Slave unit fires before TTL flash???

[deleted]

Hi all... im hoping someone can help me with a problem i a having with my Canon 300d and a Chinon Flash Autoslave M6. I am trying to use the Chinon as a slave unit but when i take a shot, it always comes out underexposed. Its like the slave is firing first and the TTL flash is compensating for the extra light provided by the slave flash.

I can get around this by using Flash Exposure Lock each time i want to take a photo but obviously this is not the ideal situation. Also im planning on using the chinon in a butterfly bracket for macro work however this is not going to be possible because when i set the flash exposure lock it sets of a flash burst which sets off the slave unit.

So as you can see im in a bit of a pickle.. i have two issues it would seem but in solving the first, i would not need to use the flash exposure lock and hence wouldnt have the second issue.

If anyone can shed any light on this problem i would really appreciate it.

Thanks
Fritz

[scottbergerphoto]

The Pre flash of your camera is setting off the slave flash. The only work arounds are to:
1. use Manual Flash or
2.use FEL to fire the pre flash and then the flash. The problem with using FEL is that the light from the slave may tell the camera to put out less light as the camera doesn't know the extra light is coming from a slave. or
3. Use the Canon wireless system. (STE-2, 420EX, 550EX, 580EX)

[deleted]

The Pre flash of your camera is setting off the slave flash. The only work arounds are to:
1. use Manual Flash or
2.use FEL to fire the pre flash and then the flash. The problem with using FEL is that the light from the slave may tell the camera to put out less light as the camera doesn't know the extra light is coming from a slave. or
3. Use the Canon wireless system. (STE-2, 420EX, 550EX, 580EX)

Thanks for your reply scott... i cannot see the pre flash going off.. or is it too fast to be seen?? It appears that there is only one flash. I agree with point 2. this is exactly what is happening.. is there any way around this???

Thanks
Fritz

[tim]

The ETTL preflash is too fast for people too see. Using manual flash is a better idea. I've read preflash causes some people to blick when the main flash is going off, so you might be better off without it anyway - though you might need more knowledge and experience to use it.

[Eric DeCastro]

or use electrical tape on some of the pins.

[RichardtheSane]

or use electrical tape on some of the pins.
How will this help?

[deleted]

The ETTL preflash is too fast for people too see. Using manual flash is a better idea. I've read preflash causes some people to blick when the main flash is going off, so you might be better off without it anyway - though you might need more knowledge and experience to use it.

Ahh i see.. Explains it. Sorry to sound ignorant but what do you mean by manual flash? Do you mean using a flash off the hot shoe??

Thanks for your response.

Cheers
Fritz

[deleted]

How will this help?

yeh.. and how do you do it exactly.

Thanks
Fritz

[tim]

The flash has different modes, ETTL, manual, and maybe others (never looked). ETTL is fully automatic because of its preflash, on manual you set the brightness yourself and there's no preflash. The flash manual will have instructions on how to use the flash on manual.

[Eric DeCastro]

i can't remember but it just removes the pre flash, you will have to look it up to find out which pins to cover.

[tim]

Removing the preflash disables ETTL, which is the same as manual mode. Save the hastle and just learn to use manual mode on your camera.

[Jon]

There's always this (http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=263024&is=REG), which will ignore the pre-flash and fire your slave on the main flash.

[Todd Jacobsen]

The ETTL preflash is too fast for people too see. Using manual flash is a better idea. I've read preflash causes some people to blick when the main flash is going off, so you might be better off without it anyway - though you might need more knowledge and experience to use it.


Tim,

I'm not sure this is true. I've set up my 580's with the camera being master (not fire) and I ALWAYS see the Master "fire" which I believe to be the "Pre-Flash". In addition, I've noted that my light meter (Sekonics L358 ) consistently gives bad incident readings as long as I'm in ETTL. I've been told this is due to the L358 catching the Pre-Flash. I've also noted double flash firing of the master flash if it is set to fire.

[PacAce]

Tim,

I'm not sure this is true. I've set up my 580's with the camera being master (not fire) and I ALWAYS see the Master "fire" which I believe to be the "Pre-Flash". In addition, I've noted that my light meter (Sekonics L358 ) consistently gives bad incident readings as long as I'm in ETTL. I've been told this is due to the L358 catching the Pre-Flash. I've also noted double flash firing of the master flash if it is set to fire.
Todd, sorry, but I'm having difficulty trying to figure out which part of Tim's post you are disagreeing with. Seems to me he's saying the same thing you are and hence the reason he is suggesting using the flash in Manual mode. :confused:

[Todd Jacobsen]

Todd, sorry, but I'm having difficulty trying to figure out which part of Tim's post you are disagreeing with. Seems to me he's saying the same thing you are and hence the reason he is suggesting using the flash in Manual mode. :confused:

Hmm, I failed to notice the contradiction...

The ETTL preflash is too fast for people too see.

Followed by...

I've read preflash causes some people to blick when the main flash is going off...

I was referring to the former vs the latter

[tim]

I guess I wasn't clear about my thoughts around this subject. I've never seen the preflash, and most people i've taken photos of and asked don't see it either, though it wouldn't suprise me to hear that some people see it fine. I've read that some (many?) people have an autonomous reaction of blinking after the preflash. It might be too fast for us to realise we've seen it, but our nervous system might make us blink anyway. I must do a few tests around this soon.

