Introduction

I have been using the Seaflash 250TTL strobes for over two years now. In fact, all my D2X underwater images have been made with these strobes. But still I wanted to write a review. I am maybe a bit biased, because I am a big fan of the Seacams and it's not a no laboratory test. But I think the result of the test will show how good they are for wide angle and how well the TTL performs.

The main reason for the test is because I wanted to check if the TTL of the strobes is working as well as Nikons SB800 system strobe. I do some exposure compensation while using the strobes in TTL, mostly +1/3 of +2/3. I do this just to get the histogram as far to the right as possible. I noticed that I needed to do this compensation many times, which made me wonder if the TTL is working as good as it is supposed to be. I would think that little exposure compensation would be needed. That is why I tested the Seaflash 250TTL strobes against Nikons SB800.

The Seaflash 250TTL is built from the ground up. The internals are completely digital. Bugs in the strobe can and have been solved by software upgrades. This makes, in my eyes, the Seaflash unique. Probably almost all other vendors are using adapters to modify their electronics in order to make it work with modern digital cameras. The Seaflash is digitally programmed to work with Nikon and Canon digital cameras. The Seaflash supports most of the functions a "normal" topside strobe has. The pilot light of the strobe for example is lit in dark conditions in order to make the autofocus work better. It is worth a test to see if this new approach from Seacam is working well in the lab and in the field (or under water).

The Seacam strobe has two bulbs. The big one is used for wide angel photography. The small bulb has a higher color temperature (almost alike the SB800 from Nikon) and will mostly be used for closeup photography. The back of the strobe holds a display that displays the output after a flash in percentages relative to the maximum output of the strobe.

Two strobes can be used together in TTL when they are connected through a piece of electronics that is placed inside the underwater housing. In that case you have one master and one slave strobe. The master strobe determines the output of the slave when used in TTL. But this is also the case when the strobes are used in manual mode. I mostly set the slave strobe in TTL (which will display A on the display). I then set the manual output that I need on the master strobe. That will automatically set the manual output of the slave unit. I love this when I am taking wide angle images with the strobes, because I need both strobes to have the same output when I am using a fisheye lens; at least most of the times.

The bigger bulb can be used without the protection ring on front of the strobe. That way you get a 114 degrees output.

I mostly use the smaller bulb in combination with the protection ring. This way you get a much smaller output angle, which is great for macro.

The strobes in the field

The 115 degrees output really works for wideangle photography. The following two images show a very big manta ray that was at least 5 meters (15 feet) wide. The other image shows some huge corals in the Maldives. I was able to light them out completely with the Seacams. Both images were taken with the big bulb which has a lower color temperature. That way the overall color of the image is what I want. Good white Mantas and nice blue water in the background. Don't forget that the white balance is done on the complete image. The colors of the fore and background (strobe and available light) have to be in balance to get images like this.

The following two images show the performance of the strobes then uses as macro strobes. I use the smaller bulb in combination with the protection ring in front of the strobe. Both images where taken in TTL mode with +1/3 exposure compensation. The small commensal shrimp was taken in combination with the wet diopters from Seacam.

The Test

I wanted to test the TTL performance of the Seaflash strobe against Nikons SB800 strobe. I made 5 reference images, all with a Nikon D2X and a 105mm closeup lens. No exposure compensation, no editing in Adobe Camera Raw.

• A white background, my table top
• A grey image, a LaCie external hard drive
• A black image, my good old Nikon F100
• A colorful closeup image, part of a small globe
• A closeup image with an open background, a small battery

The first three images were taken with 1/25o shutter speed and aperture F11. The last two were made with 1/250 shutter speed and aperture F22. I used the diffuser of the SB800 for the last two closeup images in order to have a good equal exposure.

I also made the same test images with the Seaflash 250TTL strobes. All with the same shutter speeds and apertures. The first test was with one Seacam strobe. This strobe was positioned almost the same as the SB800 on top of the housing. I used the big outer bulb for this test.

I also made the test images with two Seacam strobes. I used the small bulb for these images. The strobes were positioned on both sides of the housing.

The histograms of the images are used to compare the exposure of the images.

The five reference images taken with the SB800 are:

The results

The results are a bit hard to describe. Let's start with the test images taken with one Seacam 250TTL strobe:

What's happening here? I thought that the SB800 would be more accurate. But these images are lighter and look better exposed. We will compare the histograms later. Let's first have a look at the test images taken with two Seacam strobes:

The expose looks the same as the images taken with one strobe. Less shadows, of course, because these images are taken with two strobes. But these images are better exposed compared to the reference images taken with the SB800.

Now it's time to compare the histograms. I will compare them for all five the test images. The first histogram is the one of the SB800, the second one the one with one strobe, the third histogram is the one coming from two Seacam strobes:

A white background, my table top

The first (SB800) histogram is wider, but the Seacams produce a whiter output; as is wanted when you take an image of a white background.

A grey image, a LaCie external harddrive

No big difference. The test images were equally grey.

A black image, my good old Nikon F100

Here the TTL output of the Seacam strobes is, in my opinion, better. The histograms are a bit to the right. But that's no problem at all when you use Adobe Camera Raw as your RAW converter.

A colorful closeup image, part of a small globe

Here the TTL output of the Seacam strobes is, in my opinion, better. The histograms are a bit to the right. But that's no problem at all when you use Adobe Camera Raw as your RAW converter. The histogram of the images (the third) taken with two strobes is even better because it is more to the right.

A closeup image with an open background, a small battery

Here the TTL output of the Seacam strobes is, in my opinion, better. The histograms are a bit to the right. But that's no problem at all when you use Adobe Camera Raw as your RAW converter. The third histogram could be a little bit over exposed. But this is still better than the SB800 histogram. Why better? It's my experience that I get beautiful tif files when I use Adobe Camera Raw on histograms like this. The over exposure of histograms like this is no problem for ACR.

Conclusion

The histograms show that the Seacam strobes produce better exposed images than the SB800 strobe from Nikon does. I like my histograms to be as far to the right as possible (maybe even a bit over exposed when you only look at the histogram on the D2X camera). I would not have expected this. I mostly use some + exposure compensation when I use the Seacam strobes underwater. But I believe this + exposure compensation would be needed in combination with a SB800 strobe too. This compensation would be more on the SB800 than on the Seacam strobe.

The Seacam strobe performs extremely well in wide angle. The angle of coverage is so good; it can be used on very, very big subjects without any problem.

The TTL performance of the Seacam strobes is very good and reliable. Just as good, but probably better than the TLL exposure of Nikons SB800.

Seacam will produce a smaller version of the strobe very soon: the Seaflash 150TTL. I cannot wait to test it!

Note: It's difficult to compare histograms of different test images. The position and angle of the strobe greatly influences the exposure. But the test clearly shows that the TTL of the Seacam strobes is working very well.