Flash study. . . Conclusion ???

[aparmley]

OK guys - I need some help here.

I'm going to throw everything I thought I knew about flash out the window and start over. . .

I need a little help in the mean time. On Easter Sunday the sun was out and it made getting even exposures very difficult. I knew this is an ideal flash situation but my lack of true flash understanding made me keep it in the bag.

I kidnapped the Travelocity gnome and his trusty companion and used him as the subject today.

All images with flash used it in high sync mode. My past understanding was that flash can not be used above the high sync shutter speed - I'm pretty sure thats wrong now but can't say I graps why exactly. . .

First images - trying to stay below flash sync speed in AV mode:

http://parmley.smugmug.com/photos/65279740-L.jpg

I didn't care for these results so much. . . I really wanted to shoot with a larger aperture. but I had to open it up because of the brightness of the scene.

So I switch to manual mode. For shits and giggles I came up to 2.8 - adjusted my exposure so I would not over expose the highlights. then I turn the flash on - using the omnibounce diffuser this time - and I was suprised. At 1/1600s it did exactly what I wanted it to do. . . ???

http://parmley.smugmug.com/photos/65279744-L.jpg

Whats the High speed flash sync ceiling of 1/250 or 1/500 in some cases for then? totally confused. . . :confused:

I am now trying to understand why I saw the results I did. I was opertating under the assumption that I had to keep my shutter speeds down around 1/500 to get my flash to work properly. . . So - in fill situations I always had to use smaller apertures and I really didn't care for that too much so I never really used it. . .

I think its clear that I never really fully explored flash before and what ever knowledge I thought I had before has been blown out of the water.

Please feel free to chime in and let me know what I am failing to grasp. . .

Thanks

[cdifoto]

You can sync above 1/250th with any flash that has high speed sync compatibility. The 430EX, 580EX, 550EX, and Sigma EF-500 Super (not the ST) can all do this. You lose range though and the higher the shutter speed, the more severe the loss of range is.

Any other flash can sync at 1/250th on the XT (or is it 1/200th? I forget) and this includes studio strobes.

[aparmley]

You can sync above 1/250th with any flash that has high speed sync compatibility. The 430EX, 580EX, 550EX, and Sigma EF-500 Super (not the ST) can all do this. You lose range though and the higher the shutter speed, the more severe the loss of range is.

Any other flash can sync at 1/250th on the XT (or is it 1/200th? I forget) and this includes studio strobes.

I did not know that. I thought in order use a faster shutter speed you have to change the flash to high sync mode and that allowed you to use 1/250 - 1/500. Man what the hell was I thinking? GXX Damnit Christian! :D

Well none the less I am totally "wrapped" about this - I am going to exploring this further. . . BTW - That last image, 1/1600 + flash - I was blown away with the results. . . Image quality wise - thats what I think I should see! "Light" something else I need to explore further and expand my knowledge, because they weren't kidding - its all about light!

[cdifoto]

I did not know that. I thought in order use a faster shutter speed you have to change the flash to high sync mode and that allowed you to use 1/250 - 1/500. Man what the hell was I thinking? GXX Damnit Christian! :D

Well none the less I am totally "wrapped" about this - I am going to exploring this further. . . BTW - That last image, 1/1600 + flash - I was blown away with the results. . . Image quality wise - thats what I think I should see! "Light" something else I need to explore further and expand my knowledge, because they weren't kidding - its all about light!

High speed sync lets you use anything above the camera's default sync speed, at the loss of range. For the XT it's 1/200th. For the 1 series I think it's 1/250th...although I could be wrong on that too. Point is, it's camera specific and not flash specific. The flash specific part is whether or not high speed sync is available.

[aparmley]

Ok. so I am going to walk through the logic here.

I placed my flash on high sync mode. This allowed me to use however fast a shutter speed I want - ofcourse at the loss of range - light travels at a finite speed, if I stop the travel of light quicker it will not travel as far - makes sense.

