More flash questions!

When using a 430ex (on 30d), in manual I can set the flash to 1/1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64 power.. if I put it in ETTL mode, is the flash simply metering for me and choosing between those flash power values, or can it be more precise than i can in manual mode, ie can it output 1/48 power or 1/3, etc.. if needed?

When shooting in Av mode 1/250th sync where the flash is the primary light source, should i just leave the iso at 100 for the lowest noise/best quality or is there any benefit to increasing it?

Should there be any difference between shooting in 1/250 sync in Av mode and shooting with the same aperture and a shutter speed of 1/250 in manual mode?

Does anyone have any examples of the difference between evaluative and average metering modes? Or scenarios/cases where the two would provide noticably different results? Last night I took about twenty shots, indoors/outdoors, taking the same picture twice - once in evaluative and once in average.. and for the life of me I can't see a noticable difference.

And finally, is there any way to configure the flash 'set' button so that you don't have to hold it for two seconds to make changes to FEC or change power values in manual mode? Pretty annoying.

Thanks!

With FEC, you can set light output from the flash in 1/3 EV increments; in manual the flash output only changes in full EV value (1/2 power = -1EV, 1/4 power = -2EV)

There should be no visible difference between 1/250 Av and 1/250 in M. But you do not indicate what camera. In Av, the camera is likely to choose any other shutter speed than 1/250 as likely as not...unless you have the Custom Function set to 1/250 in flash.

Wilt wrote in post #2762183
With FEC, you can set light output from the flash in 1/3 EV increments; in manual the flash output only changes in full EV value (1/2 power = -1EV, 1/4 power = -2EV)

There should be no visible difference between 1/250 Av and 1/250 in M. But you do not indicate what camera. In Av, the camera is likely to choose any other shutter speed than 1/250 as likely as not...unless you have the Custom Function set to 1/250 in flash.

camera is a 30d. and yes by 1/250 sync i meant have the custom function enabled, otherwise the camera would expose for ambient light and the flash would only provide fill, correct?

it seems kind of silly that ettle would give you more flexibility and precision than manual.. is it the same for the 580ex?

fredmitcham wrote in post #2762280
camera is a 30d. and yes by 1/250 sync i meant have the custom function enabled, otherwise the camera would expose for ambient light and the flash would only provide fill, correct??

Yes, with CF set to 1/250 for the shutter speed selection, the result is the same as camera in M and 1/250 on the shutter.
Yes, sort of. If CF was not set to 1/250, it would pick horrendously show shutter speeds to capture ambient light in the background, but then it would use the flash to exposure the main subject in the foreground...admittedl​y underexposing the main subject unless you dialed in FEC = +2/3EV

fredmitcham wrote in post #2762280
it seems kind of silly that ettle would give you more flexibility and precision than manual.. is it the same for the 580ex?

Did you mean to say it is sill that ETTL has more flexibility than the Flash on Auto? If so, I don't agree. Auto was meant for the days when cameras did not offer TTL flash metering, so you set the flash to a specific f/stop and fired away. FEC was accomplished with the simple technique of opening or closing the lens aperture a bit while the flash output was fixed.

Wilt wrote in post #2762370
Did you mean to say it is sill that ETTL has more flexibility than the Flash on Auto? If so, I don't agree. Auto was meant for the days when cameras did not offer TTL flash metering, so you set the flash to a specific f/stop and fired away. FEC was accomplished with the simple technique of opening or closing the lens aperture a bit while the flash output was fixed.

no i meant ettl has more flexibility and precision than manual, like you said manual only allows 1 EV adjustments whereas with ETTL and FEC you can make 1/3 EV adjustments..

1) E-TTL can vary the power output in very small increments, much less than a full stop, and can go much lower than 1/64.

2) Increasing the ISO will require less flash power, reduce recycle time and improve battery life. If you're not concerned about those things, don't increase the ISO unless you need to. With direct flash, let the distance scale on the back of the unit be your guide. If it's indicating an insufficient distance, increase the ISO (or open the aperture) to get the distance you need. When bouncing the flash you'll probably want to use ISO 400 since bouncing takes a lot more power.

3) The only difference that I know of is that if you try to shoot before the flash recycles, Av mode will act as if no flash is being used and select a slower shutter speed to expose the ambient. Generally I use Manual mode at 1/250, it's just quicker that way.

4) Differences between Evaluative and Average flash metering will show up when there is something reflecting the flash back toward the camera, like a window or polished metal. White clothing can cause it to underexpose a lot in Evaluative mode.

5) Try setting the FEC on your 30D instead. After you learn to find the right button, you can do it with your eye in the viewfinder.

Curtis N wrote in post #2762658
1) E-TTL can vary the power output in very small increments, much less than a full stop, and can go much lower than 1/64.

Shouldn't manual give you complete control and flexibility? Whats the logic in providing a limited manual mode? Is this the same with a 580ex?

Curtis N wrote in post #2762658
2) Increasing the ISO will require less flash power, reduce recycle time and improve battery life. If you're not concerned about those things, don't increase the ISO unless you need to. With direct flash, let the distance scale on the back of the unit be your guide. If it's indicating an insufficient distance, increase the ISO (or open the aperture) to get the distance you need. When bouncing the flash you'll probably want to use ISO 400 since bouncing takes a lot more power.

So probably a good idea to up the iso if shooting bursts?

Curtis N wrote in post #2762658
3) The only difference that I know of is that if you try to shoot before the flash recycles, Av mode will act as if no flash is being used and select a slower shutter speed to expose the ambient. Generally I use Manual mode at 1/250, it's just quicker that way.

Ah yes, good idea. I had this problem last night where I was shooting bursts and occaisonally the flash wouldn't fire after a couple shots and I to wait for a three second exposure before shooting again because I was in Av mode

Curtis N wrote in post #2762658
5) Try setting the FEC on your 30D instead. After you learn to find the right button, you can do it with your eye in the viewfinder.

I do and its much easier however that doesn't help with using the flash in manual mode where you have to hold the button for two seconds everytime you want to make a change.

Thanks for the answers!

fredmitcham wrote in post #2762721
Shouldn't manual give you complete control and flexibility? Whats the logic in providing a limited manual mode? Is this the same with a 580ex?

The 580EX lets you adjust in 1/3 stop increments down to 1/128. A lot of flash units and studio strobes allow manual power adjustment only in full stop increments. You make the fine tweaks by adjusting aperture or distance.

That would help. Flash units really aren't designed for burst mode, but they can work for limited bursts if the output is low enough.

If you're in Manual mode and you shoot before the flash recycles, you'll get an underexposed shot. In other words, you'll get crap either way. Your best bet is to use single shot mode and watch for the flash ready light in your viewfinder.

I have another question, today I was practicing just shooting pictures of my friends fooling around on a small snowboard quarter pipe they built in their backyard.. the light wasn't ideal as we were surrounded by tall trees and the shots I took turned out fine except for the snowboarder in the shot which was dark and shadowy. So I took out my flash, set the camera and flash to manual and just messed around until I got something I liked.. the problem is, with the flash on I can't get a shutter speed higher than 1/250 and that wasn't enough to stop motion blur in a large percentage of the shots.. how can I get a shutter speed of 1/500+ but still use the flash?

Nevermind, figured it out, have to enable HSS on the flash unit. Awesome