Friday, June 19, 2009

Direct flash and TTL/BL

On page 1.) we established that TTL/BL uses the distance info from the lens "when the flash is facing forward" . Of course in most situations we want to avoid direct flash but outdoors where there is nothing to bounce off , and in bright sunlight where the flash isn't the main light source , we still use it sometimes .

Just a quick review of TTL/BL and the distance factor - first a properly focused picture ....

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Then we manually go to close focus and the flash dims down automatically

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and as we change the focus distance to 20 metres it brightens up ....

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proving that the focus distance directly affects the flash .
Now for the proof in real life . I set up my model ''Stinky'' indoors to only show the flash with little ambient to detract from the results . I left a reflector in the same position and then moved the subject under the focus point further away . This is what TTL did with the scene - it was totally fooled by that white reflector and exposed for it the whole time .

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Now on to TTL/BL . Even though the reflector was in the same position reflecting back a lot of light TTL/BL continued to meter for the active focus point on the subject and was not fooled by the white object in the frame .

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This proves that TTL/BL is superior with direct flash photography - it's a pity it doesn't have that reliability with bounce flash and wireless CLS .
Of course it isn't a simple program and there may still be some surprises when we use it but I am slowly coming to grips with its 'logic' .
Using direct flash outdoors is not the problem , predicting results indoors where the flash is the main source of light is more of a challenge because there is little ambient light to hide our mistakes as with pictures in bright sunlight .

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