YS-D1 Cutoff Issue

Hi Experts,

I recently got back from a trip to Kaua'i. I had a bunch of new (well, used but new to me) gear including a Sea & Sea YS-D1 strobe. Unfortunately, my plans for a closer, less exotic trip to practice with the new equipment got scrapped so I had to practice while in Kaua'i. In short, in many of my shots the strobe coverage was cut off for 1/4 to 1/2 of the exposure. It's a very artificial cutoff - I'm sure my strobe positioning was not good for all shots, but this seems like something different. The problem did not happen with all shots, only some. I couldn't identify what conditions were causing it for some shots and not others. Distance to subject and relative strobe position seemed to have some influence but I couldn't pin it down. I saw it in portrait and landscape shots. I usually shoot macro with the strobe above the housing, but I also saw it with the strobe moved to the left of the housing.

Equipment used during issue:

Canon 550d, Canon 60mm Macro Lens, Sea & Sea RDX-550d Housing, Sea & Sea RDX Standard Port, Sea & Sea YS-D1 strobe (1)

I have previously shot with a single YS-110a strobe and did not have this issue. When I shot with the YS-110a, I always used the diffuser. I also used the Diffuser 100 with the YS-D1 and I'm wondering if this is the issue. Unfortunately, I didn't come up with this theory until the very last 15 minutes of my last dive, so I didn't have time to really verify if removing the diffuser made the issue go away.

Examples attached:

d1issue1 - more than half cutoff

d1issue2 - portrait example

d1issue3 - 10% cutoff, but still present

Thoughts? Thanks.

Looks like you're shooting at too fast a shutter speed. On your camera I think you cannot sync faster than 1/180th of a sec. Post some of the camera settings from the exif of the photos.

I did notice this same issue while recently shooting a Sony a7, which is supposed to sync to 1/320, but the issue cropped up at time at 1/250th using rear cutain sync. You might have to use front curtain sync to get the fastest sync speeds? Not sure...

This issue should be able to be duplicated easily on dry land, just try some of your fastest shutter speeds with an external strobe and see.

Jack

Jack,

Thanks for your response. This did occur to me, but I guess I assumed that if the shutter speed were to blame, it would manifest on all shots. The problem only showed up on about 20% of the shots using the macro setup described. It didn't manifest at all with my wide shots and 2 strobes (the same ys-d1 + my older ys-110a).

All the shots on which the problem occurred were using these settings:

M (manual exposure)

1/200 shutter

ISO 100

f8-f16 variable aperture

I did not alter the default flash settings in terms of 1st or 2nd curtain firing. The other 80% of the shots where this problem did not occur also used 1/200 shutter speed.

You can't sync reliably past 1/180th of a sec with your camera. It is funny how it bounces around and works sometimes though.

Jack

Jack is correct, this is a classic example of shooting with the shutter speed too high, the curtain is closing before the strobe is firing. On the 7D, this problem is also variable, sometimes (1 in 5) it works fine but most of the time you get that kind of scenario, a black line through the shot. You can easily verify this at home on your kitchen table.

Bill

Is this because the response time of the YS-D1 is too slow or would it be the same with an inon Z240?

Thank you for the advice and I will test using 1/180 and see if I can prevent this in the future. Looking at the results, it makes a lot of sense to me. You can visualize where the curtain was closing when the strobe fired. Analyzing the situation, it does not make sense - why would it happen only 20% of the time with same shutter speed, and why would it never happen with the older strobe (ys-110a) on the same exact camera, lens, port, fiber cable, and camera settings? But the whole reason I ask the experts is that my analysis has failed me, so I'm glad to have a path to a solution!

It is possible that the YS-110 has better performance in this respect than the newer strobe and responds faster to the fibre optic sync signal. If this was a camera problem you would have the same issue with the camera outside the housing using the internal flash

Hi. Here's a couple few things you can try at home (with gear setup)

(1) Try increasing your ISO and reducing your flash power and see if this reduces the number of shots with the shutter showing. Flash strength is proportional to duration so half strength will be roughly twice as fast and therefore allow a bit more latitude for the full flash while the shutter is open. Flash duration is very small but at full power on a small strobe I'm not sure it is as short as the conventional wisdom would lead us to believe.

(2) I read on a post here that someone noticed that the frequency of shutter appearing was different between landscape and portrait shots. As the shutter is mechanical a bit of gravity (in the right direction) may possibly help.

(3) I've also read that hard wiring with sync cords gives better sync speeds than FO but I haven't seen anything that really explains why. And that also doesn't explain the difference between your YS110 and D1.

Hope that helps.

Cheers

Hi. Here's a couple few things you can try at home (with gear setup)

 

(1) Try increasing your ISO and reducing your flash power and see if this reduces the number of shots with the shutter showing. Flash strength is proportional to duration so half strength will be roughly twice as fast and therefore allow a bit more latitude for the full flash while the shutter is open. Flash duration is very small but at full power on a small strobe I'm not sure it is as short as the conventional wisdom would lead us to believe.

 

(2) I read on a post here that someone noticed that the frequency of shutter appearing was different between landscape and portrait shots. As the shutter is mechanical a bit of gravity (in the right direction) may possibly help.

