Backscatter In-Water Strobe Beam Testing

[Dave_Hicks]

Here are a pair of images of similar wide angle reef subjects in Fiji.

 

The first is from 2012 taken with DS-125s on a D800 with No Diffusers [Sigma 15mm, 1/80s, f6.3, iso100]

 

This second was taken with Inon-330s on a D850 with No Diffusers [Sigma 15mm, 1/80s, f13, iso320]

[Architeuthis]

2 hours ago, DreiFish said:

 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)

 

Yes, unfortunately the Backscatter graphs that I have posted show results from previous generation flashes...

 

Important is, however, that the light falloff from center to border is in the range of -1.5 f-stops to -0.5 f-stops, depending on zone, flash and diffuser. This is much closer to the measurements that Chris made with your screenshorts, assuming he used a linear y-axis (?). So maybe Chris's measurements are not so far away from reality (but maybe not, because of the postprocessing problem, we need unprocessed test images)...

 

=> In any case, I find the graph from the "Retra-Study" weird (and as I wrote already, also the test photos look weird)- the light fall off in Zone 3 is -6 to -7 f-stops compared to the center (!!). Did they put a snoot on the flashes for testing... ?

(seriously: this shows that one cannot test light distribution of UW strobes in air)

 

[DreiFish]

45 minutes ago, Dave_Hicks said:

Here are a pair of images of similar wide angle reef subjects in Fiji.

 

The first is from 2012 taken with DS-125s on a D800 with No Diffusers [Sigma 15mm, 1/80s, f6.3, iso100]

 

This second was taken with Inon-330s on a D850 with No Diffusers [Sigma 15mm, 1/80s, f13, iso320]

 

Do you recall how close you were to the subjects? These both look to be somewhat close focus wide angle scenes, where the subject is centralized in the shot. It's exactly the type of shot where both narrow beam angle and 'hotspotting' would be hard to notice because there's no subject to be illuminated near the edges of the frame and the coral is all different colors and textures anyway, and at various distances, so it masks light unevenness.

 

The test shots I posted earlier were at 1 meter from the subject, and the subject was basically a flat wall that more clearly shows variations in light quality. That's why I picked it -- not for any artistic merit. I'd also argue that what the exposure of the test shots is pretty spot on (at least for my taste -- some may prefer brighter subjects). Here's the histograms (Marelux first, S-220 second).

 

 

The muted reds aren't an issue of exposure -- they're an issue of distance. The strobe light needs to travel through 2 meters of water to the subject and back, and that will filter out a lot of the reds at a proper exposure level. 

[DreiFish]

1 hour ago, Dave_Hicks said:

 

My point (which I didn't make clearly) is that I would be interested in seeing how these strobes perform on the 1st, 2nd, 3rd shot in a 1 second burst. Are all 3 (or 12, 20, 30) shots delivering a similar level of illumination or is there are power drop off with later shots? How do the various strobes perform in these burst shot modes?

 

With new strobes coming on the market with more power, Li-on cells, and the ability to support more than one shot per second, this is going to be the new, and actually relevant metric to judge these strobes.

 

I've shot Ikelike DS-125, DS-161, Inon 330, and Retra strobes over the years. I'd be hard pressed say that one delivered better image results than another. I moved between models based on portability, useability, and reliability over the years. I never found any of these strobes to be dramatically better in producing useful images than the others. I do feel very limited by not being able to take more than one shot per second in high speed action situations, and look forward to experimenting with this ability.

 

 

Yes, it would be nice to have a test of repeat exposures in high speed shooting. Marelux claims that their MTL mode is specifically designed to reduce that issue.  It's a relevant topic.. but.. mostly for a niche case -- high speed action, not general reef shots. 

 

I think your example shots illustrate that subtle differences in light intensity and falloff that can be seen on a test chart (even underwater) may not be all that relevant or noticeable when dealing with real underwater subjects. That is food for thought. Probably any of the 6 strobes I listed would be 'good enough' for most typical use cases.

