External/Internal Flash Question

[ThomasL]

Since I got my Canon Off-Camera shoe for the external flash, one question is on my mind...

Wouldn't it be great if you could set the camera to use both the internal and hotshoe=connected flash at the same time?

I wonder if there are technical reasons why both flashes can't be fired at the same time, or if nobody ever thought of that?!

[BruceW]

Yeah I often think along those lines. I am sure Canon considered it but the difficulty may be controlling the power levels of the 2 flashes. The alternative is of course to use a slave unit to trigger the external flash from the internal flash, but you have to do the calculations. Trial and error is a good option with digital.

Canon have catered fo multiple flash photography by using wireless remote control, requiring either the 550EX or the ST-E2 as the transmitter.

Slave units a cheap compared to these Canon options.

Bruce

[ThomasL]

BruceW wrote:
The alternative is of course to use a slave unit to trigger the external flash from the internal flash, but you have to do the calculations. Trial and error is a good option with digital.

...

Slave units a cheap compared to these Canon options.

Bruce

Hi Bruce, thanks for your response. Slave units would be a good/cheap solution, however because Canon uses a pre-flash which unfortunately triggers the (cheap) slave, this doesn't work :( If at least that could be turned off...

Perhaps you are right and it is difficult to control the power of two flashes, but I still think it should be fairly easy, even to set both flashes to the same level if they are (Canon) controllable, or full power to the external flash if it is not controllable.

Anyway... just wondering.

[BruceW]

Thomas,

You can turn the pre flash off. In fact in it is always off in M mode.

You can turn it off in Av and Tv mode in the Menu. ie. Check the table on page 204 of the manual and look at "Flash Adjust" just below mid page. It refers to page 100 for details.

When I find my slave unit I will give it a go.


Bruce

[tonygamble]

Bruce.

I see references to flash.

I see no reference to pre-flash.


Tony

[BruceW]

Tony,

On page 101, under the heading of "Compensating the Flash Output", there is a hint that the preflash does not fire whenever the flash is set in a mode which allows manual control of the power level. It basically states output can be controlled in 3 steps, starting from FULL.

Its probably not worded the best in the manual, and I have an idea of what to expect based on using SLRs with flash over the years.

To put my interpretation of the manual, "Flash Adjust" is a menu control that sets the flash in either manual mode or auto mode. In many camera modes this control is not offered and defaults to one or the other, as per page 204. ie. The menu option of Flash Adjust is not shown. The only camera modes that allow both options are Av and Tv. Hence these are the only 2 cases where "Flash Adjust" appears in the menu. I interpret; "On" to mean Auto mode and "Off" to mean Manual mode.

So what is the difference between auto and manual, I hear you ask. Maybe not, but I will describe my interpretation of that as well.

In Auto flash mode, the camera is deciding how much light is required from the flash, for the set apeture. It does this by using the preflash, taking a reading of the reflected light and then firing the flash again with the power/duration required for correct exposure. In addition the flash compensation descibed on page 100 can allow you to add or subtract from the camera determined required flash power.

In Manual flash mode, you calculate the required flash power. You do this knowing, the GN of the flash, the distance from camera/flash to subject and the aperture.
You can control all 3 of these variables. You control the GN by using the procedure on page 101. Note, the picture on page 101 shows FULL on the far right. So unlike the Auto flash mode, you cannot add and subtract, just subtract.

Another thing you could note, is that with the internal flash, there are 3 power levels. It's not clear what they are, but probably; "FULL", "HALF" "QUARTER". This then relates to the GN value. If you connect an external flash, the screen looks different to that on page 101. You have much more control in this case. (ie. In addition to the above, there are; 1/8th and 1/16th, and also 3 steps between each level.

In case it wasn't apparent from my description above, the procedure on page 100 is almost identical to the one on page 101. The main difference comes about due to the flash being in Auto mode (page 100) or Manual mode (page 101), before starting the procedure.

Well that's my untested theory. If I am correct, then using the procedure on page 101, will disable preflash. The human operator adjusts the flash power, if FULL is more than required, and a slave flash can be fired from the internal flash. This is where calculations come into play, because you probably want the slave flash to present more light than the internal flash, and from one side.


Bruce

[DigPic]

Bruce, thanks for your ideas. Seems there is lots of testing we all need to do to get 2 flashes working with the ol'g3. I am going to start experimenting with a little set-up to see if I can recreate my ol studio 3 and 4 light set-ups. Nice weather may put this on back burner for a long time though! :)

[ThomasL]

Bruce, thanks for your responses, after reading somewhere that e-TTL can not be turned off I didn't even think about checking the "manual" (booklet and function). I am going to get a little slave trigger and then start playing again! The power of the external flash can probably be adjusted by adding paper/diffusers in front of it.
Thanks again...