[deleted]

The flash has different modes, ETTL, manual, and maybe others (never looked). ETTL is fully automatic because of its preflash, on manual you set the brightness yourself and there's no preflash. The flash manual will have instructions on how to use the flash on manual.

Anyone know how or if you can set the on-camera flash on a Canon 300d to manual? Or do i have to use a external flash on the hot shoe for this?? Sorry about the stupid questions.. im trying to get my head around this.

[tim]

Anyone know how or if you can set the on-camera flash on a Canon 300d to manual? Or do i have to use a external flash on the hot shoe for this?? Sorry about the stupid questions.. im trying to get my head around this.

I've never seen any options that would lead me to believe you could run the on-camera flash in manual. I suspect you need a 550EX, 580EX, or Sigma 500 Super thingy.

[Todd Jacobsen]

I guess I wasn't clear about my thoughts around this subject. I've never seen the preflash, and most people i've taken photos of and asked don't see it either, though it wouldn't suprise me to hear that some people see it fine. I've read that some (many?) people have an autonomous reaction of blinking after the preflash. It might be too fast for us to realise we've seen it, but our nervous system might make us blink anyway. I must do a few tests around this soon.

Tim,

Do an experiment. Set your flash, connected to your camera, to Master and inhibit it from firing. Take a picture of yourself and see if you can see the Master flash fire. If it does, it's the pre-flash. The master always fires group A.

I haven't tried this since I've only set the Master not to fire when other flashes have been present. I don't believe the Master knows how many flashes are out there, it just knows the (E-TTL) ratio for the groups so it "blindly" sends out this data. I have inhibited groups by turning off that groups flash. It doesn't seem to change the way the Master works.

I have ALWAYS seen the Master fire when Master has been inhibited. The pre-flash is hard to distinguish if you use the Master as a flash since the two flashes seem to coincide (as one flash).

Oh yeah, you can also do a gut check of what a pre-flash looks like by noting the difference in flash power between an Master set to flash vs inhibited mode.

[PacAce]

I guess I wasn't clear about my thoughts around this subject. I've never seen the preflash, and most people i've taken photos of and asked don't see it either, though it wouldn't suprise me to hear that some people see it fine. I've read that some (many?) people have an autonomous reaction of blinking after the preflash. It might be too fast for us to realise we've seen it, but our nervous system might make us blink anyway. I must do a few tests around this soon.
Tim, if you are looking through the viewfinder when you take a flash picture, you should see a flash go off when you fully press the shutter button. That is the pre-fllash going off, not the main flash which you will never see through the viewfinder because the viewfinder will be blacked out by the mirror.

So, although you may not have known it, I think you have seen the preflash go off lots of times. :)

[robertwgross]

There is another way, if you want to see the difference between the preflash and the main flash. Set your camera for a relatively long shutter. Let's say one second. Now, with an external flash like a 550EX mounted on the hotshoe, set the camera and/or the flash for second curtain sync. Now, snap a shot. The preflash will go, and then it will wait for most of that one second, and then the main flash will go.

You can shorten the shutter back down toward normal and see when they appear to merge into a single pop.

---Bob Gross---

[tim]

Bobs way sounds easiest, i'll have a play.

[robertwgross]

It was interesting to see that Fritz, the original poster, actually figured out the basic incompatible function going on by the time he posted here. I would not think that many users have that much insight when they have the same problem.

---Bob Gross---

[scottbergerphoto]

The easiest way to see the preflash is to push FEL. That causes the preflash to fire. Then when you depress the shutter button only the main flash fires.

[tim]

I was really trying to work out if I can tell the preflash from the main flash in a standard exposure. Hitting FEL doesn't really help with that, I knew about that already. Hitting DOF preview gives an interesting effect too...

[RichardtheSane]

I was really trying to work out if I can tell the preflash from the main flash in a standard exposure. Hitting FEL doesn't really help with that, I knew about that already. Hitting DOF preview gives an interesting effect too...
Ah, the strobelight :)

[deleted]

It was interesting to see that Fritz, the original poster, actually figured out the basic incompatible function going on by the time he posted here. I would not think that many users have that much insight when they have the same problem.

---Bob Gross---

Thanks for the help guys. Looks like i might have to invest in a decent flash as i was using the on camera as the master and my Chinon as the slave. I will have to use the chinon as the master off the hotshoe and try and find a small slave flash.
Any recommendation for a cheap slave flash i can use?? It doesnt have to be very powerful as it is going to be used for macro work and is all at close range.
The 550ex is a bit out of my price range for the moment.

Thanks again everyone.
Fritz

[PacAce]

I was really trying to work out if I can tell the preflash from the main flash in a standard exposure. Hitting FEL doesn't really help with that, I knew about that already. Hitting DOF preview gives an interesting effect too...
Are you tyring to determine this while looking through the viewfinder or by just looking directly at the flash?

[tim]

Are you tyring to determine this while looking through the viewfinder or by just looking directly at the flash?

By looking at the subject.