I use a Vivitar 2800 (an autoflash) with the M6 classic. For asa 400 film, the biggest aperture suggested by the flash calculator is f/4 on automode. Is there a way to reduce flash output so I can shoot at f/2 on automode when using asa 400 film? My objective in using faster film is to get a fairly decent shutter speed for ambient light when using the flash.

The flash comes with a 35mm diffuser panel which I understand reduces output by 1 stop. Following the logic, I am thinking of using the diffuser panel to clip lee diffusing papers to the flash head to reduce the flash output. Would this work?

BTW, this is a great forum! 8^)

-- Arnell Umali (atumali99@yahoo.com), March 25, 2002

Answers

I don't think you could reduce the output. The diffuser reduces MAXIMUM output, but the flash will still try and produce the stop you have asked since the auto eye is cutting it off. Use slower film.

-- charles (c.mason@uaf.edu), March 25, 2002.

use one of those stofen (or whatever) translucent plastic flash diffusors. they reduce effective output and give light a nice non- columnated quality.

-- roger michel (michel@tcn.org), March 25, 2002.

No, you can't reduce output on an autoflash by using diffusers or filters over the flashtube - the sensor watches for a certain amount of light to bounce back from the subject, and will just leave the flash tube burning a little longer to 'compensate' for the diffuser.

Wait - no, well actually you CAN - but you'll need to block the light so extremely that even at FULL OUTPUT it is not able to push enough light through the filters/diffusers to get what it thinks is correct exposure. But at that point you've effectively lost the auto capability - it's firing at full power all the time and the exposure will only be correct for a certain distance. And you won't know WHICH distance without tests - since the footage scale is based on full power without any diffusers or filters.

You CAN use a neutral density filter over the lens - f/2 and a 4x ND will equal f/4. But that only helps if you want f/2 'bokeh' - the relative flash and background exposure still stay in the same relationship.

In other words the flash you have just puts out too much light relative to the ambient light. The only real fix is to upgrade to a flash with a directly-controllable power setting, or 'exposure compensation' built in. (I think the Leica M6 flash does this). The 2800 is wonderfully small and light (it's the only flash I've used for 20 years - across 4 different camera systems) - but this is its one big weakness.

Or do like David Alan Harvey and others do and LET the background blur at a longer shutter speed and f/4. It can add a kick to some pictures - but may not be the 'look' you want.

-- Andy Piper (apidens@denver.infi.net), March 25, 2002.

Arnell. I don't know the details of the Vivitar 2800. But if it has an ISO setting dial, you could just increase the ASA setting to "fool" the flash into thinking the film is faster than it is, and open up the lens from F/4 by the corresponding amount. I don't see why that wouldn't work.

-- Eliot (erosen@lij.edu), March 25, 2002.

Eliot,
The reason why this won't work is, that the flash will just demand a higher f-stop for the autoexposure to work correctly, nothing else. If it was f 4 for ISO 400 it will be 5,6 for ISO 800 and so forth. not following the indications given by the calculator will just leed to over exposure. Arnell won't be able to reduce minimum output by this. There is no way to do it. Arnell, you need a weaker flash. To my knowledge the SF20 is best for your purpose. Cheers.

-- Lutz Konermann (lutz@konermann.net), March 25, 2002.

A 2-stop ND filter on the lens will work by reducing the amount of light the flash put out prior to its reaching the film, thus allowing an f2 setting on the lens.

Cheers,

-- Jack Flesher (jbflesher@msn.com), March 25, 2002.

Thanks for the quick response :)

Charles: My thoughts exactly on the eye sensor. The flash manual had me confused when it indicated I would needed a bigger aperture when I use the flash diffuser panel even on auto mode.

Roger: I have and use the stofen diffuser. It reduces the strobe's effective distance but the auto aperture remains the same. Its a great help when there is no low ceiling to bounce the flash. :)

Andy: I was hoping you would respond since I read in the previous posts that you use a similar model :) Thought about using the ND filter. But wouldn't I need to use a slower shutter speed for ambient light? I was hoping to use the additional stop of the faster film to get a faster shutter speed for ambient light.

Lutz: I don't know much about the SF20. Used correctly, I know you can avoid the "headlights effect" (seen Rob Appleby's pix and they are great!). Would the flash compensation work when the strobe is on auto mode used with the non TTL M6? Unfortunately, there are not too many Leica dealers in Manila for me to examine the flash up close.

Hope I'm not rambling. Just wanted to clarify some issues while on topic. This forum has been a great help! :)

-- Arnell Umali (atumali99@yahoo.com), March 25, 2002.

Arnell,

In non-TTL auto mode the SF20 will give you an f-stop choice among 2.8, 5.6 or 11 no matter for which ISO setting between 25 and 800. Additionally, you can reduce output by 1/3 f-stop increments down to a maximum of -1 stop for ISO 400 (-2 for ISO 200, -3 for ISO 100 and below, but 0 for ISO 800 because that's where the "throttle" touches the minimum!). So, with your given film speed of ISO 400, the SF20 set at 2.8 and -1 you will correctly expose with a lens set at 2.0. For a fill this is still strong (as you might wish to fill in at 2 or more stops below the key), but in auto mode, as mentioned above by Andy, there is no way of keeping the flash sensor from pushing harder whenever you try to block off the output.

Jack has mentioned a way of converting an ISO 400 film to a lower sensibility by means of grey filters. This works and occasionally does make sense, for instance when you find yourself in broad daylight with a minimum sync exposure of 1/50th on an M body... But for most other situations in which you usually have an ISO 400 film loaded - i.e. in low level, ambient lighting which you do not wish to spoil by a fill flash - the only way of reducing the output further is by switching to manual mode and diffusing or blocking off the strobe. With the SF20, you will get a manual output to correctly expose at 20m with ISO 400 and f 2.0 - so for a -2 fill at 2.5m you would have to filter the output down by 8 stops (10 stops at 1.25m)! Here's an idea on how to do that, without having to change Lee filters continuously.

Cheers.

-- Lutz Konermann (lutz@konermann.net), March 26, 2002.

Arnell:

I should have added that I agree with Lutz that the most flexible option is the use of a dedicated TTL such as the SF20.

:-),

-- Jack Flesher (jbflesher@msn.com), March 26, 2002.

Or you could go the Salgado route. I remember reading an interview with him a few years ago. He was asked if he ever used flash. "I used to have a Vivitar 283, but then Kodak came out with T-Max 3200, and now I don't know where I put that flash."

:-)

-- Charles (c.mason@uaf.edu), March 26, 2002.

I should have mentioned that Jack "Flash" (aka "The Source") Flesher originally introduced me to the SF20 (Hi, Jack...;o) and that this little unit combined with a TTL body is the only one I know of that makes flash photography M-like - weightwise, bulkwise, ease-of-use- wise. But it's great on a non-TTL, too.

-- Lutz Konermann (lutz@konermann.net), March 26, 2002.