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Trying to understand high speed sync for BIF

EverLearning
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p.1 #1 · p.1 #1 · Trying to understand high speed sync for BIF

For the last several days I have been trying to photograph bluejays coming in to a feeder. After observing their tendencies and assessing the different positions I can set up at to leverage these tendencies, I have determined the best location; considering these tendencies and the desire to have a fairly clean background (and, especially, avoiding buildings and fences in the background). The problem is the jays feed predominantly in the morning and their flight patterns and my desired background results in no catchlight in the eye.

My camera (Canon R5) / lens (Canon 100-400 II) is on a Wimberley sidekick and I have attached a Wimberley F-1 Telephoto Flash Bracket to the setup. Attached to that is a Godox V860 II, which is set to Manual. It took me a little bit to figure out I had to switch my camera to Mechanical shutter (12 fps) to get the flash to work. Next was switching the flash to High Speed Sync so I could use a shutter speed higher than 1/200 second. This is where I am bogging down.

I just want to use the flash to add a catchlight to the eye. I am about 16-18 feet from the subject (on their flight pattern approaching the feeder). So, my questions:

1. I know some experimentation will be required to get the "best" flash ratio, but what is a good starting point? 1/16? 1/32? 1/64?

2. I have read that a full flash burst lasts about 1/1000 second. I don't know how long a reduced flash such as in point #1 lasts, but I assume it is of shorter duration. I have also read that using flash helps to "freeze" action. If that is so, what ss should I be using? Without flash I have been shooting 1/3200 to 1/4000.

3. The temperatures are a little low for this time of year; about -10c to -15c (14F to 5F). My Canon camera batteries do very well in these temperatures (and much lower) but I have not shot with flash in these temperatures. So I have a two part question on that:

a. Will temperatures like this harm the flash unit?

b. Are there any tips for making the flash battery last longer. Taping a hand warmer on top of the battery compartment door?

I am definitely "wandering" in new territory here so any help would be greatly appreciated!

Nov 27, 2023 at 09:02 PM

Imagemaster
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p.1 #2 · p.1 #2 · Trying to understand high speed sync for BIF

Since most of your questions are about lighting, the most relevant forum would be the Lighting & Studio Techniques.

As for eye catchlights in birds, they are not always there naturally, so why add fake ones? If you need to add fake ones just use Photoshop.

Nov 27, 2023 at 09:35 PM

EverLearning
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p.1 #3 · p.1 #3 · Trying to understand high speed sync for BIF

Since this isn't in a studio, I didn't think that would be the appropriate forum nor necessarily where the expertise for BIF flash would be.

Thanks for the assistance.

Nov 27, 2023 at 09:57 PM

jedibrain
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p.1 #4 · p.1 #4 · Trying to understand high speed sync for BIF

EverLearning wrote:
Since this isn't in a studio, I didn't think that would be the appropriate forum nor necessarily where the expertise for BIF flash would be.

Thanks for the assistance.

I think you just need enough juice to get the catch light. I'd try setting up a stuffed animal with hard plastic eyes, and experiment on that from your location until you see the light the way you like it. And you should be able to zoom the flash to make the most out of it.

Can't answer about the flash in the cold. But the hand warmers are a good idea.

Brian

Nov 27, 2023 at 10:26 PM

Mike_5D
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p.1 #5 · p.1 #5 · Trying to understand high speed sync for BIF

1) Without TTL, you just have to guess and adjust.

2) Flash durations can be very short at lower powers, like 1/10,000 sec. If you were shooting in the dark and relying on the flash for illumination, your shutter speed becomes irrelevant. The flash duration becomes your effective shutter speed in that case. If ambient light is your primary illumination, your shutter speed is what freezes action. If you have a shutter speed too slow to freeze the action and you add flash, you get a double image: One blurry image from the ambient light and one sharp image from the flash, assuming you have enough flash power. HSS takes a lot of power so it won't go very far.

3) The manual should tell you the acceptable temp range. I don't think it'll hurt the batteries, but they won't last as long as they do at normal temps. You may want to carry an extra battery. I wouldn't use a hand warmer. Lithium really doesn't like to be hot.

Nov 27, 2023 at 10:27 PM

EverLearning
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p.1 #6 · p.1 #6 · Trying to understand high speed sync for BIF

Thanks for the reply Brian. Much appreciated.

Mike, it sounds like you are saying stick with the shutter speeds I have been using to freeze the action with ambient light (1/3200 to 1/4000) and play with the flash ratio (... 1/16, 1/32, 1/64, ...) to get the catch light. I am surprised by your comment that HSS takes a lot of power. I would have thought if I am at 1/32 ratio then I would be using 1/32 the power of a full flash. If that is not the case, then I gather it is unlikely that the flash can fire 12x/second even at 1/32 or 1/64 power and I will have some photos with a catch light and some without. I guess I could always photoshop an eye from one photo to another if necessary.