I shot in manual mode - Why? Well here I wanted to expose my photo so that the highlights were not blown. in last set of images, the hand rail on the deck was blown at 2.8 until I reach 1/1600s. In the image on the left, you see the result, hand rail not blown - Gnomey underexposed. With high sync mode selected on my flash - it filled Gnomey and his ride with enough flash to even out the exposure.

Here is something I need to keep repeating to myself:
Shutter speed has notthing to do with flash exposure. Shutter speeds only have to do with ambient light exposure - ie the light on the hand rail required 1/1600s to expose properly - hence my exposure.

Taken from the EOS Flash Bible - I guess I missed that part ;)

" This mode is useful for shooting with fill flash outdoors with wide apertures. Normally you can’t shoot outdoors and use fill flash unless you stop down the lens or use very slow film. However, changing film is a nuisance and stopping down the lens increases the depth of field. If you’re shooting a portrait, say, you probably want to blur the background and the only way to do this is to shoot with a wider aperture. But the wider aperture lets in more light, and you can’t compensate by increasing the shutter speed if you then bump up against the camera’s X-sync limit.

FP mode flash solves this problem by letting the shutter speed exceed the X-sync limit and reach the camera’s maximum shutter speed (usually 1/2000 or 1/4000 sec) instead. The primary drawback is that pulsing the light causes a reduction in overall light output and thus range ... Of course, if you’re using FP mode simply for a little fill flash (rather than relying on it to illuminate your subject) then this loss of range shouldn’t be a huge problem."



Ok I feel like I made a big leap forward here today with understanding flash and I'm happy to now know for a fact I can use my flash out doors to fill indepented of my shutterspeed. . . Thats good to know. . . I should have learned this a while ago but at least now I know.

[ktixx]

anybody know a good link for a tutorial on using manual flash? Speicifically dealing with guide numbers, etc?

[aparmley]

anybody know a good link for a tutorial on using manual flash? Speicifically dealing with guide numbers, etc?

The two most useful links I've been given are the following:

http://photonotes.org/articles/eos-flash/
http://www.planetneil.com/faq/flash-techniques.html

[Bluedog]

And to think lots of people will tell you this piece of Tupperware is useless outdoors for fill-flash. I'd like to see you post the Omni Bounce results over at POTN.

[aparmley]

And to think lots of people will tell you this piece of Tupperware is useless outdoors for fill-flash. I'd like to see you post the Omni Bounce results over at POTN.

I started my session with out it and threw it on and was happy with the results!

POTN member don't like the omni bounce outdoors for fill ? the last three weddings I went to all three of the WP used them. . . at least one of them has to know something I should think. . .

I should do a comparison of no flash, fill flash and omni bounce fill flash and post it over there huh??? LOL sounds like a hum-dinger of a good time. . . I'll do something tomorrow.

[cwphoto]

anybody know a good link for a tutorial on using manual flash? Speicifically dealing with guide numbers, etc?

Manual flash is pretty easy. At full power you simply divide the aperture value into the GN for correct subject distance. This will expose the subject correctly using flash only and you will need to take ambience into account.

[cwphoto]

High speed sync lets you use anything above the camera's default sync speed, at the loss of range. For the XT it's 1/200th. For the 1 series I think it's 1/250th...although I could be wrong on that too. Point is, it's camera specific and not flash specific. The flash specific part is whether or not high speed sync is available.

All EOS-1 series are 1/250s with the exception of the original EOS-1D at 1/500s.

[cwphoto]

Ok. so I am going to walk through the logic here.

I placed my flash on high sync mode. This allowed me to use however fast a shutter speed I want - ofcourse at the loss of range - light travels at a finite speed, if I stop the travel of light quicker it will not travel as far - makes sense.

