kli
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Veteran Member
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Posts: 4,587
Re: Using LED ring lights (not flash) for macro insects
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Antique Eruption wrote:
One thing I've never grasped with flash is the relatively low shutter speeds. ...
Whenever you take an image with flash, you're combining two different exposures from two different sources of illumination: the ambient (all the existing light already in the scene) and the flash.
Ambient exposure is controlled by iso, aperture, and shutter speed (this you know).
But flash exposure is controlled by iso, aperture, power, and subject-to-flash distance.
If you are at or below sync speed, then shutter speed does not affect the flash exposure because the flash burst duration is much much shorter than your shutter speed (typically ranging from 1/1000s (full power) to 1/40,000 (1/128 power) on a full-sized speedlight.
And because you have these differences in control between your two light sources, you can balance the ambient against the flash however you want.
If you adjust your exposure so that flash is the primary source of illumination but there's still some ambient exposure, you can get images where the subject is "frozen" by the flash, while showing motion trails (slow sync flash). And when the flash fires (at the beginning or end of the exposure) changes the direction of the motion trails.
But if you can overpower the ambient light with your flash to the point of "killing" the ambient (i.e., all the exposure is only from the flash and none of it from the exposure; typically by underexposing the ambient around -5EV to -6EV so you get a black frame if the flash doesn't fire) then you can freeze motion with just the flash, which, remember can go from 1/1000s-1/40,000s (which is why flash is used for high-speed photography, for things like bullets going through apples :-). And with the light at macro distances, killing the ambient is more easily doable.
But this is also the main reason strobes are preferred over LEDs for this: you need a lot more light output to be at +5EV (32x) over the ambient. Petapixel did a side-by-side of Godox's LED video lights and their strobes, at max. power and found that one of the full-sized speedlights metered at +1EV, while the LR150 bi-color 150 LED ringlight was at -5.3EV. So just getting, say, a $65 TT600 is going to offer you something like +6EV (64x) more power/light to play with for this type of thing. Even a $200 1000 LED panel still only comes in at -2EV. And a speedlight? Is the smallest and lowest powered strobe you can get.
LEDs are great if you'res shooting video and need continuous light, or you're doing tabletop product photography in a studio and need to see tiny angular adjustments as you're working and don't need much power to freeze motion or fill flash against sunlight. But strobes will always give you a lot more light for your money.