Cheap Slave Flash triggered from 300D - Pre-flash Problems?

[Ozyboykev]

:cry:

I intended to purchase 2-3 cheap slave sensors such as the one below, but just before doing so I noted a warning from the seller (on E-bay) stating that they are not compatable with Canon cameras due to their 'pre-flash' fired to set white balance ...

Is this true? If so, can it be overridden? If I use a flash attached to my hotshoe, will that not prevent the pre-flash?

Can anyone help/advise?

Product being considered/warning:-



Attention digital camera users: JP Optical Slave Trigger w/ sync socket

Some digital cameras fire a pre-flash just micro-seconds before the main flash (Here we are not talking about the pre-flash used by some cameras for red-eye deduction). The pre-flash is used to set the white balance* and other camera settings before the picture is taken. This pre-flash will also trigger off our slave units prematurely.

[evilenglishman]

you cannot stop the pre-flash of the built-in flash without connecting an external flash.
If you connect a manual flash to the hotshoe you should be okay.

[Olegis]

This article (http://eosdoc.com/manuals.asp?q=blankFEL) from the EOS Documentation Project may be helpful.

[robertwgross]

I think there is a fundamental misunderstanding going on here.

First, ask: What is the main purpose of a digital camera's pre-flash?

The pre-flash is a low output flash that reflects off the subject and gets to the camera to for metering purposes. The metered solution then sets aperture or shutter speed for the instant of the main flash.

It does not set white balance. White balance is a processing step that happens inside the camera regardless of the flash unit.

The statement (in red) is either plain wrong or else intentionally misleading.

On the other hand, it is correct that a dumb slave sensor will "go" on the pre-flash, which will produce other than the desired result.

---Bob Gross---

[scottbergerphoto]

I use Morris Mini Slaves and Mini Slave Wides with my 550EX. You have to use the 550EX in Manual Mode to avoid the problem of the preflash setting off the slaves. These pictures were shot using a G2, 550EX in Manual Mode and a Morris Mini Slave to light the background.
http://www.pbase.com/scottbergerphoto/ayana_bailey
Regards,
Scott

[evilenglishman]

On the other hand, it is correct that a dumb slave sensor will "go" on the pre-flash, which will produce other than the desired result.


dumb? Are you saying any flash that isn't canon e-ttl is stupid?

[robertwgross]

dumb? Are you saying any flash that isn't canon e-ttl is stupid?

There are two types of slave trigger units for non-canon flash units. One is a smart slave, and it is able to watch for the pre-flash, then ignore it, then watch for the main flash, and then trigger that slave flash unit. The other type is a dumb slave, and it cannot distinguish the pre-flash from anything else, so it triggers on the pre-flash, and that gets something completely out of sync.

Canon E-TTL is not the only system that uses a pre-flash.

---Bob Gross---

[evilenglishman]

bob, I was trying to be humerous :D

[robertwgross]

bob, I was trying to be humerous :D

Now you are trying to be humorous.

---Bob Gross---

[scottbergerphoto]

bob, I was trying to be humerous :D

Now you are trying to be humorous.

---Bob Gross---
I'm freakin dieing! :lol: :lol: :lol:
Thanks Bob.