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#1 Andi Voeltz

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Posted 27 July 2002 - 08:31 AM

...yeah guys, I don't mean the song from Creed (which is obviously nice)! :)

But you may guess when it's posted on wetpixel.com that it is a strobe arm question. I am currently a single strobe user and still try to figure out the advantages of buying a second subtronic alpha pro which will hurt my wallet with 1.075

I already own one and am very satisfied with it. It is very strong * almost too strong when it comes to macro * and can be charged without opening. Furthermore it has an integrated modelling light and access to all controls on the backside, status LEDs etc. What's also very fine is, that it fully supports the Nikonos TTL protocol. But it is a Mercedes Benz if you consider that I am still shooting with a Coolpix 990 (Volkswagen).

But I considered it as a long time investment, assuming that I would be shooting with a Nikon digital SLR someday.

I have seen on many pictures from Eric's D60 divepages, that the pros generally have two strobes to get full coverage. Also they have their strobe arms really wide open. I assume that this is for optimum perfomance when doing uw wide angles. If you take a look at Eric's
shots the results are very convincing.

As I have no experience in 2 strobe photgraphy, I'd like to know the following from some of you guys...

1. do you keep the strobes in the same position during whole dive, once unfolded?

2. If yes, can you still do macros (I hardly can believe that) or do you reposition the strobes in this case? both of them or only one? (I'd like to know as I already have a quick release on my strobe arm, when doing macros)...

3. Some of Eric's shots really look like he was able to brake the law's of physics. Can you still illuminate stuff that is more far than 3 metres with two really strong strobes? It looks like magic, on some of the shark pictures? How close have you really been?

4. What intensity do you use for wide angle,... still TTL - or do you control the two strobes manually from the camera? ..or are they set two full power?

5. If you have both strobes about 1.5 meters away from the cam, does that solve *almost* any backscatter problem?

That's basicly some stuff to start with... Any comments on further developement of my rig would be nice... Also don't really know which camera to buy next... But if I stay with the subtronic strobes, I'll stick with Nikon. Which is not that bad at all ;-)...

Cheers Guyz .oOo. Andi

PS: I already have the arms etc. just need a second sync cord with a dublicator, which is not that difficult I think...
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#2 SharpDiver

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Posted 28 July 2002 - 03:33 PM

In answer to your questions:

1. do you keep the strobes in the same position during whole dive, once unfolded?


No. I change strobe position for almost every shot. But then, I am using a zoom camera (Olympus C-4040) and shooting a variety of framing styles (wide, medium and macro). This is why I consider my arms a vital part of my camera system.

2. If yes, can you still do macros (I hardly can believe that) or do you reposition the strobes in this case? both of them or only one? (I'd like to know as I already have a quick release on my strobe arm, when doing macros)...


I shoot macro with both strobes. I usually bring them in tight and set the right slightly lower power than the left.

3. Some of Eric's shots really look like he was able to brake the law's of physics. Can you still illuminate stuff that is more far than 3 metres with two really strong strobes? It looks like magic, on some of the shark pictures? How close have you really been?


I am not Eric, so I can't say for sure, but it looks to me like he is well within three meters. And no matter how good he is, he cannot violate the laws of physics. 3 meters is a stretch. 2 to 2.5 is closer.

4. What intensity do you use for wide angle,... still TTL - or do you control the two strobes manually from the camera? ..or are they set two full power?


All manual, all the time. I think I would do this even if it was not mandated by my system.

5. If you have both strobes about 1.5 meters away from the cam, does that solve *almost* any backscatter problem?


That depends on the amount of particulate in the water. "Almost", yes. In low visibility, far removed from your subject, the angle will be difficult to light your subject and not light some particulate.

#3 Tio Loco

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Posted 28 July 2002 - 09:27 PM

Andi,

re: your backscatter question, we had a presentation at our Colorado Underwater Photographic Society meeting one month by Carl Brownd, an award winning local photographer known for his wide angle work.

