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Fast Shutter Speeds - When?


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#1 james

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Posted 29 August 2002 - 06:30 AM

When is it appropriate to use fast shutter speeds with a strobe?

For most of my wideangle shots, I meter the background blue and set my f-stop and shutterspeed. At the Flowergardens at 70' that is usually around f5.6 at 1/90th to get a good blue. Then I use my strobes to light the foreground for a good exposure.

For Macro, I shoot at the highest fstop I can get away with to maximize DOF - usually f22 or maybe f16. Then I set the shutterspeed at 1/60th or 1/90th and put the strobes in TTL.

I'm thinking I'll get better shots at the max sync speed of the camera which is 1/125th for the S2. But that is 1 stop faster that 1/60th so I will have to open up the aperture one more stop to get the same exposure (wideangle) or my strobes will have to put out one more stop. I hope they can - we'll see.

Is there any advantage/reason to want to shoot faster than 1/125th? When would one want to do that?

Cheers
James Wiseman
Canon 1DsMkIII - Seacam Housing
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#2 herbko

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Posted 29 August 2002 - 11:20 AM

Hi James,

I think you made a sign error in your reasoning about going to 1/125 on your S2 vs 1/60. Higher shutter speed -> bigger aperture for the same background exposure -> less strobe light needed for the same subject exposure. If you are not limited by DOF considerations, and in most wideangle shots you are not, higher shutter speed extends the range of your strobe.

For macro shots that do not have natural light, use the fastest shutter speed. Anything faster than 1/125 is probably about the same. If you want a blue blackgrund for a macro shot, then the problem is the same as a wideangle shot, except you have to consider the DOF requirements. Here, you should probably use the smallest aperture, and choose a shutter speed to get the background exposure you want.

Really expensive SLR's like the Nikon F5 have Xsync speeds of 1/280. It cost $$$ to make mechanical shutters that move that fast. I think the reason that the Oly E20 can sync at 1/650 with a mechanical shutter is the much smaller CCD. It's only 1/4 the size of 35mm film, so a mechanical shutter that would only sync at 1/150 for 35mm willl sync at 1/650 for the 9mm CCD. Either that or they use electronic shuttering to do that. The CCD is the same as the one in the Nikon CP5000, so they can also use an electronic shutter if they want.

Herb
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#3 james

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Posted 29 August 2002 - 12:02 PM

Hi Herb,

Thanks for the reply! I think you are right on about the E20's smaller CCD. The CCD on the D100 and S2 is aps sized, which is like 5x bigger!

I think we are both confused about the aperture-shutterspeed discussion. We both said the same thing but in different ways.

To be clear it's probably better to just say fstop instead of aperture. That's because bigger aperture = lower fstop = more light entering lens. Smaller aperture = higher fstop = less light entering the lens.

For a shot taken without a flash, the following are EQUIVALENT exposures:

f11 @ 1/60th second
f8 @ 1/125th second

You're going to get better DOF with the former, so if you're shooting a non-moving subject then the F11 is probably better.

For macro where you are shooting at f22 and using all strobe light and no natural light, then you're right - use the fastest shutterspeed you can sync at - the flash only fires for miliseconds.

For natural lighting photos and wide to superwideangle, when is it better to use the fastest sync speed?

Cheers
James
Canon 1DsMkIII - Seacam Housing
Dual Ikelite Strobes
Photo site - www.reefpix.org

#4 herbko

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Posted 29 August 2002 - 12:52 PM

Does not matter whether you call it bigger aperture or lower fstop. Higher shutter speed -> less strobe power for the same exposure. It's desirable unless you need better DOF.

Herb
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#5 james

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Posted 29 August 2002 - 01:19 PM

Interesting!

I think when you use more strobe power, you get better color saturation. That's what Burt Jones said at the class I went to. He shoots macro mostly and he keeps upping his fstop until he gets a full dump from his strobes. I think I ascribe to what he is saying - I'm going to try it next time.

Cheers
James
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Photo site - www.reefpix.org

#6 herbko

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Posted 29 August 2002 - 02:02 PM

If you do all of the following:

double the shutter speed
open up the aperture one fstop
half the strobe power

you should get the same exposure and the same colors. I've done it in my manual setup and it's true. Now I don't know for sure what TTL will actually do if you set the first two and let TTL do the third.

I don't disagree that it's probably good to use as much light from your strobe as you can. I guess my prevous message was unclear. I don't mean to say that a higher shutter speed is what you should always push towards, but it's true that a higher shutter speed has the net effect of extending the range of your strobe. It is most important when you are shooting into the sun and want a certain sunspot exposure and at the same time light up big foreground subjects.

Herb
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#7 mandarinfish

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Posted 30 August 2002 - 01:13 PM

Here's a page that gives some info on shutter speeds and flash. Really, the shutter speed plays no part in the flash part of the exposure (the duration of the flash is generally so much shorter than the shutter speed, that it has no effect). It *does* play a part in the ambient light portion of the exposure. The association with the amount of flash required when you change your equivalent exposure settings to a higher shutter and a wide aperture needs to be made to the aperture setting. That is why exposure tables for strobes use aperture and do not consider shutter speed at all.

http://www.photograp...om/page.cfm/276

The considerations that I make to choose a shutter speed are:

- How much ambient light I want or need as part of the exposure.

- What color of water am I after or do I want a black background(really, same as above).

- How fast is my subject moving (this includes primary subjects, me or light rays).

Hope this helps.

Linda

P.S. It really sucks that links aren't handled well in posts here! (But I think I fixed it)

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#8 herbko

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Posted 30 August 2002 - 02:07 PM

Hi Linda,

You're right on. After choosing the background exposure you want, there are still choices of shutter speed and aperture combinations that will give that exposure.

For a given background exposure
Higher shutter speed -> bigger aperture -> better range for your strobes.
I am able to shoot WA shots with 2 Sea&Sea YS90DX because my Oly C4040 can sync at 1/800. Photographers using film cameras typically use much bigger strobes for WA, like Ikelite 200's or bigger.

BTW. Great website! Must have been fun to be on the same boat as Chris Newbert. What was it like? Did you get to see some of his shots? I was in the Solomons this May. Some of my photos from that trip are at http://fototime.com/...D02E6FA09524C50 .

Herb
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Canon 5D; Aquatica housing; 2 Inon Z220 strobes; Canon 100mm macro, 17-40mm ; Sigma 15mm FE, 24mm macro, 50mm macro

#9 davephdv

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Posted 30 August 2002 - 10:27 PM

Fast shutter speeds are only of value when you are trying to photograph a high speed subject. In my case that has been sea lions, pilot whales, or dolphins. I find that a shutter speed of 250th sec is necessary to get such subjects. Such photos are best with a blue background so Aperature priority is necessary to get your image. Adjust your ISO to get a shutter speed of 250th. This is a clear advantage of digital over film.
Dave Burroughs, Nikon D300, D2X, Subal housing, DS160 strobes

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#10 mandarinfish

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Posted 31 August 2002 - 07:51 AM

Hi Herb,

I enjoyed the Solomons very much. I'm taking my third trip there in November, and it's still my favorite destination. Chris and Deda are funny, warm and generous people. They have helped me immensely with my photography. On the trips, they show slideshows every night with new shots they're taking. It's a little humbling, though, to be allowed a peek into the drying cabinet, only to see my strips of film next to their beauties! Another advantage of digital is that I could keep all my flubs to myself! :)

Linda

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