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TTL vs TTL/BL

Cash Chew , Nov 09, 2011; 10:35 p.m.

I tried SB-800 for TTL vs TTL/BL mode in Manual Exposure (M) mode on camera. Other than a slight less flash power given out on TTL/BL as compared to TTL mode, I still don't see any significant ambient light difference when I took sample photos in a dim ambient tungsten light cover about 1/5 of the left frame. When exactly do you use TTL/BL instead of TTL for a given situation to make a big difference?

Responses

Ariel S , Nov 09, 2011; 11:41 p.m.

A dim little tungsten light is hardly adding anything. When you'll see a difference with TTL/BL is when you're using the camera with plenty of ambient light. If you're using a dim tungsten light, even if your shutter speed is 1/60, your flash is overpowering, so you won't see a difference. If you're just bouncing the flash if you're in the shade, to provide another light source for creativity, or you're using fill flash in daylight, you'll notice a difference. TTL/BL will take into account the exposure that your camera would make if you didn't have a flash.

Michael Kohan , Nov 10, 2011; 01:40 a.m.

I always though the BL stood for back light, so if your subject has a lot of back light, use the BL setting to overcome the back light.

Peter Cohen , Nov 10, 2011; 02:55 a.m.

I read somewhere that it now refers to "balanced light," but then again that's what you need to do when you have a backlit scene. If I'm doing real estate or architectural shots, I use flash indoors set to BL and it does a great job (at least my SB-900 does) of matching interior and exterior light. Like Ariel said, use it outdoors and you'll notice the difference.

Frank Skomial , Nov 10, 2011; 07:59 a.m.

BL has never been for "back light". Why dont you use Nikon documentation ?
Balanced Fill flash lighing brings closer the flash light level to the ambient light level. This is only possible when the ambient light level is sufficient for correct exposure without flash.
Otherwise the BL flash mode will revert to iTTL providing correct exposure in the absence of sigificant ambient light level, and there will be no difference between iTTL/BL and the iTTL.

Curt Wiler , Nov 10, 2011; 11:06 a.m.

iTTL/BL can produce unpredictable results in strong back-lit settings since the flash fill will be influenced by the meter reading of the highlights and may result in overexposure of the main subject. It is best used in more evenly-lit images where the intent is to provide even fill, but generally plain iTTL gives the photographer more control of the final result. Granted that the newer bodies and flashes seem to have improved in this regard, but I try to use the BL setting sparingly if at all.

John McCosh , Nov 10, 2011; 01:28 p.m.

I am a wedding photographer based in New Zealand, where out light can be quite harsh. I use a pair of SB600 set on iTTL/BL on my D90 camera's at all times to give me fill in flash. I have never had any real problems with this set up and lets me work quickly without having to worry about the flash setup. When your shooting a fast moving wedding you don't have the luxury to adjust settings for each shot. So find the BL setting very useful. Same shots with this setup can be found here if anyone isinterested.
http://mccosh.smugmug.com/Weddings/Kieran-Stephs/Overview/19509107_2SvKMH/1560424508_9nWqR4k

Off to shoot another wedding today and yes my flash will be on iTTL/BL setting.
Happy shooting from New Zealand,
John

John McCosh , Nov 10, 2011; 01:38 p.m.

Sorry meant to attach this photo as well.


Fill flash with D90 and SB600 Flash set on iTTL/BL setting.

Rodeo Joe , Nov 10, 2011; 03:32 p.m.

If you're using program or aperture priority mode, a good way to check whether i-TTL/BL is working as the main source of light or as a fill light is to keep an eye on the shutter speed. If the camera allows a shutter speed higher than 1/60th *, then you're into "BL" territory. If the camera stubbornly refuses to go above 1/60th *, then flash will be the main source of lighting.

* 1/60th is the default lower limit to flash synch speed. If you've changed this in the menu, then substitute whatever lower synch speed you've set.

WRT back lighting. On some Nikon models, changing the metering mode to "spot" automatically changes the flash mode from BL to straight i-TTL. Since spot metering makes more sense for backlit or isolated subjects, you can follow Nikon's logic in doing this. Personally I'd rather use flash compensation to control the amount of fill-in, but to each their own.

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