[Dave_Hicks]

5 minutes ago, DreiFish said:

 

Yes, it would be nice to have a test of repeat exposures in high speed shooting. Marelux claims that their MTL mode is specifically designed to reduce that issue.  It's a relevant topic.. but.. mostly for a niche case -- high speed action, not general reef shots. 

 

I think your example shots illustrate that subtle differences in light intensity and falloff that can be seen on a test chart (even underwater) may not be all that relevant or noticeable when dealing with real underwater subjects. That is food for thought. Probably any of the 6 strobes I listed would be 'good enough' for most typical use cases.

 

Yes, exactly. These test chart shots are largely irrelevant to real world use. It's nice to see for relative power levels but must "full powered" strobes in the market are all going to deliver similar results. The far more useful metrics are in Reliability, Serviceability, Portability, and Utility (user interface, features). 

 

As we've seen with Sea&Sea, they had a lot of failures coupled with a very poor customer service and repair story. Backscatter had reliability problems with the (early) MF-1 strobes but came out ahead with a stellar service. Retra adds a lot of great features and luxury parts (bluetooth firmware updates, flash tubes). Ikelite has always been reliable and has great battery packs, but have always been bulky and heavy. Inon is the Toyota of Strobes with great function and reliability, but lack fancy features or a sexy part list. Backscatter is still evolving being with their first foray with the MF-1 and MF-2 small/snoot strobes, and entering the full power market with the HF-1 which as great specs.

 

I'll have a pair of HF-1s tomorrow, and I'll see how well the work soon. I usually dive a couple days a week and will take these out right away.

 

[Architeuthis]

43 minutes ago, DreiFish said:

 

Do you recall how close you were to the subjects? These both look to be somewhat close focus wide angle scenes, where the subject is centralized in the shot. It's exactly the type of shot where both narrow beam angle and 'hotspotting' would be hard to notice because there's no subject to be illuminated near the edges of the frame and the coral is all different colors and textures anyway, and at various distances, so it masks light unevenness.

 

The test shots I posted earlier were at 1 meter from the subject, and the subject was basically a flat wall that more clearly shows variations in light quality. That's why I picked it -- not for any artistic merit. I'd also argue that what the exposure of the test shots is pretty spot on (at least for my taste -- some may prefer brighter subjects). Here's the histograms (Marelux first, S-220 second).

 

 

The muted reds aren't an issue of exposure -- they're an issue of distance. The strobe light needs to travel through 2 meters of water to the subject and back, and that will filter out a lot of the reds at a proper exposure level. 

 

Hi Dreifish,

 

Maybe you could adjust the exposure to a level so that the brightness in the center of the strobe beam is the same. I think then (and when the distance to the object was the same), one could judge easier whether there is a difference in light distribution and/or beam angle...

 

Wolfgang

[Dave_Hicks]

46 minutes ago, DreiFish said:

 

Do you recall how close you were to the subjects? These both look to be somewhat close focus wide angle scenes, where the subject is centralized in the shot. It's exactly the type of shot where both narrow beam angle and 'hotspotting' would be hard to notice because there's no subject to be illuminated near the edges of the frame and the coral is all different colors and textures anyway, and at various distances, so it masks light unevenness.

 

The test shots I posted earlier were at 1 meter from the subject, and the subject was basically a flat wall that more clearly shows variations in light quality. That's why I picked it -- not for any artistic merit. I'd also argue that what the exposure of the test shots is pretty spot on (at least for my taste -- some may prefer brighter subjects). Here's the histograms (Marelux first, S-220 second).

 

 

The muted reds aren't an issue of exposure -- they're an issue of distance. The strobe light needs to travel through 2 meters of water to the subject and back, and that will filter out a lot of the reds at a proper exposure level. 

