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Archive 2004 · Lock synch speed at 1/200 in AV mode

EmJayPrice
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p.1 #1 · Lock synch speed at 1/200 in AV mode

When and why would I want to do this??

Thanks again...Mike

Jul 08, 2004 at 04:32 PM

nutek
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p.1 #2 · Lock synch speed at 1/200 in AV mode

I learnt about this a few months ago too.
Setting to 1/200 fixed sync flash allows you to:

have a fast enough shutter speed for most subjects while taking with flash in AV (otherwise shutter speed would be dependent on ambient light conditions, which means very slow/long exposures usually in the dark), and

also control depth of field in flash subjects while in AV mode. For example if you are taking a picture of a group seated around a round table. You will need to decrease your aperture size in order for everyone to remain sharp. Decreasing aperture size means increasing exposure time (in AV mode), so by fixing shutter at 1/200s and you setting the aperture, this forces the camera flash to fire for the subject only ala P-mode (but with everything else controlled by you).

I have found this most useful when shooting weddings and indoor group shots. Although background/ambient objects may not show up, at least you ensure your main subject(s) are all in sharp focus and correctly exposed.

Jul 08, 2004 at 05:17 PM

edtang
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p.1 #3 · Lock synch speed at 1/200 in AV mode

Not sure what the reason is, but I would *highly* suggest using M mode for flash, I find it much simpler... unless you want to do fill-in flash. Then I would typically use A or TV mode so it meters normally (no 1/200 lock) and dial down -2/3 flash.

Jul 08, 2004 at 05:41 PM

nutek
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p.1 #4 · Lock synch speed at 1/200 in AV mode

AV mode with 1/200 fixed sync is similar (i.e. gives the same results) as M mode.. So there's nothing wrong with using either mode. I use AV mode because it is one less thing to remember to change back to when I switch off the flash.

Jul 08, 2004 at 06:48 PM

drumminj
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p.1 #5 · Lock synch speed at 1/200 in AV mode

Perhaps I'm hijacking the thread here, but I have a question about using 'M' mode with flash. In Av mode, it determines flash output based on 'correct exposure' of the background (ignores exposure compensation). So if EC is set to any value other than zero, it doesn't affect the flash output. Is this correct?

If so, how is flash output determined in M mode? Is it based on the exposure you'd get from the manual settings, or 'correct exposures' of the background, like in Av?

Or am I completely off base? Yes, I've read both 10D and my 420ex manual, as well as the photonotes(I think this is where that article is) article on the E-TTL system.

J

Jul 08, 2004 at 07:14 PM

Ron Warren
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p.1 #6 · Lock synch speed at 1/200 in AV mode

Indoors.......
Say I put the camera in the Manual mode. I set it to f-8 @1/30th sec. The 1/30th will give me some background illumination due to the slower shutter. The flash "sensor" will determine when "f-8 worth" of light is reflected off the subject.
If you are using an EOS speedlight you will not be able to control this as easily as I make it sound but it is the best way to shoot. A good bounce will help to.
A good Auto flash system will give you very consistent results.

Jul 08, 2004 at 08:19 PM

edtang
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p.1 #7 · Lock synch speed at 1/200 in AV mode

drumminj wrote:
If so, how is flash output determined in M mode? Is it based on the exposure you'd get from the manual settings, or 'correct exposures' of the background, like in Av?

The flash will automatically determine the correct output of the flash at the center focus point (i think) using eTTL. So whatever the flash meters, it will output the correct amount of flash, unless you tell it to use flash compensation.

The other settings (aperture, shutter) simply affect how the rest of the picture is affected by ambient light. Use the internal meter to determine what manual settings you want to set.

Understand?

For example. Say I'm taking a pic of someone in a dim room. I set M mode to 1/200 f/5.6, the person is well lit, but the room is dark. Now I set it to 1/30 f/2.8, now the person is still well lit, but the room is now bright.

On a side note, ETTL is not a very easy system to use... *definetly* not just a point and shoot flash. The only way to get good consistent results is to keep using Flash Exposure Lock over the place you want properly exposed. (ie, use FEL on someone's face, then recompose to include the rest of them perhaps wearing a black shirt or something tricky for ETTL).

Jul 08, 2004 at 10:19 PM

drumminj
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p.1 #8 · Lock synch speed at 1/200 in AV mode

edtang wrote:
The other settings (aperture, shutter) simply affect how the rest of the picture is affected by ambient light. Use the internal meter to determine what manual settings you want to set.

