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03-30-2010, 12:51 PM   #16
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QuoteOriginally posted by Lowell Goudge Quote
really, I was thinking about this a little, with what is discussed here, there is a good one page flash functionality description that should go somewhere. Ideally, with a little editing, we could scour the pentax forums and publish a book that was a real user's guide, written in common english (by all us common folk)
I've been working on such a document for a long time. There's already some excellent info available (including from one of our own forum colleagues). Nevertheless there is a LOT of FUD out there on this subject. Did you see that crazy thread recently in which there was a shouting match about whether P-TTL works at all if the flash isn't in its 90° position? It was like a Biblical argument with people quoting the same passages of the HORRIBLE operating manual at one another. I have never wished so much that a Pentax engineer were a member of this forum.

Will

03-30-2010, 01:00 PM   #17
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QuoteOriginally posted by WMBP Quote
Hmmm. I've never thought about approaching it that way.

I just did a quick experiment. First I tried switching to Tv mode and setting the shutter speed to 1/30th sec. The problem there was that the aperture was recalculated as rather wider than I wanted. Shooting with flash, aperture still does have an effect on depth of field, which is why the "norm" for flash photography is Av mode rather than Tv mode.

Throwing Auto-ISO mode into the mix (in other words, shooting in Tv with Auto-ISO enabled and a range from 200-800), the aperture did stop down slightly, which was good, but I didn't think the image quality of the result was very good.

I could perhaps compromise on the shutter speed issue and accept 1/45th sec as a minimum, but I'm pretty sure that I HAVE to continue to be in control of the aperture. So Tv mode, with or without auto-ISO is a non-starter for me.

*

Now, to sicken the plot further, let me add one more variable: I'm using rear-curtain sync on the flash. Why? Suffice it to say that McNally says that he shoots in rear-curtain sync exclusively, all the time, and he has his reasons. And at the moment, I'm personally in "try to understand Joe McNally" mode.

Now this doesn't make a huge difference to the issues in this thread. I can still use rear-curtain either with P-TTL or Manual control of the flash, and with Av or M mode on the camera.

Will
My experience with auto ISO and flash is that the camera will move ISO first upwards to find an exposure solution, then use as little flash as possible with grainy results, I would be careful doing weddings this way.

re rear curtain sync, the one thing it does is limit sync to 50% of normal synbc speed so that the flash has time to go off before the curtain begins to move. What this does is have the blurred to exposure movement seemingly behind the frozen image as opposed to in front of it I if you can imagine blurr leading to a frozen image as opposed to away from the frozen image. I think the impact is more pleasing.
03-30-2010, 01:14 PM   #18
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You can get around that by setting acceptable ISO limits. At worst you get stuck at ISO 200.
03-30-2010, 02:13 PM   #19
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QuoteOriginally posted by WMBP Quote
McNally says that he shoots in rear-curtain sync exclusively, all the time, and he has his reasons. And at the moment, I'm personally in "try to understand Joe McNally" mode.
OK I'm obviously not Joe McNally -

I know at least one reason to shoot rear curtain sync - when shooting longer exposures with flash -

the flash freezes the image but anything still in light and moving will have motion trails -
for example if a person was running say from left to right - the the motion trail blur would be to the left of the person's image caught with the flash (ie: behind the person as one would prefer to show motion)

But with first curtain sync the flash exposure would be first freezing the person and the motion "trail" would then be in front - so looks wrong or may even be interpreted as running backwards.


However there is a good reason why I do NOT shoot rear curtain flash
- because of the delay between tripping the shutter and the flash firing - on slower shutter speeds this could be as long as 1/4 sec which could mean the subject has changed, on my subjects sometimes which side the exposure trail is on does not matter.


EXIF re-attached - on night scene mode with slow-sync flash and a 1 sec exposure..... flash freezes the image while the long shutter speed captures the "trailing" image movement/blur.
(that's one of my favorite acts - Unknown Hinson - where I got my monikor from).

03-30-2010, 02:33 PM   #20
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QuoteOriginally posted by Lowell Goudge Quote
My experience with auto ISO and flash is that the camera will move ISO first upwards to find an exposure solution, then use as little flash as possible with grainy results, I would be careful doing weddings this way.
Yes, this is what I found some time ago when I tested that. Outside of TAv mode, I just don't find auto-ISO that useful.


