which of 3 strobes for cave diving, imaging for science

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.

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

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.

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/forums/index.php?showtopic=61654

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/forums/index.php?showtopic=59961

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

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.com/strobe-vs-video-light-for-still-photography/

http://wetpixel.com/forums/index.php?showtopic=56895

https://www.scubaboard.com/community/threads/strobe-vs-continuous-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.

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.

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.

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.

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?

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

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/forums/index.php?showtopic=61675)

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.

Hi Aotus,

Just to check, making photos of cave floor, is it for photogrametry purpose?

I think its very important to define what kind of photos you really need to take.

In underwater photogrametry and for 3D reconstruction quality of picture is based on completely different set of parameters.

Geometry (including edge sharpnes) and frame overlaping is far more important than standard quality of each recorded photo. Basically, for this purpose ypu dont care about noise, its ok to set ISO of your camera to almost highest value, in order to reduce strobe power and recycle time. Gained noise will be insignificant in creating dense cloud and rendering of overal cave model. Than its important to be able to shoot as many as possible photos during one dive ensuring suitable overlaping. In this case its important to select strobe with great battery autonomy.

For that purpose friend of mine, who is expert in archeology uw photogrametry selected Ikelite DS161 strobes - huge battery capacity for money. I understand those are expensive strobes, but just trying to reference strobe selection cryteria regarding its purpose.

If I missed your focus and ussage purpose, please forgive me and ignore this post.

Regards,

Marko

One thing I can say for sure is stay away from anything Sea & Sea. If you already have something from them, sell it. I had a YSD2 and since it was new the battery contacts had issues sometimes and right when I would enter the water it would just shut off, even with brand new batteries. I scraped to all the contacts as clean as I could and it seemed to work a little better after that. Still frustrating for something brand new. Now It is no longer usable after it flooded through the strobe section of it's housing. The battery compartment was completely dry but water was around the bulb. I sent it in to get fixed and after around three months of nothing, they finally tell me they can't fix it and I'm just out $700 dollars. It was only 14 months old and the warranty was only 12 months so they wouldn't replace it either.

I've had the opportunity to use some of Big Blue Lights 15,000 lm and 25,000 lumen video lights. These are very bright and would definitely work for you. The only problem is the edge of where the light stops is very sharp. So if turned on and pointed toward a completely black wall, it would be a very sharp edged circle. I've been looking into diffusers for them that would feather the edge. There is no comparison between these and a 3,000 lumen video light. In fact a 3,00 lumen video light won't do much and is just on the edge of being enough light with such a wide flat spread. All that being said, I would definitely rather have a strobe for still photos than I would a video light. Even compared to the 2,500lm light, I can get brighter shots with a strobe.

I started cave diving a couple years ago and have been working on under water photography in the caves since I started. Not nearly as much experience as some but I can tell you what I've tried and am going to use for myself. Every cave photographer I've seen use Ikelite strobes. I've been borrowing a friends DS125 for a little while and have been very happy with what it's capable of. I've also got a DS161 I recently purchased that should arrive any day.

I've already done the research for you and have been looking into this specific topic for the last two years.I've also been researching for friends to get some strobes to photograph caves within the same parameters you listed. If you can afford it, the DS161 with Li-on batteries is the way to go. Since you're on a budget, I'm going to recommend the same thing for you as I do my own friends. Just get some DS125 and you'll be set. They are by far the cheapest and most durable strobe that will work well for you. I saw a pair of them go recently for around $375 but usually they're $200 a piece. They also have two different diffusers available as well depending on how soft you need the light.

thanks very much for all the great comments.

Marko - yes, you're right, for photogrammetry. That's an interesting point about graininess and ISO. I'll have to test that idea.

Fruit - thanks very much. I won't be able to make a change for this trip, because I leave this week. But I may have a chance to swap the strobes for the next trip next summer. I REALLY hope these work out for my needs, but having another field season already on the calendar allows for some mistakes. About the video lights, BigBlue look good but the output declines quickly, much faster and less even than Light&Motion or other lights. For you, or anyone else here with an interest, some white plastic bag and a rubber band works well to smooth out those sharp edges if you don't have a proper diffuser. As for brightness, using the light&motion 3k lights i got fine results from about 1.5-2 meters, but that was with a canon 5Diii, which is more capable in low light than my lumix LX10. I'l report back and post some images when I return next month.

thanks again.

