DreiFish

Does anyone know where I might get my hands on a Seacam 160D strobe in South Florida? Beg, borrow, rent or steal? 😄 I'd love to do some comparisons with the YS-D3, Marelux Apollo 3s, Ikelite DS230 and the Backscatter HF-1s I soon will have access to. (Same goes for the Retra Pro Max)

David, respectfully, your proposed solutions don't actually solve the problems. 1. Using longer strobe arms doesn't replicate the effect of diffusers in spreading out the light intensity evenly across the lit subject. You just end up with 2 still distinct hotspots spread further apart. 2. Turning down the power doesn't soften the light. You end up with the exact same central hotspot and proportional intensity fall-off towards the edges, just from a lower intensity starting point. 3. See #2 above. Reducing the strobe power doesn't reduce the hotspot, because the hotspot is a result of the proportional light fall-off towards the edges. 4. You can indeed change color temperature using gels, at the expense of light intensity. The HF-1s with the 5500k filters will produce light of similar color temperature with the DS230 for example, but you'll probably lose about 1/2 stop of light intensity. So if using gels on the cooler lights to match the color temperature of the warmer ones, the DS230 will be noticeably brighter. I (and others) have explained in other threads why using a custom white balance (in camera or in post) to adjust for cooler strobes is not a solution. The issue isn't the specific color temperature of the strobe -- it's the relative difference in color temperature between the strobe and the ambient light. With warmer strobes, that relative difference is greater, leading to increased color contrast between your subject and the background. You can't achieve that with global white balance adjustments -- only with separate selective adjustments for the subject and background using masks. So no.. respectfully again, diffusers (and warming gels) are not ike wearing ear-plugs at a concert and sunglasses at a movie. They're a specific tool that can be quite beneficial to achieving certain aesthetic results in your images that you can't achieve without them. Whether that aesthetic result is important to your particular type of aesthetic is a separate question, but they are definitely valuable tools in the arsenal for many underwater photographers looking to achieve a certain look. The relative light fall-off towards the edges is going to be exactly the same at full power, 1/2 power, 1/4th power, or whatever other power level you test it at. There's no magic that reduces backscatter and flare at 1/2 power vs shooting at full power. That's all down to strobe placement and the needed strobe power relative to the desired exposure. Also, it's relative -- the HF1 at 1/2 power for example should produce similar light intensity to the YS-D3s at full power.

Agreed -- the other images are at least white balanced to the same color temperature. The DS230 image is not. However, I believe the brightness hasn't been manipulated, as it accords with Backscatter's separately reported comparative GN tests at center of the strobe (GN22 for Retra, GN29 for DS230, GN32 for the YS-D3 and GN40 for the HF-1).

Which YS-D3 screenshot did you map this for? With or without diffuser? Would be great to supplement this also with the 3 different YS-D3 diffuser options and the 3 HF-1 diffuser options.

Please keep in mind that this is the original Retra flash, which used a single linear (not circular) flash tube. No reason to think it tells us anything about the current circular flash tube Retra models or that the DS161 is similar in light intensity or spread to the newer DS230/232.

Yes, that's where the graph comes from. I would caution against equating the YS-D2 results to the YS-D3.. it seems they are different beasts. The YS-D2 may well have produced more even light distribution without a diffuser. I too wish Retra could've further elaborated their testing methodology and want to point out also that this is an older test, not of the latest Retra models (though Retra themselves has claimed the light quality should've remained constant)

AFAIK, Backscatter hasn't described the test environment for this light fall-off test, but I would presume the distance from strobe-to-chart is consistent between the strobes. I would also hope the camera used is also. I also would like to know what the distance is and what angle of view the different circles represent. @James Emery -- could you share some of these details? @James Emery -- is there any way Backscatter could provide the raw files here or on Backscatter.com? These are indeed screen-grabs from the videos, and how they were processed is an unknown variable. Again, I would hope that the light intensity hasn't been adjusted between different strobes, but I suspect there's been at least white balancing applied to most of the videos (the images appear neutral and exactly the same color temperature except for the Ikelite DS232 shot, which is very blue. So at least white balance seems to have been adjusted. If anything, the DS232 should be the warmest of all of these strobes according to Backscatter's own color temperature tests.

Now drawing some conclusions: 1. YS-D3 vs HF-1, both with flat diffusers -- similar coverage, but the HF-1 is almost a stop brighter. 2. YS-D3 with flat diffuser vs Retra Pro Max with no diffuser - very similar! 3. Retra Pro Max vs. DS230 - similar coverage, but DS230 is almost a stop brighter, and perhaps also brighter at the edges. HF-1 with flat diffuser vs. DS230 -- HF-1 is maybe 1/3 stop brighter in the center, but DS230 has a more even, wider beam. HF-1 with dome diffuser vs. DS230 -- Similar, but DS230 just edges out the HF-1 in terms of evenness. I'd really love to see Backscatter test the Seacam 160D and Marelux Apollo 3. Based on Retra's tests though, I would expect the Seacam 160D to perform pretty similar to the Retra Pro Max though. Maybe 1/3 stop brighter? My conclusion? DS230 has the best combination of power, coverage and color temperature. The price and weight are also attractive for a 'big' circular flash tube strobe. But HF-1 is also pretty impressive for versatility (and probably better recycling times and battery capacity). YS-D3 still has the advantage that at 730g it's considerably lighter than the other 5 strobes in this list, and also the cheapest. Retra.. well, it has a lot of different light modifying accessories.