 

Those two Fiji pictures  are classic Wide-Angle images of a large subject. The reefs in the pics are probably 3 meters across or a bit more. Most acceptable wide-angle strobe lit images have to be within 1-2 meters or you might as well turn off the strobes. I was probably no more than 1.5 meters from the front of the reef.

 

CFWA is typically just centimeters from the subject, and smaller macro powered strobes like the Inon 220 would be better suited for that sort of shot than a wide able image in your examples and mine. 

 

To be blunt, I question your taste if you think those test shorts were properly exposed. They are grey and unsaturated, not reflecting any of the real-world color in the soft corals, fish, or hard coral reef. Your test shots should at least be exposed well enough to make post processing worthwhile to create an aesthetically pleasing image.

[Chris Ross]

8 hours ago, DreiFish said:

 

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.

with diffuser, the without diffuser shot shows only that you should always have a diffuser on that strobe.

[DreiFish]

12 minutes ago, Chris Ross said:

with diffuser, the without diffuser shot shows only that you should always have a diffuser on that strobe.

 

Dome diffuser or the flat diffuser? 

[Chris Ross]

16 hours ago, Architeuthis said:

 

Thank you Chris, interesting!

 

 

Is it this with or without diffusers (which diffuser if any)?

Could you please also make a graph with HF-1 (with and w/o diffusers)?

 

In case you normalize the brightness of each individual strobe/diffuser combination to the value at "0" (x-axis), the centre, The even/uneven light distribution would be even better visible for everybody.

Intensity comparison could be made separately from the even/uneven brightness distributions, just by comparing the absolute values in the centre, e.g. bar diagrams...

 

Here's the plots with HF-1 added:

 

and here it is normalised to the Retra centre value:

 

 

The YS-D3 is with the diffuser.  I can't see wanting to use it without the diffuser.

 

You can see that the ikelite and Retra closely mimic each others distribution pattern  and the diffused  HF-1 and YS-D3 also closely mimic each other.  The HF-1 is interesting the distribution is quite similar with and without the diffusers until close till the outer edge where the Illumination drops dramatically without the diffuser. 

 

This should not be surprising, the Retra and Ikelite both use circular flash tubes and the HF-1 and YS-D3 use a similar linear flash tube layout.  The ikelite and Retra are very close with a slight edge to the Retra on even distribution of light.  There is very little to pick between the YS-D3 and the HF-1 with diffusers apart from the additional power of the HF-1 and the batteries.

 

Why would you want even distribution of light?  with 2 strobes the edges of the beam intersect and overlap in the centre of your photo, so if the edge has more light then you can turn down the power compared to a strobe with dimmer edges.  The 160° dome diffuser though throws light around everywhere and it would be hard to avoid illuminating the dome with it.  just look at the pool wall behind the test chart to see how wide it throws the beam compared to the flat diffuser.

 

[Jerry Diver]

16 hours ago, Architeuthis said:

=> In any case, I find the graph from the "Retra-Study" weird (and as I wrote already, also the test photos look weird)- the light fall off in Zone 3 is -6 to -7 f-stops compared to the center (!!). Did they put a snoot on the flashes for testing... ?

(seriously: this shows that one cannot test light distribution of UW strobes in air)

Reading their study, Zone 3 (Magenta) is 120 cm from the center of the test wall when the strobe is placed 60 cm from the test wall. In practical terms, this means Zone 3 (Magenta) has an angle of view of about 154º, and the light needs to travel about 130 cm. At this angle, the strobe's power is significantly weaker than at the center, and the increased distance explains the measured light output.

 

The Retra light output study is the only test where all testing conditions are thoroughly detailed, allowing for replication if desired. All you need is a light meter (the exact type used is specified), a tape measure, and the strobes to test. While testing in air might not be ideal, the most crucial aspect is that all strobes were tested under identical conditions. This makes the comparison valid and verifiable.

 

In contrast, the Backscatter study lacks detailed information about their testing conditions (distance, camera settings, etc.). The results show inconsistencies between the images, making them open to interpretation.

