Can anyone explain what is happening please?

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Shutterbox

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I have been playing with a single light and light meter.

Equipment
1 x Bowens light.
Canon 5D Mk11 (manual mode)
Sekonic L 358 Meter.

Both camera and meter set to ISO 100.

Meter in ambient mode which means I can only change the shutter speed. Shutter speed set to 160th as per camera manual.

Hit button on meter and fire head, meter gives F8. When camera set to F8 and 160th, photo is underexposed.

Setting camera to shutter priority and shooting same scene, camera chooses F4 which gives a perfectly exposed result.

So, is the meter faulty? Why would the meter give F8 and camera F4. I was expecting the meter to be more accurate.

Am I missing something?

Have double (treble) checked all settings.

I am attempting to take some family photos in a couple of days and planned to use the one light and meter with camera in manual, now I am not so sure.

Would I be better to use AV and adjust light till it gives me 160th?

Thanks
 
I don't understand...
Are you using this in a studio setting, with no/very little ambient light? If so, why is your meter set to ambient, it should be set to flash

If you're using the camera meter, or using your Sekonic meter in ambient mode, how will that measure the effect of the flash?
 
Garry Edwards said:
I don't understand...
Are you using this in a studio setting, with no/very little ambient light? If so, why is your meter set to ambient, it should be set to flash

If you're using the camera meter, or using your Sekonic meter in ambient mode, how will that measure the effect of the flash?
Click to expand...

Sorry, had a dumb moment, meter set to flash mode.
 
Shutterbox said:
Sorry, had a dumb moment, meter set to flash mode.
Click to expand...

OK then, next question...
I'm assuming that the meter is in INCIDENT mode and that the dome is pointing towards the camera or flash head.

And I'm also assuming that there isn't enough ambient light to make a difference - or is there?

God, this is like pulling teeth:) Note to self, just tell the OP to tell you exactly what the situation so that some of us can work out exactly what's causing he problem...
 
Yes Garry, Incident mode with dome pointing towards light. Only light on in room is modelling lamp.

Meter says F8, underexposed.

Camera in shutter priority at 160th chooses F4 which is perfect.
 
test this.

set your sekonic to cordless flash mode

iso 100 1/200

and your flash head to about 1/2 power

get a Guinea pig, stick the meter under their chin pointing towards the camera and fire of the flash head, put the settings into the camera and take a test shot.

how does that look on the histogram?

Your camera shouldnt choose any settings for an external manual flash, its not that clever. I think :thinking:
 
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CScottMcQueen said:
test this.

set your sekonic to cordless flash mode

iso 100 1/200

and your flash head to about 1/2 power

get a Guinea pig, stick the meter under their chin pointing towards the camera and fire of the flash head, put the settings into the camera and take a test shot.

how does that look on the histogram?

Your camera shouldnt choose any settings for an external manual flash, its not that clever. I think :thinking:
Click to expand...

Thanks, tried that, still looks underexposed.

Appreciate that the camera should not be choosing the settings hence the meter, but can`t understand what is happening.
 
Shutterbox said:
Yes Garry, Incident mode with dome pointing towards light. Only light on in room is modelling lamp.

Meter says F8, underexposed.

Camera in shutter priority at 160th chooses F4 which is perfect.
Click to expand...

Hmmn...
So if I understand correctly, when you meter the flash with the flash meter it gives a hopelessly wrong reading, but when you meter it with the camera meter it gives a correct reading?

If so, it's obvious that the flash is firing out of synch with the shutter. In other words, it's going off at the wrong time and doesn't affect the exposure. Your Sekonic meter doesn't have a shutter so takes account of the contribution made by the flash, the camera meter can't measure the flash so gives you the correct exposure without the flash - does that make sense to you?

I don't know how you're firing the flash, but the only methods that work are either a radio trigger/infra red trigger or a physical cable. My suspicion is that you're using the camera's built in flash to fire your studio flash and what's actually happening is that the pre-flash from your camera flash is setting off the studio flash before the shutter has opened.
 
Garry Edwards said:
I don't know how you're firing the flash, but the only methods that work are either a radio trigger/infra red trigger or a physical cable. My suspicion is that you're using the camera's built in flash to fire your studio flash and what's actually happening is that the pre-flash from your camera flash is setting off the studio flash before the shutter has opened.
Click to expand...

I completely missed that one :bang: i blame the time of day, I agree with him ^ :lol:

or how else would your camera do the metering for you.
 
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I am using a RF/RD 616 trigger to fire the flash. There is`nt a built in flash on 5D.

Both meter and camera set to 100 ISO.

Meter in flash mode (not cable), set to 160th in front of subject with dome out and pointing towards flash, press button on meter and fire flash by pressing button on RF616. Meter reads F8.

F8 on camera picture underexposed.

Thanks for trying to help, only conclusion is that something somewhere is faulty. Hopefully the meter rather than the camera.
 
