help understanding lights

[partridge]

Hi. I know there are some really technical people on this board and would appreciate any help in understanding dive lights.

My students want to buy dive lights but I want to be fair and honest with them. They dont dive much at night but want to have their own lights. I dont want to sell them the high end models if they dont need them.

With regards to the number of batteries, does more of the same size mean brighter? How do I compute this?

What about same number but different size? Does bigger size mean brighter or longer?

I know I am vague and maybe should look for a website like "Dive Lights for Dummies". Anybody know a good online source?

 

[jonnythan]

The brightness is most closely related to the number of watts.

For instance, a UK C8 uses 8 C-cells and has about a 13 watt bulb. The C4, which uses 4 C-cells, only has a 6.6 watt bulb.

In my experience, the standard 8 C-cell lights offer the best value in a good light (UK C8, Princeton Tec Shockwave, etc). The smaller but bright handheld lights, the UK SL4 (5.5 watts, 4 C-cells), Princeton Tec Surge (8 AA cells, 7.5 watts), etc, are all good backup/daytime/look-under-rocks lights.

In general, bigger lights offer higher wattages, simply because higher wattage means less burn time, and higher wattages require the big batteries to get decent burn time.

Also, some lights have more focused beams whereas others have flood-type beams.

 

[partridge]

Wow youre quick. Thanks.

I am looking at value in terms of burn time too. Lets take the 4 C-cell lights. Does this have less burn time but is as bright as a 8 cell? Some divers take a night dive once a month only and are looking for a light that will last only for 70 minutes then they can throw away the batteries. Buy again next month.

The question may be stupid but I know next to nothing about this. If it is then just tell me so.

 

[jonnythan]

For this type of use I'd probably use something like a UK C4. Bright enough for the occasional dive, only uses 4 batteries, inexpensive, but still a nice flood style beam that most people seem to like.

 

[scububa]

I'll start off saying...I don't have as much experience as Jonnythan and his suggestions make sense...reading your requirements, I wonder if the same type of light he suggests, but with the LEDs wouldn't be a good fit. They are not too much more expensive and you get lots of burn time. Some of the brightness reports seem equal to the non-LED lights. In your scenario, with not being used a lot, the long burn time would more likely have some battery life when picked up. Also, if it is carried in a bag more than used, I think the LED will handle the banging around better than a filament bulb.

I use the lights Jonnythan mentioned, but we use them often, so we know 2 dives and the batteries are gone and they are primary dive gear, so they don't just lay around, but if I were buying now, I'd probably go LED.

(as it is, we use lights enough, I am trying to decide on HID units for my upgrade )