Scott Kelby: Rear sync balances flash and the ambient

Started Sep 2, 2010 | Discussions thread
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gisle
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Scott Kelby: Rear sync balances flash and the ambient
Sep 2, 2010

On page 21 in Scott Kelby's best-seller "The Digital Photography Book volume 2", there is a segment titled: "Rear Sync Rocks (& Why You Should Use It)".

The segment is illustrated with two photos, one with the classic white face in a coal cellar look (face in foreground lit by flash correctly exposed, background lit by ambient underexposed), and a second shot where the ambient backround is balanced with the foreground lit by flash.

Kelby does not say what camera or exposure mode he has used for these two example shots, but since he calls it "Rear Sync" (and not "2nd curtain"), we're probably in Nikon territory. And he is obviously shooting in aperture priority or program auto mode, since the difference between the two example shots is the shutter time (in the second shot, the shutter stays open longer to expose correctly for the ambient).

Now to the puzzling bit: He claims that it is changing from standard (front) sync to Rear Sync that makes the difference between the two example shots. Quote: "Changing to Rear Sync makes the flash fire at the end of the exposure (rather than beginning), which lets the camera expose for the natural background in the room first ... (my emphasis).

The first half is of course correct, but the second half (in italics) makes no sense at all to me. No digital cameras I know about meter the ambient during exposure , so it does not matter when the flash fires. Digital cameras meter, and finalize exposure setting for the ambient, at half press.

I find it puzzling that such a well regarded educationalist and photographer as Scott Kelby should be confused about how a camera determines how it exposes for the "natural background in the room" (i.e. ambient), but I see no way to interprete the sentence I've quoted above to make it right.

Testing with a Nikon D700 shows that if you set the flash mode to Slow Sync in aperture priority mode, it does not make any difference whether the flash is Rear Sync or not. In both cases, the shutter time picked by the camera exposes for the ambient (as the D700 manual tell you it will).

Now, further testing reveals that on a D700, setting Rear Sync automatically turns on Slow Sync as a side effect. There seems to be no way to pick Rear Sync without also getting Slow Sync as a "bonus". So setting Rear Sync on a D700 will lower the shutter time to expose the ambient (as claimed by Kelby), but his explanation why this works is IMNSHO bogus.

Btw. The book has a 32 page chapter "On Using Flash Like a Pro", and doesn't metion Slow Sync at all . I am less than impressed.

Any comments? Are there any flaws in my reasoning, or has Scott Kelby really misunderstood how his digital camera meters for the ambient.

(PS: I know what Rear Sync is and why I should use it. I am not asking for advice on how to use Rear Sync.)

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