I've tried to illustrate his technique with these diagrams. In the first you can see that with the strobes aimed at the subject, the illumination from the strobes intersects at some point between the camera and the subject.

image

The result that any particulate in that path is illuminated. Carl's technique is to actually aim the strobes outward, so that just the edge of the illumination catches the subject. This is a very crude illustration, but I think it illustrates the concept. In actuallity, with a wide coverage angle, the strobes should be angled outward instead of straight ahead as I have illustrated.


image

This way, even if particulate is present, it is not illuminated.

I made sense to me, and it sure works for him.

Richard

#4 Andi Voeltz

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Posted 29 July 2002 - 04:07 AM

I am not Eric, so I can't say for sure, but it looks to me like he is well within three meters. And no matter how good he is, he cannot violate the laws of physics. 3 meters is a stretch. 2 to 2.5 is closer.

Hy Jeff,
Thanks for answering... But I think you ran into the mistake, which I previously stated here. *My Fault* Of course you don't have full 3 metres for a colourful illumination. Red colour disappears after 3 metres. But you have to take into account that the light has to travel from the strobe to the object and then back to the camera lens. That leaves a max. of 1.5 m for each way. So the max. distance had to be around 1.5m - which I doubt very strongly. I think either the White Balance of the D60 is very good or Eric helped with some photoshopping...

I assume it's probably both :)

2 Tio Loco: Sorry for not really getting it on the first reading, but you recommend the method shown in the second picture, right? By the way, the pics are very informative! Is the full presentation available somewhere on the net?

Thanks, Andi
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#5 Tio Loco

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Posted 29 July 2002 - 07:12 AM

Yes Andi, the second illustration is the recommended concept to eliminate backscatter in your pix.

Carl uses what he calls the 'Rule of Thumbs' as a guide. Rest your hand, (relaxed) above the camera with your thumb pointed along the axis of the lens, like so:

image

Then point your strobes along the axis of your fingers. Granted, this will vary as different strobes have different angles of coverage, but just use it as a general guideline.

Unfortunately, Carl's presentation is not available on the web to my knowledge, although it would be a good thing to add. I'm doing the illustrations on the fly. I will try to contact him and see what we can put together.

Richard

#6 Andi Voeltz

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Posted 29 July 2002 - 07:32 AM

Hi Tio,

for myself I just did some calculations. My strobe is sprecified to 85 ... I substracted this from 180 and divided the rest by two. By this I had the angle between my camera and the "last ray of light" (=47.5) , assuming that I'll point the strobe right forward. As the strobes will be 105cm away from my cam you can do the following math exercise to see where their light lines will cross...

just take: tan(47.5) * 105 cm = 114.6 cm

114.6 cm is the minimal distance beetween you object and the lense! If you get closer you'll not be able to illuminate it with your strobes... Am I right? So it's a true wide angle configuration :) :P :D
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#7 Tio Loco

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Posted 29 July 2002 - 09:53 AM

Well, Andi I won't argue with your math, mainly because just talking about tangents makes me cross-eyed. Again, the illustrations (particularly the straight-ahead example) were just crude approximations to illustrate the point. Carl's Rule of Thumbs is also just a starting guide point. As digi-heads we have the advantage of being able to experiment with angles and see the result immediately, which is a huge advantage in this context.

My intent was just to shed some light (no pun intended) on your question #5 about backscatter. Point being that while distance from the camera to the strobe to the subject figures into the equation, strobe angle is equally or more important. If you don't illuminate the particulate matter, you don't have backscatter.

Until I heard this presentation it really didn't occur to me how to minimize backscatter this way. By instinct, I think most people just aim their strobes at their subject. I hope this has been some help.

Richard

#8 james

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Posted 29 July 2002 - 11:28 AM

Hi Andi,

Eric was shooting the 14mm lens for most of those pictures so no zoom. In most cases when shooting wideangle w/ two strobes, you don't move them around (too much). You might move them for CFWA for example compared to openwater shooting...

OTOH, it's best to keep your strobes aimed as shown in the graphix above.

Cheers
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#9 RogerCarlson

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Posted 01 August 2002 - 07:00 PM

Barry Lipman has sample pix of all this (and more) here:

http://www.barrylipm...otogs/BS/BS.htm