QuoteQuote:
re rear curtain sync, the one thing it does is limit sync to 50% of normal synbc speed so that the flash has time to go off before the curtain begins to move. What this does is have the blurred to exposure movement seemingly behind the frozen image as opposed to in front of it I if you can imagine blurr leading to a frozen image as opposed to away from the frozen image. I think the impact is more pleasing.
Bravo for that! I know very well what the general idea about rear-curtain sync is (getting the ghost of the speeding car behind the car rather than in front of it). What I found interesting is that McNally uses rear-curtain as his default, pretty much for everything, in other words, he doesn't just use it as a special effect.

And thanks for that tip about the shutter speed. In my testing and playing around yesterday and today, I have been paying attention to the slowest shutter speed and hadn't noticed that, in rear curtain, I was limited to an upper limit of 1/90th sec. Good to know.

Will
03-30-2010, 02:45 PM   #21
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QuoteOriginally posted by UnknownVT Quote
OK I'm obviously not Joe McNally -
I'll forgive you. :-)

Like your pic. Actually it's a bit Hitchcockian: Looks like the singer's skull there at the start of the motion trail.


QuoteQuote:
However there is a good reason why I do NOT shoot rear curtain flash
- because of the delay between tripping the shutter and the flash firing - on slower shutter speeds this could be as long as 1/4 sec which could mean the subject has changed, on my subjects sometimes which side the exposure trail is on does not matter.
I'm not Joe McNally either but I think he would respond to your second point by saying that, if it doesn't matter, it doesn't matter, and when it does matter, he wants the slight. As for your first point, I think McNally doesn't let the shutter get that slow. I don't think I ever shoot below 1/20th sec, with or without flash. (I'm not counting vacation landscape pics taken on a tripod, moon shots, etc.) With flash, I am pretty sure my favorite shutter speed has been 1/30th sec. Almost the only thing I shoot that moves faster than that at a wedding is the bride's bouquet, and a little motion trail there is a good thing.

This has been a very helpful thead and I want to thank everybody for the information and for helping me think out loud. What I've decided, for now, is that I'll go back to M mode on the camera (1/30th sec, ISO 200 or whatever seems right, and aperture at f/4 or f/5.6) and P-TTL on the camera. Not sure what I'm going to do about the blinkers yet.

Will
03-30-2010, 03:14 PM   #22
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What about Manual and A mode?
03-30-2010, 03:29 PM   #23
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QuoteOriginally posted by Jodokast96 Quote
What about Manual and A mode?

ON which pieces of hardware? I take it you mean full manual exposure mode (M) on the camera, and auto (A) on the flash?

Yes, it's good to be reminded of this option. I have tried Auto in the past, and actually, I thought the results were not bad. It does eliminate the pre-flash/fast blinker problem.

The reason I didn't stick with it is simply that P-TTL is supposed to be an improvement on A, because the flash output is calculated through the lens. I rather wish is that I could turn P-TTL off and use old-fashioned TTL. Just doesn't seem to be possible on my K10D/K20D bodies.

But perhaps I'll play around some more with A.

Will

03-30-2010, 04:17 PM   #24
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Why not just Av in slow-sync and P-TTL? It meters for the ambient. If the shutter gets too slow just assign Tv onto the other dial and adjust it - instant manual mode. Maybe auto-iso 100-400 or whatever.
03-30-2010, 04:23 PM   #25
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QuoteOriginally posted by Arpe Quote
Why not just Av in slow-sync and P-TTL? It meters for the ambient. If the shutter gets too slow just assign Tv onto the other dial and adjust it - instant manual mode. Maybe auto-iso 100-400 or whatever.
I don't understand your third sentence at all. If I'm in Av (either using the Av setting on the mode dial, or effective Av via the P/hyperprogram setting on the mode dial), I don't see how assigning Tv to the other dial gives me "instant manual mode."

What McNally says he does it, Av on the camera, and if the shutter gets too slow, he switches to M. That makes sense, as far as it goes. My problem with it is, if I'm going automatic, I want to go automatic all the way. I don't want to take a great shot and then realize it was spoiled because, without my noticing, the shutter speed dropped to 1.5 seconds. If I'm going to pay attention to everything, then I want to do it on every shot—which is what I'm used to.
'
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03-30-2010, 04:30 PM   #26
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QuoteOriginally posted by WMBP Quote
I'm not Joe McNally either but I think he would respond to your second point by saying that, if it doesn't matter, it doesn't matter, and when it does matter, he wants the slight.
Well, Joe McNally is not me
- and it does matter to me -
I have to catch or even predict fleeting moments with musicians and a capture lag/delay of up to 1/4 sec or more is not acceptable -
Is a camera with long shutter lag/delay acceptable?

