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10-19-2007, 08:25 PM   #1
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Flash settings and focus lock?

I have the AF540FGZ on my K10D. I shot motocross last weekend and obtained horrible results. I cannot seem to figure out how to set the flash for fill (To kill the dark shadows on the motocross riders). It is difficult enough to keep in focus without worrying about the flash.

Most the photos I did get with the flash came out looking like they were almost double exposed. (quickly moving objects) Kind of like the ambient exposure topped off with the flash exposure. (slightly overlapping) They were all partly cloudy to sunny daylight photos.

Also, is there a way to lock the auto focus for a single shot without going into manual focus? With my IST, I could pre-focus holding the button half down and it would lock the focus, with the K10D, I tried to do the same and as soon at the camera is moved, it seeks again, in my case locking on the background as I wait for the next motorcycle to come flying by. I had dozens of shots where the background was sharp as a tack and the subject was an out of focus blur, even when panning.

10-19-2007, 08:40 PM   #2
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Set your Auto Focus to Single (AF-S). That way, when you half-press your shutter, it will remain as is until you press fully. Sounds like you had it on AF-C, which would constantly adjust focus depending on what the lens sees.

As far as the flash for fill during daylight and for motocross, I don't think the flash will give you fast enough sync speed to keep up with what you might want in order to capture highspeed MotoX action. It might be best to capture a tack-sharp shot and lighten up some in post processing.
10-19-2007, 08:45 PM   #3
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QuoteOriginally posted by mudnmoto Quote
I have the AF540FGZ on my K10D. I shot motocross last weekend and obtained horrible results. I cannot seem to figure out how to set the flash for fill (To kill the dark shadows on the motocross riders). It is difficult enough to keep in focus without worrying about the flash.

Most the photos I did get with the flash came out looking like they were almost double exposed. (quickly moving objects) Kind of like the ambient exposure topped off with the flash exposure. (slightly overlapping) They were all partly cloudy to sunny daylight photos.

Also, is there a way to lock the auto focus for a single shot without going into manual focus? With my IST, I could pre-focus holding the button half down and it would lock the focus, with the K10D, I tried to do the same and as soon at the camera is moved, it seeks again, in my case locking on the background as I wait for the next motorcycle to come flying by. I had dozens of shots where the background was sharp as a tack and the subject was an out of focus blur, even when panning.

For the focus, simply make sure you are using AF-S and not AF-C

As for the Flash, not sure on the double image. I probably is related to second curtain/normal flash and your panning technique, but you would have to post a sample.

The fill flash though is a quite tricky subject. I can't get a pentax to do fill flash, I always switch to manual flash. (with canon this was not an issue)
10-19-2007, 08:46 PM   #4
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QuoteOriginally posted by Frogroast Quote
Set your Auto Focus to Single (AF-S). That way, when you half-press your shutter, it will remain as is until you press fully. Sounds like you had it on AF-C, which would constantly adjust focus depending on what the lens sees.

As far as the flash for fill during daylight and for motocross, I don't think the flash will give you fast enough sync speed to keep up with what you might want in order to capture highspeed MotoX action. It might be best to capture a tack-sharp shot and lighten up some in post processing.
The 540 supports High Speed Sych.

10-19-2007, 08:53 PM   #5
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You didn't say what settings you were using with the K10D + the 540 FGZ. I am going to assume you were using P mode on the camera and P-TTL on the flash.

You certainly CAN lock the focus on the K10D by depressing the shutter half way. However, this can be turned off in the custom settings in the Menu. Check the setting for "AF by Press Halfway" and make sure it's 1 (on), not 2 (off). Also, if the subject is moving either towards or away from the camera as you try to focus, well, that's a tough focusing problem. I've never shot motor sports but I would think that the best way to get a sharp photo would be to prefocus on a spot where you expect a vehicle to appear shortly -- and click the shutter when the bike or the car actually appears there. Or use continuous auto-focus.

I've never tried to use fill flash on a motorcycle that was racing by. My guess is that your main problem is that the sync speed for the flash (1/180th sec) is simply too slow for the speed of the subject. For a normal flash situation -- say, photographing a kid blowing out candles on a birthday cake -- the camera is fairly close to the subject and the subject isn't moving at, oh, 50 mph, and finally there's not a lot of ambient light. So 1/180th sec is quite fast enough to freeze the action, and the camera doesn't capture much more than what it sees during that brief period of time, because the room is so dark. But if you're shooting outdoors, with lots of light, well, your little flash unit isn't going to overpower the sun. It can help fill in shadows on the faces of a person or two standing 10 ft in front of you, but that's about all it can do. If the correct shutter speed for a speeding vehicle + a 200mm focal length would be, say, 1/1000th sec, and assuming that you're shooting in bright daylight, then it's much more important to hold on to that fast shutter than it is to use a fill flash! Because adding the flash unit lowers the shutter speed to a max of 1/180th sec, which given that there's plenty of light to capture the shot even without the flash means that you're going to get a blurry photo.

You could TRY high-speed sync, although to be honest I doubt it will help much with your moving subjects.

Wild guess: First, forget about the flash at least for a few tests. If you're getting shadows on the subjects, I'd try increasing the exposure +1 EV or so. Since your shutter speed is probably not negotiable, you'll have to make this adjustment either by upping the ISO or opening the aperture (and losing some depth of field). You might blow some highlights in the sky but that doesn't sound like the end of the world if it causes the subject's faces to be correctly exposed.

