- ps. i tend to use a semi automatic mode, ie either aperture or 'P' mode
I mostly dial the aperture right down to gain the quickest shutter speed & i think it goes down to about 5. I did try increasing the iso too but the flash blowout became much worse. Not sure what i was doing wrong.
Does the camera not automatically reduce the amount of flash depending on the aperture value?
Yes, the TTL flash system meters the preflash, and sets the flash power to be appropriate for the aperture and ISO it discovers is in effect at the time. Assuming it has the power capability to be able to do it (the internal flash is pretty tiny).
It's good to understand how the flash system works. We can do so much more when we grasp the system.
The camera meter (the one we can see working) meters the ambient. Not the flash, but the ambient. Which may be outside in bright sun, or it may be indoors at night. Bright sun will meter around Sunny 16, but the room indoors might meter 2 seconds or 1/2 second, or even 1/20 second, but dim, nothing like bright sun.
You can see this if if you turn off the flash (shut the internal door), and you see what the room meters. It will be dim (typically), which is why we need the flash.
After seeing what the dim room meters, (what the proper exposure of that room ambient is), simply reach up and turn on the flash (open the flash door).
In camera A or P mode, you see the shutter speed jump to 1/60 second (there can be exceptions, Slow sync, Rear Curtain sync, and of course camera S or M modes). But the default for camera A or P mode is 1/60 second, called the Minimum Shutter Speed With Flash. You are using flash, and you don't need it to be 2 seconds or 1/2 second, so it assumes 1/60. Nothing meters 1/60, it just thinks that is slow enough, since it doesn't matter anyway. It is too dim, and we are using flash.
The shutter speed does not affect the flash. The flash is faster (shorter duration) than the shutter speed. The shutter just has to be open when the flash triggers. However, the shutter itself is limited to 1/200 second with flash (Maximum Shutter Sync Speed).
So, the meter metered the ambient and set some aperture for the ambient (which is insignificantly weak indoors, but that is how it works).
In Camera P mode in this dim room (compared to bright sunshine, it is weak), the aperture is very likely wide open (because the ambient is dim, which is why we are using flash).
There are more ifs and buts, and the higher you set ISO, the farther from maximum aperture in camera P mode - which is not about exposure (ambient is still grossly underexposed), but is about the minimum EV value the system can meter. It just does.
So camera P mode is not a good choice for flash indoors (unless you want the lens wide open). However, camera P mode is a great choice for fill flash in bright sun. The difference is we actually have some ambient then.
Camera A mode is better - it lets us set the aperture to any value we want, so we can give consideration to the flash (because the system does not). Wide aperture for more effective flash power, or stopped down some for depth of field. Our choice. The TTL flash will respond to it.
The shutter speed in camera A mode will still be 1/60 second - that Minimum Shutter Speed With Flash. The flash (called speedlight) is faster than the shutter speed, and it is the flash speed that stops motion and prevents camera shake (not the shutter speed). The flash stops the motion, including camera shake.
But the 1/60 second is not doing anything for us either. Flash does not even care about shutter speed.
So... we can use camera M mode (manual) with flash indoors. We can still set the same aperture we might choose for camera A mode, and the flash works exactly the same as in camera A mode. But camera M mode also lets us set shutter speed to any value we want. The flash isn't affected, but maybe to 1/200 second to keep out more of the orange incandescent light. Which is a required given for studio work. Shutter speed will not affect the flash, but it affects continuous ambient.
It is "manual" mode, but all that is manual is the ambient exposure, which is pretty much "don't care" indoors (typically).
The TTL flash is still automatic flash in any camera mode. Repeat: the TTL flash is still automatic flash in any camera mode. The camera has a separate metering system for the TTL preflash, which sets flash power to be appropriate for whatever aperture/ISO it discovers is in effect.
And there is not much we can do for the dim ambient indoors anyway. We can imagine brighter exceptions, but typically ambient simply does not matter indoors (typically too dim to matter). We are using flash instead. However, the automation tries to set up exposure for the ambient, not for the flash.
So, since we know this, we can do things a little better for flash. At least control the aperture, to be what you want to do.
My own notion is the various diffusers are pointless on the tiny internal flash. That is not the answer. The answer is learning how to get proper flash exposure. It is easy, and rewarding (even direct flash does not have to be crummy), so I would instead suggest concentrating on getting the flash exposure right instead, it makes such an overwhelming difference.
Direct flash does tend to overexpose, because the distant background is very dark (inverse square law falloff). The TTL metering sees that dark background, and tries to brighten it (computers are stupid), which can overexpose direct flash. Even for a near background, direct flash can make dark shadows on it too.
So sometimes we do have to compensate direct flash, with -EV flash compensation, to hold it back a little. We do what we see we need to do. If it is not perfect, simply fix it.
Whereas bounce more evenly lights the room, and when it is off a little, it is probably underexposure then, compensated with +EV flash compensation.
Bounce is such a great thing, and accumulating pictures of kids for the future seems a worthy investment, money for the flash, and a bit of learning about flash. If you're gonna do it, do it right.
All this probably seems mysterious and difficult at first, but it merely takes a little experience to keep up with it. Like driving... we don't think about staying in the lane or holding speed steady or looking in the mirror before changing lanes. It was harder first day, but now we simply just do it, without thinking about it. Good skills to learn.
