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Old Jan 1, 2006, 6:19 PM   #1
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I am trying to decide on which d-SLR to purchase. My main concern is which camera is the best for capturing fast action using an external flash. I am considering the Rebel XT, or the D70s, and am limited to this price range. I mainly shoot mountain bikes, downhill, street, park, dirt. I have not done any flash photography, so this is all new to me, and I want to get a slave set-up too. I was all set to get the Rebel XT, and then I discovered this thing called flash sync speed which has put a twist on everything. I have been trying to research the subject, but can not get it all straight in my head. I think for now the main use will be as fill flash.

Honestly, I am trying to figure out if the sync speed even really matters. The D70s has a higher sync speed at 1/500 compared to the Rebel XT at 1/200. But to put it all into perspective, most of the Pro d-SLRs only have 1/250.

I found this great resource discussing flash photography using Canon cameras here. From reading
http://photonotes.org/articles/eos-flash/index.html#fp about running in FP mode, it seems the synch speed does not really matter as long as you run in FP flash mode. It states that "FP flash lets you take flash photos at any shutter speed you like, and works by pulsing the flash bulb at an extremely high rate - 50 KHz - simulating constant light at the cost of total light output." And " FP mode flash solves this problem by letting the shutter speed exceed the X-sync limit and reach the camera's maximum shutter speed (usually 1/2000 or 1/4000 sec) instead." I am not wanting to shoot at super fast shutter speeds, but I am going to need to shoot at least at 1/500 to get clear images.

BUT, it also says "Note an important point - FP mode does not help you freeze motion; the name "high-speed sync" is a bit misleading in this regard. Normal flash photography is very good at freezing motion on film, since a burst of electronic flash is so incredibly brief. When a scene is illuminated primarily by a really brief flash of light then you aren't going to get much motion blur - it's almost as if you used an incredibly high shutter speed in the thousandths of a second. However when you use FP mode flash, the flash unit pulses the light output over a longer period of time in order to simulate a longer-duration burst of light. Since the flash burst is no longer particularly brief you can't freeze motion as easily, even with high shutter speeds." Does this last sentence "can't freeze motion as easily, even with high shutter speeds." mean that exceeding the sync speed can actually do more harm than good? Basically shooting-down the argument that as long as I run in FP mode I will be fine?

I am so confused. I just want to make sure that whichever camera I purchase will be able to do what I want it to do, and right now the deciding factor is flash photography.
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Old Jan 1, 2006, 8:31 PM   #2
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Fumehood-

In all fairness all dSLR cameras are about the same when in flash mode. What you really ought to be concerned about is using a good slave flash to extend your flash range out to 60 feet.

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Old Jan 2, 2006, 2:20 PM   #3
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Well, they are about the same, but there are differences. Does one have a definite advantage over the other with a slave set-up, or not, or does it not matter? Do the other advantages of the Canon outweigh the flash issue? What do you recommend for a good slave set-up?
Thanks,
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Old Jan 2, 2006, 5:56 PM   #4
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Fumehood-

Please keep in mind that a slave flash set-up will work with any camera. Attached is a sample photo ofa typical slave flash set-up. I have sucessfully used this slave flash set-up with my Canon 350D/XT, my Pentax 1st DS, my Olympus E-300, my Olympus E-500, my Nikon 70D, and my Canon 20D. It increases my flash range to 50 to 60 feet.

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Old Jan 3, 2006, 5:35 AM   #5
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In poor light flash sync speed is irrelevant.

The reason you want a high flash sync speed is for REDUCING background exposure during bright sunlight and fill flash.

Now the D70 has a minimum ISO 200 and the XT has minimum ISO100, so to get the lowest possible exposure in bright sunlight they are essentially identical. The D70 can go to 1/[email protected] and the XT to 1/[email protected]

Nothing to choose between the cameras in this regard.




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Old Jan 4, 2006, 2:35 PM   #6
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I find myself just learning about this topic too, let see if I've got it right...

Generally when taking flash photos in dark/dim conditions you use a relatively long shutter (say 1/100) but the extremely rapid flash creates an exposure only during a fraction of the shutter-open time.

The fast sync-speed is important when there IS availible light, and the frame is being exposed during the entire shutter-open time. Primarily when using a fill flash to lighen up shadows in an otherwise bright scene.

