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(09-24-2009 03:29 PM)wrong Wrote: [ -> ]now, here is another reason for you to get a D300s

haaa but yes it was just a minor "complain" from me thanks a lot for the videos!

I seriously though of a D300S for that reason - but decided it was too expensive just to get better sound on a youtube video . I also tried recording my voice to the computer with a microphone afterwards but can't seem to get enough volume ?

Russ and I have been exchanging friendly emails now discussing the different concepts we have of TTL/BL . He still insists that TTL/BL reads off the centre of the frame like CW metering .
I'm still pretty sure it reads off smaller areas around the focus points and this test seems to suggest it works nothing like CW metering when compared to TTL flash in CW metering .




He says he doesn't want to 'go public' with the discussion but is happy to communicate directly as we exchange information .
At the moment the discussion is revolving around [URL="http://www.youtube.com/watch?v=pfONFdXhO8o"]how TTL/BL changes its output [/URL]depending on where the meter is sitting and which metering mode you are on .
He insists that TT/BL fires at the same output regardless of where the meter is and that TTL/BL measures the ambient itself regardless of what you do with the exposure while I am pretty sure that it changes its output when it detects that you are under-exposing the ambient as I saw in my tests . He told me I obviously did something wrong in those tests because my results can't be right so I did the tests again with all the settings to prove that the output does change .

In his first reply he concluded that the foreground must have been brighter than the background so this time I included a shot without flash .





Once again the picture showed that the flash fired hotter when the meter showed under-exposure .



Since he also insisted that wireless flash does not meter the same as TTL/BL but rather that it meters in TTL mode I included a shot with TTL flash and some with wireless flash . Though wireless fired weaker than all of them it showed the same characteristic of reacting to a change in the meter simply from changing metering modes .







In my mind these shots totally prove my theory that TTL/BL balances the flash with the existing ambient on the subject depending on how you choose to expose the ambient . For example , if you are shooting indoors and set a slow enough shutter speed , let's say1/25th sec , to catch the ambient TTL/BL will fire much weaker than if you are shooting at 1/200th and the meter showed that you were 4 stops under-exposed .
I'm going to do some tests now with a flash meter to see what variation we have and at what point of under-exposure TTL/BL 'takes over' completely .

I borrowed a flash meter from a friend to check my theory that TTL/BL adjusts its output depending on where the meter is . I took the pictures at very slow shutter speeds so that the pre-flash wouldn't interfere with the readings , in each picture I reset the flash meter right after the pre-flash and took each picture three times to verify the readings .
I decided to check the difference between TTL and TTL/BL under equal conditions .
Many people say they use '' TTL -1.7 " for fill flash so I think they will find the results interesting . I set the subject up in the centre of the frame which usually gives me equal results with TTL and TTL/BL in dark conditions but this time I had the meter at zero , in other words I exposed the ambient correctly .

This is what TTL deems to be the correct exposure regardless of ambient ....



This is the power TTL/BL decided to use :



I'm pretty sure the difference there is "-1.7" stops !
perhaps that is how Nikon decided the output of TTL/BL when the ambient is correctly exposed , "TTL -1.7" since that seems to be the generally accepted compensation for fill flash . Of course since they meter differently in different situations the results won't always be the same .

Then I wanted to check and be sure that they would give the same results in darkness .
When the ambient was 4 stops under-exposed TTL an TTL/BL gave the same flash power !



I opened the shutter up to 30 seconds to zero the meter - in TTL/BL the flash meter registered "F10" - once again "TTL-1.7" for correctly exposed ambient .



This proves to me beyond doubt that TTL/BL is watching the meter - it doesn't ' measure the ambient ' , it watches to see what you are doing with the ambient and balances it with the 'right ' amount of flash .


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oh another great post!! thanks desmond

Thanks for educating all on your findings and results with TTL versus TTL/BL. You are very thorough in your documentation and your blog is outstanding. I am surprised that Nikonians would not be open to your findings as they could be beneficial to all to use at their discretion.
vw