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Old Aug 5, 2006, 5:09 PM   #101
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AK Carlow-

I mentally tossed around your question and could see no reason why your flash would not work in the AV Mode. Then I took my K100D in hand, installed my external flash, which luckily is the exact same flash, moved the flash head to the bounce position and went and took these two photos.

The first photo that I took was inAV Mode. Here is how it looks:



The second photo that I took was in theProgram Mode. Here is how it looks:





Finally I switched cameras to my Pentax DS, remounted theexternal flash,and took another AV Mode photo.



I tookthree photos because I felt the second photo would act as a control photo to verify that these, and I took the final photo withmy Penatax DS as that is the camera you have.So that pretty much proved to me that at least my camera-flash combinationsseems to work in the AV Mode. The photos were taken with the K100D and the DS equipped with the Pentax 18-55mm kit lens.

A couple of questions come to mind.

(a) I find the Sigma Flash stubborn to mount and unmount on my K100D. I always make sure that it is all the way into the flash shoe on the K100D camera. The flash has to make proper contact with all four of the contacts built into the flash shoe.

(b) Is the flash unit you received the proper P-TTL flash model. My Flash box label reads: "EF-500 DG ST PA-PTTL For Pentax."

MT/Sarah

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Old Aug 5, 2006, 11:13 PM   #102
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Hi Richard,

Despite what many might say, I think that your problem is that the onboard flash on your DS is P-TTL, meaning that it preflashes to get an exposure reading, then almost instantaneously gives the main flash for exposure. Your slave fires on the preflash, and can't recharge fast enough to fire on the almost instantaneous primary flash.

First -- to convince you that there are two flashes, watch carefully through your viewfinder while taking a shot with your onboard flash. You can actually see the flash fire in the viewfinder before the exposure (if it wasn't before the exposure, you wouldn't be able to see it because the mirror is flipped up during exposure).

Now to test which flash fires your slave, place the slave in your frame, then take a shot with the inboard flash. If you can see the slave fire in your viewfinder, then it's triggered by the pre-flash, and its light will not be seen in your exposure -- in fact, your shot will probably be underexposed as the slave-firing-on-preflash will probably fool the camera into thinking there's more ambient light than there was.

Most digital cameras use a pre-flash (at least the ones I've had), so those slaves which are made for digital cameras either are designed to fire on the second flash, or are switchable to do so.

I could be wrong, but that's been my experience.

Scott


Ritro wrote:
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mtclimber schreef:
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So you have seenwhat the first slave set up looks like. Please keep in mind that a slave flash can be used by any camera. All it needs to fire is the light of another flash.

I've been using a slave flash for many years, it - an Osram S18, must be over 30 years old- worked with my Kodak dx 6490, but, not with the Pentax *Ist L. First I thought it was the pre-flash from the build in flash that fired the Osram too early, but the same happens with the Sigma EF-500 ST and that does not use a pre-flash, but infrared if i'm correct. To be sure I took a picture of the loaded slave with the Kodak and with the Pentax, you can see the flash flashing on the Kodak, but not on the Pentax.

Richard.

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Old Aug 6, 2006, 1:52 AM   #103
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Hello snostorm,



Thanks for your help.

I know that the onboard flash uses a pre-flash, the camera even uses it to focus in dark situations. I started to wonder what was happening when I got the same result with the Sigma 500 flash on the camera. That flash uses an infrared signal to focus.I see a bunch of red stripes on the wall when I let it focus in a not so well litroom.

(But it could be that it also uses a pre-flash which I did not see, that would answer my question.)

The on board flash of our Kodak DX 6490 does not use a pre-flash and yes, I can use the slave with that one. The slave also works in combination with an external -old-Philips flash on the Kodak.

Your story is true, I can see the flash flashing, but I don't see the flash on the picture. And yes, I've made some pictures withthe slave unit that's what started my questions.

Have a nice sunday, I will be in the zoo with the kids and the pentax.

Richard.







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Old Aug 6, 2006, 6:01 AM   #104
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The flash (which is the same model as yours, Sarah, the PA P-TTL) is firing, but it is not firing twice unless I put the camera in AUTO PICTURE mode. The Exif data on your three shots gives Flash Used: Yes (Manual) so at least we are getting the same effect - the camera setting for flash will only allow auto when the program mode is AUTO PICTURE.

To try and answer whether, in Av mode with the camera flash setting on manual (no choice) and the on-flash setting on TTL, you get any automatic control of the flash duration, I took three shots (one here, the other two in the following replies) at f11, f4 and f22. If there was any TTL exposure control at work you would expect the three shots to be about the same, as the camera would allow the flash to fire longer for f22 and shorter for f4. As you can see, that is not the case.
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Old Aug 6, 2006, 6:03 AM   #105
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These are the over-cooked eggs ...
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Old Aug 6, 2006, 6:04 AM   #106
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... and these are quite under-done.
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Old Aug 6, 2006, 5:31 PM   #107
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AK

Here is a series of photos that I took with my DS and our mutually owned Sigma EF-500 DG ST. I have labeled every photo with my exact settings.

















AK, you will notice when looking at the EXIF data for close up series that the aperature and shutter speed remain the same throughout the close up series. Therefore, it was the flash that was making the adjustments in flash duration.

To verify that the flash was indeed doing the quenching, I went ahead and photographed an entirely different scene using the flash head at three different positions. Once again, when looking at the EXIF data, you will see that the aperture and shutter speed remained the same, and I continued to get the proper exposure, as I did with the close up series, because the Sigma Flash was doing the work for me, automatically.

Please take note of the fact that the caption on each photo gives you the exact data concering how both the camera and the Sigma flash unit were set up.

MT/Sarah
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Old Aug 6, 2006, 8:03 PM   #108
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I sent a note to Sarah about using the Sigma DG 500 ST P-TTL flash in church this morning, and she suggested that I post a few images to demonstrate how it works in that setting. One thing I learned is to use spot metering rather than the center weight metering I usually use. Others are posted at http://www.pbase.com/drwindmill/sigma_flash, if you want to take a look.

Regards, Lawrence




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Old Aug 6, 2006, 8:08 PM   #109
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Just an observation, but I think everyone is "wearing out" on the flash thread. There was probably too much info in too short a time. So I will wind up the thread tomorrow (08/07) with a recap on external flash and I will call it a day.

Thanks a whole lot for your enthusiasm and spirited replies, but I just a have more thingsgoing on right now than I can effectively handle and manage to keep up withthe Flash Thread, as well.Hopefully, we all got to thinking a bit more about flash as a very viable light source. Becaiuse it realy is a good light source that we can very effectively make good use of when we are taking those great photos.

MT/Sarah
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Old Aug 6, 2006, 8:10 PM   #110
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Lawrence-

Those are great photos that really captured the spirit of the event rather nicely. That is a job well done!

MT/Sarah
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