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which of 3 strobes for cave diving, imaging for science

strobes cave research lighting budget mapping cave diving inon sea & sea wide angle

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#1 Aotus

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Posted 27 February 2018 - 05:02 PM

Hi.

 

I need a set of strobes to help collect surface images of the cave floor. That means flat, even lighting, while shooting 5-15' above the floor. That also means not interested in macro abilities or dramatic shadows or contrast, really not for making pretty shots (though maybe when the opportunity arises).

 

For this project, I expected to be using someone else's rig that worked well for me on a previous project in which we used video lights. The lights worked well enough because the canon 5D is awesome in low light, but still there was some edge effects that were less than ideal. This time, I will be using my own Panasonic Lumix Lx10. I like video lights, and was planning to purchase some, but everyone keeps telling me that for less money, I can get brighter light for my stills with strobes. Since this wasn't an expected expense that I could have written into my grant, I will be buying these strobes with my own money... and I'm a grad student, so that ain't a deep pool to dive. I'm looking at three budget options: Inon S-2000, Sea & Sea ys-01, and ys-03.

 

Someone at Backscatter told me that I should steer clear of the ys-03 because I will probably want lower power shots for the cave, and there's no manual control. My thought was that my focus light will allow the camera to communicate the need for a lower power flash if need be. But, more control options are usually better. Backscatter also has an article that found that the YS-01 is a lot brighter than the S-2000. But, the S-2000 has the external accessible sensor that may mean I have a wireless option to play with if I need it.

 

Any insights from more experienced photographers would be super helpful.

Thanks for any comments.

Cheers.

 


Edited by Aotus, 27 February 2018 - 07:41 PM.


#2 trimix125

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Posted 28 February 2018 - 06:41 AM

Hi,
what size will the square have, you want to lighten?
In a cave you normally never have enought light ;-))

I would think of a diffusor, and instead of S2000 of a pair of D2000.
Gives you more power and more uniform lightning.
And you can easily operate them manuall, have an external sensor.....

Regards,
Wolfgang

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#3 ChrisRoss

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Posted 28 February 2018 - 05:16 PM

I would think you might be pushing things a little with the small strobes and your stated distance away and assuming normal f stops as light falls off very quickly in water.  Why 5-15' away, why not a wider angle or more shots and closer, the stobes are closer so the small strobes would be more likely to be able to provide enough light.

 

An alternative might be to watch the classifieds, two INOn Z-240s went for about $700 recently.



#4 Aotus

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Posted 28 February 2018 - 09:07 PM

I can get closer than that, but it begins to become very inefficient. with a pair of Sola 3000 video lights and a Canon 5d mkiii I was able to get good enough images at 5-10 feet above the floor. This time I am using a less impressive camera, but the 5D was overkill and seemed to have a lot more light sensitivity than i was even taking full advantage of.

 

My understanding, from other posts, is that even these smaller (PN 20) strobes will produce more light than the Solas (3000lm). Does that sound right?

 

I'd love to find some more powerful strobes that I can afford. I created a WTB post here: http://wetpixel.com/...showtopic=61654


Edited by Aotus, 28 February 2018 - 09:37 PM.


#5 Aotus

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Posted 02 March 2018 - 03:49 PM

i've made some progress in assessing these options.... basically i've decided they aren't the best options. So, I'm looking for some more powerful used strobes. if I can't score some, I might go back to video lights because I know what works and I have connections to get discounts.

 

here's a good discussion: http://wetpixel.com/...showtopic=59961



#6 bvanant

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Posted 03 March 2018 - 12:05 PM

Remember what a GN is. GN=Fstop x distance 

For a z240 which has a GN of 24 (on land) you can expect perhaps 12 (in clear water) this means that at 15 feet (lets assume 5 meters) you will need and f:stop of 2.4 at ISO 100. Of course you can boost the ISO but strobes underwater are not meant to light up caves. For caves to get good detail I think you will need multiple strobes. If it were me, I would use the camera in movie mode and use some big video lights (yes I know you are a grad student and budgets are real) but perhaps you could rent some.

Otherwise use several strobes, you might find some good used ones here on wet pixel.

Bill


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#7 Aotus

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Posted 03 March 2018 - 04:43 PM

Remember what a GN is. GN=Fstop x distance 
For a z240 which has a GN of 24 (on land) you can expect perhaps 12 (in clear water) this means that at 15 feet (lets assume 5 meters) you will need and f:stop of 2.4 at ISO 100. Of course you can boost the ISO but strobes underwater are not meant to light up caves. For caves to get good detail I think you will need multiple strobes. If it were me, I would use the camera in movie mode and use some big video lights (yes I know you are a grad student and budgets are real) but perhaps you could rent some.
Otherwise use several strobes, you might find some good used ones here on wet pixel.
Bill

 
I'm so confused by this - I was using video lights but everyone has told me that strobes will be brighter. 
 