Not quite. A focal plane shutter typically has two curtains which control shutter speed. At low shutter speeds, the first curtain opens up all the way and then the second curtain starts to close sometime later (depending on the selected shutter speed). However for faster shutter speeds, the second curtain actually has to start closing before the first curtain has fully opened, thus the entire frame is never fully open at any one point during exposure.

The faster the shutter speed the closer the second curtain is to following the first curtain - an easy way to think of it is as a slit which travels across the focal plane. The faster the shutter speed the narrower the slit.

Drawing from this, the maximum speed at which the camera can fully open the focal plane during exposure equates to the maximum flash sync speed.

For normal flash photography, using the flash at low shutter speeds is simple:
1) first curtain opens all the way
2) flash fires
3) second curtain starts to close some time later.

However using a normal flash at higher shutter speeds will result in a partially exposed image:
1) first curtain starts to open
2) second curtain starts to close
3) first curtain open all the way
4) flash fires
5) second curtain close all the way
The problem here is that the second curtain has already "closed off" part of the focal plane when the flash has fired, so only some of the scene gets exposed by flash.

I'll give you a practical example; I did Santa photography years ago as one of my first jobs. The camera we were using (think Pentax K-1000) had a sync speed of 1/125s. My colleague accidently set the speed for 1/250s. All the shots came out with one-half exposed correctly and one-half black!:(

Now for high-speed flash, what happens is that the manufacturers designed the flash duration to exceed the shutter speed. Normally electronic flash only lasts for around 1/20,000s - 1/50,000s. To make flash photography work with shutter speeds which exceed the flash sync speed, this duration would need to equal the flash sync speed as a minimum; say 1/250s - around a ten times increase in duration.

Complicating things further, is the fact that the slit created by the first and second curtains is now acting like an aperture with regard to the effect of light intensity. So even though the flash has to last for a lower duration for the really high shutter speeds, the correspondingly narrower slit means that it has to be much more intense in order to maintain correct exposure.

Related: second-curtain sync. Normally the flash will fire as soon as the first curtain is open. Second-curtain sync means that the flash fires just before the second curtain closes. A little tip: dragging the shutter (using longer shutter speeds with flash) is best used with second-curtain sync - as the fully exposed subject will look like it's in front of the "drag". In fact, for weddings I always use second-curtain sync, even little things like when the guests throw rice upon exit of the church at a greek wedding - with second-curtain sync the rice "comets" will appear that they are approaching the subject (ie; the "tail" will be behind the direction of travel).

BTW. One reason that medium format cameras (such as Hasselblad, Rolleiflex, Bronica etc) were popular with wedding photographers is the fact that most lenses for these models have a leaf shutter (a shutter which looks like an aperture opening/closing rather than a focal plane shutter).

Advantage: flash sync at all shutter speeds (shutter is open all the way at moment of exposure).
Disadvantage: fairly low maximum shutter speeds, typically 1/500s (although Rollei have some lenses which go to 1/1000s).

[aparmley]

Not quite. A focal plane shutter typically has two curtains which control shutter speed. At low shutter speeds, the first curtain opens up all the way and then the second curtain starts to close sometime later (depending on the selected shutter speed). However for faster shutter speeds, the second curtain actually has to start closing before the first curtain has fully opened, thus the entire frame is never fully open at any one point during exposure.

The faster the shutter speed the closer the second curtain is to following the first curtain - an easy way to think of it is as a slit which travels across the focal plane. The faster the shutter speed the narrower the slit.

Drawing from this, the maximum speed at which the camera can fully open the focal plane during exposure equates to the maximum flash sync speed.

For normal flash photography, using the flash at low shutter speeds is simple:
1) first curtain opens all the way
2) flash fires
3) second curtain starts to close some time later.

However using a normal flash at higher shutter speeds will result in a partially exposed image:
1) first curtain starts to open
2) second curtain starts to close
3) first curtain open all the way
4) flash fires
5) second curtain close all the way
The problem here is that the second curtain has already "closed off" part of the focal plane when the flash has fired, so only some of the scene gets exposed by flash.

