Strobe Review: Scubalamp D-Max and Retra Pro Flash

Underwater review and strobe comparison:

For all underwater tests, we used a Sony A6300 mirrorless camera with a generic no-TTL external trigger, Sigma 19mm/2.8, Nauticam WWL-1 wet lens, and Nauticam housing.

Two Scubalamp D-Max on Nauticam NA-A6300 housing with Nauticam WWL-1.

Quality of light and maximum power

During our first test underwater, we focused on evaluating the beam distribution and intensity of the D-Max and Retra Flash Pro.

To do this, we went on a shore dive near La Paz, Mexico, where we looked for a rock formation large and flat enough to judge the quality of light produced by the strobes.

We placed one strobe at a time on a tripod set up around 1m from the wall in order to guarantee a stable and constant position of the strobes between runs. We fired the strobes with one strobe attached to the camera at its lowest power level and an Anglerfish remote flash trigger attached to the tripod and connected to the strobe under test via a fiber optic cable. Pictures were taken at equal distances from the tripod.

Test set-up.

We tested the following configurations:

Camera settings were the following and remained unchanged throughout the test: ISO 100 / 1/250s / f16

The idea here was to isolate the bright beam of the strobes from the natural light present at the fairly shallow dive site. We then edited the images in Adobe Lightroom by dropping the shadows to -100 and boosting overall exposure to further enhance the beam produced by the strobes against the faint ambient light.

D-Max at full power without diffuser.

D-Max at full power with D100 diffuser.

Retra Flash Pro at full power without accessories.

Retra Flash Pro at full power with beam restrictor.

Retra Flash Pro at full power with wide-angle diffuser. The 500K decrease in colour temperature is noticeable.

Retra Flash Pro at full power with shark diffuser. The further decrease in color temperature (-1000K compared to stock) is very noticeable, as is the lower output.

In the images, it is possible to evaluate the global intensity of illumination, and the quality of the light beam.

The Retra Flash Pro is the strobe with a higher global intensity and a very good angle of coverage, even without diffusers. In fact, the diffuser does not appear to increase the beam angle in any meaningful way and simply softens the beam further, particularly towards the edge. This is valid also for the D-Max, where the diffuser D100 doesn’t increase the beam angle, but simply softens the light while reducing the output a little.

These results are not at all surprising, as both strobes use circular flash tubes and reflectors, a design which is well-known for producing nice, even illumination even without diffusers.

These tests also show the versatility of the Retra Flash Pro when combined with different accessories. The reduction ring is very effective at providing a sharp edge to the beam, which is useful for certain techniques whereas both diffusers we used here to provide a warmer light, which will help at producing beautiful blue water in the background in tropical conditions.

The Retra Flash Pro emerges as the winner in this first test. It features the more even beam and in the center is about 0.2 stops more powerful than the D-Max. At this point in the review, it is apparent that the 250Ws output claimed by Scubalamp cannot be verified. Real-life output will be below the Retra Flash Pro’s claimed 150Ws. The D-Max does still produce a pleasing and powerful beam.

We also ran a quick side-by-side test with a D-Max strobe on one side and a Retra Flash Pro on the other to see at which power level the Retra would best match the D-Max’s maximum power. At 75%, the Retra Flash Pro roughly matches the output of the D-Max at full power, with the D-Max perhaps being a little bit brighter, which falls in line with our more artificial testing scenario above.

Scubalamp D-Max (left) at full power vs. Retra Flash Pro (right) at 100% power.

Scubalamp D-Max (left) at full power vs. Retra Flash Pro (right) at 75% power.

Scubalamp D-Max (left) at full power vs. Retra Flash Pro (right) at 50% power.

Recycle time and continuous shooting

Our second test focused on verifying Scubalamp’s extremely impressive claimed to recycle times and compare the real-world values to the Retra Flash Pro. We conducted this test in a bucket filled with water, in which the strobes were placed to avoid overheating them. We used two Retra Flash Pros: one without and one with the optional Supercharger accessory. Both Retra Pros were equipped with freshly charged, brand new Eneloop Pro batteries. The D-Max was also equipped with a freshly charged battery pack. All three strobes were triggered by fiber-optic cables.

