Flash-sync speeds - DPChallenge Forums

06/02/2003 04:25:17 PM · #1

I've read about flash-sync speeds but I'm not possitive how this information is applicable. I'm not even certain what my flash-sync speed is for my on-camera flash and external flash. Once you know the flash-sync speed is it just for you to keep in mind when you are choosing the camera settings or is it something more? I've taken flash pictures with low shutter speeds settings for some interesting motion blur affects but I'm unsure how I might apply the flash-sync information in my shots. I'm interested in learning more about flash photography and I am realizing some of the limits of my current system such as no rear curtain flash and no TTL exposure with an external flash. Any help I could receive in this area would be appreciated.

T

06/04/2003 04:35:29 PM · #2

So nobody else has a clue either? : )

T

lizardbeth

Canon EOS-10D

06/04/2003 04:56:30 PM · #3

Each camera has a flash sync speed. You cannot take a picture with a shutter speed faster than that number or else you'll get a black bar on your image. If you're shooting in aperature mode, your camera will probably take care of it for you. If you have a point and shoot your camera should take care of it too. I think this would just be an issue at full manual.

Please someone correct me if I'm wrong.

06/04/2003 05:02:11 PM · #4

I'm not quite sure what you are asking Tim.

Flash sync speed relates to how fast a shutter speed you can use with the flash and represents the upper bound. Typically you can't use a faster shutter speed without having problems/ partially dark areas that sort of thing. I think it depends on how the shutter is constructed, but the flash illumination has to be available for the entire pass of the shutter.

So, the sync speed isn't an issue for slow-sync type photography, but becomes an issue if you want to have a fast shutter speed with flash as it sets the upper bound on what you can do.

At least that's how I understand it, though I don't have a whole lot of experience/ understanding of flash techniques

I've been meaning to read this for months, though it is about 100 pages worth of info on Canon EOS flash equipment. I'm sure you could find the relevent information in there, for any kind of flash gear (not just Canon)

06/04/2003 05:02:55 PM · #5

Here is the relevant chunk from the link above:

X-sync (flash sync) speed.

Timing is critical for flash photography. The burst of light from a flash unit is extremely brief (in milliseconds), and must occur when the shutter is fully open. If the flash burst occurs when the shutter is still opening or closing then the shutter itself may prevent the entire image area from being fully exposed.

Modern SLR camera shutters are equipped with a pair of moving curtains which wipe across the opening to the image area. They travel vertically because the travel distance is less than if they travelled horizontally, and there are two curtains to make fast shutter speeds possible. At high shutter speeds the opening is actually an open slit between the two curtains, travelling the height of the image area.

This presents a problem with flash photography. If you have only a slit exposed at the time the flash happens to go off then you wonâ��t be able to illuminate the entire image area with the flash burst. An electronic flash burst is always much briefer than the fastest shutter speed motion that the shutter mechanism can achieve.

Different cameras have different shutter designs - some are faster than others. But each camera will have a maximum shutter speed at which a flash burst will expose the full image area of the film. This maximum flash-compatible shutter speed is called â��X-sync speed.â�� X-sync and flash sync are the same thing on modern cameras, since they all use electronic flash.

Maximum X-sync speed and EOS bodies.

1/90 second.
All low-end Canon EOS cameras. These are cameras of the Rebel series in North America (eg: Rebel G, Rebel 2000), the Kiss series in Japan (eg: EOS Kiss, Kiss III), and the EOS three-digit series (eg: EOS 300, 500 but not the EOS 100, 600 series or 750/850) and all EOS four-digit series (eg: EOS 1000, 3000) elsewhere.

Note, however, that some users report that their Rebel/EOS three/four-digit cameras are actually physically capable of attaining a 1/125 second X sync. That is, the shutter mechanism can sync that fast but the cameraâ��s computer has been deliberately programmed not to allow flash sync at speeds faster than 1/90 second. Itâ��s not clear why Canon did this. One theory is that it was an intentional move on Canonâ��s part to cripple their low-end cameras for marketing reasons. (ie: so that they compete less with midrange models) Another theory is that this was done because of flash duration tolerances - Canon decided to play it safe and ensure that their low-end shutters always can record a full flash burst.

