Optical TTL - P/S/A modes

[norinori]

When shooting in optical ttl with a strobe are P/S/A modes very limiting ?

My understanding is that the metering is done with the ambient light available, so for example, if I choose S with 1/250, based off of the light available it meters and gives me f/1.8, when in fact, because of the strobe, I can choose a significantly smaller aperture. Alternatively, if I was in Aperture priority mode, and I chose f/8 , it would default to a something like 1/30 for instance, limiting me to a slow shutter

Is my understanding correct ? -- is this a reason to use manual exposure mode only ?

 

[JackConnick]

It's going to depend on the camera, they all work a little differently.

But in general, the camera will read the flash into the equation, as it knows you have the flash on, on the camera. The only thing I definitely wouldn't set on auto is ISO. With external strobes it will almost always greatly over expose.

That all being said, most photogs shoot on manual as you have the most control. However I do shoot in shutter priority quite often when shooting wide angle, particularly if there's a lot of action going on.

YMMV, etc.

 

[norinori]

Thanks Jack.

I'll test it out on my rx100m2 and see how the metering behavior differs with flash fill on and off. Though if it does factor in the flash, that must still be limiting, as the built in flash(on my camera at least) is tiny and can't put out anywhere near as much light as the strobe.

 

[WPaDiver]

I'm in the same boat as you norinori figuring out how to best use my new strobe with the rx100m2. My impression of how it factors in the strobe is that it measures how much light is hitting the sensor. When the bucket is full it turns off the flash. So it doesn't really matter if the light is coming from the built in or the strobe. You're just triggering the external strobe on and off with the light from the built in. As least that's my noobie take on it.


Sent from my iPhone using Tapatalk

 

[Interceptor121]

Jack is right that every camera has a different way of handling the internal flash.

The RX100 is a slightly different camera than other compacts because the flash in the P/A/S modes is only a fill flash for the foreground and the LCD is always a live view, most other compacts instead add a number of f/stops to include the flash

This means that it makes no difference if you have the flash on or off when the camera calculates the exposure.

Translated in more simple terms if you use the metering of the camera it will mostly have an effect on the background as the flash/strobe will always expose correctly the foreground this may effect the resulting colour of the water and you most likely need to play with exposure compensation quite a bit however at that point it could also underexpose the foreground so you then need flash exposure compensation to go higher....

So for strobe shots the P/A/S modes are therefore near to useless whilst they are quite useful for ambient light shots where you need to reach the correct exposure in the whole frame