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Expodisc White Balance Filter


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#141 sjspeck

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Posted 04 February 2007 - 12:21 AM

To SJSPECK: Seems like the EVO port is an oval one, then?
It will be interesting to see what kind of results you get.

The EVO port is actually rectangular. The 82MM Expodisc completely covers the lens opening in the port. So it should work fine. See the photo Wagsy provided or the one in my previous post.

Edited by sjspeck, 04 February 2007 - 12:22 AM.


#142 Texas diver

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Posted 05 February 2007 - 11:00 AM

SJSPECK can you provide some pictures of the cable clamps and how they attach the filter? The installation looks very good. Have you had a chance to try it out underwater yet?

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#143 sjspeck

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Posted 06 February 2007 - 06:25 AM

SJSPECK can you provide some pictures of the cable clamps and how they attach the filter? The installation looks very good. Have you had a chance to try it out underwater yet?

Thanks,
Vic

There's only one "clamp" and it's visible at the top of the photo - the white piece between the port wall and the Expodisc. Right now it's just sitting there but it will be stuck and epoxied to the port wall unless I find something better in black. It's a friction fit between the clip and the metal ring of the Expodisc. So it doesn't attach to the Expodisc at all. The bottom surface of the Expodisc just sits on the bottom lip of the port.

Attaching it to the top means that it won't be visible through the camera, notice how your red filter doesn't flip all the way up. So the camera's not seeing the entire port either.

The clip is made by Wire Slips and is called a cable clip. All I did was remove the two holding tabs and it fit perfectly. PM your address and I'll send you a couple. Photo: http://www.scubaboar...00/ppuser/25243

I just got it Friday and there's not a lot of water in Arizona.... :D

I have no doubt that it will work though, the Expodisc snaps in and is held firmly in place. I smacked the housing hard repeatedly and it didn't move. There's a little nub on the clamp that also holds the Expodisc firmly in place and keeps it from shifting side to side.

Edited by sjspeck, 06 February 2007 - 12:00 PM.


#144 Nick Hope

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Posted 09 February 2007 - 01:51 AM

Pablo, please don't think that I was criticizing, I was merely giving you some feedback based on what I'd think if I'd shot that footage myself. And I am perhaps over-sensitive to "warm" footage after years of reducing the red in footage that was shot shallower than my last MWB.

Like you say, the water is a different colour in different parts of the world. "Correct" white balance is totally subjective anyway. One could argue that we should white balance against a perfect white at depth to "reveal" the colours we would see if we lifted the reef to the surface, while another could argue that we should white balance against a perfect white at the surface to show the "truth" that most of the warm end of the spectrum has gone at depth. And in a way they'd both be right.

#145 pablo

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Posted 09 February 2007 - 08:13 AM

No problem at all, Nick. I appreciate the great input from long-time people in the highly-experienced end of the spectrum. Heck, I'm not even shooting in HD yet until I sort out the AVCHD and editing software stuff.

#146 Nick Hope

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Posted 15 March 2007 - 09:31 AM

Finally got around to trying an Expodisc with my L&M Bluefin / Sony Z1P.

Unlike others who've tried the Expodisc in place of the flip macro or flip CC filter inside the housing, I didn't want to sacrifice either of those because I use them both on just about every day time dive I do. So instead mine flips down outside the housing. This also saved me getting another UR-Pro filter.

A 4" x 4" standard Expodisc (not the "warm" one) mail-ordered from Adorama in the US is mounted in a rectangle of white dive slate. Naturally a load of gaffer tape keeps it from falling apart. The "hinge" is made of 3 strips good old sticky-back velcro and gaffer tape. Three strips of the soft side of the velcro are stuck to the top of the 80-degree port. A single "tab" of velcro at the bottom of the slate holds the slate down during the white balance procedure, and up at other times by velcroing it to my LCD shade.

I need to zoom in to something like 80 on the scale of 1-99 for the Expodisc to fill the field of view. It gets partially flooded between the elements of the Expodisc during use, and there may be a little difference in functionality from having it dry and internal, but I doubt it's much different. And the elements are all plastic, so I don't see much danger in them being wet.

If I was to use this much I would want a better hinge system on top such as something using press-studs because on one dive it actually fell off as I jumped into the water. However I'm not sure I'm going to be using it often as I'm not overly impressed with the results, which I'll put in the next post...

Attached Images

  • expodisc_down.jpg
  • expodic_up.jpg


#147 Nick Hope

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Posted 15 March 2007 - 10:07 AM

OK, so armed with my shiny new external Expodisc, I set about a WHITE BALANCE GIANT TEST.