Either way you canâ��t override the cameraâ��s programming and perform flash sync with any dedicated flash unit which meters through the lens. But if youâ��re using an externally triggered flash with an optical slave or adapter cable you may be able to take advantage of this higher sync speed if your camera falls into this category (non-dedicated flash units do not communicate with the camera concerning flash exposure and thus the programmed 1/90 sec limit is not an issue). Unfortunately empirical testing is the only way to find out.

1/125 second.
Mid-range EOS cameras. These are EOS two-digit cameras (eg: EOS 10 and 50) and the Elan series in North America (eg Elan II, Elan 7). Most of the first generation EOS cameras (600, 630, 650, 750 and 850) also have a 1/125 sync, as does the original Elan/EOS 100.

1/200 second.
Semi-pro EOS cameras. These are the single-digit EOS cameras that arenâ��t in the 1 series - the EOS 3 and 5 (A2 in North America). The digital D30 and D60 also have an X-sync of 1/200 sec as does, surprisingly enough, the APS IX. (apparently the smaller physical dimensions of the IX shutter allow it to reach a higher X-sync speed)

1/250 second.
Top of the line professional EOS cameras - the EOS 1, 1N, 1V and 1Ds. The one odd one out is the EOS 620, an old camera from the late 80s which nonetheless could sync at 1/250 sec as well.

1/500 second.
The digital 1D camera has a startling 1/500 sec X-sync and a 1/16 000 sec top shutter speed. This is because both X-sync and shutter speed are normally handled electronically by the CCD and not by a mechanical shutter. The 1D does have a mechanical shutter but itâ��s used for bulb mode. Note, however, that the CMOS-based 1Ds has a top X-sync speed of 1/250 like the 1V upon which itâ��s based - the higher X-sync speed of the 1D derives from its use of a CCD image sensor.

All EOS cameras will deliberately prevent you from exceeding the X-sync value for shutter speed when youâ��re using non-FP flash.

Note the first exception - if you have an E-TTL flash on a type A body with FP mode flash enabled youâ��re fine. You can exceed X-sync at the cost only of lowered flash output. But there is a possible second exception, and that is if youâ��re using third party flash gear, particularly studio flash units that use optical slaves or generic flash units. Such a setup likely wonâ��t notify the camera properly of your use of flash, so be careful.

Message edited by author 2003-06-04 17:03:06.

06/04/2003 05:15:59 PM · #6

Wow Gordon, now that's an answer! I will need to take more time to go back and really absorb it all but for not really knowing what I was asking you did a great job of answering. Thanks.

T

06/04/2003 05:18:37 PM · #7

By the way, I think I was basically asking how I use the information about my flash-sync speed and if the camera simply took care of things automatically. I'm now slightly less confused than normal : )

T

Nikon AF-S DX Zoom-Nikkor 16-85 f/3.5-5.6G ED VR

06/04/2003 05:25:17 PM · #8

Originally posted by timj351:

Typically the camera won't let you go beyond the flash sync speed in an 'auto camera'. If it does, you'll get black bands (basically areas that didn't get any light while the shutter was moving) - which is more the problem for a manual camera.

rcrawford

Nikon D300

06/04/2003 05:34:29 PM · #9

Tim,
The other function that my camera has is a slow sync and slow sync 2nd curtain. This allows you to select when, during the exposure, the flash goes off. If you took a picture of a moving car at night with a 1 sec exposure the slow sync would give you a picture of the car frozen then the lights trailing ahead of the car. Slow sync 2nd curtain would have the lights leading up to the car. Does this make sense? I hope it is helpful.

06/04/2003 05:53:36 PM · #10

Originally posted by rcrawford:

Thanks, it makes perfect sense. In my original post I complained how my camera didn't have rear curtain flash and I really wish it did. Yet another reason to try to get a DSLR like the Canon D10, drool, drool.

T

jenarom

Sony DSC-F717

06/05/2003 12:54:26 AM · #11

I've had this same question for the last month. Does anybody know the flash sync speed for the Sony F717 and F707? I need speeds for both the built-in flash and for the hot shoe (external flash).

jenarom

Sony DSC-F717

06/05/2003 11:49:15 AM · #12

Anyone?