Peter