Problem with flash metering

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stolzy

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John Stolz
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I have a Sekonic L-508 which works fine in most situation, except using studio flash.

I set it to cordless flash and take a flash reading, say 1/250, F11, ISO 200.
But if I change the sutter speed it changes the aperture, say 1/125, F16, ISO 200.

This behaviour is clearly wrong surely? Why would changing the sync speed alter the exposure with studio flash?
 
I dont have that meter but it sounds like it's trying to balance the lighting. You'll get proper help from someone who has one though.
 
But the suggested aperture shouldn't change with the shutter speed. With (essentially instantaneous) flash 1/125 doesn't let in more light than 1/250
 
Is it set to meter flash?
If you're using a synch lead, press and hold down the Mode button and turn the set diat to select flash measurement with cord, and set the shutter speed (which typically will be 1/125th).

And, for accuracy, set it to measure in incident mode too (not reflected)
 
Garry Edwards said:
Is it set to meter flash?
If you're using a synch lead, press and hold down the Mode button and turn the set diat to select flash measurement with cord, and set the shutter speed (which typically will be 1/125th).

And, for accuracy, set it to measure in incident mode too (not reflected)
Click to expand...
Thanks for that. I'm using non-corded flash mode on the L-508 (I've tried it in corded flash mode too with the same result).

The 'flash' meter doesn't seem to understand how flash works.
 
Strange. Does the flash fire when you take the reading?
 
It sounds like you're reading the ambient and not the flash. On mine, it takes the flash reading and will then clear if you move the dial.

Are you pressing the button on the right hand side to make the flash symbol flash on and off before triggering the flash?
 
The shutter speed is almost irrelevant, so there's something strange going on. Are the readings realistic, i.e. are they based on the flash or is the meter simply ignoring the flash and giving a reading for the ambient light?

If all else fails, we could have a Skype conversation, if I saw what was actually happening I should be able to work it out.
 
Sky said:
It sounds like you're reading the ambient and not the flash. On mine, it takes the flash reading and will then clear if you move the dial.

Are you pressing the button on the right hand side to make the flash symbol flash on and off before triggering the flash?
Click to expand...
There is next to no ambient light. At 1/250, ISO200 the aperture reading from the flash is around F11 so it's obviously seeing the flash
 
Garry Edwards said:
The shutter speed is almost irrelevant, so there's something strange going on. Are the readings realistic, i.e. are they based on the flash or is the meter simply ignoring the flash and giving a reading for the ambient light?

If all else fails, we could have a Skype conversation, if I saw what was actually happening I should be able to work it out.
Click to expand...
They are realistic 1/125 at F11 or 1/250 at F8 or 1/500 at 5.6
 
So, I've been messing about (more or less at random) with the DIP switches and found a combination which seems to restore expected behaviour.
I've set all OFF except F-No.

Now I get the same aperture reading regardless of the shutter speed and when I alter the shutter speed after the reading the display resets.
 
Well, that's a start:) The problem is, nearly everyone now shoots on digital and no longer sees a need to measure the flash, but with any luck someone who still does and who has this meter will be able to chip in with the right answer.
stolzy said:
They are realistic 1/125 at F11 or 1/250 at F8 or 1/500 at 5.6
Click to expand...
Either of the first two could be realistic, the 3rd one couldn't unless you have either an electronic or a leaf shutter, and with a very low level of ambient light the shutter speed simply doesn't make any practical difference.

Assuming that your meter works, this seems to be either a mode problem or a RTFM problem:)
stolzy said:
So, I've been messing about (more or less at random) with the DIP switches and found a combination which seems to restore expected behaviour.
I've set all OFF except F-No.

Now I get the same aperture reading regardless of the shutter speed and when I alter the shutter speed after the reading the display resets.
Click to expand...
So, is the problem now resolved?
 
My dip switches are set 1. On, 2. On, 3. On and 4. Off.
 
stolzy said:
I have a Sekonic L-508 which works fine in most situation, except using studio flash.

I set it to cordless flash and take a flash reading, say 1/250, F11, ISO 200.
But if I change the sutter speed it changes the aperture, say 1/125, F16, ISO 200.

This behaviour is clearly wrong surely? Why would changing the sync speed alter the exposure with studio flash?
Click to expand...
  • Yes, if your ambient light was rather dim, changing the shutter speed should NOT alter the aperture display after metering flash...all of the light from the flash is output in a relatively short period of time (e.g. 1/1000 sec.) so the aperture should not be any different, if the ambient light is rather dim and contributing little to the overall exposure.
  • But IF the ambient light is quite bright (for the aperture and ISO being used), it might contribute enough to the metered amount of light to have an effect on aperture...but it should not ordinarily be a full f/stop different, unless ambient was really, really bright!
To illustrate, I just took these readings using my Minolta Autometer Vf and Metz flash...

1. ISO 125 Ambient = 1/3 f/2.0: with flash and shutter at 1/3 = f/16.0, with flash and shutter at 1/6 = f/16.0
2. ISO 125 Ambient = 1/125, f/1.0: with and shutter flash at 1/125 = f/11.9, with flash and shutter at 1/250 = f/11.5
3. ISO 1600 Ambient = 1/125 f/4: with flash and shutter at 1/125 = f/45.4, with flash and shutter at 1/250 = f/45.0

Certainly I can draw no conclusions about what you are seeing with your flash and flashmeter, but I am merely trying to set expections for 'normally' what can happen.
 
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It looks to me like his camera is set to "Auto" or "TTL". I don't have that exact model light meter, but I don't have this problem when the camera is set on "Manual".

Charley
 
CharleyL said:
It looks to me like his camera is set to "Auto" or "TTL". I don't have that exact model light meter, but I don't have this problem when the camera is set on "Manual".

Charley
Click to expand...
IF the flash is a digital TTL flash, the camera first asks for a fractional output preflash for the camera flashmeter to measure, so it can send at predetermined amount of light request to the flash to output when the shutter actually opens...and in this case the typical handheld flash meter measures the FIRST output and bases its suggested reading on the pre-flash!

But the typical studio flash is usually not compatible with digital camera TTL, it does not offer ability to respond to a pre-flash command from the camera.

In any event, altering shutter speed set on the flashmeter by -1EV should not have an effect of altering the resultant aperture by 1EV!
 
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