Half my shot is black?

[Michael_Lambert]

Hey guys,

Sorry i have no clue here, I was shooting a plastic model today and i am shooting against the white background and was trying to blacken out the background.

I noticed using my AB800 about 3/4 power that i could not take my 30D above 1/320 or i was starting to show black - almost as if the shutter was moving to slow for the sensor? like the shutter was only 1/2 open or closed?

[Perry Ge]

What shutter speed were you using? It could well have been above sync speed.

[Michael_Lambert]

Well i guess thats what happened.. lol, I am only playing with the AB800 just getting around to setting it up and actually using it. I did not turn down the adjustment on the back of the unit as it came in that spot so i thought thats where i would try it.

Shooting at 1/500 is where i got the subject somewhat close to properly exposed however i had a huge chunk of the image missing. so i have dialed back the power on the AB800.

Sorry not sure what you mean when you say Sync speed? Total noob here.

[Perry Ge]

I think your camera's max flash sync speed is 1/200s

[Curtis N]

Actually the X-sync speed of the 30D is 1/250, but the instruction manual recommends 1/125 when using studio strobes because of the flash duration of some units.

See p. 108 of the 30D instruction manual.

[redbutt]

Also...it's worth pointing out here that shutter speed really has nothing to do with the exposure in a studio setting when using strobes (of course there are exceptions to this, but I doubt your into playing with that kind of setting yet). You should *not* be changing your shutter speed to affect exposure. You *should* be changing the power output of the strobe and/or changing the distance of the light to the subject.

Oh yeah...sync speed. That's the max shutter speed that can be synchronized with a flash. This is why your are seeing the half black frame. The shutter is literally closing when the flash fires. Set your camera shutter speed to 1/125 and leave it there to start out. That will safely stop motion and should be safely inside the max sync speed.

[SkipD]

When using an SLR with a focal plane shutter, if you use a shutter speed that's faster than the "Max Sync Speed" (with studio strobes that cannot communicate with the camera), what will happen is one blade of the shutter will be partially over the film (or sensor) when the flash is tripped. Part of the frame will be blocked from the light coming into the camera. The maximum sync speed is the maximum shutter speed at which the first blade of the shutter is completely past the sensor (film) before the second blade starts covering the sensor (film). I say blades, because that's the way today's vertical-moving shutters work. In the olden days, a focal plane shutter was made of rubberized cloth or titanium, each side was rolled up on a roller, and they traveled horizontally.

Focal plane shutters (common on SLR cameras) consist of two "curtains", usually made of rubberized cloth (in old film cameras) or very thin metal. The first curtain (which I will call the "leading" curtain) normally covers the film or sensor, hiding it from the light coming through the lens. When you take a photo, the leading curtain moves across the film/sensor to expose it to the light. After the leading curtain has moved, another curtain (which I will call the "trailing" curtain) starts to move, again covering the film/sensor to hide the light from it.

At shutter speeds below the "Max Sync Speed", the leading curtain travels all the way across the film/sensor, fully opening the film/sensor to the light, before the trailing curtain starts to move. At higher shutter speeds, the trailing curtain starts to move before the leading curtain has completely traveled across the film/sensor. What happens to create the very fast "shutter speeds" is that an open slot between the two curtains travels across the film/sensor.

While old focal plane shutters (like in my Nikon F cameras from the 1960's) traveled horizontally, the shutters in most modern SLR's travel across the short distance of the film/sensor frame. The concept of "curtains" turns into one of "blades", but the travel concept is still the same. The leading blade moves first, uncovering the film/sensor, and the trailing blade follows, covering up the film/sensor.

The advantage of the blade style of focal plane shutter is that it can move across the whole film/sensor area faster than the old style curtains. Thus, the maximum sync speed is higher than in the old cameras (max 1/60 for my old Nikon F's, and 1/250 for the 20D).

The concept of a maximum sync speed, however, still applies. If you try to use a flash at higher shutter speeds (faster than the shutter speed at which the leading curtain/blade is fully open before the trailing curtain/blade starts to move), part of the film/sensor will be covered by one or the other of the curtains/blades when the flash (with a very short duration) goes off. Part of the film/sensor will not "see" the light from the flash, and that part of the image will be either black or very dark.

The maximum sync speed is a function of the shutter design.

Focal plane shutters have two blades or two curtains, depending on their design. At lower shutter speeds one shutter element (blade or curtain, depending on the design) will go completely across the film/sensor space, uncovering it and allowing light coming through the lens to impact the film or sensor. After the first shutter element has moved completely across the film/sensor space, then the second shutter element will start to move, re-covering the film/sensor space and ending the exposure. The timing is based on the selected shutter speed.

As you go faster and faster with the shutter speed selection, there is a point reached where the shutter elements cannot travel fast enough to fully expose the film/sensor and then start to close it off. At any faster shutter speed, the second element will start to move before the first has completely uncovered the film/sensor. Thus, a slit - of varying width depending on the desired shutter speed - travels across the film/sensor space.

