DIY macro lens mount and strobe arm

Just for fun I thought I'd make a macro lens mount for my Lumix LX3 in Coolpix housing rig.

Here's what I came up with to hold the Inon UCL-165 M67 onto the dome port.

The 90x75 PVC pipe connector was close to a perfect fit. I stuck some neoprene tabs in the 90mm end to make it a tight fit over the dome port.

I slipped a ring of PVC in the 75mm end to stop the lens pushing all the way through and bolted on small brackets to hold it in place.

For higher magnification it would be better to use a flat port but this macro lens mount means I can do macro and wide on the same dive. A stronger or stacked macro lens would be better because the closest focus on long zoom only came down to 20cm.

I also wanted to reduce the overall size of the setup so replaced the double Ikelite handles with this simple aluminium tray/arm made from 50mm aluminium flat.

Using dioptres behind a dome port

Lenses used behind a dome port may require the addition of a +dioptre. The dome creates a curved image that sits 25 to 30cm out front and if the lens can't focus this close then a dioptre is needed.

My 18-55mm does work behind the 6" dome without a dioptre but performance improves with a +4. At the 18mm end there is less barrel distortion and the corners are sharper.

I never knew whether it also allowed you to get closer to the subject so some pool testing was required.

Adding the +4 brought the closest focus from 21cm to 13cm, and sharp corners only required f/16 rather than f/22. Of course you can use wider apertures if the corners are not critical.

Fibre Optic recording indicator

Here are the latest tweaks to the Stingray housing.

The previous magnet record switch was somewhat unreliable due to alignment and flexing issues. It was also very difficult to hear the camera beeps so I was never really sure whether it was recording.

Handles and a flexible loc-line strobe arm have been added.

The magnetic switch now works by pushing or repelling a "finger" through the housing-back and I have added a fibre optic "light pipe" so I can see when the red record indicator appears on the LCD screen. This fibre optic bundle comes from a $10 fibre optic lamp found at Toy Kingdom in Geelong West.

More photos here

Magnetic record switch

Here's what I came up with to stop and start recording underwater. The magnets came from Jaycar, a magnetic handy strip for less than $15. This plastic hanging strip contains about 8 magnets encased in a long plastic strip which can be cut to length.

An external magnet attracts the internal magnet operating the right angled lever. More photos here.
Works like a charm, if everything lines up properly.

The camera beeps to let me know if it's starting or stopping record mode.

UK light cannon 100 as video light

I adapted a stingray housing to fit my Canon MVX430 DV camera, which worked pretty well, but it really needed a video light.

These excellent HID dive torches are available for around $300 posted on ebay from lightcannontoys

Here is a 5 min video from Cottage Reef showing the Light Cannon in action.

I'm now working on a magnet switch to operate the record button while underwater. At the moment I have to start recording before the dive and just let it run for 1 hr. Makes editing a pain.

+4 dioptre investigation

Flickr contact Rikke Lind commented that it would be interesting to see a comparison of DOF, zoom level etc. with and without the +4 dioptre and I had to agree. I have always wondered whether dioptres actually magnify or just allow closer focus, so here's a series of images showing what happens.

The tests show that adding a +4 dioptre.......

Set focus of 1m reduces to 38cm and Infinity changes to 39cm.
Closest focus of 24cm reduces to 22cm, giving 1.44x mag.
So the focus range Infinity - 24cm changes to 39 - 22cm. Interesting, I thought the closest focus would be a lot closer not just by 2cm.

If the camera stays in one spot, the +4 gives a little bit of magnification, resulting in slightly reduced depth of field,
But if the camera is moved back to keep the image size constant then the depth of field is not reduced.
Note: Depth of field only depends on image magnification, (and aperture and sensor size) not which lens you use.

At 18mm zoom, aperture 3.5, the +4 changes barrel distortion into pincushion distortion and reduces corner blur and vignetting! Didn't expect that.



The reason we use dioptres underwater is mainly to enable your lens to focus on the virtual image created by the dome port, many lenses cant focus close enough on their own.
Or, as with my 18-55mm, to bring the closest focus to about 10cm from the dome for our rich but murky sub-temperate water.

Strobe arm floats

The housing and strobes are still quite heavy underwater especially with one strobe positioned for rim or back lighting.

To add a little buoyancy I cut 80mm sections off a pool noodle ($3.99 from Rebel Sports) and slipped them over the strobe arms. This made the rig much easier to handle underwater. The foam does compress a bit with depth but works beautifully for shallow dives. Could be improved with even longer foam sections.

This photo also shows the white velcro strips used to hold the sync cords to the strobe arms and the green lanyard and clip for hanging the rig from my shoulder d-ring.

The flags in the map behind mark Portsea Hole, Portsea Pier and Blairgowrie Marina.

Housing handle knob

When you put the housing down it balances precariously on the knob at the bottom of each handle.

