Help canon rebel/550ex

[baz]

Hi,

Ive searched the web and found this forum because im in need of help!!

I take pictures of motor-sport, Stock car racing to be exact.

At the beginning of this year i brought a canon 300d with a 550ex flash and have found it very good.
But then there came a time where i we went along to a night meeting which is held under floodlights and the problems started!

Near enough all the shots ive taken have come out blurred or with countless shadowing around the subject that's in shot.
Last night this happened again (For the 3rd time!) so this has made me seek help and advise.

With things not looking to good i started to fiddle with the settings which all of what i tried not helping at all.
I changed the settings, such as AWB,iso,setting on the mode dial, also the mode on the flash gun and changed it on to the slave setting all with no real joy.
This puzzles me totally as last week in the day light i managed to take near enough 350 perfect shots.

The one thing i don't think i changed was the shutter speed.
Im not sure if im panning right either for the night time shots.(making me conscious and getting it wrong even more so!)

Any help would be gratefully received!

Thanks

Heres a couple of examples of the shots im getting


http://mysite.freeserve.com/bwpuploadpics/images/8-picture3.gif?0.6900619015515757

http://mysite.freeserve.com/bwpuploadpics/images/8-picture4.gif?0.8708843170697635

[DaveG]

Hi,

Ive searched the web and found this forum because im in need of help!!

I take pictures of motor-sport, Stock car racing to be exact.

At the beginning of this year i brought a canon 300d with a 550ex flash and have found it very good.
But then there came a time where i we went along to a night meeting which is held under floodlights and the problems started!

Near enough all the shots ive taken have come out blurred or with countless shadowing around the subject that's in shot.
Last night this happened again (For the 3rd time!) so this has made me seek help and advise.

With things not looking to good i started to fiddle with the settings which all of what i tried not helping at all.
I changed the settings, such as AWB,iso,setting on the mode dial, also the mode on the flash gun and changed it on to the slave setting all with no real joy.
This puzzles me totally as last week in the day light i managed to take near enough 350 perfect shots.

The one thing i don't think i changed was the shutter speed.
Im not sure if im panning right either for the night time shots.(making me conscious and getting it wrong even more so!)

Any help would be gratefully received!

Thanks

Heres a couple of examples of the shots im getting


http://mysite.freeserve.com/bwpuploadpics/images/8-picture3.gif?0.6900619015515757

http://mysite.freeserve.com/bwpuploadpics/images/8-picture4.gif?0.8708843170697635

What you are seeing in those shots you posted are basically double exposures. There are two things going on. First there's the ambient light from the track itself. That's the light that you see with your eyes. Then there's the light from your flash.

You are using a shutterspeed that's slow enough for the flash to work with the camera. Without going too far into this, the maximum shutterspeed you can use with the dRebel is 1/200 of a second. Any faster shutterspeeds will cause you to shoot "off-synch".

Now it looks to me that you used shutterspeeds considerably slower than 1/200. The ambient light is what's illuminating the background. If you JUST used the ambient light at this shutterspeed you'd get a well exposed blur.

Now enter the flash. The duration of an electronic flash is amazingly brief. If you were in a totally dark room that brief flash pulse would BE your shutterspeed. Think about this: Even though your shutter is open for one second, it's only a shutterspeed if there's continual light for the full one second. If the light came on for only a thousanth of a second then that's the effective shutterspeed, and that's what happens when you use flash.

So back to your images. I can see the ambient light's effect, but I can also see the "freezing" action from your flash superimposed on the image. If you used a higher shutterspeed it would have reduced the ambient light's affect on the image and it would have "sharpened" the results. But you also would have flash fall off. That's when you use flash and the background goes completely dark, even though you know that there was a reasonable amount of light there.

I face this situation whenever I photograph a wedding. The bride and her dad are about to walk down the aisle. Let's say that the light level in the church is 1/15 @ f2.8. If I use that exposure it will be correct but it'll also be a blur. If I use a shutterpeed of 1/60 and an aperture of f11 and "ask" the flash to output that much I will underexpose the ambient light by six stops. This will effectively make the church a "dark room". Then my flash creates the "shutterspeed" which will freeze the bride and dad's motion. But, sigh ... I will also get flash fall off and all the guests behind the subject will go black.

So the solution to your problem is to either rate the ISO as high as you can while using only ambient light - and if you can get up to 1/500 of a second you should do reasonably well. Or you can use 1/200 of a second with flash and see then whether the results are acceptable to you.

Mostly though I'd say that you are going to be very limited as to what you can accomplish at night races. Perhaps panning and doing some funky things like that. But for most sports you need light and/or extremely fast lenses, so maybe you just gracefully accept that this stuff is more of a day job.

