Am I doing something wrong flash wise?

[Recty]

I just repaired my 580EX II and I was thinking about how I use it.

Typically, I stick the camera in manual mode, I set my shutter speed to 1/250th since that's the fastest sync speed, I set ISO to 400 or under depending on how dark I want the background and I set the fstop to whatever the lens I'm using seems to have a sweet spot at. I mainly use the flash with my 50mm f/1.4 so I typically set the f stop to f/8 or so, that seems to be the clearest.

Anyway, this really underexposes the shot according to the camera. However, since I have the flash on, the pictures turn out great. I get really good results with this, but I hear all this stuff about ETTL and how the camera and the flash work together to figure everything out. I dont think mine is doing any such thing. I'm even manually setting the flash power through hitting the ISO button on my 50D and then using the thumb dial which dials down the flash.

If I go into a non manual mode like Av, I set my aperture to f/1.4 and I'm in a dark room. If I wasnt using the flash, it would want say a 1/6th second shutter speed. But in my mind, since I have the flash on, the camera should realize that and set a higher shutter speed, but it doesnt... So I end up taking a picture that is all blurry because the flash fires then the shutter stays open for half a second.

Am I doing something wrong?

 

[Recty]

I should note that I have found in my camera's settings to lock the shutter speed to 1/250th while external flash is on, so that's fine, but then it seems to me like I'm pretty much just back into manual mode.

Surely I'm doing something weird? I've heard so much about how these new flashes work together with the cameras to properly expose every time but it sure doesnt seem like it when the room is even slightly dark. It's like the camera isnt taking into account at all that the flash will be firing.

 

[Recty]

Nobody knows? Any guesses even? Or is the flash working like it should and I'm just expecting too much out of it?

 

[swjim]

The behavior you're describing sounds like everything is working as it should. Keep in mind that when shooting with flash you're shooting two different exposures, one with the ambient light, one with the flash. When you put your camera in manual you are dictating what you want the ambient photo to look like (underexposed in this case). When you put the camera in AV mode it does not take the flash exposure into consideration, it calculates the exposure setting the same way it would if the flash wasn't on the camera which is why you're getting the slow shutter speeds in low light conditions.

In both cases your flash is calculating how much power it should fire with in order to get a proper exposure, if you want to increase or decrease the amount of flash based upon conditions and/or your preferences then you should use Flash Exposure Compensation (FEC) to adjust it.

When shooting indoors I pretty much always shoot manual exposure. About the only time I use AV with flash is if I'm outdoors and using it for fill at which time you'll often need to have High Speed Sync turned on if you need shutter speeds faster than your camera's max sync speed.

Hope this helps.

 

[xtm]

Your flash is working as it should in Auto mode. The camera's meter will NOT take into consideration if the flash is attached and turned on (why would it?) This is why Manual mode is always preferred on tricky lighting situations as it is way more predictable, but on Aperture priority, you can do two things:

- Use FV lock to meter off pre-flashes, recompose, and fire. So if the preflash reading is 1/125 at f/4, it will "hold" this value until you fire the actual shot. When you release the FV lock, it reverts to normal metering again.

- On a run and gun scenario where you don't have time to use preflashes, I use this technique: Bump the ISO to 800-1100, open up the aperture, set the flash to TTL-BL, -2.0 or lower and use Slow Sync. By bumping the ISO up and opening the aperture, you increase your shutter speed for handholdability- the flash is lowered so it won't blow out the subject. When you hit the shutter, the flash fires and the shutter captures the flash at the very end (adds fill light to the foreground) and stays open to "burn" the background's ambient light -- as a result, you end up with an evenly exposed foreground and background. This is called "dragging the shutter". This is easily done in Manual mode..... in Av mode, you have to go through all that stuff and use Slow Sync.

In the studio, the best way to expose properly is to use a light meter off of pre-flashes and set the exposure manually. This method is almost foolproof.

 

[Recty]

Thanks, that is good to know. It seems weird to me the camera and flash dont work together enough to adjust shutter speed accordingly.

FEC? On my 50D, I just hit the ISO button on the camera and I use the thumb dial instead of the finger dial and it adjusts the power of the flash. I'm assuming that is what FEC is?

So if I turn on high sync speed and shoot at 1/1250th of a second, it will work with that? I always heard you couldnt get past 1/250th so I've never bothered.

 

[swjim]

Yes, we're talking about the same thing - hitting the ISO button and using the thumb dial is adjusting the FEC.

Yes, turning on HSS you can shoot beyond the camera's sync speed. The catch is that the flash emits a series of small pulses rather than the higher powered full flash you'll get within the camera's sync speed. Because of this you're getting much less power so the flash will need to be closer to the subject than it would at higher power. HSS also uses up batteries more quickly but I've never considered that a major issue.

Here is an example of where HSS can come in handy, this was taken under a tree where without the flash there would have been a lot of uneven shadowing from the limbs and leaves overhead. The shot was taken at ISO 200 1/640 f/2.2.

 

[Recty]

Is it easy to explain to me why you shot that at 1/640th instead of simply shooting at 1/250th?

Also, for the burst of flashes being less powerful, will turning up the FEC help with this or is it just a power limitation and it cant get any brighter?

 

[swjim]

I was shooting outside in quickly changing lighting conditions, the camera was in AV mode because I was more concerned with controlling depth of field than shutter speed. 1/640th just happened to be what worked at the time. The flash was on only to help fill the shadows, it wasn't there to illuminate the entire frame.

Unfortunately, you can't cheat additional power out of a single flash with HSS. The only other options would be to have additional flash(es), get the flash off camera and closer to your subject or get back down to your sync speed.

 

[maroun.c]

I would just make sure your flash is set to TTL (Nikon terms for Through the lens metering) where the flash works through light coming in the lens...
Concerning exposure I try to shoot in manual and meter as If I had no flash, this way my exposure is good and I can pick up some better colors especially from corals instead of having them washed out because of flash lighting. Exposure would be slower than 1/250 but no way close to 1/6. Flash will freeze the image you get unless there is severe motion in the time of shutter opening and colours will be acceptable as you allowed enough time for the reflected lights to form the image...
Also don'trely on shutter speed to control flash output or contribution as flash is much faster than the fastest shutter speed you're using. Try to use smaller aperture and that will control flash contribution in the image.