Sigma Flash Problems

Hi Everybody,
I have a Pentax k20 and I bought the latest Sigma flash (EF-530 DG Super)
and after reading other posts on here I still cannt sort it out. It fires on wirless mode apparently ok, but, before the shutter opens by the look of it. No messing with shutter speed shows the sigma firing in the picture, yet I can clearly see it doing so through my other eye.

Have tried various camera and flash settings to no avail, Any ideas please?

Cheers Ray H

Welcome to the forum Ray,
Hopefully we can help you.

Set the camera on manual and take one shot with the flash and one without the flash with the camera on the same iso, shutterspeed and diaphragma.
You will probable see a difference between the two photos but a lot depends also on what mode your flash is set.

If you use P-TTL then you might have the problem that the camera underexpose simply set the flash correction to +0.7 to +1 EV that would make it more acceptable.

With the other modes on the flash a lot depends on the user but if you keep track of the flash exposure range in the screen you probable should see a flash.

If all that is clear and doesn't make a diffrence please post a photo for us, we can see what happend by looking at the photo and the EXIF data with it.

Does the flash work acceptably when mounted on the camera?

I have a Sigma 530 which initially underexposed horribly, Chris sent it back for me under warrenty and they re-calibrated it, now it works fine.

Sounds rather like my Sigma EM 140 ring flash when I bought that to work with my K20, Sigma had a batch that were no good on the K20 but worked on the K10?
It was changed by SRS and Sigma for a new one and then all was well.
Why they work ok with the K10 and not the K20 I do not know, perhaps someone out there knows?

Hi Guys thanks for the replys. Haven't had time to try your suggestions yet so here is what I'm trying to do. I want to photograph a dancer, the theatre has black curtains, I want the camera flash to light the front and the sigma to be behind and to one side of the dancers pose to give a strong quarter back light.

Experiments have shown the the sigma is firing on the cameras pre flash because when I cover the pop up flash on the camera the sigma dosent fire.
Am going to read both manuals again and try once more.
Ps The sigma always seems to under light when on the camera and I have to use about +1.5 to get the exposure correct. Is it duff??
Cheers Ray H

ahhhh you have set the sigma on dumb-slave probable, you ned to set it up that it use channels. Don't know how to do that since I don't have one but I'm sure someone can help you

I also have 1 ev underexposure with my pentax flash, it's simply the camera that does that.


ps. The sigma is for the pentax right or else it won't work.
The build in always fire with a pre-flash since it doesn't have manual mode.

This does not make any sense to me. What exactly do you mean?

A wireless slave flash is triggered by light pulses from the pop-up flash. Covering the pop-up flash will render the wireless flash useless as it can't 'see' it's instruction to fire.

Peter I think he has his flash in time same setting as slave-mode 2 with the Pentax AF540FGZ, it simply fires with every flash it sees.

You may be right Stefan, but if it's working in true P-TTL mode, it is supposed to flash before AND after the mirror goes up and the shutter is released.

For info RayHutty:- the P in P-TTL stands for Preflash. A complicated sequence of light pulses are exchanged between the pop-up flash and the wireless slave, the slave is triggered and the camera's light meter measures the flash output to set the exposure and flash power BEFORE the mirror is raised and the shutter is released. After the shutter is open you get the second main flash which actually makes the exposure.

I always thought to 'P' stood for Pentax, as it's the 'Pentax Through The Lens' technology, to differentiate it from the TTL flash tech used on SLRs and the early Pentax dSLRs.

As I understood it, all TTL's pre-flash, it's just that Pentax were the first to bring out a new version that worked properly with dSLRs.

Mostly...

Nope

The original TTL is a single flash, through-the-lens metering. Instead of the flash doing the metering (as in the older "A" style flash) the camera had a separate sensor taking a reflective reading off the film - telling the flash when to stop. (The camera's multi-segment meter is only usable when the mirror is down.)

