Does flash help at a distance?

[pasoviennese]

I wonder if the camera's build in flash helps when the subject is at a distance. I have a Canon 30D, and I imagine the range of the flash is no further than 5-10 meters? Often I shoot indoor sports at a distance greater than 5meters, with the 200mm of my lens. In that case, does firing the flash help the photo at all?

[kencaleno]

No-The only practical use for the built-in flash, is to use as fill-flash on outdoor portraits.

For what you want to do, you need an accessory flashgun with a guide number of at least 80 feet (25 meters) at 100 ISO.

Flash doesn’t reach as far as you like? Up the ISO! -“Twice the distance, four times the speed”. For instance: If your flash has a Guide number (GN) of 25(metres (80 ft), the best you can expect is a realistic distance reach of 20 metres (60 feet) at Iso 100,so at Iso 400 you will get a realistic reach of 120 feet (40 metres),and at 1600 Iso, a reach of 240 feet (theoretically),but noise will play its part at high Iso’s.

© Kenneth William Caleno (Dip Phot) 2010

Regards, Ken

[RichardTaylor]

The above answer is not entirely correct
It depends.
According to this site
Canon 30D

Guide number is 13 (metres) at ISO 100

What aperture and ISO and ISO are you shooting at?

GN = distance × f-number

So if you are shooting at at F2 and a distance of 6.5 metres at ISO 100 then you should be OK

If you are using an F5.6 lens at a distance of 7M and ISO 100 and then it will not be ok (you will need a flash with a guide number of ~ 39 (metres))

If you shoot at ISO 400 your flash will have a guide number of ~26 (metres)
If you shoot at ISO 1600 then you flash will have a guide number of ~ 52m so you will be possibly getting into the ball park when shooting at F5.6.
Try upping your ISO and see, however as Ken says noise may become a problem.

[Benji]

Not only noise but red eye as well.

You will find out that a lot of things that work out mathematically correct won't work in the actual shooting situation. For example mathematical equasions don't take into consideration where you are shooting. For example if you are in a narrow hallway with light colored walls and a white ceiling with the subject at 30 feet your flash will work a whole lot better than it will if the subject is in the gymnasium at 30 feet. When I'm confronted with a situation that I don't know how effective the flash will be, I don't break out my calculator, I break out my flash meter!

Benji

[pasoviennese]

Thanks for the answers!

So I probably better off up my iso rather than use flash.

[OsmosisStudios]

The only use for the onboard flash on most cameras is to trigger off-camera ones.

And Canon can't even do that properly

[kencaleno]

Originally Posted by pasoviennese

Thanks for the answers!

So I probably better off up my iso rather than use flash.

Upping your iso is inviting noise to kill your images.

If you care about the quality of your sport ,images you should endeavour to invest in a more powerful accessory flashgun.I have one that I acquired from an online auction for 35 dollars, and another from a second-hand shop for just 6 dollars! they are both Starblitz 250 BAZ's,with a guide # of 80 ft @ 100 ISO-they have been in constant use now for 6 years,and haven't let me down, yet.

Regards, Ken

[LoveDSLR]

I still have my Metz 45 CT-4.

GN 45m/148' @ISO 100 and double with telephoto attachment 45-33.