You cannot use an electronic flash - with its very fast timing - when the shutter speed is so fast that only a portion of the film/sensor is exposed at any one time. The "max sync speed" is the fastest shutter speed that has the film/sensor totally exposed to light coming through the lens.

The ability for some Canon Speedlites to operate in a "high speed sync" mode is based on the flash emanating the light for longer than normal periods. You will get less effective light from the flash at any point in time, but it does allow for some creative flexibility in using the flash.

[PacAce]

Also...it's worth pointing out here that shutter speed really has nothing to do with the exposure in a studio setting when using strobes (of course there are exceptions to this, but I doubt your into playing with that kind of setting yet). You should *not* be changing your shutter speed to affect exposure. You *should* be changing the power output of the strobe and/or changing the distance of the light to the subject.

Oh yeah...sync speed. That's the max shutter speed that can be synchronized with a flash. This is why your are seeing the half black frame. The shutter is literally closing when the flash fires. Set your camera shutter speed to 1/125 and leave it there to start out. That will safely stop motion and should be safely inside the max sync speed.
You can also change your aperture and ISO to affect exposure, too. :)

[redbutt]

You can also change your aperture and ISO to affect exposure, too. :)

True, but for someone just starting out, I think it's a good idea to learn what the light it self is contributing before changing camera settings....which is why I suggested what I did. Once you understand what the light is actually doing, you can make ISO and aperture changes more effectively because you aren't guessing what they will do. Just my opinion.

[hawk911]

okay; I had similar situation, but my left 1/8 of the picture was overexposed. I was shooting with the 40d, 550exs on manual with ratios, and using the PC cord, not the hotshoe. I have pictures if you need to see the effect.
My shutter was at 1/160, but if I moved it to 1/250 or higher, the exposure was correct.

[Curtis N]

I have pictures if you need to see the effect.That always helps! Be sure to keep the EXIF intact, too.

[hawk911]

I'll start my own thread, so I don't mix the problem the OP has in this one.

[TMR Design]

When I had my 30D and B800's I found I could not sync at anything over 1/160s and know that every shot would be perfect. If I moved up to 1/200 I would start to see the curtain and at 1/250 is was cutting every frame in half.

I stick with 1/125 as a safe sync speed. Even with my Nikon and Elinchrom strobes I play it safe at 1/125 and also found that I can't sync at 1/250. The only time I use 1/250 is when I'm using Speedlights.

[SkipD]

When I had my 30D and B800's I found I could not sync at anything over 1/160s and know that every shot would be perfect. If I moved up to 1/200 I would start to see the curtain and at 1/250 is was cutting every frame in half.

I stick with 1/125 as a safe sync speed. Even with my Nikon and Elinchrom strobes I play it safe at 1/125 and also found that I can't sync at 1/250. The only time I use 1/250 is when I'm using Speedlights..... and when using my 20D with my AlienBees I can use 1/250 with no problems at all. That's either with one light wired to the camera or using my Elinchrom Skyport radio slaves.

[TMR Design]

.... and when using my 20D with my AlienBees I can use 1/250 with no problems at all. That's either with one light wired to the camera or using my Elinchrom Skyport radio slaves.

That's interesting Skip. Why is that? I tried it with a sync cord as well as the Pocket Wizards and could not get 100% success rate above 1/160s. I got the same thing regardless of Canon or Nikon, Bees or Elinchrom.

I'll have to run some more tests just to make sure.

[SkipD]

That's interesting Skip. Why is that? I tried it with a sync cord as well as the Pocket Wizards and could not get 100% success rate above 1/160s. I got the same thing regardless of Canon or Nikon, Bees or Elinchrom.

I'll have to run some more tests just to make sure.It is strange, to be sure.

Is is possible that you have some function turned on that takes time away from the exposure (delaying the start of the shutter movement)?

I have virtually all the "tricks" turned off in my 20D except for using Custom Function 4 = 1.

[TMR Design]

It is strange, to be sure.

Is is possible that you have some function turned on that takes time away from the exposure (delaying the start of the shutter movement)?

I have virtually all the "tricks" turned off in my 20D except for using Custom Function 4 = 1.

I never had anything in my settings on the 30D to delay shutter movement and I'm positive that on the Nikon D300 I don't have anything like that set up. I'm definitely going to look into it.

[sleibrand]

.... and when using my 20D with my AlienBees I can use 1/250 with no problems at all. That's either with one light wired to the camera or using my Elinchrom Skyport radio slaves.

Ditto. I've shot literally thousands of shots with 20D and up to 5 bees with no issues (at least none with shutter speed:) ). I don't have wireless so at least one plugged into the PC socket. The remainder set off optically or with the wired remote.