P-TTL, which uses a preflash, ditches the separate sensor (apparently there were issues with the reflectivity of the CCD in digital, plus an extra cost) and makes use of the camera's regular metering system. The flash fires before the mirror goes up (you can just discern the preflash through the viewfinder) - so the matrix metering system cna be used. When that's done, the mirror goes up and the main flash fires. The gap between preflash and main flash is usually tiny (fractions of a second), so sometimes it is perceived as a single flash.

As mentioned elsewhere, the original *ist-D and *ist-Ds were the only cameas that supported the original TTL.


For the OP's requirement (dancer on a black background) I would strongly suggest using everything in manual mode anyway. Any metering system will be wildly out when shooting against black

Start with:
* Camera to "M", 1/125s, f/8, ISO 400
* Flash to "M", power at 1/4

If the image is too dark do one or more of:
+ Use a wider aperture
+ Use a higher ISO
+ Increase the flash power
+ Put the flash closer to the subject (if remote)

If the image is too light, do one or more of:
- Use a smaller aperture
- Use a lower ISO
- Reduce the flash power
- Put the flash further away (though this makes it more of a point source)

Even then, with the camera's pop-up trying to provide the main fill you may have issues. Pentax metering is effectively two sided - even if the camera (i.e. ambient) metering is in "M", then any P-TTL flash (pop-up included) will meter on its own. So, you'll have limited control over what the pop-up can do.

For the situation you describe, the best approach is a cheap manual flash on the hotshoe, and the Sigma running as remote for the outline fill.

To be honest, it's harder to describe that to do It's the kind of setup that I could put up and adjust in under ten minutes and be ready for shooting. Once it's all set in manual mode you just fire away and don't think (since the lighting is now completely under control).

HTH!
Matt

P.S. This info and more is covered in my e-book for Pentax digital flash (Not that I'm plugging - it's just that you might find it helpful in gaining an understanding!)

Matt has explained it very thoroughly, as always.

TTL flashes produce only one flash to make the exposure after the mirror goes up and the shutter is fully open. In TTL mode, an additional light sensor inside the mirror box measures the light reflected from the film/digital sensor surface. When the correct amount of light has been used to make the exposure the TTL circuitry quenches the flash to stop it producing any more light.

P(reflash)-TTL uses the cameras normal light meter to set the flash power before making the actual exposure when it fires a second time.

Ok Guys, the is really good info. Now I have to fully confess my ignorance of Flash photography. First I usually and mainly shoot ariel stuff from a flexwing microlight using my K20 and the Pentax 50mm f1.4 lens which is razor sharp at F4.

I got the flash as I also shoot some of the marketing pics for the local college I work for. Now in my ignorance (HND electronic engineering) I assumed that wireless means RF, not light triggered (else why different channels?) so covering the camera pop up as a test, I expected the Sigma to fire (via RF). If the camera has a channel setting I can't find it.

Now, Mannesty, what I tried to describe is when I set the Sigma on the floor behind the test model (long suffering misses) although it was out of the framed shot it was supposed to provide a strong backlight effect (thats what I'm after). When I took several pics I could see it firing through my left eye, but it was not on during the cameras exposure. (Sigma 24-70 macro lens @ f4 Camera iso 200 Exp on X ) The picture only showing a dark front lit shot.

I also find using it in dark clubs a real pain (College sports awards presentations) finding, on a wide lens setting, an exposure that lit everything OK, when I zoomed in (Sigma 24-70 f2.8 ) for a better sports man of the year shot, the pic was very dark, so I had to stop the proceedings to reset for a properly exposed shot. (My old Olympus 5050z was never this much hassel).

All that aside I would like to get this shot of the dancer, back lit by this flash. There must be a way.

Cheers Ray H

Think of it like this - camera fires pre-flash trigger; Sigma fires (almost) into the lens; camera goes "woah! this is bright", and asks the Sigma to fire a tiny amount.

Manual. Manual. Manual.
Did I mention that you should use Manual mode?
The camera doesn't magically "know" that you're trying to produce a rim-lit subject - it just works on what light enters the matrix metering.

Matt

Cheers Matt,

I will try this spanish Manwell chap.

Or did you mean beat me or the flash with the instruction manual?

Seriously I'll give it a go and let you know

Cheers Ray H