The first round of tests was in 17m of clear blue water at the Burma Banks. The shutter was 1/50 and the gain 0dB on all shots. I left the iris on auto to try and even up the brightness of the various tests, and that sort of worked.

Anyway here are my own comments on the results:

1. No CC filter, auto white balance
Well it's very monochrome bluish green as expected but F6.8 is a much smaller iris than the other results with the CC filter in.
2. CC filter, auto white balance
Shows what a CC filter by itself can add but iris needs to open to F3.4 to compensate.
3. CC filter, manual white balance on the scene itself
A bit wishy washy and blue for my liking but that's not surprising with a lot of pale brown coral in the scene
4. CC filter, manual white balance on a white fin well lit by the sun (bottom right in pic)
This has been my regular method in recent years but it's definitely too red here.
5. CC filter, manual white balance zoomed in on the sun (bottom left in pic)
I like this result
6. CC filter, manual white balance zoomed on palm of hand (centre bottom in pic)
This is my favourite result of all. I think the slight pinkness of skin throws back the reds in the result a bit. After this test, this is how I started white balancing for the rest of that trip.
7. CC filter, manual white balance on Expodisc aiming towards sun
Too brown! Browner than just pointing at the sun without the Expodisc.
8. CC filter, manual white balance on Expodisc aiming at the scene
Still too brown, and surprisingly similar to the other Expodisc results, indicating the amount of averaging that the Expodisc is doing and that it doesn't seem to matter too much where you point it.
9. CC filter, manual white balance on Expodisc aiming at distant horizon
Basically the same result as aiming at the scene.

So for blue water I'm not really that impressed with the results of my Expodisc implementation. I will try to post the tests from greener water tomorrow. I'll also try and analyse the results more scientifically using the scopes/histogram in Vegas and/or Photoshop.

If you want the full size 1920 x 1080 JPEG of each white balance test you can download them here.

Attached Images

  • white_balance_17m_blue_water.jpg


#148 limeyx

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Posted 15 March 2007 - 11:43 AM

OK, so armed with my shiny new external Expodisc, I set about a WHITE BALANCE GIANT TEST.
...


I definitely prefer the "Hand" one also -- followed by the "Sun" Wb

#149 DeanB

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Posted 15 March 2007 - 12:00 PM

I liked the handjob as well...

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#150 Scuba_SI

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Posted 15 March 2007 - 12:56 PM

Dude!

Your housing has quite a bit of build up on the metal already, have you found a solution for rinse water yet?

i'd go for the hand and sun too

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#151 MikeVeitch

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Posted 15 March 2007 - 03:32 PM

thanks for that Nick, good job

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#152 videodan

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Posted 15 March 2007 - 04:02 PM

Hi Nick, great test. Too bad your results were not favorable. I wish I knew why others are not getting the same results as I get. I shot this Saturday in the Florida Keys on the wrecks USS Duane and the USS Speigel Grove, down to a depth of 99' (30M) and had excellent results. Perfect color and no browns. This is well below the depths where my camera can manually white balance without the Expodisc, so I couldn't do a comparison. I will try to do some shallower dives this weekend and do a test similar to yours so we can compare results. Maybe getting water in yours somehow changed how it works. Try sealing it up with a hot melt glue gun.
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#153 shawnh

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Posted 15 March 2007 - 04:22 PM

Dan and Nick,

I have come to the opinion that WHERE you shoot has everything to do with how much you like the expo disk. I filmed in both Palm Beach and Bahamas and was very happy with my expo results. Even at 80 feet in the Bahamas i was able to achieve pleasing results with the expodisc (with and without cc filter). I used it in SE Asia (Bali and Raja) and was quite disapppointed. I used it at all depths and in sunny and over-cast days (in all the locations). Intersting...

The reefs in Florida and Bahamas are much less vibrant than in SE Asia. The water is a distictly differenent blue color in these locations. I can imagine the combination of water color and underlying reef color may explain the difference.

Nick, thanks for the comprehensive tests....gotta respect that kind of thoroughness. Also, glad you also find the hand works the best. My hand and "pink" slate are too of my favorite CC options. I also Use the surface as a mainstay. Perhaps we are closing in on a general set of principles for UW white balance with HDV that applies to most folks.

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#154 wagsy

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Posted 15 March 2007 - 06:45 PM

Nick
You get a big GOLD STAR for that...well done my friend. :(
Great work. :ninja: :rolleyes:

WB on anything till one is happy with the colour and at the sun for deeper depths is my way and set it to auto db, exposure & shutter if it's having trouble at depth to get a fix then back to manual.

