Some technical questions if I may?

[ajax_andy]

I've started a fair few threads recently and have received some excellent advise... however I am getting myself in a slight muddle and would love it if someone could just confirm or correct me regarding the following thoughts:

1) When using fill flash I should meter for the background not the subject and use the flash to expose the subject correctly
2) If I change the shutter speed it changes the exposure of the background but not the subject, or in other words the ambient light when using fill flash.
3) If not using flash then the ambient light affects the whole pic and so changing shutter speed will indeed change exposure of subject
4) Changing the aperture will affect the exposure of the subject but not the background exposure... wider aperture means a better flash range
5) If all the above is correct does ths apply to shooting in TTL and manual, or are there slightly different rules between the different modes?
6) It's best to set your camera to maximum sync speed if possible... but what happens if you can't? i.e. it's too bright a day and 1/200 isn't fast enough? I know using an ND filter is one option, but what if you dont have one? I could change the aperture, but I thought that wouldn't change the ambient light?

Sorry I know these questions will sound really dumb but I'm learning the technical side as best I can and sometimes it takes asking dumb questions for me to straighten things out in my mind.

[sk66]

1. yes,
2-3. yes, SS is always ambient even if that's all you have.
4. no, The "camera exposure" is always for ambient. Having more ambient (wider aperture) means you need less flash and therefore get a wider flash range.
5. The rules are the same
6. Not necessarily....you need to set SS to control ambient. Not enough SS to control ambient then stop down, reduce ISO, ND, Faster SS/High speed sync.

[sk66]

I've seen it explained different ways, but it's really pretty simple.

The camera settings (SS/Aperture/ISO) always/only set the ambient exposure for the scene (under/correct/over) and thereby determine how much flash you need for an overall "correct exposure".

Which part of the scene you meter/expose for w/ the camera settings will determine the balance of flash needed, and where.

[ajax_andy]

Originally Posted by sk66

1. yes,
2-3. yes, SS is always ambient even if that's all you have.
4. no, The "camera exposure" is always for ambient. Having more ambient (wider aperture) means you need less flash and therefore get a wider flash range.
5. The rules are the same
6. Not necessarily....you need to set SS to control ambient. Not enough SS to control ambient then stop down, reduce ISO, ND, Faster SS/High speed sync.

Brilliant, thank you!

I know they were probably really dumb questions but now I feel I understand things a lot better

[ajax_andy]

Originally Posted by sk66

I've seen it explained different ways, but it's really pretty simple.

The camera settings (SS/Aperture/ISO) always/only set the ambient exposure for the scene (under/correct/over) and thereby determine how much flash you need for an overall "correct exposure".

Which part of the scene you meter/expose for w/ the camera settings will determine the balance of flash needed, and where.

Thank you it's starting to make a lot more sense now

[ceremus]

Way back when, the very first episode of DP 1 on 1 covered this actually, if a visual example helps.



Mark is addressing Key Shifting here which I'm not sure is the same as what you're asking, but seems closely related.

[ajax_andy]

Originally Posted by ceremus

Way back when, the very first episode of DP 1 on 1 covered this actually, if a visual example helps.



Mark is addressing Key Shifting here which I'm not sure is the same as what you're asking, but seems closely related.

Good video, thanks

[ccting]

6) Darken background with ND has 3 benefits over using smaller aperture
a) Higher LPPH for focused subject
b) nice bokeh
c) flash sync capability

Any ND filter to donate? i believe if you want to use ND +flash during bright day, you need high gn speedlight

Am i right , sk?

[sk66]

I'm not "the lighting expert" but to answer your question, "maybe".

The ND is going to cut back "all light" seen by the camera. If you are trying to get the "ambient exposure" back to where you can use a wider aperture and slower SS for a "normal" exposure (i.e front lit scene) then you will probably only need "normal" flash output (but it WILL be a higher GN than the same scene w/o ND).

If you are trying to kill backlighting/ contrast in a scene it won't really work because the ND will reduce the light levels equally and you will quickly run out of flash power to fill the (now even darker) shadows.

Of course, there are probably infinite possible combinations of these scenarios and entirely different scenarios... (everything is usually some sort of compromise)