SB-600 TTL vs TTL BL

chuckinsocal

Hi Gang,

I received my new SB-600 Speedlight yesterday. I haven't had a chance to try it out much so I'm just trying to learn it by reading up on it.

Among other things, I'm not clear on the difference between TTL and TTL BL. I use the flash mostly for shooting emergency incidents at night such as here.

I think the object of the game is to get the most distance I can get for wide shots and for shots where I can't get that close to the subject, and at the same time, get a wide angle of light so the scene is evenly lit (I think these two goals may be mutually exclusive).

So, the main question is: Do I shoot in TTL mode, the TTL BL mode, or in manual mode with my own settings? Also, if anyone has any other advice, I'd welcome that as well.

As always, thanks for your help.

ziggy53

A pretty good series of tests and conclusions here:

http://www.planetnikon.com/forums/index.php?showtopic=12603

chuckinsocal

ziggy53 wrote: »

A pretty good series of tests and conclusions here:

http://www.planetnikon.com/forums/index.php?showtopic=12603

Thanks for that link, Ziggy. There's some great information there. The trouble is maybe my mind is getting feeble and I just can't get my head around the issue.

As best as I can understand it, the TTL BL mode attempts to light the subject to match the ambient or back light. Hence, fill flash.

The TTL mode doesn't try to match anything. It just lights the entire scene enough to get a decent exposure.

The lighting at incident scenes can best be described as chaotic. There are the flashing red and blue lights on the emergency vehicles; flood lights on the fire trucks; street lights; traffic lights; headlights; tail lights; reflective material on the fire fighters gear, and more. I doubt I'll ever get a perfect exposure under these conditions.

I think the only way to get an answer is to experiment with the various modes and see which works best.

Thanks again for your response.

photogreen

Here is another test: Nikon SB-600



i-TTL / i-TTL BL

Desmond

chuckinsocal wrote: »

Thanks for that link, Ziggy. There's some great information there. The trouble is maybe my mind is getting feeble and I just can't get my head around the issue.

As best as I can understand it, the TTL BL mode attempts to light the subject to match the ambient or back light. Hence, fill flash.

The TTL mode doesn't try to match anything. It just lights the entire scene enough to get a decent exposure.

I've done my own studies on TTL-BL
TTL flash thinks it is the only light source and doesn't know or care what you are doing with the ambient exposure so you need to dial in exposure compensation accordingly .
TTL flash meters off an area like this :

and it measures that area and averages it out so the size of the subject affects the metering .

TTL-BL on the other hand meters off an area like this :



and has the ability to 'map out' it's subject which means it is not affected so much by image size . It also uses the distance info from the lens for more accurate exposure - especially with direct flash .
TTL-BL no longer works as a 'back-lit' mode , the manual is misleading .
It aims to exposure correctly for the subject regardless of the background lighting and adjusts its output depending on how well you have the ambient exposed - in other words it automatically dials back the flash the more you have the ambient exposed .