Nikon TTL/BL flash explained

[Desmond]

I haven't been here for a while but since I recently did some tests and 'research' into TTL/BL flash I thought I would share my findings with Nikon users .
First of all if you do a search on "Nikon TTL/BL flash " the most popular site that comes up - which is the official TTL/BL site (http://nikonclspracticalguide.blogspot.com/2008/01/nikon-ttl-bl-flash.html) is totally wrong ! It will tell you that the subject has to be central and that there needs to be strong backlighting for it to work ..... this is only true if you are shooting with a D100 or older camera . My tests regarding the " new '' TTL/BL (http://desmonddowns-ttlblflash.blogspot.com/2009/06/nikons-new-ttlbl-flash-and-cls-wireless.html) prove that Nikon have changed the information that the camera body sends to the flash and , in fact , the built in speedlight , the SB400 and wireless "TTL" are all metering in TTL/BL mode ! When I shared my results with the author of that site he got quite angry and locked my thread because all the information makes his site redundant and all the questions he has answered on the subject are now wrong !
For those of you that prefer hearing and seeing it explained I did a youtube video on TTL/BL (http://www.youtube.com/watch?v=he35-IRSd2c)
I hope this all helps to clear up a lot of the confusion caused by Nikon's not explaining it all properly to us :D

[Qarik]

I haven't been here for a while but since I recently did some tests and 'research' into TTL/BL flash I thought I would share my findings with Nikon users .
First of all if you do a search on "Nikon TTL/BL flash " the most popular site that comes up - which is the official TTL/BL site (http://nikonclspracticalguide.blogspot.com/2008/01/nikon-ttl-bl-flash.html) is totally wrong ! It will tell you that the subject has to be central and that there needs to be strong backlighting for it to work ..... this is only true if you are shooting with a D100 or older camera . My tests regarding the " new '' TTL/BL (http://desmonddowns-ttlblflash.blogspot.com/2009/06/nikons-new-ttlbl-flash-and-cls-wireless.html) prove that Nikon have changed the information that the camera body sends to the flash and , in fact , the built in speedlight , the SB400 and wireless "TTL" are all metering in TTL/BL mode ! When I shared my results with the author of that site he got quite angry and locked my thread because all the information makes his site redundant and all the questions he has answered on the subject are now wrong !
For those of you that prefer hearing and seeing it explained I did a youtube video on TTL/BL (http://www.youtube.com/watch?v=he35-IRSd2c)
I hope this all helps to clear up a lot of the confusion caused by Nikon's not explaining it all properly to us :D

interesting..thanks for that.

[thegridrunner]

Interesting...I plan to test this out this weekend! :nod

[Desmond]

Interesting...I plan to test this out this weekend! :nod
Feel free to add anything interesting you find out !
The 3 main concepts I have concluded is that :-
1.) TTL/BL uses focus distance when the flash is facing forward .
2.)TTL/BL meters off the brightest focus point in the frame .
3.) TTL/BL reacts to changes in the meter with regard to ambient exposure if you are in manual , and compensates accordingly . [ if your meter shows -1.3 stops under TTL/BL will fire +1.3 stops brighter ]

[rsquared]

Thanks!! :clap

I had never heard of TTL/BL until a few days ago when I came across a link to that site you mentioned (Which by the way I don't think is "official", just another photographer putting his info out there...).

It was really nice seeing the results of your test in the video. Makes a whole lot more sense that way. I've got your blog bookmarked. Haven't had a chance to read through it all yet, but I look forward to it.

[Desmond]

Thanks!! :clap

I had never heard of TTL/BL until a few days ago when I came across a link to that site you mentioned (Which by the way I don't think is "official", just another photographer putting his info out there...).

It was really nice seeing the results of your test in the video. Makes a whole lot more sense that way. I've got your blog bookmarked. Haven't had a chance to read through it all yet, but I look forward to it.

Thanks for the input ! Everyone generally accepts that other site as the 'official' TTL/BL site (http://nikonclspracticalguide.blogspot.com/2008/01/nikon-ttl-bl-flash.html)because Russ McDonald was on the Texas Instruments team that designed the TTL/BL chip for Nikon back in the 80's [ according to him ] and that is the site everyone refers to when discussing TTL/BL .
According to an email he sent me to try and tell me my results were impossible , he states that the center of the frame is determined to be the 'subject' and the brightest point in the surrounding area is deemed to be the 'background lighting' and the system was designed to calculate the difference in the two exposures and add enough flash to 'balance' them .
The focus distance info from the lens was back-up in case the pre-flash reading failed due to the bright sunlight .
By that reasoning he told me it was impossible for me to have it working inside with no bright background because to 'balance' the subject with the background would require no flash output and it should always fire at its weakest .
When I proved him wrong on Nikonians he sent me an email telling me that my pictures are horrible and he is locking the thread . Eventually he sent me an email telling me that Nikon have obviously changed the information that the camera body sends to the flash - I told him "Isn't that what I've been trying to tell you ?" .
Essentially this happened back when the D100 was replaced - the D100 will fire at minimum power when there is no bright background - all the later models will work in the 'new ' TTL/BL (http://desmonddowns-ttlblflash.blogspot.com/2009/06/nikons-new-ttlbl-flash-and-cls-wireless.html) mode which is what my blog describes .
Now what really annoys me is that after Russ eventually admitted that it no longer works the same way as he thought he continues to answer questions on his site saying that the subject must be central and there must be a bright background for it to work ..... but whatever you do , don't approach him about it - he gets very upset when he realizes that his site has been obsolete since the D100 was replaced !:D

[rsquared]

Thanks for the update Desmond. I had never seen the site until a few days ago, so I had no idea people considered it official, and I hadn't read through enough of it to know what his background was on the subject. It's kind of sad to see that he's so defensive of the info he has out there instead of taking what you've shown him and updating the site...

I haven't gotten very far into your site yet either, but I noticed both here and in the video you mention Nikon changed TTL/BL after the D100, but on the first page of your site you say "that's only true for cameras older than the D200." I've got a D70s, which I believe came out between the D100 and D200. Do you know if it's got the newer version?

[Desmond]

Thanks for the update Desmond. I had never seen the site until a few days ago, so I had no idea people considered it official, and I hadn't read through enough of it to know what his background was on the subject. It's kind of sad to see that he's so defensive of the info he has out there instead of taking what you've shown him and updating the site...

I haven't gotten very far into your site yet either, but I noticed both here and in the video you mention Nikon changed TTL/BL after the D100, but on the first page of your site you say "that's only true for cameras older than the D200." I've got a D70s, which I believe came out between the D100 and D200. Do you know if it's got the newer version?

I think the D70S works according to the 'new ' TTL/BL because it has built in wireless control that meters in ''TTL/BL'' mode . The way to test any camera is to take a picture in a dark room with flash in TTL/BL mode - if it fires at its weakest it is the 'old' TTL/BL looking for a bright background to balance with - if it gives acceptable results it is the 'new ' TTL/BL .