axd
Newly Enlightened
Someone who has never seen tritium-based lights in action, might be surprised by the weak brightness. Here I'm talking about "illuminators", not the small "locator" trits.
Pictures of such devices will not always give the right message to someone who is not attentively reading complete threads, so I was wondering if there exist better criteria to define the "usefulness" of such lights.
Values such 100-1000 microlamberts don't say much to the uninitiated, and even charts such as e.g. Surelite's do not help a lot.
One poor man's way (i.e. one without light measuring equipment) could be to compare the output to common devices such as eg a Nokia 3310 lighting up in the dark: I tried this with my Torch, and it seems that both produce the same output when at the same distance from a wall - guess this is similar to a ceiling bounce test.
Maybe an improvement is to use well known lights - such as the Nokia - except that not everybody has such a model. Even this comparison is not complete, as it compares two less known items (even the trits are not so known to everybody).
How about following criteria to categorize such lights? Maybe such criteria already exist... This could give a better idea to the interested whether to invest in such lights or not.
The idea is to have a white sheet of A4 with a grid of (what seems to be called) optotypes with size increasing from top to bottom, and contrast (ink blackness?) increasing from left to right. The top-leftmost character will probably not be readable by anyone, while the bottom-right one will be by everybody.
An attempt with the fonts available here, just to give the idea (imagine random letters lined up in a grid):
qwerty
qwerty
qwerty
qwerty
qwerty
qwerty
qwerty
Edit added: I'll try make such a sheet Monday.
The idea is to report the faintest readable letter in each row.
Maybe three readings could suffice instead: smallest font (highest line), lightest colour (leftmost column), and one in-between (although there's probably no linear relationship between the three points).
The measuring would be in two phases. In a first (reference) phase, the subject performs the test in bright daylight, to get an idea of his/her visual acuity.
Then, the test is repeated with fully adapted night vision, using the device to light the same sheet of paper. I'm sure there will be differences; that could give a good impression on the usable brightness of a device!
Problem with all these approaches are that (IMHO) much depends on the visual acuity of the viewer: someone with bad eyes will report different from someone with excellent eyes, but the reference would give an indication there.
But the main point is to avoid having to judge a light based on pictures, because it is very difficult to take those pics, and IMO such pics can't give a true impression of the value of a light. And the criteria above - if they can be refined - could allow to categorize various GID sources more accurately (other than by lamberts, lumens, or luxes...)
-alex- (somewhat bitten by GID :tinfoil
ps - There is also the "walk to the toilet":toilet: criterion - further subdivided into "crawl to the toilet"
...
see also
http://flashlights-axd.wikispaces.com/Betalight
http://www.candlepowerforums.com/vb/showthread.php?t=159057
http://www.cpfmarketplace.com/mp/showpost.php?p=1142097&postcount=29
Pictures of such devices will not always give the right message to someone who is not attentively reading complete threads, so I was wondering if there exist better criteria to define the "usefulness" of such lights.
Values such 100-1000 microlamberts don't say much to the uninitiated, and even charts such as e.g. Surelite's do not help a lot.
One poor man's way (i.e. one without light measuring equipment) could be to compare the output to common devices such as eg a Nokia 3310 lighting up in the dark: I tried this with my Torch, and it seems that both produce the same output when at the same distance from a wall - guess this is similar to a ceiling bounce test.
Maybe an improvement is to use well known lights - such as the Nokia - except that not everybody has such a model. Even this comparison is not complete, as it compares two less known items (even the trits are not so known to everybody).
How about following criteria to categorize such lights? Maybe such criteria already exist... This could give a better idea to the interested whether to invest in such lights or not.
- be able to walk around with the light
- be able to read a book such as a Penguin Book
- be able to read a map
- ...
The idea is to have a white sheet of A4 with a grid of (what seems to be called) optotypes with size increasing from top to bottom, and contrast (ink blackness?) increasing from left to right. The top-leftmost character will probably not be readable by anyone, while the bottom-right one will be by everybody.
An attempt with the fonts available here, just to give the idea (imagine random letters lined up in a grid):
qwerty
qwerty
qwerty
qwerty
qwerty
qwerty
qwerty
Edit added: I'll try make such a sheet Monday.
The idea is to report the faintest readable letter in each row.
Maybe three readings could suffice instead: smallest font (highest line), lightest colour (leftmost column), and one in-between (although there's probably no linear relationship between the three points).
The measuring would be in two phases. In a first (reference) phase, the subject performs the test in bright daylight, to get an idea of his/her visual acuity.
Then, the test is repeated with fully adapted night vision, using the device to light the same sheet of paper. I'm sure there will be differences; that could give a good impression on the usable brightness of a device!
Problem with all these approaches are that (IMHO) much depends on the visual acuity of the viewer: someone with bad eyes will report different from someone with excellent eyes, but the reference would give an indication there.
But the main point is to avoid having to judge a light based on pictures, because it is very difficult to take those pics, and IMO such pics can't give a true impression of the value of a light. And the criteria above - if they can be refined - could allow to categorize various GID sources more accurately (other than by lamberts, lumens, or luxes...)
-alex- (somewhat bitten by GID :tinfoil
ps - There is also the "walk to the toilet":toilet: criterion - further subdivided into "crawl to the toilet"
... see also
http://flashlights-axd.wikispaces.com/Betalight
http://www.candlepowerforums.com/vb/showthread.php?t=159057
http://www.cpfmarketplace.com/mp/showpost.php?p=1142097&postcount=29
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