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I think this is such a great posting that I tried a first blog-post. Thank you WayneF for that great explanation

Quote Originally Posted by WayneF View Post
Quote Originally Posted by Blacktop View Post
Thank you Wayne for this simple explanation. I never would have thought to use the P mode. I've been trying to do this in Aperture priority.
Also been using Spot metering.

My in camera flash doesn't have a TLL-BLT mode, just a TLL plus some other manual flash settings mode.
I'm going to try your tip and report back later when I get home.


Camera P mode is not essential, it is just easy. There are other ways, but P mode knows how to do it (fill flash in bright sun).

Camera A or M mode works too, and would be the same if you set the same aperture as P, however then you have to know that Sunny 16 will require an aperture up near f/11 or so in bright sun. Because, shutter speed cannot exceed maximum flash sync speed (in the ball park of 1/200 second maximum with flash), requiring the aperture to be stopped down. Sunny 16 says bright sun (at ISO 100) exposure is 1/100 second at f/16, or 1/200 second at f/11. P mode knows about all of that, does it automatically. If camera A or M, you have to know it. If you start off in A mode by setting say f/5.6, you just see an error flashing, because the camera cannot change aperture in A mode, and f/5.6 is not going to work in bright sun (at maximum sync speed shutter speed).

In bright sun, the TTL BL system will automatically underexpose the flash about -2 EV, which 1) does not overexpose the subject with TWO correct exposures adding, and 2) is just about right degree for fill flash in bright sun.

And Spot metering changes the flash mode from TTL BL to instead be TTL mode, and then TTL is NOT balanced fill flash. TTL mode (and thus Spot metering mode which forces TTL mode) will try to give full flash exposure, regardless of any ambient (not because flash is Spot metering - the flash does not do Spot, but it does change the flash to TTL mode. There is no concept of background in ambient Spot metering, so there can be no balanced flash. Exif shows this mode that was used.

If using Spot metering, then you get TTL mode (instead of TTL BL), so then it has to be you that sets about -2 EV flash compensation, but then that works fine too (fill flash in bright sun).

The flash menus that simply say TTL (internal flash, SB-700, SB-400, Commander, etc) are in fact TTL BL mode by default.
I can't swear that every third party flash is the same, but surely most are - Nikon is a TTL BL system. It is the camera that does this. The Exif wil show what it has done, but can be confusing to decipher.

We of course have to account for the bright sun too, and P mode does this. Some choose to underexpose the sun a stop or two, to darken the background (it is another "look", a choice), and camera mode A or M can easily do that, but then, you would use TTL mode, not TTL BL mode. Then Spot metering can force TTL Mode in flashes otherwise without an overt menu.

So then, maybe we intentionally underexpose the ambient background -2 EV, and then fully expose with the flash. Makes the subject stand out against the background, but can have a unnatural look. Actually, this ambient underexposure is done more for sports action, so the ambient at 1/200 second won't blur the action (the flash is faster). Technically, this becomes ambient fill for flash instead of vice versa.
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  1. Michael J.'s Avatar
    That is such a helpful posting to me. Thanks again WayneF for that great explanation and Thank you Blacktop starting this topic.
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