Hi,
that a lot of cave divers is using Ikelites, is no wonder...
Most cavers in mexico are americans, and Ikelite is a lot cheaper there....

Inon strobes are fine, easy to change batteries, not waiting for loading or expensive batterie packs.
Had / have some D2000 & Z240, work fine ...
Have / had because i have tried to get now only type 4..
Will ignite even without a fibre wire cable!

Sea & Sea had great strobes, specially the YS 250 pro if you need a lot of light ;-))
The newer onces are a bit heavy to ignite, and have troubles with the flash tubes...

Please tell us your results and show us some pics!!!
Wish i could spend more time in caves-...

Regards,
Wolfgang

I just got my Ds161 in the mail and thought I would do a comparison of output powers . It wasn't exactly controlled but close enough to get the idea. I set up a DS125 and DS161 in the same spot and then at a marked distance about 20 inches away took a reading with my Sekonic 758 light meter. The DS161 has ten power levels and the 125 only has 4. The lowest power setting on the the DS125 was level 3 on the DS161 meaning you could go almost 2 stops lower on the DS161. Each level on the DS161 was about .5 EV at the lower end. As far as full power the DS 125 had the same max power as the DS161 did, in fact the DS125 would be about a tenth of a stop brighter. If you need fine tune lighting, go with the DS160 or DS161. Both these strobes work off TTL, which means you can get the same results with the DS125 as you can with the DS161 using TTL. The biggest difference is price since the DS125's are substantially cheaper. So if you don't need small incremental changing in the amount of light you want the DS125 is what you want. You can also use an EV controller which has 10 power levels available. If you can trigger it optically as a slave with the setup you have the DS125 will do everything the DS161 will for a smaller price.

Lets compare the price between the two setups for remote slaves.

DS125 - $250 on ebay + EV Controller $180 = Total $430

DS161 / DS160 + EV Controller $180 = $880 / 630

$700 / $450

All setups should give the same results but the DS125's are substantially less.

You pretty much have to have remote strobes for the caves. So for me it's an easy decision.

My first rig was a Ikelite Rig for a Nikon D90 and i had one DS125.

I bought it and could not use it for a couple of months, when i tried it first time strobe was dead.
After some emails with Ikelite it seemd that strobe lamp was dead and i had to ship it back on my expenses from Costa Rica to US and then repaired back to Roatan.
The whole shipping added about 300+ on the bill.... After the strobe was working fine, just very bulky and heavy plus you need a charger to charge the battery pack.

I switched to INON Z-240 and never looked back,
- perfect quality, some of my strobes have hundred of dives
- fiber optic cables, no corrosion, no expensive cables, you can buy bulk fiber optic cable and run long distance between camera and strobe,
- use normal AAA batteries, rechargeable batteries work just fine
- perfect automatic TTL working perfectly with every camera i had (d90/D7000/D800/Fuju E900/Canon G11/G12/GX1/Panasonic LX-100)
- you are able to remote trigger the strobes on a certain distance, you just need that the optic sensor is looking towards the camera with the main strobe,
this avoids that you have to run electric/optical cables all around the cave

In your case for cave lighting you may better use very strong video light as it makes positioning much more comfortable as you can place them much quicker

and this will avoid to stir up sediments while doing try and error to find the right position. Basically the same why you use fixed lights in studios.
Very wide and even spread video lights are the 8000 lumen Keldane, expensive beasts but worth every penny.

My buddy does UW video and has two of them and when we dive in the caverns they illuminate very well!

You can see some pictures shot with twin Z-240 on arms and without any planning, putting more effort on them lighting the pictures would be much better,
but i made them while diving with clients and that limits the time i can invest in finding the right strobe position.

https://www.facebook.com/pg/SardiniaDivers/photos/?tab=album&album_id=224280364287095

https://www.facebook.com/pg/SardiniaDivers/photos/?tab=album&album_id=202679009780564

Chris