I guess these knobs are for attaching accessories to the tray. The handles are secured by a thin nut not the knobs, so I removed them and now the housing sits on the tray base and is much more stable.
The blue covering is heat shrink tube just to cover the sharp thread. One day I may add a second nut just for peace of mind.

I also fixed the slipping control wheel problem.
I pulled off the slipping rubber ring then stuck it back on using thick, strong, foam backed double sided tape. This means the rubber ring now pushes harder on the camera control wheel.

D80 sunburst

Digital cameras generally don't capture sunbursts as well as film cameras. With just a little overexposure you end up with a big ugly cyan blob around the sun.

To get this image I had to reduce exposure as far as possible.

iso 100
1/200th
f/22
Sigma 15mm at 5m depth
Mid morning sun in about 5m horizontal vis.

Brain issue of the day: Just realized that because I wasn't using flash I could have used a shorter shutter speed. Fool!

Housing issue: The dial that operates the front control wheel has started sliding across the wheel rather than turning it. Will have to give the rubber ring more grip somehow.

Oceanic Shadow frameless mask

I've been keen to find the best mask for looking through the viewfinder and settled on the Oceanic Shadow after asking here.

This comparison shows the problem, you can't see the whole frame when composing the shot. Even without a mask this is about as much as you see. So you need a mask that does not make it worse by placing your eye too far from the eyepiece.

My Mares X Vision is a very comfortable wide view mask but the glass slopes forward at the top (to give better down view when diving) which puts your eye to far away.
My old Oceanic mask was better but has a deepish frame in front of the glass which clashes with the knobs and protrusions on the back of the housing.
The Oceanic frameless has a lower profile silicon rubber lip in front of the glass and one big wide glass lens. This means the you can put the glass right on to the eyepiece and even move around a bit to take in the whole frame. The black silicon blocks out light from the sides also. Mask photos here.

Leak detector instructions

Here are step by step instructions for putting together your own leak detector.

This one fits in my Coolpix 5000 housing. Just needs minor reconfiguration to fit other housings.

Sigma 15mm FE arrived today

The first thing needed was a comparison of angle of view. How wide is this lens with the DX sensor?
Being a fisheye lens the normal angle of view ratios dont apply. With a rectilinear lens you just multiply by the crop factor so a 15mm film rectilinear = 15 * 1.5 = 22.5mm on the D80. A 15mm fisheye is much wider than a 15mm rectilinear lens.

Nikon Coolpix 5000 with WC-E68 wide converter - TOP
Nikon D80 with Sigma 15mm FE - BOTTOM

The Coolpix wide setup gives the same angle of view as a 19mm lens on a full frame camera.
Calculation - 7.1mm Coolpix = 28mm film, multiplied by .68 (Wide adapter) = 19mm

D80 with Sigma 15mm FE gives a slightly wider horizontal view (maybe like an 18mm lens on film) and slightly less vertical view. So the equivalent would be about a 12mm rectilinear lens.
Calculation - 18mm divided by 1.5 (Crop factor for D80) = 12mm

Pay no attention to image quaity. Coolpix image cropped top and bottom from 4:3 to 3:2.

Blairgowrie marina 60mm macro

Jan, Trevor, Rich and I set off in the boat to Blairgowrie. It was a choppy trip over with 10kn easterly but conditions were great at the marina. This is probably the best pier dive in the bay. So many nudibranchs, gobies, blennies, crabs, cephalopods and abundant fixed life.

The 60mm macro was sensational here. 75 min and 100 shots passed too quickly. Here are the results.

We called in to Portsea Pier on the way back but recent pile works and annoying surge detracted from the dive. 2 dives at Blairgowrie in the future.

This was the first decent dive with the new rig. In a word.....awesome.
Now I feel like I am only limited by what I can find rather than whether the equipment can capture it.

First test in the ocean. 60mm macro

15th Sept 07
St Leonards Pier
Now for the real thing. The wind was in the right direction so the sea was flat but vis was bad, maybe 2m.
Most of the shots from the pool were underexposed so I darkened the review screen for this dive and of course most of the results turned out overexposed. I was checking the histogram occasionally but need to interpret it better next time.

Here are the results which I thought looked low contrast and washed out unfortunately. Needed a fair bit more Photoshopping than I'm used to.

First test in the neighbours pool. 60mm macro

14th Sept 2007
Time to get wet!
I asked over the fence if I could jump in the pool (still unheated from winter - 13c, so donned the drysuit and scuba gear) and after checking the orings too many times took the first slow steps into the water.

I took a few colourful objects to photograph like Nuditor the test nudibranch and Fragmento the test great white shark.

Using the 60mm macro and flat port here are a few of the first shots.
First impressions
The very first thing I noticed was the restricted view through the viewfinder! I was not expecting this! With my Mares X vision mask, which slopes forward at the top, I could not get my eye close enough to see the full view. Note: Next dive try my older smaller mask. (This improved the view markedly but could still be better)

Once I accepted this issue I started to have fun with the lightning fast and accurate autofocus. It was like using a real camera again, just brilliant.