First, Marelux Apollo 3s at full power, with diffuser I judged good exposure to be ISO 100 F16. Second, the Inon S-220s at full power, with the 4600k filter Best exposure was at ISO 100 F11. The Inon S-220 picture was probably a few inches closer with slightly different framing (you can see from how much of the wreck was captured) I'd say that basically power is 1 stop lower, but the big difference is that the S-220 has less wide coverage and much more of a hotspot. Also, please keep in mind that 2 strobes are used in each picture, at 10 and 2 o'clock. So this is the exposure you'd get with 2 strobes, not just one.

RomiK, the two photos you have in your quote are both the Apollo (with and without diffuser). That's why they look the same.

Could you explain point #3? I think actually the higher aperture needed for wide angle (WACP line notwithstanding* -- you can shoot the WACP-1 at F5.6 or even F4 on full frame just fine) is directly counterbalanced by better iso performance. F16 ISO 800 gives you the same dynamic range and image quality (diffraction) as F8 ISO 200 on m4/3, and therefore the strobe power needed is also the same.

It starts off at 6600k according to Backscatter tests. Same as the Marelux Apollo 3 I have and measured. So I suspect just like the Marelux, you need the diffuser + 1/4 CTO to get to 4800k, with is 0.5 stops.

Same coverage and power, but cooler color temperature. I suppose if you filter it warmer, it will match in power output.

According to the specs, the YS-D3 dome diffuser loses you 1.5 stops of light. Not sure about the flat diffuser. But effectively, with the dome diffuser it's a GN19 strobe. Half a stop less powerful than the Retras (or about the same as the Retra with the wide diffuser, which drops power by .6 stops and lowers color temperature 500k according to Retra). That said, the weight is 610g without batteries or 730g with batteries, so they're very light. I wouldn't put them in the same weight class as the Retras, Backscatter HF-1 or Ikelite DS230s.

Thanks Adventurer. I've made the file editable.

What I should add is that I'm a bit skeptical about the 44GN claim at full power -- I'll have to measure it when I'm back home. That said, 2 Apollo 3s can light a big scene, at full power. Here they are at full power with the diffusers and 1/4 CTO gels. (so probably -1 stop because of the diffusers and gels? I couldn't find published specs on how much light the diffusers reduce). F8, ISO 200, 1/125th with the Canon 8-15mm fisheye. Subject distance is about 2 meters?

Hi Phil, You're right -- the manual only speaks about the situation with the wireless trigger. Reading comprehension fail on my part. I'll have to test again -- but when I actually tried shooting 3 fps at level 12 in MTL mode, there were at least noticeable differences in exposure between shots. (this is with fiber optic cables from a nauticam manual flash trigger)

Interesting concept. In the first instance, I'd actually attribute the difference between 6808k and 7082k readings as within the bounds of the margin of error of the Sekonic, rather than reflecting an actual difference in color temperature between Manual and MTL modes. So.. without further testing, which I can do when I'm back home, I wouldn't read too much into it. As for the flash tubes being used in sequence for MTL rather than all firing at once.. I suppose that's one way to implement it, but it would lead to pretty discernable changes in lighting and hotspots from shot to shot. Again, I haven't tested this, but it's straightforward to test on a blank wall. Will perhaps do it at home.

Some excerpts from the manual, especially when it comes to the MTL functionality. Basically, you can only shoot 10fps in MTL mode at power level 5 or below. That's, according to Marelux, GN 6.8 or lower from the claimed GN 44 of the strobe on land*

Sadly I've misplaced my Ulbricht Sphere. It's probably somewhere inside the bag of infinite holding 😄 (I did do the testing in darkness to try to minimize ambient light impact) Mmm... I didn't observe the same results with the Marelux Apollo 3, but I suppose that uses 3 shorter straight flash tubes, not one large circular tube. It'd be interesting if someone could test this with another circular flash tube strobe like the Retra or Ikelite or Seacam. Marelux in MTL just shifts the power scale so that the top setting is actually 1/4th of full power according to their manual and observations. The color temperature is the same as at full power (within measuring error).

2 x 21700 = 3 x 18650 batteries. Same weight and energy density. Current probably is better with the 21700, but the Marelux Apollo 3s use 3x18650s.

You can also increase the reach using beam-forming devices that limit the spread of the flash. Like the Retra Reflector, which cuts the beam spread to about 60 degrees. This is probably a more effective method for truly far subjects than trying to get longer arms.

Charging 8 (or 16) individual AA batteries was the main frustration I had with my Retra strobes. If a single (lithium) battery pack can replace the 4 or 8 AAs, that'd be a major bonus in my view.

This. I tested the OneUW extensively with the Sekonic specrometer. -- they're the OEM for Seacam strobes as well, as far as I know. Interestingly, there is a big jump to warmer color temperature around -4 stops. If the Seacams behave the same way.. I find this rather deceptive and frustrating in use as well.