Does Metering System works with Flash ?

[aroy]

I have found that Matrix metering works best with flash. The CW or Spot is not consistent. Professionals use specialised flash meters to calculate the reflective light and then set their exposure accordingly.

For indirect flash, you have to find out how much compensation is needed. It cannot be fixed, as each room has different reflectivity. The contribution of fill flash will be less for a bright ambient and increase as the ambient light decreases.

 

[WayneF]

There is more to it. Matrix, Center Weighted, or Spot metering modes are only about ambient light. The flash system instead has and uses its own central metering system. So the flash system does NOT do spot metering, but since spot metering is NOT a balanced situation, then Spot does switch flash metering from TTL BL (affected by balancing with ambient), to be TTL (unaffected by presence of ambient).

Nikon is a TTL BL system, and the default mode for flash is TTL BL.

For fill flash outdoors in sun, TTL BL is very handy, doing automatic flash compensation (flash reduction, i.e., balanced flash).

For flash indoors, TTL BL can tend to underexpose, and TTL mode becomes a favorite. TTL comes ahead on as metered, regardless of any ambient.

A few flashes have a TTL vs TTL BL menu to select flash metering mode. Frankly, this does help understanding and use. Those that don't have the menu default to TTL BL, but we can specify Spot metering or FV Lock to make sure the TTL flash has full capability indoors (the flash never does Spot metering). In that way, Spot metering commonly helps flash indoors, but the thing about Spot though, if you don't reset it Off when you go back outdoors, expect some bizarre results then when you have ambient.

 

[Jleary]

Ok, I have written about this here somewhere here but can't find it so here it is again. First understand how the flash works - power is controlled by the duration -see the spec here -scroll down to "Flash duration" for the SB700 At full power 1/1, the duration is 1/1024 sec and at 1/128 power the duration is 1/40,000 of a sec. Now, this is how TTL works in Nikon - you set the camera in M(anual) mode but you are NOT in Manual - you have transferred the automatic function from the camera to the flash. Because the flash speed is faster than your shutter speed, your shutter speed contribute very little to the exposure - so just set it to 1/200 or 1/250 ie fastest sync speed.

Now, set your aperture for your liking base on depth of field you want. (That's the fundament art of photography - right?) When you take a picture, the flash sends out a "pre-flash" and the camera reads the reflected light level and based on its zoom setting and aperture, instructs the flash what power to use to light the subject - and this is when you are set on spot metering - meter the subject. It doesn't matter if you are pointing the flash head straight at the subject (Never do that unless you have a soft-box) or up the ceiling or in many cases, behind you with a white wall. The camera by reading the preflash light level will tell the flash the proper level to use. IGNORE THE LIGHT METER READING - it doesn't apply here! If you turn on the beep in the SB700, you can by the beeps tell if there's enough light after you press the shutter - 3-beeps means not enough power - put light closer to subject or set up a 2nd or 3rd speedlight!

Now, if you are using the flash as a fill-in flash, (BL mode) then use Matrix or Center-weight. Here, the shutter speed will control the brightness of the background but the TTL flash will control the brightness of your subject.

A note about pointing to the ceiling - the ceiling is the best softbox ever but only if it's lower than a 10ft ceiling and a white or off white ceiling. If you bounce off a 20ft ceiling, you won't have enough light power with an SB700 - I use 3 when I do that. If the ceiling is not white, you'll need to change your white balance, in-camera or post-production. When using the SB700 or any Nikon, set white balance to "Cloudy" - not "flash." When you have high ceiling like convention halls, try bouncing off a wall behind you! Or invest in a $50 portable softbox or one of Gary Fong's rubbermaid cups!! In any case, don't fret about having to manually compensate for the non-direct lighting or any light-modifiers - the TTL system will take care of that for you.

Hope this clarifies how TTL flash works. With NIKON, when using TTL speedlites always shoot in MANUAL mode - even if you have never done so, don't panic - you are not really in manual - the exposure is taken over by the speedlite based on what the camera tells it the setting is.

Now, High-Speed Sync (HSS) aka FP mode next ... never mind...

Amazing explanation!