[Architeuthis]

3 hours ago, Jerry Diver said:

Reading their study, Zone 3 (Magenta) is 120 cm from the center of the test wall when the strobe is placed 60 cm from the test wall. In practical terms, this means Zone 3 (Magenta) has an angle of view of about 154º, and the light needs to travel about 130 cm. At this angle, the strobe's power is significantly weaker than at the center, and the increased distance explains the measured light output.

 

The Retra light output study is the only test where all testing conditions are thoroughly detailed, allowing for replication if desired. All you need is a light meter (the exact type used is specified), a tape measure, and the strobes to test. While testing in air might not be ideal, the most crucial aspect is that all strobes were tested under identical conditions. This makes the comparison valid and verifiable.

 

In contrast, the Backscatter study lacks detailed information about their testing conditions (distance, camera settings, etc.). The results show inconsistencies between the images, making them open to interpretation.

 

Hi Jerry,

 

Fortunately, UW-photography is regarded to be not a science, but an art...🙂

There are, however, physical principles in photography and also in UW-photography, that cannot be neglected. I fear a little, that we are coming to the stage were we are going to count peas, but I just cannot leave your post uncommented:

 

#1.: I fully agree that the Backscatter "study" lacks info about conditions, I have no reason to brighten the Backscatter communications. In addition, also the screenshots from the videos certainly suffered some postprocessing and therefore also will not give 100% accurate results (There are people from Backscatter posting in this flash forum and I wonder why they are so quiet...).

Unfortunately we cannot translate the "Retra zones" in "Backscatter zones" directly. I guess, maybe, that every "zone" in the Backscatter images corresponds to 40° AOV. Then "zone 4" may correspond to 160° (and approx. to "Retra Zone" 3), but who knows?

You cannot calculate light intensity projected by a light source that is several cm in diameter at a distance of 60 cm from the "distance square law", since this law is derived simply from geometry and only applies to light sources that are represented by a point (!) without dimensions. For an UW flash this means many meters of distance, until the light source can be regarded as such (=a single point) and this law delivers solid results. Therefore better do it the empirical way and make controlled test photos and measure the light distribution...

 

#2.: It is not enough for an exact study to use a light meter and give a reference to the manufacturer. One also needs to know how to use it and how to make the measurements:

In the normalized graph, that was kindly provided by Chris (where all flashes start at (estimated) 72 a.u. at the center), -1 f-stop corresponds to a value of "36", -2 f-stops to "18" (only HF-1 w/o diffuser goes below 20 at "zone 4" in Chris's graph). -7 f-stops would correspond to a value of "0.6" in Chris's graph - this would be practically black.

According to the "Retra graph" (posted by Dreifish at the beginning of this tread), the light falloff, already in "zone 1" is between -3 f-stops and -4 f-stops (that would correspond to "9" and "4.5" in Chris's graph) - such strobes would be pretty unusable...

 

#3.: It is not that "...testing in air might not be ideal...", it is just not possible to test UW-flashes in air and draw solid conclusions for UW work. Not only the beam angle will be different in water, also the light scattering will be completely different, as it is almost absent in air, but substantially in the water.

 

As a proof of my statement, please have a look at the light distribution of YS-D2 and Z330 "test images" (both without diffusers; the last two images at the bottom left) from the Retra "study"

I post here (again) the link: https://www.retra-uwt.com/pages/flashgun-light-comparison

(I hope this allows me to paste the graph into my post, if not, please delete the graph, but leave the link)

 

 

=> I am using both YS-D2 and Z330 for years (also without diffusers), but never have I been able to get such

 a weird light distribution pattern. This must have been produced by the lack of water in the Retra "study". I see no point in analysing intensities in such patterns (even when the measurements are done correctly, but the resulting f-stop numbers seem to be completely wrong)...