Have never used my own hand though...to WB that is :(
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#155 MikeVeitch

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Posted 15 March 2007 - 06:53 PM

interesting about the sun, i am never happy with the colours i get when i WB off the sun....


I much prefer my off white slate....

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#156 Nick Hope

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Posted 15 March 2007 - 07:44 PM

Thanks for the feedback guys.

The great thing about using my hand is that generally I know where it is and it tends not to become detatched on entry. Plus with Shawn's "cuddle the housing" techinque it's less of a contortion than aiming the camera at a fin. With some housings I imagine white balancing on a hand would be impossible, unless you have 3 of them.

Should have really had a pink fin or slate in these tests for real thoroughness. Next time perhaps.

Simon, no I haven't yet, other than deciding I should dry the whole housing after each dive, not just the glass port. My old Stingray II housing has plenty of "build up" like that but it never advanced to what I would call "corrosion" so I'm not desperately concerned yet.

More results from different coloured water shortly...

#157 Nick Hope

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Posted 16 March 2007 - 02:53 AM

By the way, that first set of tests above was soon after midday and in extremely clear blue water well offshore at the Burma Banks. So loads of light for the depth and not really typical of the other dive sites in the Andaman.

I did a similar set of tests at 1pm in about 23m at Hin Taleh (Fan Forest Pinnacle) which is further inland in the Mergui Archipelago where the water was much less clear and rather green. Again the shutter was at 1/50 throughout and gain at 0dB except for one test where it crept upto 3dB.

This time the Expodisc performed much better and my favourite of the bunch this time would be the white balance on the Expodisc aimed towards the sun.

Again the three Expodisc results are pretty similar, indicating that it doesn't seem to matter much where you point it, it just refracts and averages the light passing through it.

White balance on the hand is my next favourite but not really green enough considering the conditions. Pretty good again though, and definitely passable if you don't have an Expodisc!

White balance zoomed in on the sun came out too blue and wishy washy for me this time.

White balance on a white fin was truly horrible this time. Much too red. In fact I think I'm basically going to stop using that technique completely as it hasn't impressed in either test. And to be fair, I had to reduce the red on most of the clips in my Reef Life DVD that were balanced that way with my VX2K.

So this time the Expodisc wins it, although I feel a similar result could probably be achieved with exactly the right tone of pink on a slate or fin.

So Shawn, looks like you're absolutely right in saying that the location and conditions play a huge part in whether the Expodisc is a benefit or not.

Dan, I doubt the repair changed the function of my camera. I didn't notice any difference before and after the repair. Likewise I doubt the partial flooding of the Expodisc has changed things much, but I suppose it's possible. Don't really want to seal up the edges yet just in case I decide to sell it.

Again the full res grabs, deinterlaced this time, are on my server if you wish to download them.

I did some more tests at Richeleu Rock. I'll check them out and post them up if they add anything to the debate.

Attached Images

  • white_balance_23m_green_water.jpg


#158 DeanB

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Posted 16 March 2007 - 04:34 AM

To be honest after trying different tactics myself and reading everyones points of view..

Wouldn't we say W/B and colour is all a bit circumstantial to where we are and also personal preference..What is the right colour..What I see or what you see..Or what the viewer will see.

If you get it close enough to YOUR personal taste then enhance it in post...Fair play.

We all seem to be looking for the one true colour..But is there really such a thing. I've seen so many variations on different programmes of what filmmakers perceive as good colour balance but sometimes it does not look right to me...

Will we ever be happy

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#159 Nick Hope

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Posted 16 March 2007 - 05:08 AM

I guess my aim with a lot of the heavily white balanced footage is to make the subjects in the foregroud look similar to how they would if they were lifted to the surface. But if you look at Mark's Palau turtle in the other thread, that looks great and is obviously not manually white balanced much, if at all. So yes, it's all subjective. If Mark and I tried a joint venture with our Z1 footage, we'd be buggered because nothing would match. Likewise if a third party sourced footage from both of us.

This exercise has been useful however to weed out techniques that obviously over-correct the footage or skew the colour temperature in the wrong direction. For example those overly red or overly blue results.

#160 DeanB

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Posted 16 March 2007 - 07:20 AM

Don't get me wrong big boy...

The tests you did were great and very informative..But I just think, as its been said, you'll get different variations of CC where you live and what conditions you dive in...If your happy with what you have achieved then fantastic..But don't fret to much..Results can be reached in other ways.

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