Can't get flash exposure low enough

I have a hard time getting my flash power low enough when I shoot in the shade or after dark. Could this because I'm always using wide aperture, between f/1.2 and f/2.8? I'm doing that to get as much bokeh as possible, but also after dark so I can pickup some background (including background lights), while keeping shutter speed high enough. Like1/60th to 1/100 for people standing still or posed.

What iso are you using? The flash will feeeze motion so you should adjust your shutter speed as needed to control the background exposure.

You don't mention which flash unit you use, so I have to give a generic answer, and assume you have a Canon 580EX (and shooting at ISO 100) ...

1. At full power the Canon 580EX has a 'normal lens' (32mm on APS-C or 50mm on FF) Guide Number of about 135.
   
2. If the Canon 580EX had 1/16 power as its minimum, that is GN of about 33
   
3. At GN33 and f/2, you would be overexposed if closer than 16-17'
   

From 2m my TT685 gives a reading of F/2 at minimal power. A ND filter wouldn't disturb much if wider aperture or a closer distance is needed but getting the flash off camera + using an appropriate modifier is a better solution. I honestly have difficulty seeing the problem.

I suspect some flaw in your approach. But regardless there is always the option of adding diffusion to the front of the flash. A mostly useless diffuser like a omnisphere would cut the power by a stop.

have you tried the flash in TTL with exposure compensation, many flashes will fire at a lower power in TTL than they will when set manually

Mike

If you just want to shoot with the prime lens wild open, use a flash/strobe with HSS. Increasing the shutter speed will lower the flash output 4-5 stops below the minimum at standard sync.

If the strobes are too strong in the shade, use a speedlight.

To balance the night scene with strobes, I would pump up the ISO, and use the modeling lamp as the main light.

Samples below are shot with the same 600ws strobe, one with HSS, the other with modeling light only, both at F1.4.

gonzogolf wrote in post #18894418
I suspect some flaw in your approach. But regardless there is always the option of adding diffusion to the front of the flash. A mostly useless diffuser like a omnisphere would cut the power by a stop.

^^^

Shooting in eTTL mode, even a rather powerful flash like the Canon 580EXn can reduce its power to 1/256 power which is -8EV lower than max power...so while that that has GN135 (or so) at full power, it has GN8 which permits an f/2 lens to shoot as close as 4'.

But we still do not know what flash the OP is using.

And with the flash in HSS mode, with the camera shutter set to 1/3EV faster than X-sync speed, it loses another -2EV and gets to GN4 which allows f/2 to get to 2'. Yet use of HSS is counter to the OP desire to 'shoot after dark...and pick up some background'.

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gonzogolf wrote in post #18894418
But regardless there is always the option of adding diffusion to the front of the flash. A mostly useless diffuser like a omnisphere would cut the power by a stop.

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Does the OP really need to use a diffuser to get less light from the flash? . Couldn't he just set the power of the flash to fire at 1/2 power, 1/4 power, 1/8 power ..... all the way down to 1/128th power? . That seems more straightforward to me than sticking something in front of the flash to physically block the light.


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I'm guessing that the OP has already reduced the power to the flashes minimum and it's still too much. Without knowing what flash the OP is using and what mode they are shooting in, and weather it supports TTL/ETTL or is a full manual flash, it's hard to offer meaningful suggestions.

In the old days of 35mm one layer of a white handkerchief over the flash head effectively reduced the light by about 1-stop and also provided some diffusion of the light. Multiple layers didn't work well as I recall, but worth the experiment since you can immediately see the image.

Thanks to everyone for the replies. My sincere apologies for not mentioning the flash I'm using. It's the ORLIT RoveLight RT 610 HSS TTL for Canon. External and internal diffusers in a softbox, and also a diffuser dish inside the softbox.

I shoot manual exposure with the camera and usually manual flash power. 1/128 power has often been too much. I have been able to lower the flash power with TTL instead of manual flash, but even that is too much sometimes.

I'm usually at ISO 200-400, but sometimes 800 or even higher to pickup background lighting on buildings or whatever. I never tried slow shutter and letting the flash freeze the subject. And I never thought of using a shutter speed above sync speed to get reduced power from using HSS. I need to experiment with both of those. I've been using slower shutter speeds to pickup ambient light without raising ISO too high.

Recently I've been trying a Rotolight Anova Pro 2 at night, which of course allows much lower light output.

...add a Neutral Density filter. Over the flash, reduces the flash. Over then lens makes it harder to see subject/focus

Increase the strobe distance to the subject and/or use a larger modifier.

You can also buy neutral density gel sheets for the flash, but assuming the flash has been set up close to the subject in the past, a little distance can make a big difference.

Feathering the modifier will also help.

ORLIT RoveLight RT 610 is even more powerful and has an ISO 100 GN221, which is a fundamental issue when really low power is needed. The manual range of power is from setting 1 - 9, so you get 1/256 power from it. The lowest Guide Number is about GN14 at ISO 100, but it is GN19 at your preferred ISO 200. At f/2 you have to be at 9.5' away at your preferred ISO, and 16' away at your preferred f/1.2