I am very interested in purchasing one of these two lights. LP has them for the lowest price. C8 for 75.00 and C4 for 55.00. I read somewhere that the difference is that the C8 shines bright even when the batteries are low, and the C4's light dims as the batteries get low. Can someone please tell me any other differences between the two. Is the C8 worth the extra 20.00? Thanks in advance.
UK Sunlight C8 eLED vs. C4 eLED
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ShakaZulu
Contributor
Both the C4 and C8 lights dim as the battery power goes down. The only way to eliminate that effect would be to add DC-DC converters. The C8 will just take longer as it has twice the capacity. I have the C4 and recommend you go with the C8.
LOW
C4 ~ 1450 at beam center. (38.08 Comparison Chart equivalent)
C8 ~ 1450 at beam center. (38.08 Comparison Chart equivalent)
HIGH
C4 ~ 2450 at beam center. (49.50 Comparison Chart equivalent)
C8 ~ 3500 at beam center. (59.16 Comparison Chart equivalent)
LOW
C4 ~ 1450 at beam center. (38.08 Comparison Chart equivalent)
C8 ~ 1450 at beam center. (38.08 Comparison Chart equivalent)
HIGH
C4 ~ 2450 at beam center. (49.50 Comparison Chart equivalent)
C8 ~ 3500 at beam center. (59.16 Comparison Chart equivalent)
lairdb
Contributor
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ShakaZulu:
Make sure you're comparing apples with apples -- the C4 and C8 are incandescents without regulation circuits and dim rapidly as the batteries are consumed. The "C4 eLED" and "C8 eLED" are LED-based, do contain regulation circuits (as most (though not all) LED-based lights do, though to widely varying levels of sophistication), and do have much flatter dimming response (see text of the review we both cited.)
ShakaZulu
Contributor
Agreed, the eLED must have some sort of regulated supply. In that case the C8 eLed will have a longer flat profile. My only concern is that according to the article, the C8 iLight is brighter initially by about 2.5 times the eLed. Question - do you want the brightness or the duration. Since all my diving is rec, 1 hour max, I'd prefer the brightness...........
illumiGeek
Registered
The C8 eLED is brighter on high than the C4 eLED. And, of course you get much longer run time.
The problem, I believe, is current consumption. Regulators trade voltage for current. So the lower voltage 4 cell will draw much more current; and I don't think the Alkalines can cope with it (not for very long, anyway). Hence, less light even with regulation.
Using rechargeables in the C4 should help as they are much better at delivering high current. I have been meaning to test this, but have not gotten around to it.
The problem, I believe, is current consumption. Regulators trade voltage for current. So the lower voltage 4 cell will draw much more current; and I don't think the Alkalines can cope with it (not for very long, anyway). Hence, less light even with regulation.
Using rechargeables in the C4 should help as they are much better at delivering high current. I have been meaning to test this, but have not gotten around to it.
illumiGeek
Registered
I've been playing around a bit more with the UK eLED module. I haven't taken it apart (yet) or done any real voltage/current measurements, but I'll bet it only runs fully regulated on high power mode in the C8 eLED light, and not in the C4 eLED.
Both lights are pretty bright, but the C8 eLED is noticeably brighter on high, and in a regulated light this should not happen. The regulator is supposed to compensate for variable battery power and supply constant power to the light engine. On low mode both lights seem equal, but on high there is a difference. If it was a proper buck-boost regulator then light output would be the same (at the expense of some additional battery life in the C4).
Since this doesn't seem to be the case, I suspect it is a buck regulator only, and the C4 is running in direct-drive mode on high. A buck regulator needs to have a bit more power than the device it is trying to drive. For instance, if you are trying to power an LED with a vf (input voltage) of 6.8v, the buck regulator would need more than 6.8v to function. Let's say the regulator needs 0.2v over vf to run; that means once the voltage has dropped below 7v the regulator will no longer funtion. Most buck regulators will go into "Direct-Drive" mode once vf is too low. Direct Drive means it is just passing all of the power through (minus circuit resistance losses).
If this is the case (and I'll bet it is) then the C4 is only running off of 6V (minus circuit resistance losses) on high, and the typical Luxeon 5 watter needs about 6.8 to run at the correct current. This explains the brighness difference, and also why the C4 dims more as batteries are used up.
Aloha, iG
Both lights are pretty bright, but the C8 eLED is noticeably brighter on high, and in a regulated light this should not happen. The regulator is supposed to compensate for variable battery power and supply constant power to the light engine. On low mode both lights seem equal, but on high there is a difference. If it was a proper buck-boost regulator then light output would be the same (at the expense of some additional battery life in the C4).
Since this doesn't seem to be the case, I suspect it is a buck regulator only, and the C4 is running in direct-drive mode on high. A buck regulator needs to have a bit more power than the device it is trying to drive. For instance, if you are trying to power an LED with a vf (input voltage) of 6.8v, the buck regulator would need more than 6.8v to function. Let's say the regulator needs 0.2v over vf to run; that means once the voltage has dropped below 7v the regulator will no longer funtion. Most buck regulators will go into "Direct-Drive" mode once vf is too low. Direct Drive means it is just passing all of the power through (minus circuit resistance losses).
If this is the case (and I'll bet it is) then the C4 is only running off of 6V (minus circuit resistance losses) on high, and the typical Luxeon 5 watter needs about 6.8 to run at the correct current. This explains the brighness difference, and also why the C4 dims more as batteries are used up.
Aloha, iG
I just got a new UK LED C8 last week. UK makes great products! I've been carrying their SL4 with me on all my dives since last year. Anyway, I was extremely happy with my LED C8 on my first night dive with it. It totally outshined my dive buddies' lights (conventional-bulb 8 cell lights). The LED C8 also has high and low settings if you're worried about conserving batteries. I think it's better to have the C8 over the C4 for the extra light though, especially for a primary.
I got mine from Scuba Toys:
http://www.scubatoys.com/store/Scuba_Lights.asp?PAGE=2
Their price is slightly higher, but chances are that they really do have the item in stock unlike some of their competitors that I won't mention. They're also an authorized dealer so you get the full manufacturer's warranty with it too.
Just my 2c
I got mine from Scuba Toys:
http://www.scubatoys.com/store/Scuba_Lights.asp?PAGE=2
Their price is slightly higher, but chances are that they really do have the item in stock unlike some of their competitors that I won't mention. They're also an authorized dealer so you get the full manufacturer's warranty with it too.
Just my 2c
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