For example:
http://uwlightdude.c...ll-photography/
http://wetpixel.com/...showtopic=56895
https://www.scubaboa...s-light.379817/
 
I could go with video lights, and I know what I'm doing with them better, but plan on using strobes because they're supposed to have more punch. DISTANCE shouldn't matter, right? if the strobe emits more light, then it should cover more area given the same diffuser (and I know they'll be different, but assuming everything else is constant, brightness = coverage).
 
If I'm wrong about any of this, PLEASE correct me. I'm trying to learn this through the internet and there is not east way to test anything for myself before I spend a lot of money.

I have a pair of sea & sea ys-d1 strobes on the way (haven't tried them yet), but if I need to use video light instead I could still go that direction. Any thoughts are very much appreciated.


Edited by Aotus, 03 March 2018 - 07:54 PM.


#8 Barmaglot

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Posted 04 March 2018 - 12:15 AM

A strobe emits a single strong pulse of light that is only a few milliseconds long (disregarding high-speed sync here). This is useful for freezing motion with a short exposure (typically 1/250s or 1/160s for system cameras; less for compact cameras with a leaf shutter), and constant lights can't get even close to a strobe's brightness within that brief instant. However, if you're photographing static subjects (which it sounds like you are), and can manage a long exposure (very much not trivial underwater, but not impossible), you can end up gathering more luminous flux from a constant light than you would from a strobe.

 

All things being equal, distance is the factor that matters the absolute most - the intensity of the reflected light that reaches your camera lens decreases with the fourth power of distance between the emitter/receiver (your camera rig with lights) and the subject - i.e., if you double the distance (for example, from 5 feet to 10 feet), the amount of light that reaches your lens decreases sixteenfold. Triple the distance (from 5 feet to 15 feet) and your light goes down by a factor of eighty-one. The LX10 has a fixed lens, so it can't natively go wider than 24mm equivalent (add 30% for a flat port), but I would suggest considering getting closer to the floor and either using a wet wide lens to increase the field of view so that you can cover the same area from a shorter distance, or just taking more smaller images and stitching them together in software later on.



#9 Aotus

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Posted 04 March 2018 - 08:07 AM

thanks for those comments. 

 

I have a wet wide angle lens. in much of the space I will be shooting from 5', because there isn't enough room overhead to get any higher. 5' really don't feel very far at all, and unless i don't understand about these strobes, i have a hard time believing that they don't have a good punch and spread at 5 or even 10'. My primary light blows out a shot if the spot is in the frame even at 15' from the camera.

 

 

I guess there will just have to be a trial day to see how well it does in different scenarios. 



#10 Barmaglot

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Posted 04 March 2018 - 08:16 AM

Your primary light is illuminating a relatively tiny spot - concentrating the beam does wonders for light intensity, but it doesn't help you take photos. With a wide-beam video light, those thousands of lumens of output get spread over tens or even hundreds of times as much surface area, with a corresponding decrease in returned light. Also, if you have an overall dark picture, with a small spot brightly illuminated by your light, the camera is likely to do its metering on the dark areas, and unless you're lugging a dynamic range monster like a D850, the bright spot illuminated by the light will get blown out.



#11 Aotus

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Posted 04 March 2018 - 10:05 AM

that makes sense.

 

 

OK, so from the previous post, you do still think that strobes are the better option, but that I should be mindful of my distance. right?



#12 bvanant

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Posted 04 March 2018 - 01:04 PM

I am not sure about the 4th power you are thinking about, I think it really is the inverse square law that is in effect here. In any case, you will have more light (photons/second) from strobes but you do need to remember the whole guide number thing.  It is really hard to get really soft and still bright LED lamps, using a wide diffuser on a strobe will give you more light.

Bill


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#13 Aotus

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Posted 04 March 2018 - 01:08 PM

thanks.

 

 

I may start another thread about diffusers, because I don't know if the aftermarket dome diffusers are worth the money. 

 

(edit: I DID start that thread, here: http://wetpixel.com/...howtopic=61675)


Edited by Aotus, 05 March 2018 - 07:08 AM.


#14 Barmaglot

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Posted 04 March 2018 - 01:14 PM

I am not sure about the 4th power you are thinking about, I think it really is the inverse square law that is in effect here

 

It's inverse square when you go one way (emitter to target), but then it's another inverse square when you go back from reflector to receiver, yielding a total of fourth power reduction.







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