 

 

Respectfully, Wolfgang

Edited June 12 by Architeuthis

[Jerry Diver]

The absolute measurements on the Retra graphs may not perfectly represent how we perceive lighting underwater, but they do correlate well with the provided images of the light outputs without diffusers when strobes are aimed at a blank wall. 

 

Additionally, Retra has provided images of the strobe light output with diffusers, which clearly levels the playing field. If they wanted to showcase the supremacy of their strobe, they likely would have not shown those images.

 

Conclusion: The Retra study highlights subtle differences between strobes (all are within +/- 1 F-stop range), though these differences may not be immediately noticeable when shooting underwater scenes with various colors and textures.

[Dave_Hicks]

None of these test images or graph can tell me if a new strobe is going to burn out the day after the warranty expires. That data point is infinitely more important that the degree of light fall-off at the edges of a swimming pool.

 

The reality is that award winning images have been made with every single one of these strobe models. They are all capable of contributing to the creation of incredible artwork in the right hands. 

 

Buy the one that you can afford and trust for reasonable service &support with a set of features you value.

Edited June 12 by Dave_Hicks

[ChrisH]

4 hours ago, Architeuthis said:

=> I am using both YS-D2 and Z330 for years (also without diffusers), but never have I been able to get such

 a weird light distribution pattern. This must have been produced by the lack of water in the Retra "study". I see no point in analysing intensities in such patterns (even when the measurements are done correctly, but the resulting f-stop numbers seem to be completely wrong)...

 

 

Yes, the shots in air do not show how the light distribution will be underwater. As water is a diffusor by itself, you will not get those patterns from the YS-D2 or Z330 if you use the strobes underwater. 

But the water ist the same for all strobes 😉 So strobes that have a nice even beam will benefit from the water the same (or even more?) than the strobes with a narrower or more uneven beam. I think the Retra test shows the differences of the strobes very well. it is not to say that the strobes will give you the light pattern as in air. It is just to have a comparison of the strobes, so you can make an educated guess on what light another strobe will give you compared to the strobe you already own and know. 

I think it is more complicated to do the same test in water, as you would have to shoot the strobes in total darkness in the swimming pool to not get any (!) light interference. Shooting them in a dark room is much easier.

[DreiFish]

2 hours ago, ChrisH said:

 

I think it is more complicated to do the same test in water, as you would have to shoot the strobes in total darkness in the swimming pool to not get any (!) light interference. Shooting them in a dark room is much easier.

 

I think Backscatter should be commended for doing the test in water. 

 

4 hours ago, Dave_Hicks said:

None of these test images or graph can tell me if a new strobe is going to burn out the day after the warranty expires. That data point is infinitely more important that the degree of light fall-off at the edges of a swimming pool.

 

The reality is that award winning images have been made with every single one of these strobe models. They are all capable of contributing to the creation of incredible artwork in the right hands. 

 

Buy the one that you can afford and trust for reasonable service &support with a set of features you value.

 

Are we not perhaps over-hyping the reliability issue? While I agree that all these strobes could produce award-winning images, what has led you to the conclusion that there's meaningful reliability differences between them that should be the basis of someone's buying decision? With the exception of the YS-D2s, which (at least in the original versions) did have significant reliability issues (I owned 4.. 3 of them failed and the 4th was on its way to failure), I haven't heard any complaints about the quality of any strobe manufacturer. So.. what reliability data should we be using exactly to pick between these strobes? I'm betting that just like any of them could get you very good shots, any of them would also be reliable as well in the absence of any evidence to the contrary.

[Dave_Hicks]

1 hour ago, DreiFish said:

 

I think Backscatter should be commended for doing the test in water. 

 

 

Are we not perhaps over-hyping the reliability issue? While I agree that all these strobes could produce award-winning images, what has led you to the conclusion that there's meaningful reliability differences between them that should be the basis of someone's buying decision? With the exception of the YS-D2s, which (at least in the original versions) did have significant reliability issues (I owned 4.. 3 of them failed and the 4th was on its way to failure), I haven't heard any complaints about the quality of any strobe manufacturer. So.. what reliability data should we be using exactly to pick between these strobes? I'm betting that just like any of them could get you very good shots, any of them would also be reliable as well in the absence of any evidence to the contrary.