(I'm just trying to piece together what I've read, I've not yet taken good flash pictures myself)
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Old Jan 4, 2006, 2:37 PM   #7
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I meant to ask, what exactly is being syncronized? By listing a max sync-speed of 1/200 are the manufacurers saying that at 1/1000 second the flash will fire while the shutter is closed?
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Old Jan 4, 2006, 8:13 PM   #8
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For sports photography I often use 1/250th or 1/500th shutter speed to freeze the athlete's motion.

My Canon 20D has a max flash synchro of 1/250th a second.

Which means, if I want to use some "fill flash" to pull my subject out of the background, I'm stuck at 1/250th.

If I want to use "fill flash" at 1/500th, I can't do it. The camera is incapable of it.

Some Nikons have flash synchro up to 1/500th.

I sure wish my Canon could do 1/500th, because I would use fill flash at 1/500th very, very often if I could.

One minor limitation of the Canon 20D, but I still love my Canon!

-- Terry


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Old Jan 4, 2006, 11:22 PM   #9
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Terry, thank you so much for owning a Canon and letting us know what it can and can not do. I thought there would be more Canon owners out there wishing the same thing, or telling us that this FP mode is the best thing since sliced bread, and there is no issue (I would prefer the later). Peripatetic says it does not matter, but I feel that for fast downhill shots a shutter speed faster than 200 or 250 is probably better…and your statement confirms that. I think I have decided on a 20D over the Rebel XT, but the sync speed is still an issue, so the D70s is still in the playing…but, if the Pro models only have a 1/250 sync is it really an issue, or are all the pro's just able to pan really fast and smoth?
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Old Jan 5, 2006, 12:09 AM   #10
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What lighting conditions are you going to be shooting in?

peripatetic is correct (flash sync speed is irrevalent in poor light).

For fill flash in bright light, a faster flash sync speed can be desirable. Nikon does have an advantage in this area.

But, there are ways around it. Most modern DSLR models have an available external flash system that can be used at shutter speeds faster than the camera's sync speed. But, you don't have as much flash range using this type of system (because of the way it pulses the light to try and "hit" the target while the shutter is opening and closing, without being timed just right for sync purposes that you'd need with a single flash burst).

But, in poor light, it's rarely an issue.

You don't need fast shutter speeds to freeze action in poor light using a flash. You can freeze action with 1 second shutter speeds using flash if light is low enough. ;-)

Heck, I've got a little pocket camera that I keep set to 1/15 second in some low light conditions with flash (even though the camera defaults to a faster shutter speed), and it freezes action just fine at f/2.8 and ISO 200 in many low light conditions.

The reason you don't need fast shutter speeds to freeze action using a flash, is because in most conditions needing a flash, the subject is only exposed properly during the flash burst (which is very fast -- typically 1/1000 second or faster, depending on the range to your subject).

So, if you're shooting in typical indoor conditions, with tyical settings a camera's autoexposure would use with flash (where you'd have dark exposure using something like 1/60 second and f/4 at ISO 200 without the flash), the flash burst can freeze virtually any action (since it's so short and the sensor is only seeing the subject well enough to expose the image during the flash burst).

Where it can become an issue (not able to freeze action) is when you have *too much* ambient light entering the image. The trick is to make sure your camera settings are such that you're not going to expose the subject, except during the flash burst (controlling ambient light impact via aperture and/or shutter speed).

If you want ambient light to contribute more to the exposure (typically by using higher ISO speeds and wider apertures), then you'll want to keep your shutter speeds as fast as possible to reduce blur.

But, for indoors sports, etc., as long as you keep camera settings so exposure from ambient light alone wouldn't show your subject, then the flash can freeze the action, regardless of shutter speed.

Here's an example of freezing action with a flash using my little pocket camera at a much slower than default shutter speeds, even though I'm using a higher than default ISO speed.

Please excuse the redeye (it's a pocket camera with the flash located close to the lens, and this is straight from the camera with no post processing of any kind).

1/15 second, f/2.8, ISO 200 with flash (and I can assure you that everyone didn't stand still for the photo). ;-)

The full size original is here:

http://www.pbase.com/jcockfield/image/39350509/original

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