Re the battery and the cold, I can't imagine at those temperatures that a hand warmer would do anything but slow down the heat loss of the battery rather than actually warming it.

Nov 27, 2023 at 10:42 PM

Mike_5D
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p.1 #7 · p.1 #7 · Trying to understand high speed sync for BIF

In non-HSS, the flash dumps all of the energy at once and you get a big burst of light. At shutter speeds beyond sync speed, the entire sensor is never exposed at once, so the flash pulses the light at very high frequency while the shutter opening moves across the sensor. This results in much less light delivered.

Nov 27, 2023 at 10:54 PM

jeffbuzz
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p.1 #8 · p.1 #8 · Trying to understand high speed sync for BIF

HSS uses much more power per pop than "normal" synced flash output. Hence the effective flash range is greatly reduced. If you use a remote flash placed closer to your subject, the power output on subject will be much greater. Or, you need a much more powerful light at the current distance.

Nov 27, 2023 at 11:04 PM

melcat
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p.1 #9 · p.1 #9 · Trying to understand high speed sync for BIF

If you weren’t using high speed sync, you could calculate the flash power to use as follows:

Your flash has a guide number (GN) of 60 metres. Since

GN = f-number × distance

and you are at ~5m distance, you would need to shoot at f/12 for correct exposure. But you don’t want correct exposure, but just a catchlight, for which I would start at 3½ stops down so that the subject itself gets no more exposure. (Someone might correct me here, since I’ve never tried it.) If you’re actually shooting at f/11, add another ½ stop for 4 stops in all, or 1/16 power (2⁴ = 16).

But what effect does using HSS have on the power setting in HSS? Maybe your flash manual tells you: is 1/16 power 1/16 of GN 60, or is it 1/16 of the best the flash can do in HSS (which will be much less than GN 60)? You can figure out the effective GN of the flash using HSS by testing the flash with a setup in a dark room – no bird required. Then plug that GN into the calculation I did above instead of 60.

Edited on Nov 28, 2023 at 12:29 AM · View previous versions

Nov 28, 2023 at 12:26 AM

Imagemaster
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p.1 #10 · p.1 #10 · Trying to understand high speed sync for BIF

Nov 28, 2023 at 12:27 AM

mike650
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p.1 #11 · p.1 #11 · Trying to understand high speed sync for BIF

My guess it that the flash effective power or GN would drop proportional to how much shorter your exposure time, shutter speed, is relative to the flash sync speed. In your case, if the sync speed is 1/200 and the shutter is 1/4000, then the ratio would be 20=(1/200)/(1/4000). So the flash would have to fire 20 times to completely illuminate a single frame as the narrow shutter slit moves down across the sensor. The power per flash would be reduced internally to about 1/20th of the 1/1 full power value in order to be able to deliver those 20 flashes from a fully charged internal capacitor. And that's for just one shot. The flash won't recycle fast enough for 12 fps, maybe 1 fps? If the flash is set to 1/128th power, then you could get more shots before the flash needs to recharge/recycle.
The manual also says the flash may stop after 15 consecutive HSS single shots so I suspect it's boosting the power above the normal mode 1/1 full power and overheating the flash tube and electronics.
Photoshop seems like an easier solution by cloning in a natural catchlight from another photo from the same bird.

Nov 28, 2023 at 01:09 AM

rscheffler
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p.1 #12 · p.1 #12 · Trying to understand high speed sync for BIF

EverLearning wrote:
2. I have read that a full flash burst lasts about 1/1000 second. I don't know how long a reduced flash such as in point #1 lasts, but I assume it is of shorter duration. I have also read that using flash helps to "freeze" action. If that is so, what ss should I be using? Without flash I have been shooting 1/3200 to 1/4000.

Actually the majority of on-camera 'speedlite' type flashes, AFAIK, have fairly long flash duration at full power, approaching 1/250. But yes, as output is reduced, flash duration decreases (becomes faster) due to how this is achieved with IGBT control.

There is a good overview about this at the Paul C Buff website.

Another thing to consider is that flash duration may be reported as t.5 or t.1. The latter is a better representation of 'freezing power' but t.5 is often used for marketing purposes because it implies better performance than is actually the case. Anyway, this is probably getting beyond the scope of the discussion here.

As others have stated, HSS 'chops' up the total light output into smaller 'slices' that the flash outputs very rapidly as the shutter slit travels across the image area. Because of this the actual exposure at a given moment during shutter travel is considerably lower than the maximum possible by the flash in a normal full power dump.

There is another 'higher than sync' option available with certain flash systems called hyper sync or hi-sync. This implementation requires a long flash duration for relatively even light output for the duration of the shutter slit's travel across the image area. This is effectively like continuous light output for 1/200 or slightly longer. But due to how flash output peaks, it's never quite consistent intensity across that timeframe. In any case, the advantage of this method is more efficient use of the strobe's full output, however, the higher the above-sync shutter speed, the narrower shutter slit captures less of this light at a given moment, meaning effective strobe exposure is still reduced relative to normal sync exposures.

