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Expodisc White Balance Filter


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#121 CamDiver

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Posted 09 January 2007 - 07:38 PM

How thick is the 4x4 Expodisc?


"Gulp"! Mine's embedded in a whole pile of silicon sealant so can't measure it. Its made up of three elements but all told I don't think its more than 1/8th". Anyone else?

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#122 videodan

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Posted 09 January 2007 - 08:04 PM

Thanks Wagsy, but it's not a done deal yet, but good luck to you also. sjspeck, the three combined elements of my 77mm Expodisc are 6mm thick or .236". I would assume they would all be cut from the same material, so it should be the same for the 4 x 4. This is the thickness ot the filter elements removed from the holder. You can call Expoimaging for exact dimensions of the holder.
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#123 sjspeck

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Posted 09 January 2007 - 10:58 PM

sjspeck, the three combined elements of my 77mm Expodisc are 6mm thick or .236". I would assume they would all be cut from the same material, so it should be the same for the 4 x 4. This is the thickness ot the filter elements removed from the holder. You can call Expoimaging for exact dimensions of the holder.
Dan

Thanks for the quick response, but it sounds too thick for what I wanted to do. The existing plate is only a 1/8" thick and the slot is just under 1/4". So at .236, I don't think it would slide in/out. Not something I want to pay $200 for a filter to "modify" to find out.

#124 Nick Hope

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Posted 09 January 2007 - 11:07 PM

Yes, my 4"x4" Expodisc is 6.0mm thick. And the removable aluminium frame is 7.7mm thick. Now I just need to get around to fitting it.

Mark, the colours on your comparative stills look the same to me. Just the exposure is brighter with the slate.

Dan, your white balance is much bluer than I am getting with the Z1 using white duct tape on my fins.

In general I am finding white balanced video from the Z1 to be generally greyer and gloomier than my VX2000. Hence I'm now running a Picture Profile with the colour cranked up to +4. I think it's helping but I still don't have a proper monitoring method for the footage. Also in the day I was running in auto exposure mode a lot with the AE down at -1 or -2 but I've now just set that to 0 to counter the gloominess. Sometimes you've got to let the highlights blow out a bit can see the detail in the shadows.

#125 pablo

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Posted 15 January 2007 - 07:30 PM

Here’s my “mini-saga” on the Expodisc WB filter. I have an Ikelite housing and the filter size for the W/A lens is 67mm - I didn’t know that at first. I was simply thinking about getting an Expodisc for use with my SR1 on land, so I measured the width of the lens including the outer focus ring and etc. and then ordered a 67mm “cap” style Expodisc for $55. The people at Expo Images made it sound like a lens cover and not a filter type arrangement, so that was the closest size given that the OD of the lens was 2.5” or 63.5mm.
When I got the “cap” style Expodisc it turns out that it is actually designed to fit as if it were a screw-in filter. The little push buttons on opposite sides squeeze in a segment of filter threads so that they can then expand into the inner threads of a lens or adapter ring. That’s a nice idea but they sure didn’t explain it very well, The people at B&H Photo didn’t seem to be very knowledgeable either.

While waiting for the filter to arrive I had ordered the Ikelite W/A lens. After the Expodisc had arrived and I could see it wouldn’t work on the camera for land use, I called Ikelite and they told me that the filter size (i.e., threaded) for the W/A lens they shipped is 67mm. So then I began to think how I could utilize the filter I already had for U/W since it was exactly that size.

The “cap” style Expodisc has an outer frame with an inner ring which screws into it. It has two slots to install or remove. I suspect the manufacturer had a tool made that was just the right size. I went to a specialty tool store and bought a tool that I could adapt and got the ring unscrewed. Then I removed the round discs (the two “white” ones with the thin film in between). Then I took some silicone seal and adapted a small nozzle to the tube so that I could squeeze a thin line of the sealant around the flat shelf or edge where the discs sit before you screw the ring back in. I coated it, worked it into the threads, then reinstalled the screw-in ring. Then I coated the outside of the ring and joint around the Expodisc. It isn’t necessarily pretty with a bead of goop around the outside, but perhaps it has a chance of keeping seawater out of the inner areas now. The outer flat surfaces of the two discs making the filter “sandwich” are still going to be exposed to seawater, but perhaps they will survive that OK if they get rinsed after each dive.

When I talked to Ikelite I suggested they look at the Expodisc and consider making a waterproof version for U/W use. They seemed very interested in the idea but whether it will amount to anything or not is another question altogether; and Expo Images owns the rights and would control anything that happened, etc.

