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Thread: Guesstimating relative lumens output

  1. #1
    Enlightened
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    Default Guesstimating relative lumens output

    Seeing that lumens is just the total output of a light, am i right to say that if i were white wall hunting, but instead of having all the lights i'm comparing at the same distance, i adjust the distance to the wall of each light such that the final beam on the wall covers the same area. With this, would i be right to say that the brighter beam on the wall conclusively has a higher lumen output than a dimmer beam?

  2. #2
    *Flashaholic* Marduke's Avatar
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    Default Re: Guesstimating relative lumens output

    No, because beam shape and tint are HUGE factors in how we perceive brightness. A ceiling bounce test is the most reliable method to compare lights without access to any equipment, but even that still carries the same downsides to a lesser extent.

  3. #3

    Default Re: Guesstimating relative lumens output

    +1 on the ceiling bounce. I didn't think my TK40 was 3x brighter than my TK11 until i did the ceiling bounce test. Then i soon realized it was

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    Flashaholic* ANDREAS FERRARI's Avatar
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    Default Re: Guesstimating relative lumens output

    Quote Originally Posted by Marduke View Post
    A ceiling bounce test is the most reliable method to compare lights without access to any equipment ...
    +2-by comparing light in a small,confine room(bathroom) you should be able to see a difference.If a light manufacturer claims 200lm. but the actual measurable lumens are 190-do you know what that means? Nothing!!! The human eye can not tell the difference! Even if the lumens are 170 you would be hard pressed to tell.To me beam shape and clarity are more important and as far as I know there isn"t a machine to measure that!
    My girlfriend said if I bought one more light she would leave me...........I'm sure gonna miss her.

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    Default Re: Guesstimating relative lumens output

    Quote Originally Posted by Marduke View Post
    No, because beam shape and tint are HUGE factors in how we perceive brightness. A ceiling bounce test is the most reliable method to compare lights without access to any equipment, but even that still carries the same downsides to a lesser extent.
    Good to know. I was thinking making both beams the same size on the wall would have taken care of the beam shape issue.

    In this case, does anyone have an idea on how to guesstimate the output of a J bin MC-E stuffed into a Jetbeam Jet I Pro on eneloops? Ceiling bounces aren't really working since the only other lights i have to compare against with a known figure are all Q5-WCs.

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    *Flashaholic* Marduke's Avatar
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    Default Re: Guesstimating relative lumens output

    You could calculate the brightness increase proportional to the efficiency increase at that drive current.

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    Default Re: Guesstimating relative lumens output

    So according to the emitter flux datacalculator from CPF, assuming the Jet I Pro puts out 130 emitter lumens, which the calculator says is about 450ma at 3.37V. This means i have 1.5165W driving my MC-E which turns out to be 125ma at 2.98V.
    Does this math look correct?

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