I hope that this helps.

[Belmondo]

DaveG has just given a very succinct explanation of a problem we all face at various times when using flash at night. The proof off his reasoning lies with the image of the car; the portions nearest the camera (left front wheel) are sharp, and evidently illuminated by the flash. The farther away you get from the camera, the worse the motion blur is.

One thing that can help in a situation like this is to pan, and to use the second-shutter sync, although I'm not sure this is available on the Rebel. This way, the 'blur' is trailing the object.

Good work, DaveG. I'm going to add you to my list of heroes.

Thos.

[Wickedfn4u]

David that was a great explanation for use students. Ok next level, if it were a 10D how fast could you shutter sync? Would it then be crisper with out the "dark room" effect you mentioned?

[baz]

Thanks for your advice.
Ill try again when im next out and see what happends or as you say stick to the day light!

Thanks.

[GenEOS]

I don't think those are stock cars..look like midgets or outlaws to me!
2nd curtain sync and panning will help you output, but lighting those races is a real pain in the ass. You need larger guns than a 550EX to get enough light there to do what you are after. But you can get good results, just on the artsy side of things...
A larger test shot may help us see more of the image and help a little more...exif data too.

[Wickedfn4u]

Gen or Dave can you explain the 2nd curtin you are talking about.

[scottbergerphoto]

Gen or Dave can you explain the 2nd curtin you are talking about.
I'm not Gen or Dave, but 2nd curtain sync, is when the flash fires at the end of the exposure instead of at the beginning of the exposure. In the pics above, the shutter opened, the flash fired, and then ambient light continued to reflect off the subject on to the CMOS sensor. That resulted in a clear image of the car from the flash and blurry trails in front as the car continued to move after the flash. In second curtain sync, the ambient light exposure occurs first followed by the flash. That gives you a sharp picture of the car with blurry trails behind it. It's just a matter of when you freeze the action, at the beginning or at the end of the exposure.
Regards,
Scott

[Wickedfn4u]

Very cool, thanks. I just ordered the 550 ex and I am sure it will talk about that in some form. Thanks for the help

[DaveG]

Gen or Dave can you explain the 2nd curtin you are talking about.

First off you have to understand how a focal plane shutter works. A FP shutter is made up of two curtains. At shutterspeeds below the flash synch speed, the first curtain fires and goes across the "focal plane" - thus the reason that it's a focal plane shutter. Once it reaches the end of the focal plane the film or sensor is completely exposed to the light coming through the lens. If you are using flash on first curtain synch, which is the default, and often only synch setting, it will fire now. Then the second curtain fires and zips across the focal plane, thus closing the shutter.

Remember when you use flash and ambient light you are doing making a double exposure. The flash pop, since it's so brief will freeze the subject while the ambient light part of the exposure will blur it. You probably can see that there could be some cool uses for this effect. A runner running with a blur behind them, or the same thing with a car.

But there's a problem if you use a very slow shutterspeed and first curtain synch if you are trying to photograph something that's moving. Instead of the blur being behind the subject, the blur is in front of it and the viewer infers that the subject was moving backwards. With rear (sometimes called second curtain) synch the first curtain fires but instead of the flash popping immediately when that first curtain gets to the end of the track, the camera will hold the flash pulse until the exposure is almost over. Then the flash fires, resulting in a blur BEHIND the direction that the subject is traveling.

This can only make a difference if you are using pretty slow shutterspeeds. At higher speeds there may be no visable differences in the image.

Just to end this. At higher than synch speeds the second curtain fires BEFORE the first curtain has reached the end of the focal plane. The second curtain in effect chases the first across the FP. As you change shutterspeeds the width of the "slit" is changed with very fast shutterspeeds having a very narrow slit indeed. That's why at shutterspeeds higher than "synch" you can't use flash since the shutter is partly in the way, and is blocking the film/sensor.

There IS a highspeed flash capability in the 10D and some other cameras, but that works by having the flash pulse for a long time (in the 10d's case 1/200 of a second) in order to be "on" for the full time that the shutter slit is moving across the focal plane. This significantly weakens the power of your flash, and from my point of view can't be all that good for the long term health of your flash. That thing is going to get HOT, so if you use this technique don't shoot a bunch in a row or you could seriously damage the flash.

[baz]

They are Brisca F2 stock cars (from england.)

Please see these to site's for more info on the cars and some of my pics from the day light!

www.tonysmithracing.cjb.net
http://www.dudley100.freeserve.co.uk/web.html

Hopfully this is a bigger image, if ont i could email it to you if you like?

Thanks again for all your help.

http://mysite.freeserve.com/bwpuploadpics/images/8-picture.gif?0.8800012985861428