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sharky1961

shutterspeed

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Hi,

 

I am going to Egypt this week hopefully shooting some thressure sharks. These sharks will be in a little deeper waters around 30-45 meters. To shoot them I have a few questions.

owning a VX2000 in light&motion housing.

1. to what depht will whitebalancing be possible with the vx2000?

2. what happens to whitebalance if I did MWB in 30 meters and suddenly there is a shark swimmming over my head so that I have to make a sequence against the sun?

3. normaly I have a shutterspeed of 50. What will happen if I increase shutterspeed to say 120, does this have the same effect as using the ND-filters?

4. should I use a redfilter in this depths? will it get to grainy with a filter or how can I avoid this?

 

 

Rob

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It really depends on the clarity of the water you're in. W/O a filter, the VX2000 can probably MWB compensate somewhat up to 13-15m, depending on the viz. I've had shots that were half decent down to 45m but this was in 50m viz on a very sunny day.

I would suggest you use 1/50 shutter speed and try it with and without the filter. You lose about 1.5-2 stops with a filter. 1/50-1/120 is about 1 stop.

If it were me, I'd shoot with filter and daylight WB and correct in post if the viz is decent. Obviously if the viz isn't great, then I'd leave the filter off.

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The vis should be good in the southern red sea, but light levels tend to take some time to come up and they drop very quickly at this time of year. The last time I was there in the winter was a couple of years ago and the dives before 10am and after 3pm were almost like diving in twilight once you got past 15m or so. That trip was around Sharm and Hurghada though, so you may have better light levels the further south you go.

 

Have a great trip!! :)

 

Cheers, Simon

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1. to what depht will whitebalancing be possible with the vx2000?

Rob, the VX2000 is excellent in low light. From what I recall Drew's figures are about right for no CC filter and with a UR-PRO CY filter I could white balance to 30m or even deeper (but see point 4, below).

 

2. what happens to whitebalance if I did MWB in 30 meters and suddenly there is a shark swimmming over my head so that I have to make a sequence against the sun?

Not usually much of a problem at those sort of depths, although at shallower depths like 10m then the surface tends to turn reddish. Think about water as a giant filter. Light travels from the surface to your subject, then bounces off the subject and travels to your camera. So the total path of filtered light is the addition of surface>subject plus subject>camera. So if you are at 30m and you are shooting straight at the surface you have 30m of filtration. If you are shooting a shark 5m away at that depth then you have 35m of filtration which proportionally isn't a great difference (ratio 6:7). However at 10m the difference would be 10m of filtration for a direct shot of the surface vs 15m of total filtration for the shark shot which is a ratio of 2:3. Don't worry, it's very easy to correct a reddish surface in your NLE with a keyframed colour balance or levels filter. I've done it loads of times.

 

3. normaly I have a shutterspeed of 50. What will happen if I increase shutterspeed to say 120, does this have the same effect as using the ND-filters?

It has basically the same effect on exposure but there is a crucial difference. If you keep the shutter at 1/50 then your camera is recording all the motion it sees over time. So each frame will be blurred (this is known as "motion blur") but when the frames are "joined together" as the video is played this gives the effect of smooth sharp motion. If you record at a higher shutter speed then the camera is simply not recording some of the motion and so on high-movement scenes you will get a staccato effect like a flip book. I found this out at my expense on my recent Lembeh trip where I used a lot of faster shutter speeds to reduce the light instead of ND filters. For example where I have baby anemonefish or sweetlips flapping their tail like crazy, the motion is "steppy" because of the gaps between recorded motion. If you're shooting say sharks zipping about then it would be a problem. It's not a problem for locked-down shots of cowries :) . Note that the camera "wants" you to use the ND filter rather than increase the shutter speed. If you leave shutter on auto it will prompt for ND filters if the iris cannot close down any further rather than increase the shutter speed. Spare a thought for those poor Phenom users who had to sacrifice ND filter access for access to manual white balance :( They have to use faster shutter speeds.

 

If I were you I would use 1/50 for everything unless you have ND2 flipped in and iris fully closed and you're still overexposed (in other words a submarine is heading straight at you with its lights on full beam).

 

Faster shutter speeds can in some circumstances be used as part of a strategy to make video look like film. A 24p camera like the V1 defaults to 1/48 and so will only capture half the motion, and film cameras often record at even faster shutter speeds. But with an interlaced camera like the VX2000 I would forget that.