In that case I've got it wrong - but if you really have set both camera and meter to the same ISO setting then what you're saying doesn't make sense to me...
The meter might be a bit out, after all all that a meter does is meter, it isn't magic and the results need to be interpreted, but we're talking about an error here of 2 stops and any error will be nowhere near 2 stops.

And as I've said, your camera meter can only measure ambient light, the flash doesn't register on the reading, so if the camera meter is registering the correct reading then it has to be the correct reading for the ambient light (in this case for the light from the modelling lamp) which means that the flash can't be firing in sync with the shutter - unless of course the camera and the Sekonic meter are set to different ISO settings.
 
hmmmm, the only other thing i can think of is either the sekonic has exposure compensation set or the calibration compensation has been played with then.

The instructions to reset them are in the manual, if you havent got it you can download from here

http://www.sekonic.com/images/files/L-358.pdf
 
Garry Edwards said:
In that case I've got it wrong - but if you really have set both camera and meter to the same ISO setting then what you're saying doesn't make sense to me...
The meter might be a bit out, after all all that a meter does is meter, it isn't magic and the results need to be interpreted, but we're talking about an error here of 2 stops and any error will be nowhere near 2 stops.

And as I've said, your camera meter can only measure ambient light, the flash doesn't register on the reading, so if the camera meter is registering the correct reading then it has to be the correct reading for the ambient light (in this case for the light from the modelling lamp) which means that the flash can't be firing in sync with the shutter - unless of course the camera and the Sekonic meter are set to different ISO settings.
Click to expand...

Thanks garry, I appreciate that it does`nt make sense and have checked the ISO numerous times as that was the obvious culprit.
 
The other thing is that an incident reading is the equivalent of a grey card reading and can't always be used directly without adjustment for the tone of your main subject. I think you really need to post an image which will help people to help you.
 
None of this makes sense to me :thinking:

Post a pic. What power level is the Bowens on? What light modifier?
 
I read the first post and decided this had to be a sync problem. Pre flash or whatever.

Read the rest of the stuff and saw you were using a radio trigger.....hmm.

My money's on a sync problem ;) I've seen this with an RF602 - the sync pulse can drift so that it fires at the wrong time.

Drop the battery from the transmitter and wait a few minutes (really - a couple of seconds won't do it). Refit and try again.
 
I'm no flash expert but I'd also say it's a sync issue, and easy to check for - set the wb to daylight and look at the test shot - my guess is that it's lit by th modelling lights only. You could even turn off the modelling lamps and see if the image is further underexposed.

Do you have sync cord for the flash - might be worth a shot too.
 
Is the flash actually firing?
What mode is the camera in?
 
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The camera in shutter priority is metering for the ambient and does not include the flash in its calculations as the flash will only trigger when the shutter opens but the metering is done pre shutter opening.

When using the flash meter have the dome over the sensor, stand were your subject will be standing and point the dome at the camera (not at the flash). Take the flash trigger off the camera and use it to trigger the flash at the subject position.

To check if your flash is triggering when the shutter is open do the following.
1) Switch all ambient lighting off and close any curtains. Minimise ambient lighting.
Set camera in manual mode at iso 100 and 1/125 and f16. Switch flash off. Take a shot. You should have a largely black image or very underexposed image.

2) Switch flash on and set flash to maximum output. Camera in manual mode and iso 200, 1/125 and f4. Take a shot. You should have an over exposed image. This confirms that the flash is firing when the shutter is open. If you still have a very under exposed image then the problem is the flash triggering.

3) Disconnect radio triggers and do step 2 again but using a sync cord. If image is over exposed then set flash to half power and take another reading using meter but with sync cord attached to meter and in flash cable mode. Set camera as per meter and connect sync cable to camera. Take test shot. Should be properly exposed.

If 3 works then problem is radio trigger firing out of sync with camera.

Let us know how you get on.

John
 
The thing is that is striking me here is that all sensors are different but all flash meters are pretty much the same, you do need to adjust sometimes, when my flash metere says F11 sometimes I need to stop down to F10 or F9 to get it exposed right.
 
kiteninja said:
The thing is that is striking me here is that all sensors are different but all flash meters are pretty much the same, you do need to adjust sometimes, when my flash metere says F11 sometimes I need to stop down to F10 or F9 to get it exposed right.
Click to expand...

Yes, but we're not talking about 1/3-1/2 stop of adjustment here, we're talking 2 stops.

I and everyone else who has suggested a synch problem has to be right, that's all that it can possibly be.
 
+1 sync issues. In shutter priority its only metering for the ambient light, and if it comes out properly exposed, with the flash firing, then its firing at the wrong time, under normal circumstances you'd expect the image to be massively over exposed in this case. The modelling light is contributing to your exposure, the flash isn't.

Try another radio trigger or a sync lead and report back :)
 
Thanks for all the replies.

Have access to another trigger tomorrow, will try that and hopefully that will be the problem.

Will report back.
 
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