KG

Note, I'm not talking about flashes here. Just the body.

This is something I was thinking about recently, and I would like to hear some opinions on this matter.


First, take into account the fact that shutter speeds above camera's flash sync speed are achieved purely by moving the second curtain before the first one fully opens. So it seems like anything above the camera's flash sync speed (which is the highest speed at which the sensor gets completely uncovered) would not work for freezing motion. Different parts of the sensor would be exposed at different times.

So while each "row" of the sensor would experience shorter exposure time, the entire picture would be composed of snapshots taken and different points in time. Rolling snapshot.

Of course the difference would be microscopic, but we are talking about freezing the action.

So it seems that higher shutter speed is a mechanism for controlling the amount of light that gets onto each photosite of the sensor to control overall exposure settings, but it won't work for freezing motion.

Am I correct?

notnoBuddha

I believe you are overly complicting this or I am too simple.
The shutter is nothing more a device for recording a moment of time - the speed dictates how long the moment is. If the question, is does all of his happen at the exact same time as far as the sutter all the way open or all of the way shut then yes that would be correct - anything that moves uses some time to reach it's extremes. Now is it of such duration that the human eyes can discern- not even close.

bobmielke Loc: Portland, OR

Huh? Fast shutter speeds are not useless. If you want to get a shallow depth of field on a bright sunny day your shutter speed will sometime meet or exceed 1/4000 of a second. That's where neutral density filters save the day. Equate shutter speed to frame rate in motion pictures. The only way to stop motion is with a faster shutter speed in available light photography.

KG

I didn't say it's useless. I said it's useless for freezing motion. As for shallow depth of field on a sunny day -- that's exactly what I outlined as a valid use for high shutter speed.

But as far as freezing the motion, if I understand how the shutter mechanism works, then I don't see how it would achieve a crisp image even with 1/8000 shutter speed.

The opening between the two curtains would roll exposing each part of the sensor for 1/8000th of a second. But the entire sensor would not be exposed at the same time.

So in a case of rapid subject motion, different parts of the sensor would record the subject at different times (a few milliseconds apart).

liv2paddle Loc: Wall, NJ

I know what I know..and a high shutter during very fast action will suspend the movement... at what point does this not work..not sure. But the other instance for high shutter may have nothing to do with action but light..as Bob has already reiterated..comes in handy to shut down light at wide open apertures.

notnoBuddha

Okay so - there are sounds the human ears cannot hear, light that the human eyes cannot not discern, tastes the human palate cannot differentiate, and so forth - so what difference on a practicale scale does it make? Lets say we all agree portions of a camera sensor is in fact exposued at nano-seconds seconds apart in time - can you tell? As to the use of various shutter speeds in connection to motion and the freezing of; I would submit that years of photography have proven it's use. if you are convinced not - then there is one less setting to be concerned with in regard to motion. If there is something more you would like for me to agree to - let's say I do.

user2071 Loc: New England

Fast shutter speeds are great if you have sufficient light to use them. I don't think it is EVER bright enough around here to use 1/4000. You'd have to be out in the Arizona desert or something.

I don't think I've ever used a shutter speed above 1/1500 in 40 years of shooting. It's simply never been possible with available lighting conditions.

Paw Paw Bill Loc: d

Wow! Did you receive a load of crap here in response to your post.

You are correct. Fast shutter speed for freezing motion is useful ONLY when the motion is slow relative to the shutter speed. When the action is near the shutter speed, it creates a highly distorted and inaccurate image. That's why high speed cameras were invented. It takes special gear to record high speed action.

bobmielke Loc: Portland, OR

Wrong!

photosbysexton Loc: Knoxville, TN

Maybe I read my manuals incorrectly, but there aren't two shutters in the camera body. 1st curtain is when the shutter opens, 2nd curtain is when it's closed. Also, the shutter doesn't control the amount of light coming in, the aperture does. The shutter controls the time that the light is allowed in. Or am I just an idiot?

bish Loc: Tully NY

It seems like people are talking about two different things here. The original poster is referring to "freezing" motion, such as high speed actions, which is where special equipment would become necessary to do the job. Others are talking in a more practical sense of using a normal DSLR for shooting things such as sporting events, etc. where the camera would for all PRACTICAL purposes, freeze the motion as far as our human eye could detect. The original poster would be correct in his post, but for normal shooting of things like sports action, high shutter speeds do give the appearance of freezing motion.

bobmielke Loc: Portland, OR

If he wants to freeze motion then I was off base. You don't get faster shutter speeds to freeze motion by taking away from the available light using neutral density filters. My apologies to the original poster.

DougP

Never possible??? Just open your aperture in the middle of the day and check your light meter. It's possible.

But I think the subject of this post was more about the inner workings of the camera at speeds above the camera's flash sync speed. Correct me if I'm wrong but this thread has gotten a little off topic.

My opinion (for what it's worth) about that subject is that the difference between 1/4000 and 1/8000 is pretty insignificant. Unless you're shooting a Nascar event. I mean, what kind of motion are we trying to stop here? I've been able to freeze splashing water droplets using 1/1000 without a problem.

As for the capabilities of individual cameras and flash sync speeds, I think that would depend on the type or quality of the camera itself. Just like someone mentioned about video cameras - the better the camera, the more frames per second captured at higher resolutions. As with anything - you get what you pay for.

Tallvol

Wow! I wish I knew as much about cameras as you guys do.
I was having trouble trying to freeze the action in indoor volleyball pictures. The arms and ball move at incredible speed and I was getting the comet effect alot. Sometimes that was OK but not in all my pictures. Shutter speed didn't seem to matter until I bought an 85mm 1.4 lens. Now I can stop the action if I can get myself to stop moving the camera as I follow the action.
Note: shutter speed does affect the crispness of the shot. Also, since it is a sporting event, I am not using a flash.

BigD Loc: The LEFT Coast

The faster the Shutter the more it is capable of stopping action "period". A "high speed camera" simply has a faster Shutter, OK a WAY faster Shutter. What you are referring to is how the Shutter is made faster. It does so by essentially moving across the sensor so fast that it exposes the sensor to light almost like a tiny slit. In other words the first curtain (when the Shutter opens) and the second curtain (when the Shutter closes) are virtually simultaneous. This limits the amount of light hitting the sensor and your aperture must be set accordingly for a proper exposure just like any other picture you take. All that being properly set the exposure will freeze the action better than any slower Shutter Speed will. As for flash photography at higher Shutter Speeds that is called High Speed Sync and THAT is a subject you should all learn to do because it is amazing what you can do with it. I can take a portrait in a totally darkened room at 1/8000 sec. with an ISO of 100 and an Aperture of say f/16 and with a wireless strobe trigger, and freeze a Tennis Players swing completely. Cool stuff...