I'm sorry I am not trying to tell anyone what to do........
only the reason why I do not do it -
and it does matter to me.
03-30-2010, 04:31 PM   #27
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Warning - I haven't actually tried this!
Instant semi-automatic? Use Av, but then if the shutter is getting too slow, change it using the other dial. I guess if it's too slow then it will already be maxing out your ISO anyway, so maybe that last bit is irrelevant, though auto ISO would still be useful for the brighter shots. So basically I'm saying the same as Joe, but with Pentax you don't actually have to shift the dial to M, just assign Tv to the other e-dial.

Auto all the way - maybe you have to use Tv with a highish auto ISO so you don't get too large an aperture? Obviously he pays attention to the camera settings, as he changes modes.

Or just stick the camera on P!
03-30-2010, 05:38 PM   #28
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First, you can't assign shutter speed to a dial in Av. To do what you are saying, you have to shoot in P, as was already said. Second, there are a bunch of odd variables that using P introduces. For example, at f/2.8, I can press the green button and get 1/30. No problem dropping it lower. But if I drop the speed, I can't bring it back up again without hitting the green button once more. Stopping down to other apertures has similarly odd effects. What you say sounds right on paper, but is goofy in reality.

So far, Manual on the camera with either A or P-TTL on the flash, or TAv on the camera with an Auto ISO of 100-200 (or 400 if one is happy with that) and P-TTL on the flash seems to be the easiest options of getting the exact shutter speed you want.
03-30-2010, 08:13 PM   #29
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QuoteOriginally posted by UnknownVT Quote
I have to catch or even predict fleeting moments with musicians and a capture lag/delay of up to 1/4 sec or more is not acceptable -
Is a camera with long shutter lag/delay acceptable?
Well, the answer to pretty much every question like this is, "It depends."

But to be less evasive, I'd say, no, a 1/4th sec shutter speed would be too slow, for shooting human beings in action. That's why I almost never go below 1/30th sec, when using flash. Shooting an event like a wedding, in a church, without flash, if my subject is standing frozen still (as is often the case) I'll risk 1/20th sec. But at that point, I'm worried about camera shake (even with shake reduction enabled) so I don't dare go slower, at least not without a tripod. Do remember that back in the old days—100 years ago and before that—shutter times in the several seconds were common. All those famous portraits required the subjects to FREEZE AND HOLD for several seconds. I rather like some of the group portraits where the grown ups are all sharp but the kid is a bit of a blur, because he squirmed.

Anyway, back to flash. No, I'd not go below 1/30th sec. And perhaps 1/45th sec—Pentax's preference, apparently—would be even safer. However, you should remember that shooting with flash is really quite a different thing from shooting without flash. The flash now freezes the action as much or more than the shutter speed. So even if the shutter speed seems too slow for use in normal, good ambient light, it MIGHT very well work with flash.

Consider the attached shot. Settings: f/5.6, 1/20th sec. My cat Mao was walking through the living room, not running, but walking fast enough that without the flash the shot would have been blurred at 1/20th sec. In fact, if you were able to look at this really closely, you could see some very slight traces of movement. Nevertheless, the flash freezes the moving cat pretty effectively. (NOTE: This is a very tight crop showing less than 10% of the original photo.)

Will
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03-30-2010, 08:35 PM   #30
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QuoteOriginally posted by WMBP Quote
Well, the answer to pretty much every question like this is, "It depends."
But to be less evasive, I'd say, no, a 1/4th sec shutter speed would be too slow, for shooting human beings in action.
I was talking about lag between pressing the shutter button and capturing the image seen.
With rear curtain flash the flash fires just before the curtain starts to close - so on a longer shutter speed the longer the delay.

About 1/4 sec being too slow for humans in motion -
sorry, different style of photography.

Try this example -

EXIF re-attached (caveat: PhotoBucket can lose metadata)
this is a 1 sec exposure with slow-sync flash to freeze the person, but allow for the trail of movement blur.

If I had used rear-curtain flash, heaven knows where the frozen/flash image would have been -

similarly with the previous image I posted that was also a 1 sec exposure - if I had used rear-curtain flash the flash/frozen image probably would have been that what you called the "skull" position - not the pose I captured -

That's why I have to use first curtain flash, then I more or less captured the image I saw within the pre-focus shutter lag time of pressing the shutter button.

Again I am not trying convince you of my methods - just that these are important points for me - as I do use slow shutter speeds often that can actually be slower than 1/4 sec to achieve the effects I want.

Last edited by UnknownVT; 03-30-2010 at 08:42 PM.
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