But let me say again: I've never shot motocross so I do not really know. Be interested to hear from anybody here with real experience in this situation.

Will
10-20-2007, 05:04 AM   #6
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I have tried high speed sync, no luck

"My guess is that your main problem is that the sync speed for the flash (1/180th sec) is simply too slow for the speed of the subject. "

I didnt know that, that explains the "good" shots I got when the angle was right or the bikes were moving more slowly.

I used every setting on the flash except the 2nd curtian sync...

Apeture was set anywhere between 2.8 and 6.7
10-20-2007, 05:07 AM   #7
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here is a sample, as you can see the eyes are somewhat in focus

Last edited by mudnmoto; 11-05-2007 at 06:05 PM.
10-20-2007, 04:19 PM   #8
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Quite simply, he moved too much in relation to your framing to be using a fill flash.

You either need to do some panning (and zooming you your case, so this is really not an option), or an extreemly high shutter speed.

The reason why the eyes look sharp is because they are getting 90% flash, where the rest of the rider is recieving sunlight.

You also focused behind the rider.

BUT, assuming you want a little bit of blur (you would have some without the flash assuming you keep this shutter speed), second curtain will make it look much more purposeful.

Just in case you didn't know, high speed sync only allows you to use flash with a shutter speed less than 1/180. If you turn it on on the flash and use 1/100 as a shutter speed, that setting change will have done NOTHING!

10-20-2007, 06:34 PM   #9
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I like the blur-tells me they're moving
if they pin sharp you might as well done them in the car park-posed
10-20-2007, 08:16 PM   #10
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QuoteOriginally posted by mudnmoto Quote
Also, is there a way to lock the auto focus for a single shot without going into manual focus? .

You can of course choose AF-S and not MF for this, BUT, I have my camera set on AF-C all the time and have disabled the shutter button from focussing and only allow the AF button to focus. This way the focus hunts only when I hold the AF button and is easily controllable. Using AF button to focus becomes very natural soon and I LOVE this setup for me. I like to fire away at will when the situation demands in an instance. So far the only reason I have to switch to AF-S is when I need the focus assist lamp with the built-in flash.
10-22-2007, 06:13 AM   #11
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I always pan on the racers, I used this photo as an example, notice the dirt around the closer rider, all tack sharp, I understand now what the flash is doing. I am using AF-C. How do you disbale the shutter button and only us the AF button?
10-22-2007, 08:46 AM   #12
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QuoteOriginally posted by mudnmoto Quote
I have tried high speed sync, no luck

"My guess is that your main problem is that the sync speed for the flash (1/180th sec) is simply too slow for the speed of the subject. "

I didnt know that, that explains the "good" shots I got when the angle was right or the bikes were moving more slowly.

I used every setting on the flash except the 2nd curtian sync...

Apeture was set anywhere between 2.8 and 6.7
If you were indeed using highspeed sync, then you are no longer bound by the 1/180th shutter speed limitation. You should be able to shoot as fast as the camera can handle, all the way to 1/4000th.

QuoteOriginally posted by mudnmoto Quote
I always pan on the racers, I used this photo as an example, notice the dirt around the closer rider, all tack sharp, I understand now what the flash is doing. I am using AF-C. How do you disbale the shutter button and only us the AF button?
1) The dirt being tack sharp actually shows us that you did NOT pan on the racer. A panned shot will have your rider in focus and streaked ambient. Like this (credit to flickr):


2) Look in your custom menu. As Will said earlier, it's the AF by press halfway option.

Couple of notes... if you're finding the flash parts of your photos over-exposing. Turning your flash exposure compensation down a bit. Since you can't really have the flash off camera in those situations, that's probably to best way to avoid the harsh flash look.

Lastly, why not use 2nd curtain sync? A panned 2nd curtain sync can freeze action very well and it'll freeze the frame at the last possible moment giving you a blurred trail behind (not before) your racer.
10-22-2007, 01:19 PM   #13
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1) The dirt being tack sharp actually shows us that you did NOT pan on the racer.

2) Look in your custom menu. As Will said earlier, it's the AF by press halfway option.

Couple of notes... if you're finding the flash parts of your photos over-exposing. Turning your flash exposure compensation down a bit. Since you can't really have the flash off camera in those situations, that's probably to best way to avoid the harsh flash look.

Lastly, why not use 2nd curtain sync? A panned 2nd curtain sync can freeze action very well and it'll freeze the frame at the last possible moment giving you a blurred trail behind (not before) your racer.[/QUOTE]

I think I need to read the flash manual again

You are correct, after looking again, the rider was coming toward me...I had so many bad photos last weekend.

I know about the blurred trail behind, I did not know it could be effective in sunlight.

I have to get accustomed to the camera, flash and lens I think. I was out again this weekend and the photos came out much better, although I had bright blue skies all day and with the sun's angle this time of year I did not need to flash fill the shadowed areas of the riders. I also noticed that the Sigma lens reacts differently on the K10D and the *IST dl. It focuses and locks a lot quicker on the IST

Last edited by mudnmoto; 10-22-2007 at 01:25 PM.
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