Problems with built in flash

Having not really bothered in the past I have decided to buy a dedicated flash for my K100D Super.
This was partly brought about by a couple of trips to the Cold War museum at RAF Cosford, where my in built flash showed itself up quite badly.
However before I take the plunge and spend some money I have concerns about the way my camera performs with flash.
I was with a friend who has an Olympus 410 (despite having a mint LX and many lenses), and his inbuilt flash took many good shots at closer range (GN15). I got under exposed shots. Now whilst taking a shot of a tank I noticed the reflection of the flash firing IN THE VIEWFINDER before the mirror flipped up. Thinking I had imagined it I tried a few more with the same result. As I have said I have never been into flash in a big way, but my understanding of how it works is this.
When you press the shutter release
1. The mirror flips up
2. The shutter opens
3. The flash fires
4. The shutter closes
5. The mirror drops
Am I wrong?
If not how could I see the flash in the viewfinder?
Is this a setting problem on the camera?
Is this what caused the under exposed shots?
How deep is the ocean?
How high is the sky?
Come to think of it I can find the answers to the last two questions!

I was using the Auto Pict setting after about 20 shots on Av with the same results on both settings.

Rob

Well I dont know much about this at all, but in my view it depends on the speed your shooting;

The mirror pops, flash fires, so that the shutter captures the light on the tank it opens after?

however

you may have set a setting to reduce the power of the flash by a considerable amount (thus, it fires earlier perhaps?)

Infact ive just gone and grabbed my camera, and yes, the flash fires as the shutter opens - so you see the reflection, not the flash? or vice versa.
There is a setting in menu (I use a K100D, not super, but i think its probably the same) - Flash Exp. Comp. - To compensate for underexposure with the flash, boost it up to +1.

Hope that helps.

What you're seeing is the pre-flash and it's quite normal - it's used by the camera for evaluating the amount of flash required for the picture itself. You won't see the actual flash of course because your mirror's in the way (as you rightly surmise). So the order of play is;

Press shutter
Pre-flash fires
Camera "reads" pre-flash and calculates amount of light required
Mirror flips up
Shutter opens
Main flash fires
Shutter closes
Mirror drops

Most built in flashes are a little weak, some would say the manufacturers do it deliberately in order to sell external flash units - how cynical!

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Open its hallowed pages (take care lest the light therefrom blind you with its purging brightness).

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Read it from cover to cover and have Magic Lantern guide, read that to Oh Great Sarky One

So basically, to solve your problem, go on the menu and alter the value for the "Flash Exp. Comp." to 1.0

To be honest, the manual can be a bit vague from time to time. It's worth reading Mattmatic's guide to PTTL flash here: https://www.pentaxuser.com/forum/viewtopic.php?t=4950 , which gives some common pitfalls etc, although it's mainly biased towards flashguns rather than the built-in flash. However, it's worth reading up on apertures and subject distances if you haven't before.

Dan

Just tried setting the flash comp to +1 and stepped outside to try it and found no difference. I have tried this before with the same results after reading the oh so helpful Manual which tells you how to do this without telling you what you might expect from doing so.

What is the interval between the pre flash and the main flash by the way?

The interval between the pre- and main flashes should be so short as to be barely perceptible. I don't have figures but we're talking a split second here (just long enough for you to glimpse it before the mirror rises).

*edit*

Take the camera away from your eye and hold it away from you while firing the shutter, this way you'll see both flashes. Good luck finding a stopwatch to time the gap though!

They can indeed.

But you see P-TTL in the manuals, all over the forums, etc...

.. and it never occurs to you to wonder what 'P' stands for?

I have read the manual as I stated and it clearly states that P-TTL is only available with the 360 & 540 flash units and I am talking about the internal flash. How am I supposed to know the pre flash happens with this too when the manual written by Pentax for a Pentax camera does not state this.
I seriousley think that the guide number for the built in flash (15.6) is feet NOT metres.'cos that's what my photo results seem to bear out!

Another thing to remember with flashes (built in and external) is that the guide number will drop off dramatically when wider lenses are used. For example, a lens at 20mm will require roughly 3 times the flash power of a lens at 100mm to cover the same distance (because you're having to light up the edges like a floodlight, rather than throwing a narrow beam like a spotlight). Another thing that affects guide numbers is the sensitivity, if you set your ISO to a higher value then you'll find your flash coverage is more effective. Try it and you'll see what I mean...

Guide numbers generally (but not always) refer to full power with an 85mm lens at ISO100.

You're right, of course.

It is a bit obscure. What they mean is that you can't get P-TTL with any other external guns other than the two Pentax P-TTL compatible guns. Even that's no longer true, of course, since there are now at least three Sigma P-TTL guns, two Samsung ones, and a Metz, that are all compatible with P-TTL, apart from the AF360 and AF540 FGZs. And there's the baby Pentax P-TTL gun too (AF200? 220?)

I guess I was just lucky - I saw the flash in the viewfinder, thought "huh?", just as you did, then I took a picture looking at the flash unit and saw both flashes. Which made me do a bit more reading.

It's a lot clearer from the flash gun manuals, but I do agree that the K10/100D manuals don't exactly explain what P-TTL really is.

How clever of Pentax to sell a camera with a minimum ISO of 200 and give the guide number at ISO 100 and not tell you a conversion factor is needed. I'm going to bin the manual or rip it up and put the pages on a nail in the outside loo.
It does not tell me anything I really need to know and it assumes a certain amount of knowledge from the reader about far to many areas. How could a new comer to photography (digital or otherwise) expect to get the best from their camera with this piece of "head up their own arses" junk.
I hope the same crew don't start writing Haynes Manuals for cars.

To be fair to Pentax, the guide number of 15.6 on the K100 is based on an ISO of 200 (I did say the 100 thing was a general rule). To put this in perspective, the K10 has a built in flash with a guide number of 11, however, this is based on ISO100 and so while it appears to the casual observer to be a weaker flash unit it is in fact roughly the same (+2EV on the ISO will double the guide, ie the K100 is 15.6 @200, 31.2 @800 and 62.4 @3200).

Your friend's Olympus 410 has a guide number of 10 @100 meaning it's slightly weaker than yours but only by a gnat's chuff! I'd suggest he was maybe taking pictures at a longer focal length / higher ISO than you were, hence he was getting better results from his flash.

If you want to start using flash on a regular basis then I'd heartily recommend buying an external unit (I've got a Pentax 360 and I adore it); the built-in flash will only end up frustrating you in the end - to use another car analogy, it's like driving at night with your halogen headlights replaced with a pair of candles...