Meanwhile, if any of you are considering the “cap” style for land use, it works the same as the “non-cap” style (not the 4” x 4” model which is different altogether) except that you squeeze two little knobs to insert it into the filter threads and then release them – so far as I can see that saves having to actually screw the Expodisc on and off. The size you order is for the size of filter threads you would otherwise order for any other screw-in filter. For land use, I ordered an adapter to take my SR1 from 30mm to 37 mm, then another to get from 37mm to 52mm and ordered another Expodisc of the 52mm “cap” style size. So I'm set for land use at least.

I don’t know how this modified item is going to work, and in any event it may not help me with the Ikelite red filter that fits on the W/A lens. But that’s my story and I’m sticking to it. I’ll report when I get back from Tahiti (leaving this Sat.) on what works or doesn’t.

Edited by pablo, 16 January 2007 - 02:15 PM.


#126 Texas diver

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Posted 16 January 2007 - 09:26 AM

Anyone want to share ideas on how to make an Expodisc work on the Amphibico EVO for the A1 (wagsy?)? I'm open to ideas, and have a mini grinder.... :P

Thanks

Edited by Texas diver, 16 January 2007 - 09:27 AM.

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#127 pablo

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Posted 16 January 2007 - 06:37 PM

Update - more info: When the W/A lens arrived, it wasn't 67mm on the outward side (away from camera) but on the inward side. Ah, communications - how difficult they can be sometimes! Anyway, I took the cap that came with the housing, and cut a hole in it and mounted the 67mm Expodisc so that works fine for when I won't be using the W/A lens. Now I have to work on something for the W/A lens. Tommorw I'm ordering the 4x4 overnight to see if I can get something rigged up before we leave.

Does anyone know if it makes any difference whether the Expodisc is turned one way or the other? I would suspect that it has to be put in front of the lens in the expected direction but don't know for sure.

Edited by pablo, 16 January 2007 - 06:38 PM.


#128 Nick Hope

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Posted 18 January 2007 - 12:11 AM

Pablo I would say for sure it matter which way around it is because the whole point is that the little prisms gather light from a wide angle, and they will only work properly the correct way around. The frame on my 4"x4" also says which side should face the camera.

#129 videodan

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Posted 18 January 2007 - 04:43 PM

Pablo, as Nick says, you must have the clear prism side of the Expodisc facing your subject. The Expodisc must be in front of the color correction filter, then you manual white balance through both simultaneously, remove the Expodisc, and begin shooting through the color correction filter. Also, white balance toward the sun for wide angle shooting, and right on your subject for close up, and rebalance often while descending. Experiment and let us know how it worked. I wish you good luck, and have a great trip to Tahiti.
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#130 sjspeck

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Posted 20 January 2007 - 10:34 PM

Anyone want to share ideas on how to make an Expodisc work on the Amphibico EVO for the A1 (wagsy?)? I'm open to ideas, and have a mini grinder.... :D

Thanks

I've been looking for a way to mount the 4x4 Expodisc on my EVO for a few days now. But I haven't come up with a good solution.

What I think I'm going to do instead is order the 82MM Expodisc and just snap it on to the front of the port to WB.

Since the 82MM filter is 3.228" and the vertical dimension on the port is 3-3/8th", a small plastic piece glued in place should provide enough friction to hold it in place temporarily. Maybe something with a little ridge/dimple to snap it under. Should be able to make something with the Moto-Tool pretty easily. There's almost 1/2 in of black plastic on the top/bottom of the lens port to glue it to that isn't seen by the camera through the port.

I also plan to order the discontinued "Classic" Expodisc as it has a plastic housing as well as a nice little lanyard that should keep it nearby while shooting.

Edited by sjspeck, 20 January 2007 - 10:43 PM.


#131 Texas diver

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Posted 22 January 2007 - 03:15 PM

sjspeck-
Please keep us posted with the results of your modification. I was wondering if there was a way to use the slot where the white plastic lens protector is inserted, but I think it is bigger than 4x4.

Vic
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#132 sjspeck

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Posted 22 January 2007 - 05:05 PM

sjspeck-
Please keep us posted with the results of your modification. I was wondering if there was a way to use the slot where the white plastic lens protector is inserted, but I think it is bigger than 4x4.

Vic

That was my original plan but the 4x4 Expodisc is too thick. It actually would fit in the slot if it were thinner. Without the frame. See my previous posts here. And it would be impossible to widen the sides of the slot without a lot of grief.

So the only way to use it seems to be a flip down and there's not a lot of material on the top to secure it to since the slot is there. Unless you lengthened the arm of the flip down so you could screw it to the back of the port. But there's other screws back there already and Amphibico gas fills the port so that's not something I want to attempt.