Anyway, back to the OP's question - I agree with another suggestion to do some tests. It'll probably be a matter of selecting the correct ambient light exposure, putting the flash in HSS, starting off at an arbitrary manual power output, then adjusting up or down as required.

Nov 28, 2023 at 08:38 AM

EverLearning
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p.1 #13 · p.1 #13 · Trying to understand high speed sync for BIF

Thanks to Brian, Mike, Jeffbuzz, melcat, mike650 and rscheffler for your helpful contributions. All good stuff!

Nov 28, 2023 at 09:08 AM

Norm Shapiro
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p.1 #14 · p.1 #14 · Trying to understand high speed sync for BIF

Having started making photographs in the ‘60’s and still doing it now in the digital era I’m scratching my head over questions like this one from the original poster. We can experiment to get the effect we want very easily with the use of digital recording. The only thing I’ve seen in this tread is the question of batttery life in the flash. Why not just go out and see if you have a problem?

Nov 28, 2023 at 01:40 PM

Imagemaster
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p.1 #15 · p.1 #15 · Trying to understand high speed sync for BIF

Nov 28, 2023 at 02:06 PM

Gochugogi
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p.1 #16 · p.1 #16 · Trying to understand high speed sync for BIF

Norm Shapiro wrote:
Having started making photographs in the ‘60’s and still doing it now in the digital era I’m scratching my head over questions like this one from the original poster. We can experiment to get the effect we want very easily with the use of digital recording. The only thing I’ve seen in this tread is the question of batttery life in the flash. Why not just go out and see if you have a problem?

Hands-on trial and error is a powerful way to learn, especially if you're patient and have the time to fail until you rock. On the other hand, reinventing the wheel is time consuming and it's nice to learn from the collective knowledge and experiences of others. At least you have a solid starting point instead of grasping at straws. Plus, many FM members enjoy sharing their knowledge...

Nov 28, 2023 at 02:15 PM

EverLearning
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p.1 #17 · p.1 #17 · Trying to understand high speed sync for BIF

Imagemaster's raison d'etre is to give people a hard time so I guess I fed the beast today.

Norm, I think you missed/misunderstood part of my question. I have seen info online about fill flash for stationary birds; both to lighten shadows and to put a catchlight in the eye. But there is precious little about using flash for BIF. Experimentation would, eventually, answer my question about "proper" flash ratio but not about flash/sync/hss/BIF (nor about safety of the flash in "cold" temps and battery (in fact, for the former, experimentation could be costly, hence the question)). Gochugogi nailed it with his comment. Being pointed in the general direction for starting trial and error, plus possibly avoiding expensive mistakes, is highly beneficial. There are many highly knowledgeable people here; some of which enjoy sharing their knowledge and hard lessons learned (for which I am always appreciative).

if one doesn't think a question belongs here or shouldn't be asked, please keep in mind that questions are posted with good intent and are aimed at those who like to share and help the growth of fellow photographers. If a question isn't appealing to you, there are literally hundreds of other questions that may be more appealing and up one's alley and whose OP would be grateful for the help. No harm, no foul.

Nov 28, 2023 at 03:02 PM

Zenon Char
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p.1 #18 · p.1 #18 · Trying to understand high speed sync for BIF

I put a lot of time into flash when I prepped for my first wedding. A primary use for High Speed Sync was so you could increase shutter speed past sync speed to balance subject and ambient exposure. The faster the shutter speed the more the pluses the flash has fire which has a real detrimental effect on it's power. Your subjects need to be close. I remember seeing photogs like Syl Arena having 8 to 12 flashes mounted on an array to get enough power to shoot a model during the day while outdoors.

I've always liked this video. Covers flash and distance. Yo may or not find it helpful. Add power loss of HHS.

I've just use flash to freeze my subject.

Here was a little experiment I did. I prefocused and kept the shutter half pressed. As I swept the camera from side to side on an angle and pressed the shutter. The T-shirt was close enough to freeze it.

Nov 28, 2023 at 03:30 PM

Zenon Char
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p.1 #19 · p.1 #19 · Trying to understand high speed sync for BIF

Oh yeah. Those streaks were from the lights on Christmas tree behind the T-Shirt. Fall Off was too great to freeze them. Or too much distance. Whatever lingo works for you.

Nov 28, 2023 at 03:59 PM

jwolfe
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p.1 #20 · p.1 #20 · Trying to understand high speed sync for BIF

With modern editing techniques and sensors I see no point in using fill flash for birds if you are shooting in the correct light. To me you’d be far better off using a longer lens to blur the background and shoot with the sun hitting the bird then trying to blast the thing with fill flash. Even using High Speed Sync you’ll maybe get two or three frames before the flash runs out of power. You’re not gonna get 12 fps for 20 frames or whatever.

Nov 28, 2023 at 04:29 PM

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