Godox AD400 sync speed with MkIV

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SamR Photo

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Sam
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Hey there, just a quick one:

I've used Bowens 500 heads for a decade now. Flash sync speed (using Godox X-Pro and any other system really) is 1/125. If I go faster there's a subtle curtain blur at the side of the frame, about a half stop or so. darker in the last 20%.

I want to get a pair of AD400, and I believe the curtain issue is the length of flash (or maybe responsiveness) of my old Bowens heads that overlaps the shutter closing.

Has anyone direct experience with sync speed with AD400 in the studio? If you use them for location people style shoots it might sometimes be hard to notice the issue, but it's obvious on clean backgrounds in a controlled environment.

The reason is is that if I can sync at 200th (like a speed light) I definitely don't need to get AD600s to knock out the daylight.

It's really hard to Google this because everyone wants to talk about HSS.

Thanks!

Sam.
 
That's super interesting, it's almost like pumping them up to 800 heads (shutter speed wise) compared to the old Bowens. If that's the case I'm surprised it's not mentioned more.
 
SamR Photo said:
Hey there, just a quick one:

I've used Bowens 500 heads for a decade now. Flash sync speed (using Godox X-Pro and any other system really) is 1/125. If I go faster there's a subtle curtain blur at the side of the frame, about a half stop or so. darker in the last 20%.

I want to get a pair of AD400, and I believe the curtain issue is the length of flash (or maybe responsiveness) of my old Bowens heads that overlaps the shutter closing.

Has anyone direct experience with sync speed with AD400 in the studio? If you use them for location people style shoots it might sometimes be hard to notice the issue, but it's obvious on clean backgrounds in a controlled environment.

The reason is is that if I can sync at 200th (like a speed light) I definitely don't need to get AD600s to knock out the daylight.

It's really hard to Google this because everyone wants to talk about HSS.

Thanks!

Sam.
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I think what you're referring to is common to all focal plane shutters at max x-sync speed, when used with any flash head having a flash duration at full power of 1/200-1/250sec (t.1). That's most big flash heads, including Godox. Canon handbooks actually say to use longer shutter speeds in this situation.

The problem is the shutter blinds take about 2-3ms to travel from top to bottom of the frame, depending on the camera. So at 1/250sec shutter speed (4ms) that only leaves 2ms (1/500sec) at best when the sensor is completely uncovered. That's obviously not long enough to capture the full flash pulse which results in the top of the sensor receiving less light as the second shutter blind closes. Bearing in mind that the image is reversed by the lens, the bottom of the image appears noticeably darker.

To see this in action, just drop the shutter speed and the image will get brighter because the full flash pulse is then captured. Or, reduce the flash power and with an IGBT-controlled flash (eg Godox) the flash duration will be cut dramatically shorter, meaning that you can then shoot at 1/250sec and still get all the light.

TBH, it's a problem that flash manufacturers need to fix (like Elinchrom has with their faster flash duration Action heads, and some older Bowens heads) as it makes a real difference when you need every drop of power in the battle with bright daylight outdoors, as well as freezing movement better. On the other hand, I use AD400Pros and they're bright enough for me outdoors even with HSS, but I generally use an efficient umbrellabox (about half a stop brighter than a similar double-diffuser softbox) from around 1m or so. If you're using bigger softboxes from greater distance, that could change the game completely.
 
Hey, thanks so much for your detailed reply Richard - it's great to understand this issue better. Now I know the flash pulse for speed lights is much shorter (which is not surprising at 50 watts or so), which is why they can sync at 200th or 250th. However I was told that the flash pulse of the Godox AD400 is short enough (even at full power) to be able to set a shutter speed of 200th of a second on my Mk4. Maybe making them act a little more like those super expensive Elincrom they use for sports. However I'm wondering if anyone had any real world experience of this. If it is the case it'd be great as it'll save me getting the AD600s.
 
SamR Photo said:
Hey, thanks so much for your detailed reply Richard - it's great to understand this issue better. Now I know the flash pulse for speed lights is much shorter (which is not surprising at 50 watts or so), which is why they can sync at 200th or 250th. However I was told that the flash pulse of the Godox AD400 is short enough (even at full power) to be able to set a shutter speed of 200th of a second on my Mk4. Maybe making them act a little more like those super expensive Elincrom they use for sports. However I'm wondering if anyone had any real world experience of this. If it is the case it'd be great as it'll save me getting the AD600s.
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How much light do you need? What are you shooting, what softbox etc, at what distance, and under what ambient conditions? TBH, if you can't do it with an AD400Pro, then the AD600Pro isn't going to make much difference at just half a stop brighter.

Also consider efficiency. Not all softboxes are the same. Or you could try ND filters instead of HSS. Or maybe play around with hypersync (long-tail sync). There are quite a few workarounds worth trying before just blitzing it with wattage, like simply avoiding bright sun outdoors..
 
Thanks for your reply Richard. I didn't really want to go much below 500w but thought I could get away with it with the Godox. The Bowens (and possible AD400s) are for things like studio catalogue style work normally. I normally use a fairly large calumet soft box (about 120cm?) as a fill alongside a smaller onesfor key. But sometimes larger soft boxes on both when even light is needed, and I might struggle with power slightly in that context sometimes.

