Strobe tests: Inon Z330, Retra Flash and Symbiosis SS2

Power and beam angle tests

Wetpixel tested the three strobes, along with a Seacam Seaflash 150 as a control sample, using remote triggers and by tripod mounting the strobes. This ensure that the strobes were held at a uniform distance away from the subject.

Bear in mind that the Seaflash 150 has an output of 150 W/s.

All the strobes were fitted with fresh sets of batteries. Test were carried out both with and without supplied diffusers.

Tests were all taken using a Nikon D500 with a Nikon 10-24 f/3.5-4.5 at 10mm, Seacam Superdome. Settings were: 1/200 at f/13, ISO 100.

Without Diffusers

Seacam Seaflash 150

Inon Z330

Symbiosis SS2

Retra Flash

With Diffusers

Seacam Seaflash 150

Inon Z330

Symbiosis SS2

Retra Flash

The results are somewhat hard to read at screen resolution, but unsurprisingly, the Seacam has the highest output both with and without a diffuser. Second is the Inon Z330, again with and without a diffuser.

Without diffuser, number three is the Symbiosis SS2 and the least powerful is the Retra Flash. However, when diffusers are added, the Retra is brighter than the Symbiosis.

Comparing the beam spread, again unsurprisingly, the Seacam is the widest. Perhaps more pertinently, the Retra Flash and the Inon Z330 are almost identical in terms of beam angle. The Symbioses SS2 has the narrowest beam, both with and without diffusers.

Nikon D500, Nikon 8-15mm f/3.5-4.5, Seacam FP Port, one Retra Flash. 1/125@f/10, ISO250

Light Quality

This is a more subjective criteria that is perhaps the hardest to assign an objective criteria to. Arguably, it is also the most important since harsh lighting, regardless of all other factors will ruin an otherwise perfectly composed and exposed scene.

What constitutes “harsh?” Ideally lighting should draw out color and detail, without being obvious. Often, the biggest single detractor revolves around the color temperature of the light produced by the strobe. Very cool lighting tends to be harsh as does light that is very directional.

In my opinion, the best quality of light was produced by the Retra Flash with its warming diffuser.

Nikon D500, Nikon 8-15 f/3.5-4.5, Seacam FP port, Retra Flash . 1/200@f/11, ISO250

That said, the Z330s produce a very pleasant light too. My understanding is that Inon will be releasing warming diffusers soon too. I imagine that these will improve the light quality for blue water shooting.

center>Nikon D500, Nikon 8-15 f/3.5-4.5, Seacam FP port, 2 x Inon Z330. 1/200@f/11, ISO250

The Symbiosis SS2 is a unique product that offers a versatile solution. It offers concentrated and powerful output. The supplied diffusers are somewhat basic and the quality of light from the strobe could be improved by versions that soften and warm the strobe’s output.

Nikon D500, Nikon 10-24mm f/3.5-4.5, Seacam Superdome, two Symbiosis SS2 strobes. 1/250@f/10, ISO500


Underwater photographers are fortunate to have such great choices for lighting their images. Manufacturers are responding to demands for increased power and beam angle, whilst maintaining the quality of the light provided.

Technically, these devices are all capable of performing very well. In general, getting these strobes to work reliably is easier than it has been in the past. Certainly, reliable optical triggering along with opto-electrical converters within housings means that thus technology has come of age.

As mentioned in the introduction, it is likely that there will be additional new strobes released in the near future. It should be stressed that there is no timeline for these yet. There is one new strobe that is available now that did not make it to us in tome for the review, so we will likely do a separate review of it soon.

Thanks again to Takuya Tori of Inon, Peter Mooney of ScubaPix, Leo Grower of Ocean Leisure Cameras and Emperor Divers, Marsa Alam. These strobes are all available now, please consult you local specialist retailer for prices.

  1. Introduction.
  2. Strobe Fundamentals.
  3. Inon Z330.
  4. Retra Flash.
  5. Symbiosis SS2.
  6. Test results and conclusion.