Incident flash meter doesn't register under ~f/8?

<p>Hi all,</p>

<p>I'm in the process of learning how to meter for off-camera flash using my manual strobes and a Sekonic L-508. I set up a very simple one-light portrait setup in my basement studio where the ambient light was pretty dim. I had no problems metering my one strobe. When I moved my setup outside into overcast skies, my meter doesn't report anything under f/11. I'm probably missing something extremely obvious. Any suggestions?</p>

<p>My setup: one Elinchrom Quadra head on a stand about 6' away from my subject, camera left. Meter in incident mode (the L-508 has a spot meter, too; I triple-checked it was in incident), dome raised, in flash mode. With the dome pointed at my camera, I hit the meter button, trigger the flash to take a reading. I can adjust my flash power all the way down to about f/11, and then if I drop it further, the meter reading drops straight to 0. Flash power at this aperture is about 50%, so I've got some room to lower power output further. Taking an ambient light reading from the same location shows about f/5 - about two stops lower than the flash.</p>

<p>What am I missing? I'm assuming it's user error on my part, but could I have a defective light meter? I'm not playing with any of the fancy bells and whistles of the Elinchrom system; I'm not exceeding my camera's sync speed. All readings were done at ISO 100, and a shutter speed of 1/200.</p>

<p>Forgot to include: I verified with Sekonic that, in flash mode, my meter will function from f/1.0 to f/128.9 in 1/10-stop increments.</p>

<p>Check your manual. I am going to guess that even though the meter is in flash mode, it is also reading the ambient light, so that would be an exposure floor that you are not going to get below.</p>

Hi Gary,

 

Thanks for the suggestion. The manual and Sekonic tech support seem to indicate otherwise, but even if there were a threshold,

wouldn't it be two stops lower than what I'm metering (i.e. my ambient reading of f/5.0)? I still don't see why my "floor" is f/11.

Hi Patrick, I don't know what's going wrong, but I've spent a lot of my working life figuring out ways to troubleshoot

oddball problems. Although I've seen plenty of flaky equipment, my guess is still that it's something you're doing, but I

don't know what.

 

First I'd verify that the meter can report in "that" range, which I think you mean including f/8 and f/5.6, etc. Since your

problem is showing up when you trigger the flash from the meter, I'd try letting the meter trigger itself (you put the meter

on a stand, using a "non-cord" "flash" mode, which I presume it has). Then you walk back to the flash and fire it with the

self-test button. Then keep reducing flash power and see if the meter readings can go through the missing range this way

(I'd be writing down the power setting vs meter reading to make sure they follow the expected pattern - one stop wider

aperture each time you halve the flash power).

 

If this test works ok, I'd go back to the cord/radio trigger and repeat those tests, looking for the same readings. If this test

does NOT pick up the missing readings, I'd try it outside, in "ambient" mode, making changes in the meter's "shutter speed"

setting to run through different f-stop readings.

 

BTW, you said, " I can adjust my flash power all the way down to about f/11, and then if I drop it further, the meter reading

drops straight to 0." I'm not clear what you mean - since there is no f/0, what does this mean? Is it a symbol that no

flash was detected, or perhaps an error code, such as low batt? Also, is it possible that you inadvertently have another

flash unit firing via an optical slave?

This sounds like a timing issue between the flash

and gating time of the meter. Is there a radio

trigger involved between flash and meter by any

chance? Also check the gating time (shutter speed)

set on the flashmeter.

 

 

What happens as you reduce flash power is that

the flash duration gets shorter and shorter. Now if the meter doesn't start reading immediately the flash starts, then it's quite possible for the flash pulse to finish before the meter responds. Any radio trigger introduces a decoding delay, and that would explain the meter reading suddenly bottoming out at a certain power setting.

 

If you're using a digital camera, what do the images look like? Regardless of what the meter indicates.

<p>Hi Bill, Joe. Thanks for the suggestions. I should have mentioned in my original question: my meter isn't triggering my flash. My meter is at my subject (just under her chin); with the meter in "flash" mode she hits the meter read button, and I hit the flash fire button on my camera (which, yes, is triggering my flash remotely, but via radio and not IR or pre-flash).</p>

<p>So, I'm leaning towards a timing issue, too - but I think perhaps the issue could be that my flash duration might be too short for the meter to pick up? But if that were the case, why would I be able to meter down below f/5.6 in my dim basement, but not outside? </p>

<p>I'm going to do some additional tests, but it <em>seems</em> like I'm not doing anything wrong (i.e I'm going through the proper motions for metering a scene). I'd like to test my flash using both ports available (i was using the higher-output "A" port while outside, but I suspect I was using the lower-power "B" port inside. How this affects flash duration I do not know) . I'm also planning to rent a different meter to see if I get the same results/feedback. Other than that, I'm at a loss. In a pinch I can just dial it in by eye, but I prefer the control I get when knowing specifically what my lights are putting out.</p>

<p>Thanks again for the suggestions.</p>

Patrick, I suspect your meter's response time varies

with ambient light. Most meters are designed to

detect the sharp increase in light caused by the

flash firing. In dark conditions it's easy for the

meter circuit to detect this, but in daylight there

may be insuffient difference between ambient and

flash to trigger the meter. Or it may be slower to

respond to the change.

 

The answer is to use the meter to trigger the flash

by cable. Thus eliminating any delay or pulse

detection issue.

<p>Yeah, if you're using the cordless flash mode, it's most likely a timing problem. The meter will only look for a flash for so long before it times out—if you and your model aren't in good sync, you may be running into this. Naturally occurring ambient flashes can also interfere in cordless mode, since all the meter knows is "at some point before I time out, something is supposed to flash at me."</p>

<p>Try hanging a trigger (Tx mode — the meter's popping the strobe) off the meter's PC port and set it to corded flash mode. If it works as expected then, you've got your problem and your solution nailed down.</p>