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L&M Bluefin HD AE Override Mod


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#1 Nick Hope

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Posted 14 March 2007 - 11:07 PM

One drawback with the Light and Motion Bluefin HD housing for the Sony FX1/Z1 is that there is no access to the 3-position GAIN switch.

This means that you have only 2 choices for gain: Either auto or a single pre-selected value.

Personally when running in manual exposure mode I find this somewhat limiting because:

1. I don't really want to have the gain permanently set to something higher than zero as this is unnecessary where there is a lot of light and may introduce noise.
2. I also don't want the gain permanently set to zero because when I'm deep and the subject is out of range of my lights the picture gets dark and I need some gain.
3. I don't want to run in auto all the time because sometimes this introduces unwanted blown-out highlights, especially when using lights against a dark background.

OK, it is possible to set a gain limit in a picture profile so you could have various picture profiles with various gain limits set but this is rather cumbersome and the gain levels are not fixed, just limited.

I decided that for a lot of the time I would like to try running in auto (or partial-auto with shutter speed locked) but with the camera's AE Override mode on.

So what I did was order up a spare FX1 side button actuator moulding (Part #661-1044-A) from L&M and modify it so that the housing's IRIS button actually operates Assign button 3 which I have programmed to operate AE Override.

I cut out some parts of the moulding and superglued on an extra-long arm made from a piece of rigid dive slate. It does exactly what I intended and has lasted 20 dives so far. The attached picture should explain.

Once the housing's IRIS button is pressed, AE Override is activated and the IRIS knob on the housing becomes a simple "darker/brighter" control, operating a combination of IRIS and GAIN to +7 or -7 increments which is enough to compensate for blown-out highlights, even on night dives with silvery fish against jet black backgrounds. As far as I can tell, AE Override will adjust IRIS until it's fully open and then GAIN after that but I must admit I haven't analysed my tape data code yet to check exactly what's happening. If desired the shutter speed can be left on 50 or 60 or whatever to stop that from changing. One could additionally set AE shift down a stop or two in a picture profile, but I have stopped doing this to keep my footage nice and bright.

The downside of my mod is that the exposure cannot be fully locked. This hasn't bothered me so far because the vast majority of my shots are fairly static and with a constant light level. I was shooting a boxfish at night the other day and the exposure was pumping a bit as it rotated, but this was the only time that I've thought a locked exposure might have been better. Having AE Response set to "middle" seems to be best. On "Fast" there would be more pumping as the exposure changes and on slow I don't think it would change quick enough. I think the type of scenario where a non-locked exposure might be more of a problem is if one was inside a wreck, panning across bright windows. Then the exposure would pump no matter what I did and a fully locked exposure would be preferable.

I'm by no means suggesting that everyone goes off and does this to their housing, but for "run and gun" style underwater work it definitely makes life easier.

Attached Images

  • AEoverride.JPG


#2 CamDiver

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Posted 14 March 2007 - 11:35 PM

Hi Nick,
This is what I am talking about when so many people ask me about underwater video housing selection etc. The camera or housing is only half the issue. One of the main things is that you start with a housing and then you tailor it to suit your needs or shooting style. I must admit way back when I would moan and get niggled that the gear I had didn't do exactly what I wanted it to do. Manufacturers are going for the numbers, the common denominator so they generally tend to put out housings that allow the shooter to access the gimmick features of the cameras or even hold the shooter to ransom if he / she wants to have access to those controls deemed an absolute necessity for professional manipulation of the housing. That said, camera and housing manufacturers are in business to make money, period.

So to be able to step back, take a look at what you've got and asses what you need to do to get what you want from the lot you have is a very important part of this work. It takes balls and guts to take a hacksaw, drill or other power tool to a precision piece of equipment in order to 'bodge' together a solution to your needs but something that needs to be done in most cases nonetheless.

Congrats on your customization technique. With the Gates I don't have access to pic profile anyway. I always work manually with gain, shutter speed, exposure and of course focus. Ain't it pleasing to get those great locked down shots?

Cheers,
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#3 DeanB

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Posted 15 March 2007 - 12:35 AM

Nick,

I'm starting to think you were the 'Idea's' creator for Blue Peter... :rolleyes:

Or the mad scientist in back to the future..

Or even one of the A-team we didn't see... :ninja:

Good on ya

Dive safe

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#4 Nick Hope

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Posted 15 March 2007 - 01:15 AM

Haha Dean, I never even got a Blue Peter badge, despite all those hours spent watching John Noakes and Peter Purvess (and slobbering over the young Sarah Greene). Saved up shitloads of silver bottle tops though!

Mark, it didn't take much bravery, I've still got the other untouched moulding so I can switch to the standard setup any time I need to.

I always work manually with gain, shutter speed, exposure and of course focus. Ain't it pleasing to get those great locked down shots?

Sure but I find it's also really easy to get wrong, especially in a fairly rushed situation, which is often the case for me. The shutter can be locked off at 50 for most situations (PAL camera), and the zebras help, but it's still easy to screw up the exposure, especially in bright surroundings and come out with footage that's too dark or bright. Switching to full auto, then back to full manual, is something I've done to get the exposure right to start with in terms of what the camera thinks it should be, but that stuff takes time I often don't have in front of skittish marine life.

All that being said, if I had full access to the gain control, as you have, I may well perservere and use full manual more often.

#5 wagsy

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Posted 15 March 2007 - 01:30 AM

Nick
Can you get into the camera's menu?
If so you can change the db setting in that while underwater.
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#6 Nick Hope

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Posted 15 March 2007 - 02:54 AM

Yes Wags, that's another option and one I haven't tried underwater yet. But it's a bit involved:

1. Press menu button
2. Press SEL/PUSH EXEC dial
3. Rotate dial to GAIN SETUP
4. Press SEL/PUSH EXEC dial
5. Press SEL/PUSH EXEC dial again (assuming switch is on H, otherwise more rotating needed)
6. Rotate SEL/PUSH EXEC dial to desired setting (0 to 18 in 3dB increments)
7. Press SEL/PUSH EXEC dial
8. Press menu button

But I suppose I could put GAIN SETUP at the top of the P-menu, which I also have access to. That would get rid of steps 3 and 4 but it's still a lot to do frequently during a dive.

On a typical dive lit by ambient dive I guess one could do this two or three times on the way down and two or three times on the way up. But say I was set up at depth with 9dB and something swam overhead, I'd want to go back to a lower dB setting very quickly. I guess then I could just go auto with the one-push gain button and let the gain find it's own lower level.

Thanks for pointing that out though Wags. I will switch back to the standard setup for some dives and try it.

#7 wagsy

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Posted 15 March 2007 - 03:17 AM

Well at least you can get to it if you really have to, thats the same this end, but I only ever go to 3 max. Normaly locked off on 0.
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#8 Nick Hope

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Posted 15 March 2007 - 03:35 AM

For shallower well-lit dives I think what you're doing is the right solution. However I'm quite regularly down in the gloomy 30s or 40s at the start of dives but then spending a long time shallower later in the dive (my Aladdin Pro seems to like it that way round :rolleyes: ).