 

The only other time you'd want a fast shutter is if you were shooting specifically for grabbing sharp stills from the footage.

 

4. should I use a redfilter in this depths? will it get to grainy with a filter or how can I avoid this?

Yes, when your iris can't open any further the camera gain will kick in. As this amount of gain increases the amount of graininess increases. So to prevent that all you can do is keep the filter out and then add artificial light if your subject is close (note you shouldn't try to increase light reaching the sensor by slowing your shutter slower than 1/50 on scenes with motion or you will get a "strobey" effect). But if your shallower footage is manually white balanced with a CC filter then you're going to have hell trying to match the footage in post. There will be this cut-off point between your colourful shallow footage and your monochrome green deep footage. Even if you light the foreground with your lights, the distant water will be a different colour.

 

This is why some shooters recommend not manually white balancing. But if you do that then you lose those wonderful colourful reef shots from around 15m where you manually white balance with the filter in place. The VX2000 is great at those and they can't be fully reproduced from footage that was shot with fixed daylight white balance. But you won't see many MWB shots like that on big productions like "Blue Planet". I think we love the shots from those productions regardless because of other factors that show the production quality like clarity, camera steadiness and accurate, fine differences in colour and tone. But if you're on a dive trip and show some nice manually white balanced footage with a full spectrum of colours it can blow the viewers away because you're revealing colour and detail that they couldn't see with their own eyes.

 

Some people talk about grain-due-to-gain like a total evil that you must avoid at all costs. I disagree with this. Sometimes it's better to accept some visible graininess than a massive shift in colour balance, which can look like a different dive site. In my Reef Life DVD I have a couple of shots from 35m or even deeper that were shot manually white balanced with the CC filter in and they look grainy but OK.

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1. to what depht will whitebalancing be possible with the vx2000?

 

can't speak for the VX2000 but our PDX10s which my team still use for their Daily Dive DVDs rock - they happily MWB down at 30m on a cloudy day! Imagine my dismay when I got my hands on our FX1s..... :) Your lens is larger than our PDX10s and - if I remember correctly - the VX200 has a lower minimum lux level - implying that it will see more light than the PDX10s, therefore implying that it should MWB down at a similar depth or more..... (maybe I'm wrong, but that's my presumption...) Maybe start a quick thread titled "VX2000 maximum MWB depth in tropics". You'll most likely get a VX2000 user (or ex) who can give you a fully informed answer....

 

2. what happens to whitebalance if I did MWB in 30 meters and suddenly there is a shark swimmming over my head so that I have to make a sequence against the sun?

 

In my experience - nothing. Down deep the vertical column of overhead water is still absorbing the red light whether you're looking at the sun or not.... it's when you come shallower - and less red light is absorbed - that it all starts getting freaky....

 

3. normaly I have a shutterspeed of 50. What will happen if I increase shutterspeed to say 120, does this have the same effect as using the ND-filters?

 

Don't forget, the shutter speed is virtual - it is always recording 50 fields/second. If you have it set to 1/50th it allows the light to hit the CCDs for 1/50th of a second. If you crank it up to 1/120th then it still opens and closes 50 times/second but only stays open for 1/120th of a second for each field. If you sat at the surface and it's over-exposing and hinting for you to turn on your ND filters, then by cranking up the shutter speed you will effectively be allowing less light in as the shutter will remain open for a shorter period. The ND filter prompt will also stop flashing..... Best to keep your ND filter off as if it's on and you head deep then the cam will crank up the gain creating grain... more on gain to follow... Don't forget that your iris / aperture will also affect how much light hits the CCDs.... e.g. if you have the cam set for auto iris / aperture and manual shutter speed and set that to 1/50th then you may be given a very high f-value of f10 or so on the surface in the tropics.... (as the bright sunlight will need to be stoppd from burning out the CCDs - just like your own iris in your eyes - stare at the midday sun and it shuts down to a pinprick-sized hole.....) if you then cranked up the shutter speed (allowing less light to hit your CCDs) then the cam will compensate by lowering the f-value (opening up the iris / aperture)......

 

4. should I use a redfilter in this depths? will it get to grainy with a filter or how can I avoid this?

Rob

 

the use of your CC filter seems to boil down to individual preferences - some say yes others say no.... We all fundamentally have the same aim, though - to obtain nice, crisp, sharp footage......