I also thought about using some little u-shaped aluminum clips that would fasten to the outside edge of the metal frame of the Expodisc and be the right length so that when pushed into the slot from the top, they would hold it tight against the very front face of the port. But I don't know if you could drill into the Expodisc frame without shattering one or more of the elements while trying to attach it to the clips. And welding it seems like a really bad idea.

But then I thought of my new idea which seems simpler - and about $100 cheaper. I'll probably order it now and get around to it later next week, this week is too busy. Will post a picture if/when it's done.

I'm also thinking that a piece of velcro on the outside surface of the Expodisc with it's mate on the top (or bottom) of the inside lip of the port will be sufficient to hold it in place.

Edited by sjspeck, 22 January 2007 - 05:13 PM.


#133 pablo

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Posted 29 January 2007 - 08:41 PM

Here's my post on the Tahiti trip so far as the Expodisc stuff goes. Equipment: Sony HDR-SR1, Ikelite 6038.90 housing with Ikelite W/A lens. Pictures shot last week off Moorea, French Polynesia.

= = = = =

The first shot shows, on the left, the 82mm standard Expodisc I fixed up for the regular port (I just glued this one to the poly cap and you can spot where the sealant against the plastic cap was coming un-stuck on the left half but the filter itself didn't leak), and the stock "cap" model Expodisc that I got for land use. You just squeeze the two buttons (only one is visible from this angle) and snap the filter on or off. The part showing below it is a standard filter adapter to take the SR1's 30mm filter receptacle size to the 37mm of the most-appropriate Expodisc size.

For the second picture, I propped up the housing under a box, with W/A lens mounted (didn't have the base on it at the time) and showing the 4x4 Expodisc that was cut down to a 3 5/8" diameter and mounted within 2 aluminum rings I had a local shop fabricate for me. (The black lanyard is the CC filter on the W/A lens.) Before assembling everything with the 6 stainless steel screws/bolts/lockwashers I sealed all including the screws themselves, and then added a wiring terminal connector under the one bolt of the screw that I deliberately chose to be longer. Then I ran a small piece of line through the sleeve - the part you'd normally crimp - and tied a knot while making a loop on the other end that was large enough to slip the whole assembly through for attachment to the housing. If you get a terminal that's made for, say #10 wire like this one, then it's plenty strong enough to hold the whole cap; I didn't even worry about it hanging around when I was in the water (did note it float up into the bottom of the FOV once though). It was easy to slip the cap on and and off to do a W/B, although not as simple as the flip-up arrangement inside a housing like others have done. Unfortunately, this fancy one leaked for some reason. I guess I didn't coat something properly when I was assembling it the night before we left. I intend to dissasemble and redo it in the hopes that another attempt will seal it properly. The cost to have a machinist make the rings on short notice was about $175 so it wasn't cheap, but it did make a solid arrangement that doesn't look bad. The 4x4 filter cost $160 at B&H, although if you use this round configuration (v. rectangular) you could buy the $105, non-cap 82mm version like in the first shot and get the same effective filter exposure area while saving $55.

For anyone who wants to get the poly caps, here's a good source that is helpful, inexpensive, and has a lot of sizes from small to large: Alliance in Santa Fe Springs, CA: 800-847-0486. I bought a small batch of them to mess around with, from 3", 3 1/2, 4, to 4 1/2, etc. They cost from $3.50 to $5.25 each plus nominal shipping.

= = = = =

Then I have 4 shots taken with the camera after using the Expodisc for MWB. They were all taken from between 40 and 60 feet (sorry I can't be more precise). Since I don't yet have any HD editing software I shot in SD video. These were poor diving conditions: 30-40 feet of visibility, lots of junk in the water due to rain runoff and surge, and cloudy skies. The second dive was even worse that the first since there was more runoff by afternoon and the visibility lost another 10 feet from what it had been.

Given that we got in only two dives and that I was happy just to get the camera/housing operations all working and MWB done with the Expodisc, I didn't try to do comparisons like WB with a slate and then the Expodisc for the same shots like I had originally planned. I was glad to get things recorded after all was said and done although I know that makes the shots less valuable for comparison. But using the Expodisc the color reproduction is pretty true to what my eyes saw. (There is no PROC on any of these pics - just frame grabs saved as JPG files.) No lighting was used.

I have to say that I really love the SR1 and the hard disk type of operation. It's fast, easy to throw away junk shots, easy to save off, holds a monstrous capacity (6-7 hours of HD, 10-12 SD), and worked flawlessly. I do wish the "One-Touch" MWB were a button instead of a menu choice, but it was workable. It has a lot of nice features and is an excellent camera. And my land shots were really nice too so far as I was concerned.