Understand?

Yes. And no. I understand the effect this has on the background. What I don't understand is the effect is on the exposure of the subject, as well as the flash output.

I generally use Av mode. When I did some quick tests a while back, it seemed that, without any FEC, if I dialed in EC to +1, obviously the background was more brightly lit, but the subject was as well. This indicates to me that the E-TTL system determines flash output not on the actual shutter and aperture values, but on the "ideal" ones. But perhaps my tests were flawed, or I mis-interpreted?

For example. Say I'm taking a pic of someone in a dim room. I set M mode to 1/200 f/5.6, the person is well lit, but the room is dark. Now I set it to 1/30 f/2.8, now the person is still well lit, but the room is now bright.

I understand the effect the different settings have on the exposure of the background. I assume that in both scenarios, the exposure of the subject is indentical? However, in the second case, the flash/ambient ratio is lower? So, in this case, E-TTL figures out what the exposure of the subject would be with ambient light and the given aperture and shutter settings, and sets power output to properly expose the subject. Is this how it behaves? That seems contrary to the behavior I've observed in Av mode, but again, maybe I misinterpreted the results or my test was flawed. I don't use the flash all that often, and haven't had time to really set up and do some in-depth testing.

J

Edited by drumminj on Jul 09, 2004 at 08:43 AM GMT

Jul 09, 2004 at 08:54 AM

tungsten
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p.1 #9 · Lock synch speed at 1/200 in AV mode

I tend to shoot most of my indoor shots these days w/ synch locked at 1/200 and shoot w/ apertures ranging from 5.6 - 8. My lens (older 28-105) is just not as sharp as I'd like when opened wider so keeping it stopped down is important. Without synch locked, though, my shutter speeds are too low for my unsteady hands to use.

The flash, a 420ex, is always bounced off of the ceiling and with my Omnibounce attached. I rarely - if ever - shoot with the flash straight on.

Is that the right way to use it? Unsure! But after lots of experimentation it is the best way for me to capture the shot as I'd like. Until I splurge and have nothing but fast, L primes, that is, or move to fully manual mode. (I'm just about there with daylight shots, but dim w/ flash is still too much.)

I'd have to agree with edtang's comment about E-TTL not being easy to use - though intuitive might be a better word than easy. Once you "get it" the system makes sense.

Jul 09, 2004 at 09:15 AM

edtang
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p.1 #10 · Lock synch speed at 1/200 in AV mode

drumminj wrote:
I generally use Av mode. When I did some quick tests a while back, it seemed that, without any FEC, if I dialed in EC to +1, obviously the background was more brightly lit, but the subject was as well. This indicates to me that the E-TTL system determines flash output not on the actual shutter and aperture values, but on the "ideal" ones. But perhaps my tests were flawed, or I mis-interpreted?

Not sure exactly what you are saying, but yes, ETTL determines flash output based on the subject metered, which are affected by the actual shutter/aperture values. But you don't need to worry about that, no matter what shutter/aperture values you set for the background, the ETTL will put out the same amount of output each time, in theory.

I understand the effect the different settings have on the exposure of the background. I assume that in both scenarios, the exposure of the subject is indentical?

Yes, the exposure of the subject should be identical (though different aperture values will affect the DOF).

However, in the second case, the flash/ambient ratio is lower? So, in this case, E-TTL figures out what the exposure of the subject would be with ambient light and the given aperture and shutter settings, and sets power output to properly expose the subject. Is this how it behaves? That seems contrary to the behavior I've observed in Av mode, but again, maybe I misinterpreted the results or my test was flawed. I don't use the flash all that often, and haven't had time to really set up and do some in-depth testing.

Yes, this is how I believe it behaves. The flash output should be the same (though with a longer exposure ambient light may also change how your subject looks).

Using Av (or Tv) mode with flash, without the lock, should behave the same as Av (Tv) mode without flash. It should always meter ambient light and set the shutter speed accordingly. The flash is just a system on top of that, determining output with it's own ETTL system. This may not be good in many situations, especially dark ones. If you're using Av (no lock) in a dark room, it will probably choose a *really* slow shutter speed based on ambient light, and thus will create blur (then the flash will freeze the subject on top of that).

edtang

Jul 09, 2004 at 09:39 AM

drumminj
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p.1 #11 · Lock synch speed at 1/200 in AV mode

edtang wrote:
Not sure exactly what you are saying, but yes, ETTL determines flash output based on the subject metered, which are affected by the actual shutter/aperture values. But you don't need to worry about that, no matter what shutter/aperture values you set for the background, the ETTL will put out the same amount of output each time, in theory.

