Fenix light output graph

PeteHall

Moderator
Can someone please explain the scales on this graph for the Fenix HM23 that I've just bought:

Fenix-HM23-Headlamp-runtime.jpg


At first, I thought that they were log scales, but they definitely aren't log scales and it's been too long since I had to look at anything like this to know where to start...

What is the first mark on the X axis? I'm guessing 1 minute...

What are the two marks on the Y axis? I have absolutely no idea with these...

Are these even actual scales, or are they just a visual representation?
 

Roger W

Well-known member
Try searching the site for "lamp output graph". This question has been dealt with before.  Basically the diagram you have posted is saying that your lamp will start off at 240 lumens or 70 lumens or whatever, but after an hour or so you will be crawling along at something like 10 lumens or less.
 

Fjell

Well-known member
It?s a light-hearted sketch.

Extremely unsurprisingly for a 1.2-1.5V lamp the output drops like a stone if you pull it hard. A single Eneloop Pro is about 3W.hr. So about 80-100lm for 3 hrs if it was current controlled, which it isn?t. I imagine the best compromise would be at the 70lm level. Give it a run test - I would have thought it should be reasonable for more than hour. The type of battery will make a big difference.

I am not sure if you run into voltage operating trouble with a 1.2V NiMH, but normally a 1.5V Duracell would be worse. Possibly not in this case, but that is annoyingly wasteful. I would think you will carry several spare batteries...

240lm if true would pull 2A from the battery at 1.2V. That would free fall. It?s a look at the ceiling for 30sec sort of setting.

For sure the 4lm setting is for checking your watch.

If it all goes pear-shaped buy the stick-on helmet mount for your Pixa-1/2. Thoroughly sorted.
 

MarkS

Moderator
This was discussed before at https://ukcaving.com/board/index.php?topic=26640.0. They just look like visual representations to me.
 
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