The poor reliability of multi S&S models over the years is well know. Their sub-standard and disappointing service and repair policies are also well know. That is easy to measure and track. Let's see some reporting on that. Sadly, the testing driven by manufacturers and retailers does not consider or value this. I would like to see the strobe brands compete on customer service as well as features. 

[Chris Ross]

While it would be interesting to know Backscatters test setup, if we assume that they have taken reasonable care to have a reproducible setup as far as distance from strobe and camera position is concerned and taken basic care to do minimal image processing and do the same for each test, I would argue  we don't really need to know the details of their test setup.  I would assume they just insert the still images into the video to display them rather than take video .

 

The images snipped from the video should then be usable as a comparison tool.  The plots I got out of the images just taking eyedropper readings look remarkably similar to the plots Retra produced.  They should give reasonable basis for comparing flash performance.  You really need both plots to make sense of things, the first plot shows how much brightness difference at full power is and the normalised plot shows distribution differences.

 

While it's commendable that Backscatter does these tests, just putting them into a video review really doesn't help anyone as looking at a bunch of separate clips showing the beam pattern, the human brain really can't make much of a comparison.  To be truly useful and helpful for prospective flash buyers providing a link to a standardised test image from the product page of each strobe they have tested would be a good start.  @James Emery  any chance of providing access to test images?

 

 

[Architeuthis]

On 6/12/2024 at 2:54 AM, Chris Ross said:

You can see that the ikelite and Retra closely mimic each others distribution pattern  and the diffused  HF-1 and YS-D3 also closely mimic each other.  The HF-1 is interesting the distribution is quite similar with and without the diffusers until close till the outer edge where the Illumination drops dramatically without the diffuser. 

 

This should not be surprising, the Retra and Ikelite both use circular flash tubes and the HF-1 and YS-D3 use a similar linear flash tube layout.  The ikelite and Retra are very close with a slight edge to the Retra on even distribution of light.  There is very little to pick between the YS-D3 and the HF-1 with diffusers apart from the additional power of the HF-1 and the batteries.

 

 

This sounds logical. In this context it will be interesting to see the light distribution of the Marelux 3 strobe with three linear flash tubes arranged in triangular shape near the outer rim of the strobe front...

[DreiFish]

On 6/11/2024 at 8:16 PM, Chris Ross said:

with diffuser, the without diffuser shot shows only that you should always have a diffuser on that strobe.

The flat diffuser, right, not the dome diffuser picture?

[DreiFish]

5 hours ago, Architeuthis said:

 

 

This sounds logical. In this context it will be interesting to see the light distribution of the Marelux 3 strobe with three linear flash tubes arranged in triangular shape near the outer rim of the strobe front...

I have the Marelux Apollo 3 strobe, but no way to replicate Backscatter's particular test without a similar chart I could put in my pool and some information on the distance from strobe to chart.

 

What I will say is that the difference in coverage between the strobe without diffuser and with its diffuser is not really discernable on a real underwater scene. So probably the coverage is actually quite even even without the diffuser. Here are two pictures taken, one with diffuser, one without. 

 

Without Diffuser, full power, 1 meter distance, 15mm fisheye, ISO 100 F16

 

With Diffuser, full power, 1 meter distance, 15mm fisheye, ISO 100 F16

 

 

Edited June 13 by DreiFish

[Phil Rudin]

Having reviewed a bunch of strobes myself I can appreciate the amount of time and effort it takes to do this type of testing and I applaud Backscatter, Reef Photo and others for taking the time to compare the brands they represent. 

 

I would also like to point out that Sea & Sea has changed hands and bashing the new owners for past fails, new management  introduced YS-D3 is really pointless. 