What I'm saying is that, for a fixed aperture, if I use EC to give me two different shutter speeds, it appears that the flash output is fixed as well. Therefore, if the EC I dial in results in a slower shutter speed, the subject is overexposed because of the flash. Does that make sense?

Most everything else you said makes sense. I think you and I are using slightly different terminology, but in theory, I think I understand how things should behave. Bottom line, I suppose I just need to get out there and play and isolate variables to see exactly what effect they have on the image.

Yes, this is how I believe it behaves. The flash output should be the same (though with a longer exposure ambient light may also change how your subject looks).

Are you saying the flash output is constant regardless of the exposure due to ambient light?

Using Av (or Tv) mode with flash, without the lock, should behave the same as Av (Tv) mode without flash.

Depends on what metering mode you're using, I believe. If you're using evaluative, it meters differently when a flash is being used.

I'm sorry if it seems I'm haggling over minor points. It's just these minor nuances that I don't quite understand. In practical use, they don't affect me that much, but I'd like to understand how the system will react in certain situations.

Thanks very much for taking the time to try to explain these things.

J

Jul 09, 2004 at 09:51 AM

edtang
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p.1 #12 · Lock synch speed at 1/200 in AV mode

drumminj wrote:
What I'm saying is that, for a fixed aperture, if I use EC to give me two different shutter speeds, it appears that the flash output is fixed as well. Therefore, if the EC I dial in results in a slower shutter speed, the subject is overexposed because of the flash. Does that make sense?

I think it is overexposed from ambient light because of the longer exposure, not because the flash has fixed output. I think I was using the wrong phrase "same power output" maybe "same flash exposure" would be better. ETTL will determine how much flash to put out based the flash metering of a subject, so EC should not affect that. ie. if you shoot one shot at f/2.8 and another at f/4, the ETTL should know to double the flash output resulting in the same flash exposure.

Are you saying the flash output is constant regardless of the exposure due to ambient light?

I think "constant" isn't the right word. Let's say the flash output and metering is independent to the ambient light. ie. same subject shot under different shutter/aperture should be lit almost identical when using flash.

Depends on what metering mode you're using, I believe. If you're using evaluative, it meters differently when a flash is being used.

I think you're right on this one, but it seems to be just a slight difference.

Jul 09, 2004 at 10:22 AM

drumminj
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p.1 #13 · Lock synch speed at 1/200 in AV mode

Thanks for helping clear all this up. Once I get my camera and flash back from Canon factory service, I'll have to take some time to formally confirm all of this. I assumed this behavior would be the case, but never saw it documented anywhere.

Oh, and sorry for hijacking the thread

I actually couldn't think of a use for locking the sync speed either, so I've learned a lot here.

J

Jul 09, 2004 at 07:26 PM

edtang
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p.1 #14 · Lock synch speed at 1/200 in AV mode

drumminj wrote:
Thanks for helping clear all this up. Once I get my camera and flash back from Canon factory service, I'll have to take some time to formally confirm all of this. I assumed this behavior would be the case, but never saw it documented anywhere.

Oh, and sorry for hijacking the thread

I actually couldn't think of a use for locking the sync speed either, so I've learned a lot here.

J

So our discussion is finally over? *whew*

Yeah, I see no point in using the locked sync speed either, just use manual. Good luck with your camera and service!

edtang

Jul 09, 2004 at 08:01 PM

drumminj
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p.1 #15 · Lock synch speed at 1/200 in AV mode

edtang wrote:
So our discussion is finally over? *whew*

Well, I can ask another question based on something you said

I was going to just test it later, but since you seem to enjoy the discussion so much....You mentioned that I may have ended up with an overexposed subject in my tests because I simply overexposed the background - assuming the subject was at least as lit as the background (because I was using +1 EC). In this case, would the flash decide to not fire? If the subject is properly exposed, does the flash decide it's not needed? Or will it ALWAYS fire (assuming "auto-reduce" is turned off), and just use the minimum output?

I'm sure I could just test this myself, but seeing that my camera is in UPS's hands right now, well...

Sorry if this has been a challenging discussion. Sometimes I can be dense on certain things.

J

Jul 09, 2004 at 08:14 PM


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