Help Me Understand Guide Number: DS51 vs. D2000 vs. YS110

[JahJahwarrior]

Studying budget strobes...

Guide number divided by aperture you want to use for the shot equals the number of feet illuminated by the flash, correct?

so, if I use f2.8,
DS51 with an underwater guide number of 28 illuminates about 9 feet
DS160 with an underwater guide number of 38 illuminates about 12 feet
YS110 with a guide number of 20 illuminates less than 9 feet
D2000 with a guide number of 20 illuminates less than 9 feet.

Am I missing something, or wrong about something? The DS51 seems like an incredibly capable flash, at a lower price than the YS110. But, we all know what they say: if it sounds too good to be true, ask Scubaboard because you probably made a mistake!

 

[jdfmail]

Take a look at this for side by side comparisons. Underwater Strobe Comparison Guide - Digital Diver Network
DS51 has a GN of 17 and less coverage.

 

[flareside]

And another source of good information would be Underwater Camera Articles: as actual performance may not be as good as claimed specifications. (And I do wish these guys would update their information to current models as I would like to know if the Oly UFL-2 is anywhere near as powerful as it claims.)

 

[Puffer Fish]

JahJah, The numbers are metric system. An underwater guide numbers are very dependent on how clear the water is.

It would not be fair to compare the YS110a to the DS51...the YS110a has a much wider field of view, it has a focus light, a very nice sttl control system and is somewhat floaty (which is good or bad, depending on your point of view and camera).

Wider angle is only a value if you are shooting wide angle... or have your strobes close to the camera. The wider the strobes are placed, the more they are shooting at an angle.

I have YS110's and UH-1's... both work very well with a point and shoot. Using a DSLR, with a high f stop, and the UH-1's work out to about 2 ft, the YS110's out to around 4 ft.. in terrible vis water... but at 4 ft the backscatter is terrible....so I tend to use the UH-1's more. Clear water, wide angle and the YS110a is the way to go.

On land, YS110's are very powerful strobes.

flareside - the UH-2 only works with oly and panasonic cameras, and is a variable focus strobe (ok, you can use them in manual)... as you make the beam wider, obviously the guide number goes down. At widest they are roughly equal to the YS110's. So it will depend on how wide you need to go, but at their best, they are very powerful. I like oly strobes, as they can take an amazing number of flashes with higher end batteries. 100 strobe flashes with a UH-1 use, on average, around 400mah...with only two batteries. YS110's used for the same number of flashes, use just over twice that across 4 batteries.

Note: lighting the same distance and scene.

 

[JahJahwarrior]

Ikelite claims 28 but 17 sounds much more reasonable thanks!

 

[JahJahwarrior]

My photography is almost all in relatively clear caves. As such, any strobe I buy now will have a chance of eventually ending up as a slave strobe fired well off the camera, being held by a lead diver to light up passage in front of them, while that diver is lit up by another strobe on the camera. The Ikelite strobes, mounted on an arm, with the EV controller on the other end, are perfect for this. Diver can hold the strobe in such a way that the arm is parallel to their arm, with the EV controller by their elbow and the strobe by their hand, making it disappear in some shots, and not stand out to the viewer.

I don't think I can do this with the Sea and Sea strobes, though. Can anyone comment on this?

I see that Ikelite lists the guide number in feet and metres, I suppose the Sea and Sea only lists in metres, and that is why I was confused.

 

[PatW]

The major drawback of the D51 is its angle of coverage.

Also, you have to think of the practical aspects.

As to range of the strobe, even 7' has to be thought of as wide range. Remember the light has to travel from the strobe to the object and back. Water absorbs red light in 15'. At 7', you have a 14' round trip which means almost all the reds will be gone. In practical terms, the closer the better. The need to get close is why wide angle lenses are so important in many underwater photo applications.

 

[bvanant]

There is some confusion here I think between GN given in meters and feet. The DS51 has a GN of 28 feet or 9 meters underwater and 17 meters on land at ISO 100 with a beam angle of 70 degrees. The DS160/161 has a GN of 38 ft/12 meters with a beam angle of 90 degrees UW. The YS110 has a land GN of 22 meters. If we use the same ratio of land/water as the DS51 then the YS110 has an UW GN of 11 meters or 33 feet which is a bit more than the DS51. The D2000 has an air GN of 20 meters or 65 feet.

The conclusion of all this is that the DS51, the YS110 and the D2000 are all about the same power. The DS160/161 is a bit more powerful.

Bill

 

[Puffer Fish]

You can daisy chain YS110a's together, just need long enough fiber optic cable.

sTTL is faking the camera into thinking it is getting light from it's strobe. It uses time...so all the strobes would turn on ... and shut off when the camera's strobe shut off. My guess is that would not result in a good image every time, but would work some of the time. You can also put one on sTTL and any others on manual, and just set the amount you want from them..

I would guess (have not tried this) that one would eventually run into timing problems at some point of going from strobe to strobe to strobe, etc, etc..but given we are talking the speed of light, it may be a lot.

You can also make double (perhaps triple) fittings, so they are all connected together (which is better depends on the route).

Always keep in mind that guide number and beam width are connected.. make the beam narrower, and you will have a higher number. I would think the wider beam, in your case would be an advantage.

Note: Oly UH-2 can be remotely controlled from the camera, so in manual one could turn the power up or down without it being connected.

My photography is almost all in relatively clear caves. As such, any strobe I buy now will have a chance of eventually ending up as a slave strobe fired well off the camera, being held by a lead diver to light up passage in front of them, while that diver is lit up by another strobe on the camera. The Ikelite strobes, mounted on an arm, with the EV controller on the other end, are perfect for this. Diver can hold the strobe in such a way that the arm is parallel to their arm, with the EV controller by their elbow and the strobe by their hand, making it disappear in some shots, and not stand out to the viewer.

I don't think I can do this with the Sea and Sea strobes, though. Can anyone comment on this?

I see that Ikelite lists the guide number in feet and metres, I suppose the Sea and Sea only lists in metres, and that is why I was confused.

 

[JahJahwarrior]

My confusion was due to Ikelite using feet and metres, and assuming Sea and Sea's GN was listed in feet, when it was in fact, metres.

The EV manual controller with an ikelite strobe is the perfect solution for off camera strobe use, where the diver is 10 feet away from the camera. Fiber optic cable would not only be in the photo, but would be an inconvenient way to do this.

I've only been on a few dives as a model with this setup, but it works pretty reliably and well. I wanted to start with strobes that will allow me to move up to that system in the future once I have more strobes.

I'm not a camera idiot, but all of my experience is with land based SLR's mostly with ambient lighting, and carrying a point and shoot on a lot of dives in caves, using ambient light. I've enjoyed the photography I've already done, but super slow shutter speeds and ambient light only go so far, adding a strobe is a definite priority.