Maximum burst rate

We first tested the maximum burst rate at minimum power. All three configurations (D-Max, Retra Pro with/without Supercharger) were able to continuously fire at 8fps for about 5 seconds, after which we stopped the test. The Retra Flash Pro without Supercharger did display a “charging” light so would not be able to keep up forever whereas the one equipped with the Supercharger remained in a “ready” state. We are struggling to think of a scenario where anything more than a couple of seconds of shooting at 8fps would be at all useful though. In the specifications of the D-Max, Scubalamp claims “15 frames high-speed continuous shooting at 1st mode. 12 frames at 2nd mode”. We took this to be 15 and 12 frames per second, which we could not verify, as the D-Max would occasionally miss frames at 10fps, the highest frame rate the Nikon D500 we used for this test can achieve. After further clarification from Scubalamp, it appears that they referred to 15 and 12 continuous frames at 7fps. However, as that 7fps burst rate is mentioned nowhere on the spec sheet, these claims are somewhat confusing, if not misleading.

Recycle time at maximum power

To determine the recycle time at maximum power our initial plan was to fire the strobes and record a video of the back of the units to see when the ready lights would indicate readiness to fire again. It was at this stage that we realized that the LED on the back of the D-Max was not, in fact, a ready light but instead nothing more than a “power on” and battery level indicator. This meant that we had to adjust our testing method.

For the Retra Flash Pro, we did use the technique outlined above, determining the exact recycle time in a video editing program by measuring the time between the flash and the status LED changing color over several runs. For this test, we used one flash with and one flash without the Supercharger. The results were as follows:

Recycle time at maximum power:

Retra Flash Pro without Supercharger: 4 – 4.6s
Retra Flash Pro with Supercharger: 1.7 – 2s

The Supercharger proves to be a great improvement over the otherwise sluggish recycle times of the Retra Flash Pro and therefore greatly improves real-life usability of the strobe. Even with the Supercharger the Retra Flash Pro is by no means a fast strobe though.

For the D-Max we first tested the claimed 0.5s recycle time by setting the camera to fire at 2fps. This resulted in three successful flashes and then six frames during which the strobes did not fire (amounting to 3 seconds), followed by three successful flashes, and so on. To determine the maximum continuous firing rate of the flash we used a metronome app to fire at different intervals as accurately as possible, as the camera does not provide a way of triggering at less than 1fps, which was still a little too fast to see the D-Max fire consistently. The D-Max would reliably fire once every 1.5 seconds. While we could not confirm the claimed recycle time of 0.5s at maximum power the D-Max still achieved very impressive results. Being able to shoot three images at full power in just 1.5 seconds can make a huge difference in fast-paced situations. However, continuous shooting at 0.5-second intervals (as the spec sheet would suggest) is not possible. It should also be noted that the D-Max does not fire at all when not ready to do so. By comparison, the Retra Flash Pro will always fire when triggered. While this will not result in an accurate exposure when the flash has not yet fully recycled, it might still produce a salvageable result so is the preferred behavior.

Maximum number of flashes on a single charge

Our third comparative test focused on the number of flashes each model can produce on a single charge. Once again Scubalamp’s claims are very impressive. We conducted this test in a bucket filled with water, in which the strobes were placed to avoid overheating them. We used two Retra Flash Pros: one without and one with the optional Supercharger accessory. Both Retra Pros were equipped with freshly charged, brand new Eneloop Pro batteries. The D-Max was also equipped with a freshly charged battery pack. The strobes were set to maximum power and fired in intervals of around 15-25 seconds until they would not fire anymore and this test was repeated three times. The average results were as follows:

Number of flashes on a single charge at maximum power:

The values for the Retra Flash Pro are well above Retra’s claims of 150 without and 350 with the Supercharger. As mentioned previously the Supercharger is a must-have accessory for wide-angle shooting in our opinion. The huge improvement in the number of flashes will get most people during a full day of diving.

The D-Max achieves the claimed amount of flashes on a single charge, which is an extremely impressive feat! In fact, using a Sony A6300 to trigger the strobe the camera’s battery had to be swapped before the strobe’s battery died!

  1. Introduction
  2. Scubalamp D-Max
  3. Retra Flash Pro
  4. Underwater review and strobe comparison
  5. Comparison and Conclusion