I find with the 500 heads I can still pick up a bit of ambient sometimes at 1/125. That's why I was super interested if I could get to 1/200 of a second. The 500 heads and 400 are just about powerful enough in other ways, am able to stop down to f9 or f11 which is just about fine depth of field wise (and smaller if I put the iso up a bit).

Would prefer to go to battery powered and lighter which would be another bonus.
 
SamR Photo said:
Thanks for your reply Richard. I didn't really want to go much below 500w but thought I could get away with it with the Godox. The Bowens (and possible AD400s) are for things like studio catalogue style work normally. I normally use a fairly large calumet soft box (about 120cm?) as a fill alongside a smaller onesfor key. But sometimes larger soft boxes on both when even light is needed, and I might struggle with power slightly in that context sometimes.

I find with the 500 heads I can still pick up a bit of ambient sometimes at 1/125. That's why I was super interested if I could get to 1/200 of a second. The 500 heads and 400 are just about powerful enough in other ways, am able to stop down to f9 or f11 which is just about fine depth of field wise (and smaller if I put the iso up a bit).

Would prefer to go to battery powered and lighter which would be another bonus.
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In the studio, you have options.

If ambient light pollution is a problem, and it must be pretty high to be an issue with 400-500Ws available, reduce the ambient. If flash power is a problem, then raise ISO. One stop of ISO is the same as doubling the flash wattage in terms of exposure, and that's a very effective workaround with modern cameras, provided the ambient is under control.
 
Hey yep cheers. I know all that. Tricky to reduce ambient in some studios!
Just wanting to know if they’ll sync at 200th or above if anyone knows. :)
 
SamR Photo said:
Hey yep cheers. I know all that. Tricky to reduce ambient in some studios!
Just wanting to know if they’ll sync at 200th or above if anyone knows. :)
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You mean, will a 5D4 at 1/200sec sync with an AD400Pro at full power? Yes, it will - as in you won't get black bars appearing. But as explained above, no camera with a focal plane shutter is able to capture the total light output at that shutter speed when the flash duration t.1 is in the 1/200-1/250sec zone. There will be a slight loss of max brightness and some just visible shading down the frame. To achieve maximum brightness without any shading, you either need a longer shutter speed like 1/125sec, or a shorter flash duration in the region of 1/700sec or less. The AD600Pro will probably be very close to 1/700sec at 2/3rds or half power, when it will still be putting out roughly the same light as the AD400Pro at full power.

But I have to say, while these effects are real and visible under controlled test conditions, they are rarely an issue except in very critical situations. And even then, there are usually workarounds. However, a photographic studio with high ambient light that can't be properly controlled isn't really worthy of the name ;)
 
yep, the specs say the flash duration is about 1/240th on full power.

HoppyUK said:
There will be a slight loss of max brightness and some just visible shading down the frame.
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Yep that's what I'm talking about - oh well good to know and thanks for the info.

HoppyUK said:
But I have to say, while these effects are real and visible under controlled test conditions, they are rarely an issue except in very critical situations.
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I do quite a lot of fine art reproduction so evenly exposed across the full frame is mission critical.

HoppyUK said:
a photographic studio with high ambient light that can't be properly controlled isn't really worthy of the name
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I set up and shoot quite a lot in artist's studios. And just the other day some spot lamps (which couldn't be turned off) were causing small orange dots on some ceramics, this was at 1/125 and f13.

I also stop down to around f2 quite a lot for detail shots etc, and it would be nice to have even 0.75 of a stop less natural light, but guess this is a situ where I could use HSS.

(y)
 
SamR Photo said:
Or I wonder why they can't make the shutter travel faster?!
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Mechanical devices have a steep curve on price v performance. They already move v fast (sync speed was 1/60 when I started shooting).

the technological answer to fast sync speeds is a global electronic shutter not mechanical, Canon (and others) have patents already but no ones in production yet.
 
SamR Photo said:
yep, the specs say the flash duration is about 1/240th on full power.

Yep that's what I'm talking about - oh well good to know and thanks for the info.

I do quite a lot of fine art reproduction so evenly exposed across the full frame is mission critical.

I set up and shoot quite a lot in artist's studios. And just the other day some spot lamps (which couldn't be turned off) were causing small orange dots on some ceramics, this was at 1/125 and f13.

I also stop down to around f2 quite a lot for detail shots etc, and it would be nice to have even 0.75 of a stop less natural light, but guess this is a situ where I could use HSS.

(y)
Click to expand...

That qualifies as critical work, and if there are things like bare light bulbs in the studio or bright specular reflections coming off shiny objects, then they could be a real problem and hard to get rid of with flash power alone. The best policy is probably to simply eliminate them by shading the subject with flags or black V-flats (google). If you need to travel to different studios on a regular basis, then collapsible/portable versions are available. And use a grey card or colour checker for white balance ;)
 
Ha yes I have an x-rite. :)

It’ll be a great day for my back when they get electronic shutter.

cheers

Sam
 
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