Adjusting settings with flash - DPChallenge Forums

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

09/09/2007 11:47:43 PM · #1

When using flash, the camera locks the settings to 1/60th and whatever aperture fits that. It won't let me change.

Is the only way to adjust settings while using flash to shoot in manual mode and do the exposure calculations in my head to get it to expose right?

Surely it isn't that difficult.

SamDoe1

Canon EOS-350D Rebel XT

09/09/2007 11:50:11 PM · #2

What mode is the camera in?

The 30D should sync to 1/200th but the camera will meter the exposure off the background and use the flash to expose the foreground. This is where the varying settings would come in.

kyebosh

Canon EOS-20D

Canon EF 80-200mm f/2.8L

09/10/2007 12:01:22 AM · #3

I'm guessing you're in P mode, try switching to M.

_eug

Nikon D50

Nikon AF Nikkor 50mm f/1.8D

09/10/2007 12:04:18 AM · #4

I shoot in Aperture and adjust it for the look I'm going for. If I want more ambient light I'll shoot Manual between 1/30 and 1/5 second regardless of the aperture (usually around f/4 to f/8).

If you have a flash that does TTL then this works flawless. non-TTL requires much more thought.

Message edited by author 2007-09-10 00:05:26.

Canon EF 24-70mm f/2.8L USM

09/10/2007 12:57:23 AM · #5

I'm shooting in P with TTL flash (Canon). I'll try changing to Aperture and see what happens.

Theoretically, I should be able to shoot at any speed up to 1/200th and the camera should still expose it correctly without me having to do much right?

I think the last time I tried to shoot AV it used a shutter speed way too slow--like it didn't know the flash was going to go off (like the flash wasn't attached).

What should I expect?

dwterry

Canon EOS-1D Mark III

09/10/2007 05:35:09 AM · #6

I'm almost always in Av mode ... right up until the time when flash becomes my main source of light. Then I switch to manual mode.

In Av mode, your camera is going to use flash solely for the purpose of fill flash ... regardless of the amount of light. So if it's bright outside ... fast shutter speed and ... fill flash. If it's dark inside ... slow shutter speed and ... you guest it ... fill flash.

Basically, in Av mode, regardless of whether the flash is turned on or not, your camera is going to pick a shutter speed that, when combined with the aperture you have chosen, will result in a proper exposure. So in a dark room, the camera is forced to pick a slow shutter speed to go with whatever aperture you are using.

The moment flash becomes your dominant source of light, you need to take control and tell the camera what to do. Basically, the faster your shutter speed, the more the flash becomes the *only* light. (i.e. backgrounds will go dark and even go black). Slower shutter speeds will allow more ambient light to enter the scene. It's up to you to balance your need for speed and the amount of ambient light you want to let in.

In my opinion, ambient light sets the mood. So at weddings and receptions, I'm usually bumping the ISO all the way up to 1600 and then shooting somewhere around 1/80 to 1/125 at an aperture somewhere between f/2.8 to f/4.0. (slower shutter to see more of what's going on, faster shutter to freeze more motion, wider aperture to isolate the subject, smaller aperture to get more than one subject in focus - those are my decision points)

Hifi

Canon EOS-1D Mark IV

Canon EF 70-200mm f/2.8L IS USM

09/10/2007 07:33:22 AM · #7

Originally posted by dwterry:

I wish I had of seen this post on Saturday night before I had to photograph a street parade in the dark, they only had street lights and a few spot lights which had gels on them to give the desired carnival feel. I did manage to get some good shots but I would have had better results trying this I think.

Message edited by author 2007-09-10 07:37:02.

Canon EF 70-200mm f/4.0L IS USM

09/10/2007 09:35:20 AM · #8

Originally posted by dwterry:

I know what you are saying is right but it doesn't make sense to me right now - I think I'll have to just go experiment.

It would seem to me that the darker the room, the slower the shutter speed, the more the flash would be your main source of light. But you say "Basically, the faster your shutter speed, the more the flash becomes the *only* light."

Perhaps you are just saying that if I go too fast with the shutter speed it will only have time to pick up the flash rather than the ambient light.

I don't know - sounds like I just need to go experiment.

fotomann_forever

09/10/2007 09:46:13 AM · #9

Originally posted by KevinG:

Perhaps you are just saying that if I go too fast with the shutter speed it will only have time to pick up the flash rather than the ambient light.

That's exactly what he is saying. What he is describing is commonly called dragging the shutter and is your tool for balancing foreground flash light with background ambient light.

With flash photography, you use aperture to control flash exposure and shutter speed to control ambient light exposure.

latentflip

Canon EOS-400D Rebel XTi

09/10/2007 09:54:48 AM · #10

Originally posted by KevinG:

It would seem to me that the darker the room, the slower the shutter speed, the more the flash would be your main source of light. But you say "Basically, the faster your shutter speed, the more the flash becomes the *only* light."

Perhaps you are just saying that if I go too fast with the shutter speed it will only have time to pick up the flash rather than the ambient light.

I don't know - sounds like I just need to go experiment.

I'll try and help explain.
Changing your shutter speed will have no effect on how effective your flash is at lighting a scene. The 'flash' is very brief, quicker than your shutter (as long as you are below the sync speed), so even if you increase the length of time your shutter is open for, your sensor will see the same amount of light from the flash. To change how effective your flash is at lighting the scene therefore you must use either ISO, aperture or change the power output of your flash.

Changing your shutter speed will have an effect on ambient light. This is much more obvious as you see it all the time when taking pictures. For a continuous light source, the longer your shutter is open, the more light will hit the sensor.

With these two facts in mind you can go about balancing your flash with the ambient lighting. Set your aperture, ISO and flash power to get your subject being lit by the flash to the desired level. Then change your shutter speed to bring up/reduce the ambient lighting. (Clearly aperture and ISO also affect the ambient lighting too so you may have to iterate a little).

So when dwterry says, "Basically, the faster your shutter speed, the more the flash becomes the *only* light." He is correct, because with a fast shutter speed the less light you will see from the continuous ambient lights, but the flash will stay the same.

Hmm, hope that makes sense and doesn't ramble too much.

Edit:fotomann beat me too it :)

Message edited by author 2007-09-10 09:55:42.