 

(3) I've also read that hard wiring with sync cords gives better sync speeds than FO but I haven't seen anything that really explains why. And that also doesn't explain the difference between your YS110 and D1.

 

Hope that helps.

 

Cheers

Re point 3 that would not be really be easy to understand. As fiber optic relies on light that is actually faster than current I would say it would depend on how the circuits are implemented

In general the X sync speed is the fastest speed you can sync but it is not guaranteed unless you use recommended equipment (house a canon land flash connected to the hot shoe)

What it looks like here is that the YS-D1 a more powerful unit than the YS-01 and YS-110a is slower to respond to the first curtain through the same connection method and you end up with a black bar

I would do a test on land to see if there is an

I think that the idea that wired strobes have faster cycle times is because with a wired strobe, you can shoot faster, since you don't have to charge up the internal strobe. As for the speed of light in a fiber and the propagation of charge in a wire (the speed of the electricity) I think the difference in a few feet of wire is in the picosecond range, not measurable in any way relevant to photography (even though the actual electrons move quite slowly, the charge propagation is at the speed of light in the medium).

Bill

So this is in fact an issue of shooting at a shutter speed that is beyond the max sync speed. The principle is actually sort of simple to explain but easy to understand.

When your camera shutter opens, it is only ever open fully (meaning the entire surface area of the sensor is exposed to light at the same time, at or below the sync speed, which I think someone said was 1/180th on your camara model). At any speed faster than 1/180th, the first shutter curtain opens, then the second one begins it's trip over the sensor before the first completes it's trip across.

Since the shutter is never fully exposed to light (strobes in this case) you will see a dark band. The reason this is not an issue with ambient light, is that their will be sufficient light to expose the frame regardless of the entire sensor being open or not. At 1/1000th or 1/5000th, the shutter actually passes over the sensor in a fashion like a small sliver; meaning the first shutter curtain starts to open, and the second one starts to close right away.

Your flash is firing correctly.

As to the reason why this seems to be an intermittent issue, that is simple too. The flash sync speed is 1/180th of a second, but your shutter speed is not always 100% consistent. It may expose at 1/180th on one exposure, but 1/200th on the next, 1/175th on the next, etc. While it's close enough to provide an exposure that well within the correct range that you would be hard pressed to see either over or under exposure in ambient light, you can clearly see some difference in the relative size of the black band when exposing with strobes.

The other thing you will notice is that on some landscape images it may look worse than on a portrait image, that is because the effects of gravity can also have a very small impact on the speed at which the shutter travels.

So, if your sync speed is in fact 1/180th, set the camera to manual, and place the shutter speed at 1/125th, which will be the closest and fastest shutter speed at which you will not get these black bands. You can try it at 1/180th, but if the shutter is at all faster than 1/180th, you will run the risk of a small amount of black banding.

Hope this helps!!

Is this because the response time of the YS-D1 is too slow or would it be the same with an inon Z240?

Interceptor,

This is not really an issue of response times of any given strobe.

Most all cameras will trigger the flash to fire ONLY once the first shutter curtain is fully open. The speed at which the electronics cause the strobe to fire, plus the speed of the light travelling to the subject than back to the camera sensor (or film, if you remember that stuff), is so fast, that the entire frame will be illuminated before the second curtain begins it's trip across the sensor plane.

If the flash were to fire before the first shutter curtain was full open (meaning out of the way of the sensor), you would get a similar black band but on the other side of the frame.

Bottom line is that the ONLY way to get a shot made with a strobe that has even illumination across the entire frame is for the entire sensor to be open when the flash fires, or put another way, make sure you shoot at or below the max sync speed.

By the way, rear curtain sync simply the camera telling the flash to fire right before the second shutter curtain begins it's trip across the sensor, not at teh completion of the first one finishing it's trip.

Interceptor,

This is not really an issue of response times of any given strobe.

 

Most all cameras will trigger the flash to fire ONLY once the first shutter curtain is fully open. The speed at which the electronics cause the strobe to fire, plus the speed of the light travelling to the subject than back to the camera sensor (or film, if you remember that stuff), is so fast, that the entire frame will be illuminated before the second curtain begins it's trip across the sensor plane.

 

If the flash were to fire before the first shutter curtain was full open (meaning out of the way of the sensor), you would get a similar black band but on the other side of the frame.

 

Bottom line is that the ONLY way to get a shot made with a strobe that has even illumination across the entire frame is for the entire sensor to be open when the flash fires, or put another way, make sure you shoot at or below the max sync speed.

 

By the way, rear curtain sync simply the camera telling the flash to fire right before the second shutter curtain begins it's trip across the sensor, not at teh completion of the first one finishing it's trip.

I think you are not understanding what am saying. For any given camera the shutter is only fully open for a given time. For this camera is 1/200th or 5 ms. A strobe burst lasts around 1 ms or less depending on quality. However it takes some time for the strobe to respond to the electrical or optical trigger. If this time is for example larger than 5ms for example 5.2ms then your total time needed becomes slower like 1/180th shutter speed. So it looks like with this specific camera the YS-D1 is slower to respond than the other strobes the op has tested and can only reliably sync with shutter speed lower than x-sync, this in a way is not a surprise as the x sync is the max possible speed

Time to get out the oscilloscope and play, (Yeah).

Bill