 

Having photographed lots of pool walls I have come to the realization that the only thing that really maters is how these strobes work in the real world. Backscatter has posted some excellent examples of images taken with the new Hybrid strobes which I find more useful than shots of charts in or out of water.

 

Since Marelux Apollo III has been mentioned in this thread and not included in the tests above I will attach a few real world shots taken with the diffusers to help with skin tone. All shot with the Laowa 10mm in the Marelux 230mm dome port.

 

null

 

[shokwaav]

Not sure if I'm allowed to link to another forum, but Backscatter provided more details regarding their setup here:

https://scubaboard.com/community/threads/backscatter-hybrid-flash-hf-01-preliminary-review.645397/post-10293597

 

Copied for posterity.

 

Quote

A few points of order...

The photos are unprocessed from the camera except for dropping in to the video timeline. No other edits were done. No contrast, no exposure, no nothing. The screen shots on Waterpixels look correct.

The way the video is edited is that we have the main A camera (which is Thomas speaking), a B camera of the closeups and product shots, and another channel for the still images. This way we can color correct for the studio lighting of camera A and B separately without affecting any of the other channels. So the photos of the wall are on a different channel that does not have any editing or correction, there is no global correction to the video because there re different cameras and lenses and lighting used for various shots and it would be impossible to apply a global color correction.

The wall chart is 1 meter away from the strobe. We use a meter stick to measure this. The camera is placed 1 more meter away from the flash. We make sure the the flash is square to the target by taking test shots and we use a level to make sure it is pointed straight. This takes more time than you could ever possibly imagine.

The camera is an a1 with a Nauticam WWL-1. Same for all tests. We choose the a1 so we can get higher flash sync speeds. Shutter is at 1/320 as some strobes are on the limit for flash duration approaching 1/400 and we wanted to capture the whole duration. This is why the Ike 230 video has 2 photos in it, 1 at 1/320 and 1 at 1/100 so it can show the full flash duration at max power. The Waterpixels post shows the one at 1/100 with more ambient light. ISO is 100, F22 for all shots.

In a perfect world we would have access to a pool at night so that we would not be competing with any ambient light.

The guide numbers are measured with a Sekonic light meter 858D-U in our own custom made underwater housing made just for this pool testing purpose. This is at 1 meter and we take painstaking measurements to make sure it is exact and that the strobe is square to the light meter. Setting on the light meter is ISO 100.

Sorry I can't share file formats right now as I'm in Little Cayman prepping for the shootout and James and other Backscatter staff are stuck in various airports due to flight cancellations on the way to the shootout, but as I said above the screen shots are looking correct.

An in air test of an underwater strobe is useless to determine how it would perform underwater. Optics, domes, and reflectors all have an effect when combines with water, which is why we started doing these pool tests after we made our light meter housing.

We want these tests to be as standardized as possible and take great pains in that effort. This way when someone calls up Backscatter we can give them the best objective advice on the differing products to find the best one that suits them. As stated in these videos, we're not sure how each individual manufacturer tests their gear, so we decided to make our own standard test to do a direct comparison.

Please let me know if you guys have any more questions. And yes there are more strobe tests coming, please be patient.

Feel free to share this over on Waterpixels as I don't have an account yet.

Edited June 14 by shokwaav

[Architeuthis]

3 hours ago, shokwaav said:

Not sure if I'm allowed to link to another forum, but Backscatter provided more details regarding their setup here:

https://scubaboard.com/community/threads/backscatter-hybrid-flash-hf-01-preliminary-review.645397/post-10293597

 

Copied for posterity.

 

 

This is interesting news...👍

 

As long as the screenshots are taken from a calibrated monitor (no extra contrast, HDR etc...) the analysis is be valid...

[shokwaav]

 

Quote

 

WS007:

Just one more question: What are the angles of the different zones (the rings in the test image)?

30 60 90 120

 

 

 

Also from the other forum.

Edited June 15 by shokwaav