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Strobe or Continuous Ligting


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#1 bvanant

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Posted 18 May 2003 - 09:57 AM

This may be an heretical question, but given the fact that with most Digital SLRs underwater, the magic of ATTL, DTTL, xTTl doesn't work well and we need to use the strobes manually, would you not be better off with continuous lighting. If you use strobes, you have no shutter speed control, only f stop and thus DOF. If you use continuous, you might be able to trade off perfect exposures and DOF, while with strobes you need to re-power and re-shoot. Are there unknown benefits of strobes (power maybe) that need to be considered? Just wondering and looking lustfully at my wife's video lights that look like they might mount directly on my Sea and Sea D60 rig.

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#2 craig

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Posted 18 May 2003 - 10:14 AM

Power is the issue. I tried dual 50W video lights on a night dive and did not have enough light to get exposures with my D100. Stronger lights or a faster camera may improve things, but strobes offer a great deal more firepower in a smaller package.

You would find it much easier to make manual strobes work right that make continuous lighting strong enough.
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#3 marscuba

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Posted 18 May 2003 - 05:22 PM

Dual 50W halogen or HID lights?

#4 bvanant

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Posted 20 May 2003 - 12:47 PM

To further Matt's point, is it thus true that digital video is much more sensitive than digital still? If that is true, it is surprising since I would have thought that the sensor technology and thus the amplification electronics should be roughly parallel.
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#5 craig

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Posted 20 May 2003 - 04:59 PM

Dual 50W halogen or HID lights?

50W halogen. Won't find no HID in my bag. My 50W bulbs provide about 1000 lumens each in my application. LMI HID lamps by comparison are 1300 lumens.

Digital video has very low resolution compared to digital still. It's circle of confusion can be much larger due to it's poor resolution, so it has good DOF even at low numerical apertures. It's pixel sites are still quite large compared to digital still of similar sensor size, so I believe intuitively that digital video has a significant light sensitivity advantage. That's not considering 3CCD vs. 1CCD, but now days 3CCD cameras offer very good low light performance.

I tried dual 50W halogens in Watervisions heads. I mentioned that because Watervisions heads are quite wasteful of light. Still, my setup provided reasonable illumination over a field broad enough for the Nikon 16mm fisheye that I shot with, and I was using a D100 which has a minimum ISO of 200. I could not get satisfactory stop motion of fast action even at f/2.8. It was my intention to use 100W, 3000 lumen bulbs but I screwed up.

I believe 50W halogens may be acceptable for P&S cameras without wide angle optics, but I believe you'll be disappointed with their performance with a D60. For anyone considering HID, their inherently low CRI means they render color poorly, so performance will be worse than strobe or halogen. For photography work, the standard rule is that lights should have a CRI of at least 90, but you could probably bend that a little. Typical lower power HID lights have CRI's of 70-75 and are not suitable.
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#6 marscuba

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Posted 20 May 2003 - 06:56 PM

The reason I asked is that I just sold a dual 50W HID video light setup...has yet to be tested out on a L&M video housing system.

I didn't think the CRI was so low, but for 10W HID, could be.

Are we talking about CoCs for digital now?!?

#7 craig

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Posted 20 May 2003 - 07:49 PM

The reason I asked is that I just sold a dual 50W HID video light setup...has yet to be tested out on a L&M video housing system.

I didn't think the CRI was so low, but for 10W HID, could be.

Are we talking about CoCs for digital now?!?

CRI for the lower wattage HID lamps is low---well below 80. People confuse them with HMI which are specifically modified to raise their CRI to be suitable for photographic use.

I brought up CoC because the CoC for digital video is actually much larger than the traditional 25-30 micron definition since their resolving power is so poor. For that reason a videographer can get away with a much larger aperture and feel like he gets greater light sensitivity. In a way, he does. A friend of mine is shooting HD video and really struggles with critical focus. In his work he's using massively powerful lights to shoot macro because, like still photographers, he needs much more light than NTSC/PAL videographers are accustomed to. His base setup is 1000W/40,000 lumens of combined power but he's trying to bump that up with surface-fed lights.
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#8 Alex_Mustard

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Posted 21 May 2003 - 03:26 AM

I am rather a fan of a particular continuous light source with digital.

It is called the sun and if you choose you dive site and the time of your dive carefully it is a great way to light digital images. Its quite bright too, though it doesn't seem to work well here in the UK.

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#9 james

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Posted 21 May 2003 - 04:59 AM

Alex,

Craig and I will send you some - we have plenty here in Texas right now.

Cheers
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#10 Simon K.

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Posted 21 May 2003 - 05:25 AM

Its quite bright too, though it doesn't seem to work well here in the UK.


we have plenty here in Texas right now.



It seems to have region code 1 and you need to have region code 2 version in Europe.

You can also use a codefree sky but this is illegal ;-)

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#11 Alex_Mustard

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Posted 21 May 2003 - 05:58 AM

I managed to get the sun to work when I was in Spain, yesterday. They seem to have some patch working.

I was there to give a talk at a scientific symposium on plankton.

Digital cameras are proliferating in plankton imaging systems these days and there were several papers at the symposium on the subject. Some of the high magnification techniques might be of interest to wetpixel people. The only stuff I could find quickly on the web is here. There are a few lab movies of close-ups of copepods doing stuff (pretty cool if you read the text). There are also some new low light, fast virtual shutter speed cameras being used which might have creative interest for UW photographers for taking impossible shots in available light?

Have any wetpixel people played around with some of the more unusual digital cameras underwater. I have been trialing a Swiss built camera in the lab to photograph plankton from a moving ship. The CMOS camera is capable of incredible shutter speeds in low light and lets us freeze <0.5mm animals and identify them while they whizz by. (Flash isn't fast enough to stop them!). It takes C mount lenses and would be fun to try UW.

Sorry got a bit off topic there. Alex

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#12 Craig Ruaux

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Posted 21 May 2003 - 06:13 AM

Alex, the plankton imaging system sounds monstrously cool.

I have always had this urge to take a phase contrast microscope out into the gulf to photograph plankton, but our microscopy people don't want to loan one to me :D . Perhaps I should just lie...

I will agree with James, we have plenty of that sun stuff going on here at the moment and could probably spare you some (though this morning is cloudy and cool, which is a pleasant change). Have you ever noticed that PAL sunlight seems to be more "pastel" than NTSC (well, NTSC in the south west anyway).

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#13 Simon K.

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Posted 21 May 2003 - 06:35 AM

The Plankton videos are really great!

#14 Helge Suess

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Posted 17 June 2003 - 11:58 PM

Hi!

I used 2 halogen lights 50W mounted on the camera and a 3rd mounted on my buddy :D for macro pictures. It works pretty good. I wasn't fully satisfied with wideangle shoots because the light didn't reach that far. I'm currently processing the images I took in México during my holidays in May. They'll be online as soon as I recovered from the crash of my raid array. Macro samples from the Philippines and the Sudan are already online.
I'll take sample images (halogen, HID, flash) the coming weekend. I'll get a LED video light later this year for testing too. I think, that continous light has the big advantage to help the autofocus to do its job. It also scares off creepy creatures :(
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