 

At the end of the day, work out at home first how much gain your cam can provide without creating too much grain..... Ideally plug it into your TV in a darkened room and check out at what level the gain increase creates an unacceptable level of grain... If you were to perform this test using only the cam's onboard monitor then - due to it's small size - you may not get the ideal result.... a little gain shouldn't do you too much harm... too much and your footage ends up looking like old VHS material!

 

good luck with it and - above all - have fun! hope you see the Threshers......

 

Chris

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Ha! ;);):guiness:

 

That'll teach me to take so long typing - Nick covered all those points brilliantly. Plus he's an aforementioned VX2000 user who could give you the informed facts....)

 

Anyways, next time I'll either type quicker and / or leabve all my pelling mitakes in thre wihtout correctinf anuy of them and generally save my time,

 

cheers Nickyboy!! :) P :(:guiness::blush::(

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Hi Nick,

 

Ignore any stick you get about your long post. For a novice like me with lots of new knobs to twiddle and buttons to press it was brilliant.

 

Cheers

 

Roger

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Spare a thought for those poor Phenom users who had to sacrifice ND filter access for access to manual white balance :) They have to use faster shutter speeds.

Ohhh that's harsh! :(

Faster shutter speeds can in some circumstances be used as part of a strategy to make video look like film. A 24p camera like the V1 defaults to 1/48 and so will only capture half the motion, and film cameras often record at even faster shutter speeds. But with an interlaced camera like the VX2000 I would forget that.

Nick, 24P cameras default to 1/48 because it mimics film based shutter speeds and thus effect. For example, the stoccato/effect in Saving Private Ryan's opening battle scenes were shot at 45° shutter opening at 24fps, effectively 1/192 shutter speed. However the standard 180° shutter gives 1/48 which is why the digital cameras follow suit.

The only other time you'd want a fast shutter is if you were shooting specifically for grabbing sharp stills from the footage.[\quote]

And also for specific slow motion shots. NLEs fill in frames so having less motion blur allows for better interpolation of video. The shutter speed is multiplied by the factor of delivery fps.

 

This is why some shooters recommend not manually white balancing.

Amen! ;) However that depends on the shot. Reef scenes and closeups are great in color but why bother with a whale in open sea? Or a long shot of a shark swimming in the open? Obviously the depth and turbidity rules the choices. A colorful reef may show up in WA shots but the color fades in the distance, which isn't always esthetically pleasing.

 

Some people talk about grain-due-to-gain like a total evil that you must avoid at all costs. I disagree with this. Sometimes it's better to accept some visible graininess than a massive shift in colour balance,

Those people shoot canon ;) There is always that addage of an ugly shot is better than no shot. However, your DVD is in SD, and with the advent of HD, everything that is not nice is vividly clear. Plus the soft grainy look can also ruin a sequence as badly as mismatched reef colors.

 

For most situations deeper situations, maintaining the shutter speed at 1/50 and letting the AE deal with the exposure. With the VX2k, I'd shoot at AE-1 because Sonys like to overexpose.

At depth, if your viz isn't great, I would seriously consider not doing a MWB at first. Get the shot of the thresher then experiment. Depends on how much time you have and what you want.

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Nick, 24P cameras default to 1/48 because it mimics film based shutter speeds and thus effect. For example, the stoccato/effect in Saving Private Ryan's opening battle scenes were shot at 45° shutter opening at 24fps, effectively 1/192 shutter speed. However the standard 180° shutter gives 1/48 which is why the digital cameras follow suit.

:wacko: *makes mental note to go and read about shutter angles on Wikipedia*

 

with the advent of HD, everything that is not nice is vividly clear. Plus the soft grainy look can also ruin a sequence as badly as mismatched reef colors.

True. And gain noise on my Z1 is kind of ugly, like horizontal lines. On my VX2000 it's literally just "grain".

 

At depth, if your viz isn't great, I would seriously consider not doing a MWB at first. Get the shot of the thresher then experiment. Depends on how much time you have and what you want.

But remember that the VX2000 doesn't like to make big jumps in white balance. So you can't just get all the way down there and then do a MWB. It won't do it. You need to do it in steps on the way down. But of course when you're down there you can switch to auto white balance to get your first shot and then back to MWB mode.

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And also for specific slow motion shots. NLEs fill in frames so having less motion blur allows for better interpolation of video. The shutter speed is multiplied by the factor of delivery fps.

Oh and thanks very much for this Drew. I hadn't really got my head around that, and having done almost zero slo-mo work myself, I hadn't learnt this the hard way yet.

