Is it possible to delay the flash on a T5i to fire at the end of a long exposure shot

[BillyJack]

I'm wanting to take long exposure shots of dancers and would like the flash to fire at the end of the exposure instead of the begining to increse the depth of field right as the shutter closes. Is that possible using the on camera flash of a T5i and if so what are the settings?

Thanks,

John

[ebiggs1]

Under "Flash Modes" there are these choices, auto mode, fill-in mode, flash OFF mode, rear curtain sync, red-eye reduction.

You want rear curtain sync.  But you really need an off camera flash like the 430EX or 600 EX,

[BillyJack]

Thank you for the reply! Will the Off-Camera flash give me additional functions? On-Camera, under flash controls it gives me only the options for Curtain1 and Curtain2. Curtain1 being normal flash at open, Curtain2 the flash fires at the opening and closing of the shutter. I only want it to fire at the close and have not found a 3rd option. 

[Skirball]

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@BillyJack wrote:

Thank you for the reply! Will the Off-Camera flash give me additional functions? On-Camera, under flash controls it gives me only the options for Curtain1 and Curtain2. Curtain1 being normal flash at open, Curtain2 the flash fires at the opening and closing of the shutter. I only want it to fire at the close and have not found a 3rd option. 

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That doesn't sound right.  It should fire at the beginning or the end, not both.

Off-camera flash gives you much more flexibility in flash placement and control of the flash direction, shape, quality, etc.  It's a very technical type of photography, but one that I find very rewarding.  It's not everybody's cup of tea though.  It's also a bit of a pandoras box, as the more you get into it the more you get - with modifiers and stands and radio triggers.  Now simple little shoots take 30 minutes of prep as you get stuff setup.  That said, you can get photos that are impossible without it.

Off-camera flash comes with it's fair share of complications too.  For example, the expensive Canon 600ex-RT that eBiggs cites above, the flagship of Canon flashes and the first to have integrated radio triggers - can't do second curtain sync through radio triggers.  Go figure.  Learning all these little nuances just takes time and experience.

[BillyJack]

Skirball, that's what I thought too, but sure enough the on-camera fires open and close on the Curtain2 option. 

What I meant by increasing the depth of field (and I may be terming it improperly) is when shooting the dancers I've been setting up low output ambient lights that allow me to capture their movement, but right at the end of the exposure I hit them with a hard light which not only freezes the dancer in exposure, but also brings out the details in the background. I have an old SunPak without a control cable that been using the test button to supply the hard light, but my timing is scarcly perfect and I end up with after trails. When Light Painting stationary subjects what I'm using has been fine, but for motion effect it's lacking proper timing and throwing money out for good off camera flash is sorry to say not an option this close to the hollidays. 

[Skirball]

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@BillyJack wrote:

Skirball, that's what I thought too, but sure enough the on-camera fires open and close on the Curtain2 option. 

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Perhaps you have the flash on TTL (I suppose it's always on TTL for on-camera flash?) and the first flash that you see is actually the pre-flash, and it goes a moment before the shutter actually opens.  The preflash is how the camera judges how much power the flash needs.  Are you actually seeing two images in the final picture?

[Skirball]

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@BillyJack wrote:

What I meant by increasing the depth of field (and I may be terming it improperly) is when shooting the dancers I've been setting up low output ambient lights that allow me to capture their movement, but right at the end of the exposure I hit them with a hard light which not only freezes the dancer in exposure, but also brings out the details in the background. I have an old SunPak without a control cable that been using the test button to supply the hard light, but my timing is scarcly perfect and I end up with after trails. When Light Painting stationary subjects what I'm using has been fine, but for motion effect it's lacking proper timing and throwing money out for good off camera flash is sorry to say not an option this close to the hollidays. 

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Ok cool, you have a bit more going on than I expected (you never know who you're talking to and what kind of experience or setup they have).

Having ambient lights where you can control the direction and quality will help immensly.  I would highly recommend getting a flash to light your subject, and have it triggered by the camera.  What model SunPak is it?  Better yet, what kind of trigger does it have?  It must have a PC port or something?  If that's the case you could sync it via cable or even wireless for not too much money.

Once you get a method to trigger your flash on the second curtain, then I would look at shooting in bulb mode.  That way you can stop the shutter when you want, instead of relying on a long shutter that hopefully stops at a good time.  Do you have a remote shutter release?  It'd be easiest, and you just push it twice quickly (one to open the shutter, one to close).  It's take some experimentation to get it right, but it's doable.

[BillyJack]

My Off-Camera flash is a SunPak Auto511 that I have no control cable for. I've been free handing it, using the "TEST" button to activate the flash for my Light Painting. Up til now that has been sufficient because I'm shooting in pitch black and only wanting to catch a single moment of the subject.

I do have a bare bones basic remote shuttter release (Open, Close, Lock)  but perfer to use my laptop to control the camera for my indoor shots where I can set up on a table. Better preview of the raw shot that way. The dancers will be in a studio, so the laptop will be the controller.

One thing I did not know is, that the first flash in Curtain2 was for metering before the shutter openned. Because it flashed twiced when I selected the option and that's not what I wanted, I did not try it in practicle application. In the video samples I saw online, of course everyone was using Off-Camera flash, I did not see a metering flash in the overview so when mine flashed twice, I just assumed I had the settings incorrect. I'll set up the room here in a bit and see if it does what I'm looking for. Works or not, either way I know I need to buy a new Off-Camera flash.

