Flash sync speed on the 300D question.......

At the risk of exposing my ignorance....

Recently bought a 300D, plan to replace my 5050. I am a big fan of sun rays and dark backgrounds for kelp shots and fish portraits, and frequently use shutter speeds of 1/650 - 1/800 to get these. i.e....

1/650 shutter speed

Flash sync speed on the 300D is 200, and I know some have pushed it to 1/250, but is that the fastest I'll ever get with an external strobe? It won't matter for sun rays, since that's ambient light, but I'd hate to lose the ability to black out the background in kelp shots. If that is the case, I am not a happy camper.......I hope I am just missing something

So have I just blown the opportunity to get black BG shots? Or is there some "equivalence" factor that makes a 300D 1/250 nearer to a 5050 higher shutter speed.

Chris

You can usually get a black background with shutterspeeds of 1/125th with f16 and above. So don't worry...:-)

I can post MANY examples if you need them Chris. My lowly S2 only sync's at 1/125th and I have plenty of black background shots.

Cheers

James

As James said, I've gotten some nice black backgrounds with f7 @ 1/250 on the 5050. I could post a kelp shot at that setting but.......I'm not worthy. LOL!

Why does the 5050 sync so fast?? I've gotten light on subjects @ 1/1000.

Chris, that's a beautiful shot!

Hi Rand,

It's because the 5050 uses an electronic shutter. Meaning, the CCD turns on, captures, and then it turns off. It doesn't care if there is a mechanical shutter or not, and it doesn't care if the flash fires for 1/1000th or 1 full second - since it's only recording for 1/1000th.

Cheers

James

Thanks James and rand, I feel better now :-). I wouldn't have thought my fear was reality, but.......

I assume the 5050 has an electronic shutter, and the 300D has a mechanical shutter, taking longer to open and close

Chris

Ahh, that's right, the cutting edge of modern electronics. The dSLR's use a mechanical (read old fashioned) shutter? LOL!

Thanks for the explanation James. Your shot is extraordinary, love it.

Rand

The d70 will feature an electronic shutter, allowing syncing up to 1/500th of a second. But, you need it to make up for having a lowest ISO of 200.

The Rebel's 1/200th at ISO 100 should be more than usable...

So long as you can stop down the lens you can usually achieve a black background in most underwater situations (white sand shallow water being an exception).

The reason that dSLRs with mechanical shutters are often limited to comparatively slow synch speeds is that focal plane shutter (when set to shutter speeds above the synch speed) does not actually expose the whole frame at once. The slit that is open in the shutter moves rapidly, vertically across the frame. To synch with a flash (which can be thought of as instantaneous) you need the whole frame open through the shutter when the flash fires.

Alex

I really like the kelp shot at the top of this thread.

If you are shooting manual flash you can trick your dSLR. Occassionally i shoot my D100 at shutter speeds greater than its 1/180th synch speed. This means that my flash will only light the section of the frame that is open at the time. At 1/250th this only causes a thin strip (<10%) of the frame to remain unlit at the bottom of the frame (on front curtain synch - I presume it would be the top of the frame on rear curtain synch).

If your subject is in the middle of the frame then it doesn't matter that there is no strobe light at the bottom of the frame.

Alex

Alex, can you post a sample showing the dark bands from "over-syncing" please?

I shot a few w/ the D100 at 1/250th and above and I started to see them as well. But don't have any examples handy.

Cheers

James

I agree with Alex's statement above, and I get anywhere from 1/3 to 1/4 frame masking at 1/320th.

Where my observations differ is the location of the masking. I ALWAYS get it at the top of the frame,and I always shoot front curain sync. Exif backs me up on this one. We do shoot different strobes, so that may make a difference.

Yes, a more "powerful" strobe will actually fire for a longer duration.

So different strobes will result in different masking patterns.

Cheers

James

See the DR test results posted here:

link here

There's no problem with pushing it to 1/250 and only a very thin dark line at the bottom of the frame at 1/320.

The strobe will be a factor if the flash duration is longer the than the time that the shutter is completely open. If this is the case the exposure will decrease with increased shutter speed. I've tested my Inon Z220 using the histogram of the Olympus 5050 and saw no exposure difference up to 1/500 shutter speed.

Masking Examples

1/250

1/320

1/400

Thank you all, this has been a very informative thread for me...

Ryan, those pictures are worth a thousand words

Chris

Ryan, my mistake. I must have got my front and rear curtain synchs confused. All my shots are on my hard drives at home attached to my new computer!

If you are shooting against blue water the effect is more subtle because the black strip is lit with ambient light - and you can really get away with it. So for example a fast moving dolphin, frozen at 1/320th in the centre frame, can be filled with flash and an unflashed strip at the top or bottom of the frame really doesn't matter.