I'll give you a practical example; I did Santa photography years ago as one of my first jobs. The camera we were using (think Pentax K-1000) had a sync speed of 1/125s. My colleague accidently set the speed for 1/250s. All the shots came out with one-half exposed correctly and one-half black!:(

Now for high-speed flash, what happens is that the manufacturers designed the flash duration to exceed the shutter speed. Normally electronic flash only lasts for around 1/20,000s - 1/50,000s. To make flash photography work with shutter speeds which exceed the flash sync speed, this duration would need to equal the flash sync speed as a minimum; say 1/250s - around a ten times increase in duration.

Complicating things further, is the fact that the slit created by the first and second curtains is now acting like an aperture with regard to the effect of light intensity. So even though the flash has to last for a lower duration for the really high shutter speeds, the correspondingly narrower slit means that it has to be much more intense in order to maintain correct exposure.

Related: second-curtain sync. Normally the flash will fire as soon as the first curtain is open. Second-curtain sync means that the flash fires just before the second curtain closes. A little tip: dragging the shutter (using longer shutter speeds with flash) is best used with second-curtain sync - as the fully exposed subject will look like it's in front of the "drag". In fact, for weddings I always use second-curtain sync, even little things like when the guests throw rice upon exit of the church at a greek wedding - with second-curtain sync the rice "comets" will appear that they are approaching the subject (ie; the "tail" will be behind the direction of travel).

BTW. One reason that medium format cameras (such as Hasselblad, Rolleiflex, Bronica etc) were popular with wedding photographers is the fact that most lenses for these models have a leaf shutter (a shutter which looks like an aperture opening/closing rather than a focal plane shutter).

Advantage: flash sync at all shutter speeds (shutter is open all the way at moment of exposure).
Disadvantage: fairly low maximum shutter speeds, typically 1/500s (although Rollei have some lenses which go to 1/1000s).

Thanks for the explanation! I had no clue. . .

Complicating things further, is the fact that the slit created by the first and second curtains is now acting like an aperture with regard to the effect of light intensity. So even though the flash has to last for a lower duration for the really high shutter speeds, the correspondingly narrower slit means that it has to be much more intense in order to maintain correct exposure.

So is this why High sync flash modes use multiple strobes for flash at high sync speeds? I was reading that high sync mode isn't good for stopping motion because of the multiple strobes. . . ??

Thanks again.

[cwphoto]

So is this why High sync flash modes use multiple strobes for flash at high sync speeds? I was reading that high sync mode isn't good for stopping motion because of the multiple strobes. . . ??

Thanks again.

I haven't read that before but it would make sense to me.:)

[aparmley]

I haven't read that before but it would make sense to me.:)

EOS flash bible excerpt:

" Synchronizing flash exposure with both curtains of focal plane shutters was as much of a problem in the days of single-use flash bulbs as it is today with electronic flash units. For that reason flash bulbs designed to work with focal plane shutters were developed. Such bulbs produced light quite rapidly and sustained their light output for the full duration of the shutter opening. They were called FP bulbs.

With E-TTL Canon introduced an implementation of an electronic FP flash mode, which is a way of circumventing the X-sync limitation in certain cases, and another flash technology pioneered by Olympus. FP flash lets you take flash photos at any shutter speed you like, and works by pulsing the flash bulb at an extremely high rate - 50 KHz - simulating constant light at the cost of total light output. FP stands for “focal plane,” by analogy to the old FP flash bulbs, though Mark Overton memorably refers to it as “fast pulse” mode in his FAQ, since that’s exactly how it works today.

This mode is useful for shooting with fill flash outdoors with wide apertures. Normally you can’t shoot outdoors and use fill flash unless you stop down the lens or use very slow film. However, changing film is a nuisance and stopping down the lens increases the depth of field. If you’re shooting a portrait, say, you probably want to blur the background and the only way to do this is to shoot with a wider aperture. But the wider aperture lets in more light, and you can’t compensate by increasing the shutter speed if you then bump up against the camera’s X-sync limit.