[BruceW]

I found my slave unit and have done a couple of quick tests. It worked as expected. I set the camera in manual mode, at F8, 1/60th sec. The camera was about 5 ft away from subject and flash was full power.


The second flash was a cheap manual flash with a GN of 16m at ISO 100. It was also about 5 feet away but from the left side. The result was reasonable, but I have not been able to load to a PC yet, since my house was burgled yesterday and they stole my PCs. Hadn't backed up for 2 months, so not happy about all the photos I lost. I had the G3 with me at the time.

The test needed either more light from the internal flash or less from the 2nd flash. Moving the 2nd flash further back did not work because the slave was not able to pick up the first flash. I have another flash I tried using but it would not connect to the slave. I may look for an adaptor.


Bruce

[ThomasL]

Bruce,

I am very sorry to hear what happened to you. Computers are replaceable, but photos and memory usually not...

Rather than moving the second flash away from the subject, do you think one could add diffusers (paper?) to reduce the flash power? Or bounce it off something? Of course, it then depends on the reflectivity of the subject... but "film is cheap" these days to do a lot of trial & error.

[tonygamble]

Bruce,

I think we both find those instructions on pages 100 and 101 pretty hard to follow.


I wasted a lot of time trying to get my G3 to work with an on camera 550 gun triggering several off camera 550's.

The gun on the camera produced a sequence of three, maybe four, pre-flashes. It was horrendous and quite intolerable for any portraiture. Regardless of what Canon say you cannot turn off the white bulb in the gun on the camera.

I then bought the ST triggering device. That has no white bulb so it could not do a pre-flash. However, it did make the remote guns pre-flash. The saving factor was that (a) they only did a quick flash and (b) they were not sitting just above the lens into which the sitter was probably looking.

However, I could not get the 'ratios' to work - so had to rely on moving the lights back and forward. As the camera was in Manual mode (the only safe way you can shoot that sort of flash shot) the TTL metering was not working either. That was one of the prime reasons why I needed to move to SLR digital.

However, I did try putting a 220 flash on the hot shoe yesterday as I wanted to do some fill flash shots. In Time mode, the way I do my fill flash work, I found the TTL flash metering did work. And I was able to dial in a reduction in flash power via the camera. In this Time mode you get a choice of plus or minus two f stops - none of this quarter, half full business.

If I get a chance to do some more testing over the weekend I will do so - but I don't hold up much hope that we'll get the control we are looking for.

Tony

[CpnCaveman]

I use canon flashes with an EOS film camera but recently purchased the G3 because it was advertised as working with them. I was extremely pleased with the Canon Speedlite 420EX and the G3, using it in bounce flash mode, and have good results using an ST-2E to control the 420EX off camera with an umbrella.

I recently purchased a 550EX to be able to use 2 flashes (main, fill) with ratio control using the ST-2E, but was disappointed that it didn't work as advertised (especially since using canon flashen is not an inexpensive proposition)! I did some further testing and found out that using the ST-2E as a master and the 420EX and 550EX as slaves, I was able to control the ratio of the 550 to the 420, but not vice versa. It seems that while the 550EX is on, the 420EX will ignore requests to moderate its output. Numerous calls to canon only proved to frustrate the tech support as they instructed me to try all sorts of things...

In summary, here is what I found. Both the 550EX and 420EX work great as on camera flashes (but the 550 is truly monstrous when on the G3 (think great dane on a poodle...you get the idea). Using the ST-2E to control the 2 flashes simultaneously works, but ratio only works to control the output of the 550 (flash output on the 420 IS moderated when the 550 is off, but there is really no point to "ratio" using only one flash...in this instance, the ratio control works as a flash output control).

Using the 550EX as a master to control the 420 works but as someone noted, the 550 communicates with the 420 using visible light (ostensibly this was to increase the wireless range of the 550 over the 420 (both the 420 and ST2E communicate with the non-annoying but less reaching infrared flashes)) which causes a cacophony of flashing lights.

THE QUESTION REMAINS: in my investigation, I cannot figure out if the 420EX does not work with ratio, due to technical limitation or interference with the 550, or if I just have a faulty unit ... Is there anyone out there with either 2 420's or 2 550's and an ST-2E who can see if they can do ratios and help me figure this one out?

Thanks

CaptainCaveman