Hi all --

Couple of questions I realized I just don't think I understand exactly. I'm trying to understand a bit more about TTL flash when I shoot in manual mode on the camera (which I find myself doing).

1. When I look through the viewfinder and look at the metering level, I'm assuming that the meter is only showing me the levels based on the current available light, like it normally would. Just because of a flash in TTL it isn't modifying the meter because it knows that the flash is going to fire right?

2. Assuming i understand #1 correctly, when the flash's pre-flash fires it is essentially getting a new meter reading, and using that to give me a correct exposure right? So if I see the meter as underexposed about 2 stops, the flash is going to try to compensate for that 2 stops when it fires. Is that right?

3. Now lets say I go outside and get a meter reading on a subject and adjust the camera so the meter shows it perfectly exposed. What is the flash going to try to do now when it fires? Would the pre-flash fire and see its over-exposing it based on the meter, and simply not fire?

Thanks much!

Originally Posted by Helvegr Hi all -- Couple of questions I realized I just don't think I understand exactly. I'm trying to understand a bit more about TTL flash when I shoot in manual mode on the camera (which I find myself doing). 1. When I look through the viewfinder and look at the metering level, I'm assuming that the meter is only showing me the levels based on the current available light, like it normally would. Just because of a flash in TTL it isn't modifying the meter because it knows that the flash is going to fire right? 2. Assuming i understand #1 correctly, when the flash's pre-flash fires it is essentially getting a new meter reading, and using that to give me a correct exposure right? So if I see the meter as underexposed about 2 stops, the flash is going to try to compensate for that 2 stops when it fires. Is that right? 3. Now lets say I go outside and get a meter reading on a subject and adjust the camera so the meter shows it perfectly exposed. What is the flash going to try to do now when it fires? Would the pre-flash fire and see its over-exposing it based on the meter, and simply not fire? Thanks much!

1. Right!

2. Yes, typically.

3. No. But Too many variables. Look here: http://nikonclspracticalguide.blogsp...-bl-flash.html

Just for a clarification on 2. The OP mentioned using a TTL flash but the camera in manual.

In this case the the amount the light the flash produces will depend on the amount of ambient light in the scene and the flash compensation setting on the camera but the ambient light in the scene won't control the aperture (or shutter speed) as it does in an automatic mode.

So if the meter said the scene said the scene was under exposed, you could end up with a dark background but properly lit subject because the flash by itself cannot compensate for a dark background if it is too far away... or any of a number of variations on this.

Anyhow that's my understanding from making images with really dark backgrounds... not because I wanted to though.

1. correct
2. correct
3. the flash will fire no matter what. I expect it will fire at it's lowest setting. you can over expose it manually and the flash will still fire. As long as the flash is in the hot shoe it will fire regardless of what meter says.

You want to make sure you have your flash synch speed set to 1/250 (Auto FP) in custom setting menu e1. If you don't you'll get ugly results if you try to shoot faster than 1/250 sec. You probably already know this, but others on the forum may not. NOTE: This specifically applies to Nikon. I don't know from Canon.

Yup, John, if you try to shoot with a speedlite attached in the hot shoe with a Canon DSLR, the highest shutter sped you will attain, - no matter what you set it at, even in Manual Mode, - will be 1/250th of a sec - UNLESS you set your speedlite up for High Speed Synch.

Out of doors, this causes a lot of over exposed image when using fill flash, until one wises up and realizes that the shutter speed is being reset to 1/250th despite what you manually set the shutter speed dial to read.

If you turn on High Speed Synch ( and not all Canon speedlites support HSS - like the 320ex ) then you can dial in 1/4000th and expect to have it remain at 1/4000th. This can be quite useful at times.

Thank you everybody for the responses. Very helpful.

Originally Posted by Icebear You want to make sure you have your flash synch speed set to 1/250 (Auto FP) in custom setting menu e1. If you don't you'll get ugly results if you try to shoot faster than 1/250 sec. You probably already know this, but others on the forum may not. NOTE: This specifically applies to Nikon. I don't know from Canon.

Yep, Auto FP is on on. One thing I found strange was that my new SU-800 which I'm using to fire the flash, doesn't seem to register that the Auto FP is one. It works of course, and I get no banding from the shutter or anything, but according to the instructions, it looked like I'd see an "FP" on the screen for the SU-800. Not a real big deal, but if anybody uses one, maybe they can comment.

Thanks!