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Attached Images

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  • f1.jpg
  • i1.jpg
  • i2.jpg
  • i3.jpg
  • i4.jpg

Edited by pablo, 29 January 2007 - 09:16 PM.


#134 Nick Hope

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Posted 31 January 2007 - 04:53 AM

To my eye they look on the warm side, particularly the last 3. The one of just coral looks like my footage looks if I've white balanced then ascended a few metres without white balancing again. Personally if I was using those in a project I would reduce the red.

When my Locline bits and pieces arrive I'll make a holder for my Expodisc, do some comparative tests and post them here.

#135 pablo

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Posted 02 February 2007 - 02:26 PM

It could very well be that I did ascend since the white balance in one or more of the shots. Would like to say, though, that the water was very brown due to the muddy runoff that was spilling gradually out of the reef entraces into the diving areas. And the reproductions - given that I don't have a computer monitor that is color balanced and all that kind of fine-tuned technical stuff - the raw shots reproduced very well to match what the "monitors" between my ears saw. If they were colder they would not represent what I saw.

I'm not that up to date anymore on various aspects of the video world (I go back to the old 2" tape hardware days!). I used to work as a sound/audio engineer in Hollywood and although I worked primarily in film that included video shoots at times. I was more up on video technology and such in those days but it's been quite a while, so I hesitate to suggest that my opinions amount to a lot in today's field. I do note, however, that a certain small portion of those responding to the Expodisc stuff in the forums here seem to like things colder than others. And it could be that using the Expodisc might actually require some re-balancing fo the filter components they're using in order to make it more true in an U/W environment. I've only had these two limited dives and was just happy, after all was said and done and all the setup and prep I went through to get to the point of the red "REC" lamp showing! - to just let the camera roll for two dives and see that I ended up with visible footage.

It was interesting that beyond not even having any rinse tanks, the dive operator and divemasters didn't seem to have any clue about what would be required to set up a video system. I told them in advance that I needed to stop around 10 feet for a minute and remove the W/A and filter and make sure the bubbles were cleared from the lenses (wet lens and wet filter) and set up W/A focus (getting it set and the locked to start with), and then to stop at the bottom long enough to do an initial MWB. Nevertheless they dropped on down the anchor line straight away and wandered off without me and I was left to locate and join them once I had things set up. I suppose this is something others have all adjusted to long ago but it was an interesting first experience for me. (When my wife was with me, as my partner she naturally hung around until I got those things done.)

#136 videodan

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Posted 02 February 2007 - 05:05 PM

Pablo, as long as you're happy, that's all that matters. Everybody has different tastes as to what looks like good color. Only the one who actually did the shooting knows for sure, and frame grabs do no justice compared to how the footage looks on a good HDTV. With your camera/housing combo manual white balancing is a chore, and you are not as likely to re-balance as often as people with "one touch" balancing would. I will not shoot without the Expodisc now, because of the great color balance I acheive with it, and the ability to get great white balancing far deeper than without it. My footage is excellent by anyone's standards, and far better than before I had one. I had to recapture some older tapes, and I cringe at the difference in color balance on some of the older stuff which is still great by most people's standards, but not up to par for me anymore. So tell us more about Tahiti, would like to hear about it.
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#137 sjspeck

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Posted 02 February 2007 - 05:44 PM

sjspeck-
Please keep us posted with the results of your modification. I was wondering if there was a way to use the slot where the white plastic lens protector is inserted, but I think it is bigger than 4x4.

Vic

Got my Expodisc yesterday. The 82MM metal one. Placing it in front of the lens on the outside of the EVO port it's almost a perfect fit. I cut the top off one of those stick-on cable clamps and that takes up the gap nicely. The piece of cable clamp also has a hole in it for a screw which catches part of the Expodisc outer ring, so it "snaps" in yet you can easily pop it out. The piece is just under 1/8" thick.

#138 pablo

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Posted 03 February 2007 - 04:40 PM

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

DAN: I posted a Tahiti trip report in the "Crazy Dive Stories and Trip Reports" forum. I tried to add in all the details about the trip (besides camera tech stuff, etc.) there. If you have any additional questions from what's there please feel free to ask.

#139 wagsy

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Posted 03 February 2007 - 04:58 PM

Hey sjspeck

Do you mean it just slid into the slot at the front?
Great work. :blink:

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#140 sjspeck

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Posted 04 February 2007 - 12:12 AM

Hey sjspeck

Do you mean it just slid into the slot at the front?
Great work. :blink:

No, it's too wide for the slot. It's just literally on top of the port and the piece of the clip secures it in place. You can see it at the top of the port in this photo:
http://www.scubaboar...00/ppuser/25243

Edited by sjspeck, 04 February 2007 - 12:27 AM.