FP mode flash solves this problem by letting the shutter speed exceed the X-sync limit and reach the camera’s maximum shutter speed (usually 1/2000 or 1/4000 sec) instead. The primary drawback is that pulsing the light causes a reduction in overall light output and thus range.

When you have FP mode engaged you typically get about a third less range than you would if you were shooting with normal flash. With a powerful flash unit like the 580EX this may not be a big problem, particularly if your flash subject is fairly close to you. But this loss of range could be a serious impediment if you’re using a smaller flash unit (eg: the tiny 220EX), if the subject is far away, or if you’re using slow film. Of course, if you’re using FP mode simply for a little fill flash (rather than relying on it to illuminate your subject) then this loss of range shouldn’t be a huge problem.

Note an important point - FP mode does not help you freeze motion; the name “high-speed sync” is a bit misleading in this regard. Normal flash photography is very good at freezing motion on film, since a burst of electronic flash is so incredibly brief. When a scene is illuminated primarily by a really brief flash of light then you aren’t going to get much motion blur - it’s almost as if you used an incredibly high shutter speed in the thousandths of a second. However when you use FP mode flash, the flash unit pulses the light output over a longer period of time in order to simulate a longer-duration burst of light. Since the flash burst is no longer particularly brief you can’t freeze motion as easily, even with high shutter speeds. The mode is called high-speed sync since it lets you synchronize flash exposure with high shutter speeds, not that it lets you take high-speed photographs. "

Maybe that answers both our questions. . . ?

[ReF]

damn, you know a lot CW

parm, i don't shoot a whole lot of people pics outdoors on sunny days but i've had good results shooting with the camera in AV/TV mode and the flash on ETTL, high speed sync mode. the only problem is the frickin sigma flash drops out of high speed sync mode if the shutter speed ever drops to 1/200 or lower (even if you don't take the shot). i don't know if it's any different for the canon flash.

when there is enough time for two test shots, i set the camera and flash in manual, set the camera to expose for the background, etc., and the flash to expose for the subject.

to me it seems a lot easier shooting at night w/flash cuz settings stay more consistent (being able to stay in manual mode) and i don't have worry about high speed flash sync.

[cdifoto]

damn, you know a lot CW

parm, i don't shoot a whole lot of people pics outdoors on sunny days but i've had good results shooting with the camera in AV/TV mode and the flash on ETTL, high speed sync mode. the only problem is the frickin sigma flash drops out of high speed sync mode if the shutter speed ever drops to 1/200 or lower (even if you don't take the shot). i don't know if it's any different for the canon flash.

when there is enough time for two test shots, i set the camera and flash in manual, set the camera to expose for the background, etc., and the flash to expose for the subject.

to me it seems a lot easier shooting at night w/flash cuz settings stay more consistent (being able to stay in manual mode) and i don't have worry about high speed flash sync.

I can't speak for the other models since I didn't retain any of my research on 'em, but the 580EX stays in high speed no matter what the shutter is when you enabled it. It doesn't lose power when at 1/200th or below...but it doesn't drop out of the mode either. Makes it kinda nice actually.

[aparmley]

I can't speak for the other models since I didn't retain any of my research on 'em, but the 580EX stays in high speed no matter what the shutter is when you enabled it. It doesn't lose power when at 1/200th or below...but it doesn't drop out of the mode either. Makes it kinda nice actually.

I can confirm this concerning the 550EX - It stays in high sync mode. . .