 

So for example if I was deliberately shooting a cuttlefish feeding, I might be intending 1/4 delivery speed. So then I would want to aim for say 1/200 shutter, which is 4x default. Right?

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I have a question, Nick, on what you said about big jumps in MWB. I can't imagine what the technical reason is for that. Can you explain it? It would seem that if you do a WB you get "balanced" and why should the camera have a problem with it whether it's a big jump or a little one? Don't the electronics react the same way every time? I've read this before here on the forum but have never understood it. Why would Auto WB make any difference other than it continually corrects while MWB does an instant in time?

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I have a question, Nick, on what you said about big jumps in MWB. I can't imagine what the technical reason is for that. Can you explain it? It would seem that if you do a WB you get "balanced" and why should the camera have a problem with it whether it's a big jump or a little one? Don't the electronics react the same way every time? I've read this before here on the forum but have never understood it.

I have no idea either. It's just how the camera works internally. Remember that the cameras are not designed to work underwater, and once you're down there you're talking about a huge change from typical topside conditions. One of your 3 channels is almost entirely lost. So it's not surprising that the camera struggles. Some cameras seem to be better at it. Someone brought a Canon point-and-shoot stills camera on the boat and that seemed to be able to white balance on anything.

Why would Auto WB make any difference other than it continually corrects while MWB does an instant in time?

Not quite sure what you mean here but do you realise that an auto WB at depth, even with a red filter, gives a hugely different result from a MWB on something white?

post-3234-1194977421_thumb.jpg

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I was trying to say what I was thinking - possibly "dangerous" as my wife might say. I meant that if you leave it on AWB then the camera is continually correcting, isn't it? But if you (with the camera in manual mode) do a MWB, then it just makes a correction matching the instantaneous conditions? Probably shouldn't have thrown that in as it muddies the question.

 

My overall question is if the camera reads the conditions and makes a correction based on preconceived algorithms in the software which react to what is seen through the lens to the CCDs (or whatever receiving device the lens sends it to), I can't understand why it would make any difference whether you did it 10 times each ten feet along the way down to 100 feet or just did it once at 100 feet - if the scene and lighting were exactly the same at the 100-foot mark why should it make any difference? And I'm assuming the balance being set on the same white medium in this example - everything the same except that you do it a few times on the way down v. once when you get there and MWB in every case (no AWB in this case to foul up the experiment). Why would it make a difference how often you did a MWB on the way down v. once at the target depth?

 

Please - not questioning your experience or veracity. The questions are spawned from my ignorance; in fact I remember reading similar input from someone else on the forum. I've learned a great deal from reading what you and others here have posted. In this case I'm trying to understand what the physical phenomenon is that would make the difference.

 

PAUL

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I understand what you mean but if you don't do a MWB at all on the way down and then try to do one at depth, the camera just says "nope, i'm not doing that". The MWB symbol will just flash at you and the white balance will not change at all.

 

You'd have to ask a Sony engineer the exact reason why.

 

If you normally use say a white slate or a white fin or your hand to white balance, and you find you've descended too far and can't get a succesful MWB, you can sometimes rescue the situation by white balancing directly on the sun as a "halfway house", and then white balance on your slate/fin/hand. Otherwise you have to ascend until you can get a MWB or just accept the last MWB you did.

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OK - I think I get what you're saying now. In some cases you can get a WB if there was one earlier on, whereas right down from the top you might not be able to get it. I can see where that could happen as the differences hitting the algorithm might be too great for it to even try. Thanks.

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Nick,

 

Great first reply! Thanks for taking the time to write up your answer. Reading these kinds of posts really helps me to learn.

 

I also love your picture of the nine different color correction shots! What a great example for learning about the different effects that each methods has. I'm going to print it out for reference. I have just one question about something I noticed:

 

In the upper right picture, you say that this is "CC filter, MWB on the scene as shown, F4.0"

 

In the lower left picture, you say that this is "CC filter, MWB zoomed on sun, F3.7"

 

It seems strange to me that you would need a wider appature when shooting at the sun than when shooting at the scene. Can you explain this? Was the day partly cloudy, and the light level variable?

 

Thanks!

 

--Mark

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Mark, the iris was on auto and the iris value shown is what the camera gave me for the actual shot you see, not what it had been when I made the MWB. No doubt it would have been down at F11 or close when I pointed at the sun.

 

There is no significant difference in iris for all the shots with the CC filter in place, but it is worth noting the significantly bigger iris (F6.8, top left pic) where there was no CC filter in place.

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