Fill in Flash Help ... (1 Viewer)

Hi All

I have been looking around for help on fill in flash but can't seem to find the answer i am looking for. Here is how i understand it soo far:

Expose for the photo as you would normally and then simply dial in -ve flash compensation (more or less depending on the subject) on the flash and away you go.

However i read somewhere that you cannot go above the sync speed of your flash or you'll get black banding across the photo. So if the sync speed for arguements sake is 1/250th, does that mean that you then have to adjust all the other parameters (Iso, F stops) to expose for the photo correctly. Also is there any importance in reducing the shutter speed of the camera below 1/250th or is it ok to stick at 1/250th and just alter the other parameters.

Also what is high speed sync and how does that work?

If someone could walk me through the process they use for fill flash and the settings they use roughly that would be great.

Thanks

As no one else has responded here goes - my advice is to practice on your local robin - mine used to perch a couple of metres from my camera and put up with repeated flashes as it hopped around for ages - it knew that it would be well rewarded if it stayed put mind you.

The following is probably a bit simplistic for most for which I apologise.

This answer applies only to cameras fitted with straightforward focal plane shutters (most slrs).
As you know a focal plane shutter releases the first blind to start the exposure and then releases the second blind to finish it. As the blinds can only traverse the sensor at a fixed speed the shortest exposure in which the entire sensor is totally exposed is limited by this traverse speed.

For shorter exposures the second blind is released while the first is still crossing the sensor resulting in only a strip of sensor that is exposed at any one instance. This strip narrows as the shutter exposure gets shorter. So the max synchronisation speed is the highest speed at which the blinds are fully open.

At night exposing at speeds faster than the synchronisation speed will result in black bands either side of the strip of sensor visible between the shutter blinds unless you are using a flash unit that is designed to handle this problem by emitting a long steady stream of light (your high speed sync). This effectively illuminates the whole sensor area for the full time that the aperture between the blinds is crossing the sensor (wasting most of the light) - however these have a reduced flash output when used this way and are not generally suitable for bird use (unless it is a robin ie very close). I used it a bit in the 1980s when Olympus brought it out but it was of limited use and I havn't used it much other than pet or people portraits.

With daylight fill in flash using normal sync, taking a shot with a speed higher than the synchronisation speed will not give you black bands, probably dark bands but generally will not provide a decent shot. In addition you will need to ensure that the camera will actually fire a flash above its syncro speed anyway - not all will apparently.

So back to your para 3 to which the general answer is yes. For most wildlife you shoot at the max speed possible to freeze movement unless you wish to record flapping wings as a blur for effect say. You then have to calculate the aperture and iso that will give you a decent shot of the environment (hedge) in which the bird is sitting that will also allow your flash to provide the necessary fill in to lift the bird - generally I do this manually based on pre testing with a flash meter. Don't forget that your off the shelf flash gun will be very limited in its range unless you are using a custom lens on the flash to increase this.

To be honest I find it too much hassle for birds and generally avoid it (unless I need a new robin shot for a calendar or something). Others - who have more patience - do produce excellent pictures using this technique and it is definitely a useful skill if you are up to it.

Hi

So as i understand it and after doing some more research:

1) Expose for the photo as if i would without flash, but making sure i have high speed sync on so as to be able to use shutter speeds above the sync speed.

2) Then on the speed-lite dial in negative flash compensation depending on the scenario etc (TTL).

3) Take the photo and hope for the best

I understand that using high speed sync will reduce the flash output but it will be paired up with a better beamer to try and extend the range. Also as it is fill flash I don't want the flash reaching the subject to be too high, of course i say this now but no doubt in the future i will be wanting for more range/flash output. Also seeing as the flash output has been reduced, does this mean the recycle time will be reduced also?

Thanks
Ryan

Crudely high speed sync uses all the power available from the flash, but is 'shared out' such that if you were exposing half the sensor at any one instance such as exposing at twice the sync speed you would get a 50% reduction in useable light - it is a bit more complicated than that, but the end effect is that the flash has to completely recharge even though the sensor is receiving less light, so your recycling time willl not normally be shortened. A lot depends on the type of kit you are using so it would be wrong to be too dogmatic about it.

To be honest I suspect that you will find it easier not using high speed sync, but you will only be able to make up your mind by trying it - the better beamer will certainly make a difference.

Really the best advice is to go out and get lots of practice - you dont necessarily need a real bird - in fact stick a thermos flask. book or whatever in a tree or bush and take lots of shots adjusting things until it works for you. That way you stand a sporting chance of getting it right first time with a real bird. Of course it may be that you get it right first time anyway..... it has been known to happen.

Personally I underexpose the background slightly so the bird will stand out.

Best of luck.