Thank you so much for your insight and taking the time to help! Today was day one of being on the forum, but I know this place will be a very useful resource as I work to expand my skills.

[TCampbell]

When you use a TTL flash (Canon's E-TTL or E-TTL II) the camera uses a multi-zone metering system (think of an imaginary grid system overlaying your image) and (1) meters with no flash at all, then (2) fires a pre-flash at very low power while simultaneously metering again.  It then compares the difference in each zone between #1 and #2 to determine how much of a difference the flash made.  By doing this it can identify highly reflective surfaces (e.g. mirrors, glass, reflective metals, etc.) and eliminate those from the flash evaluation.  It can also find zones where the flash seemingly made no difference at all (e.g. if there was a light source in that zone... such as a lamp) and elminate those.   Light sources and reflections would ordinarily fool a flash metering system into thinking it had produced enough light ... even if it hadn't.  With those zones safely eliminated it can then compare the difference for each zone between #1 and #2 to determine how much addtional power should be necessary to correctly light them.

It does all of this during the pre-flash.   The shutter is closed when it does this (the light will not affect your image.)

Then the shutter opens and at some point it fires the flash again... only this time using the power level calculated during the pre-flash phase.  Only this second firing of the flash will show up in your image.

If you switch the flash to manual mode, you wont get a pre-flash.

The on-board flash is useful as a "fill" flash (decreasing the severity of shadows) and it can be used as a primary flash IF the subject is reasonably close (e.g. around 10' is fine... 14' feet is a stretch and beyond that... not so great.)

An externally attached speedlite flash can provide significantly more power.  It can also be located off-camera to provide better lighting (on camera lighting is "flat" because there's no highlight/shadow side to any 3D surface... textures look 2D as a result.)

As for "depth of field"... this is a different problem and the flash can help, but there are some caveats.

If you're shooting indoors with only the available light in the room, then you're likely in challenging circumstances and using lenses with wide-open apertures.  Hence the depth of field is fairly narrow.

If you could increase the lighting then you could reduce the aperture opening and increase the depth of field.

But there is a catch.... light exhibits a property sometimes called "fall off".  This is because it follows a rule in physics called the "inverse square law" whereby the intensity of light decreases as the distance from the light source increases.  Each time the distance from the light source increases by the square root of 2, the light intensity is cut in half (exactly half... that's not an approximation.)  E.g. the amount of light illuminating a subject which is 14.1 feet away from the flash will be exactly half as compared to a subject which was only 10' away.  The square root of 2 is approximately 1.41.  So 10 x 1.41 = 14.1.  

This means if you are photographing two subjects... one is 10' away and the other is about 14' away then the more distant subject will only receive half as much light.  Suppose we go to a crazy distance... and we have a flash 100' away.  NOW the second person has to be 141' away before they get half as much light.  This means two subjects within just a few feet of each will not receive "noticeably" different levels of light.

While placing the flash farther from the two subjects will reduce the difference in illumination on your near vs. far subject, built-in flashes cannot handle these larger distances... they don't have enough power.  But an external flash brings more power for you to do this.  

Canon's speedlite model numbers actually provide an indication of their power level.  If you delete the trailing zero from the model number (e.g. in a 430EX II you'd omit the "0" and get "43"... in a 600EX-RT you'd omit one "0" and get "60', etc.) the number you get is the flash "guide number" in meters.  The "guide number" is an indicator of how far the flash can adequately illuminate a subject... but the f-stop and ISO settings you use on the camera will change this.  So the "guide number" uses a baseline ISO of 100 and a baseline f-stop of f/1.  Of course you don't have an f/1 lens but the baseline is used because it makes the math easy. You divide the guide number by the f-stop you are using.  e.g. if you are shooting at ISO 100 and f/8 then you'd divide your guide number (suppose you have a Canon Speedlite 600EX-RT.. that's a guide number of 60 meters) and you'd get 60 ÷ 8 = 7.5 meters.  Convert meters to feet and that works out to 24.6 (about 25').  Of course that's at ISO 100. Bump up to ISO 200 and you can multiply that distance by 1.41... or bump up to ISO stops to ISO 400 and you can double the distance (about 50'... and that's at f/8).

I should caveat that this assumes you are pointing the flash directly at the subject and there are no light modifiers in use (no soft-diffusers, you aren't "bouncing" the flash off a ceiling or wall, etc.)

Here's a Youtube video that might help you understand the light fall-off problem.

[BillyJack]

Thank you Mr. Cambell, believe it or not that all makes perfect sense to me and shall prove helpful in my thinking as I'm setting up my shots.

I've been a sports photographer for a little over 8 years and only a month or so ago became interested in learning light painting. Because I've refined my skills in low and adverse light, the camera setup for light painting was not a challenge. Hard part of that art form was the brush technics and tools to create the effects. With stationary models my hand held flash aimed to capture the subject and cast controlled shadows was relatively simple. Through my research into light paint however, I've also been drawn into other forms of long exposure photography and their technics. This is a HUGH difference in the thought process I'm accustomed to because now I'm controlling the light instead of trying to maximize the existing light. Bits of information the likes you just provided me will prove invaluable.

Thank you again,

John