[ReF]

I can't speak for the other models since I didn't retain any of my research on 'em, but the 580EX stays in high speed no matter what the shutter is when you enabled it. It doesn't lose power when at 1/200th or below...but it doesn't drop out of the mode either. Makes it kinda nice actually.

that's cool, and gives me another reason to upgrade flashes. thanks for the info. feel kinda lame when i'm shooting people pics on the go, the flash drops out of FP mode (overexposure from 1/200 SS) and i gotta stop them and say "oh wait, wait, that one didn't come out, you gotta go back so we can do it again." and you KNOW it's gonna happen more than once on a day out

[cdifoto]

that's cool, and gives me another reason to upgrade flashes. thanks for the info. feel kinda lame when i'm shooting people pics on the go, the flash drops out of FP mode (overexposure from 1/200 SS) and i gotta stop them and say "oh wait, wait, that one didn't come out, you gotta go back so we can do it again." and you KNOW it's gonna happen more than once on a day out

Yeah it wasn't one of my upgrade reasons but now that I actually have that feature, I remember all the PITA moments with the Sigma :eek:

[ReF]

I can confirm this concerning the 550EX - It stays in high sync mode. . .

nice. i've read that the canon flashes are also a lot more consistent in ETTL mode than my sig, so i'm thinking AV mode + ETTL mode + FP mode + a little EV adjustment here an there on the flash and everything's good. btw, what mode was the flash in when you took the test shots?

[aparmley]

nice. i've read that the canon flashes are also a lot more consistent in ETTL mode than my sig, so i'm thinking AV mode + ETTL mode + FP mode + a little EV adjustment here an there on the flash and everything's good. btw, what mode was the flash in when you took the test shots?

I had the flash in ETTL mode, but I shot with camera in M. When I did shoot with flash I was in AV mode most of the time - but realized in doors that I didn't always get the exposures I wanted so I'd shoot in M for better bounce results. . . I see a trend forming now that I will most likely only shooy in M mode in days to come. . . now that I'm more comfortable with everything I think M is going to be the way to go for me in the future. . . I like the awareness one must have when using the camera in M mode - helps you slow down think a little more. . .

[ReF]

Yeah it wasn't one of my upgrade reasons but now that I actually have that feature, I remember all the PITA moments with the Sigma :eek:

yeah someday i'm gonna have everything OEM, even the 15mm fishy. not sure if the canon is any better but it should focus faster. don't think the fishy nets any $$$ used though

[ReF]

I like the awareness one must have when using the camera in M mode - helps you slow down think a little more. . .

i like that the equipment's random exposures don't get tp screw up the shot :D


I had the flash in ETTL mode, but I shot with camera in M. When I did shoot with flash I was in AV mode most of the time - but realized in doors that I didn't always get the exposures I wanted so I'd shoot in M for better bounce results. . . I see a trend forming now that I will most likely only shooy in M mode in days to come. . . now that I'm more comfortable with everything I think M is going to be the way to go for me in the future. . . I like the awareness one must have when using the camera in M mode - helps you slow down think a little more. . .

maybe it's because the sig flash doesn't communicate with the camera very well, but i've kinda settled on M mode (both camera and flash) for pretty much all flash photography except shooting ppl in bright sunlight. there i can't deal with the varying shutter speeds, shadows, angles of the sun in sky, in front, in back, to side of the subject, etc. fast enough in M.

[aparmley]

i like that the equipment's random exposures don't get tp screw up the shot :D




maybe it's because the sig flash doesn't communicate with the camera very well, but i've kinda settled on M mode (both camera and flash) for pretty much all flash photography except shooting ppl in bright sunlight. there i can't deal with the varying shutter speeds, shadows, angles of the sun in sky, in front, in back, to side of the subject, etc. fast enough in M.

Well if the people are moving like kids, nope you can't do it - gotta have AV mode. . . but if you have the time - its worth the time I'm thinking =)

[cdifoto]

It's usually M indoors and Av outdoors with me when the flash is on. Without flash, it's usually Av all the way. I'm generally lazy and aperture is my main concern. EV can be used where necessary with no flash outdoors quicker IMO. Even though it's all the same. heh.