Sekonic L-558R in Cordless Flash Mode

I'm having trouble understanding how my Sekonic L-558R works in cordless flash mode (not using PW's).

I have a two flash setup, camera set at 1/125s and f/7.1 and with the power dialed down on both flashes such that the exposure is correct (no clipping in the histogram and image looks correct in CS3).

I then:

1. Set my Sekonic light meter to incindent reading (dome up), cordless flash mode (lightning bolt) and 1/125s to match the camera shutterspeed.

2. I push the measuring button, position the meter to read incident light falling on the subject then fire away.

The meter then gives a reading of f/2.8 ... not 7.1, which is what is confusing me. I've also tried cumulative mode and manually tripping the flashes in case the pre-flash is messing up the reading but get the same result.

If the image is properly exposed shouldn't the result be f/7.1, or am I reading it wrong? If I set the camera to f/2.8 the image is totally blown out.

When I set the meter for reading ambient it gives a reading that matches my cameras light meter.

Same ISO on the camera and the light meter?

Lotto wrote in post #7105242
Same ISO on the camera and the light meter?

Yes, same ISO.

The more I look at this the more I think the problem is that the Sekonic is metering the preflash instead of the final illumination.

I'm using a Nikon D700 as the "Commander" with a SB-900 and SB-600. Just like with the Canon system the results are more consistent using manual settings instead of E-TTL or iTTL, but I have a feeling that to be able to use my light meter I may need to go with true manual with either a wired system or use PW's.

For now it looks like doing a bunch of test shots and looking at the preview images and histograms is the only way I can set things up.

Bob_A wrote in post #7105958
The more I look at this the more I think the problem is that the Sekonic is metering the preflash instead of the final illumination.

Bingo.

Using a light meter to measure the light from an automated flash system (where the flash emits a pre-flash as part of the exposure control scheme) is not only virtually impossible but is a rather useless effort.

If, on the other hand, if you put your flash and the camera into fully manual modes then a flash meter will become useful.

Bob_A wrote in post #7105958
Yes, same ISO.

The more I look at this the more I think the problem is that the Sekonic is metering the preflash instead of the final illumination.

I'm using a Nikon D700 as the "Commander" with a SB-900 and SB-600. Just like with the Canon system the results are more consistent using manual settings instead of E-TTL or iTTL, but I have a feeling that to be able to use my light meter I may need to go with true manual with either a wired system or use PW's.

For now it looks like doing a bunch of test shots and looking at the preview images and histograms is the only way I can set things up.

It is not iTTL preflash that's hosing the meter reading because with the flashes in manual mode, there is no preflash to speak of. What's hosing the meter is the command flash from the commander to the slaves. But in any event, you are correct in that the solution to your dilemma is to trigger the slaves by some means other than using the commander, such as using an RF remote or a long sync cable.

Thanks guys.

I discovered this anomaly when using the ST-E2 as well. The solution was to hand hold the STE, and make sure the command signal was not visible to the meter.

Works perfectly every time.