Rebel 2000 Auto Flash reduction in manual mode or FEL?greenspun.com : LUSENET : Canon EOS FAQ forum : One Thread
I understand that Rebel 2000 will execute auto flash reduction by reducing 1-1.5 stops flash output if the EV level is high. Will the auto flash reduction for Rebel 2000 be activated in manual (M) mode? What happens if 380Ex is attached and FEL is used instead? Will FEL be affected by auto flash reduction mode?
-- Jasonpgc (email@example.com), November 10, 2001
With E-TTL metering (What you usually get with a Rebel 2000 and an EX series Speedlite) the auto fill flash reduction doesn't behave quite the same way as the TTL since there is a comparison of ambient to flash just before the exposure and the computer makes a judgement call as to how much fill flash reduction to employ. The exact method of determining this and the amount or reduction is Canon's propriatary information. However if the light levels are high enough (over EV10) a reduction of up to 2 stops can take place.
As I understand it, the reduction takes place in all camera modes and FEL doesn't change the reduction amount. The only thing that's different is the exposure is determined earlier.
-- Jim Strutz (firstname.lastname@example.org), November 10, 2001.
Thanks, as far as I understand it, ETTL preflash and meters it with the 35 segments. It is understandable that the program will take the ambient into account and perform a flash reduction.
However, as for FEL, I think it only meters the same area as the Partial Metering. It is reasonable to assume that the subject distance is consistence and the ambient is not of any importance when you use this mode. FEL may have been a flash exposure mode similar to partial metering. I really wonder why Canon would build in an auto flash reduction for it?
Therefore ETTL not equal FEL. Can anyone enlighten me?
-- jasonpgc (email@example.com), November 11, 2001.
"However, as for FEL, I think it only meters the same area as the Partial Metering."
Unfortunately, that's not true. E-TTL stands for "Evaluative TTL", As such it always uses the full multi-area evaluative metering pattern. Contrary to what some believe, Canon never uses partial or spot metering for flash on any of cameras. It does bias the exposure towards the area surrounding the active AF point, but all areas are considered.
Pressing the FEL button doesn't change this. I'm not sure what happens with the ambient metering when using FEL. I suppose it uses the partial area meter since it's the same button, but I'm not sure. What I do know is, the flash doesn't use partial metering.
-- Jim Strutz (firstname.lastname@example.org), November 11, 2001.
"What I do know is, the flash doesn't use partial metering."
This discussion reminded me to check on some test slides I did when I bought the 550EX. In one of the tests I shot my 6 year old, wearing a dark green shirt, in front of a bright off white wall. 1st was basic ETTL with the active focus point dead center of the dark green shirt (center of the frame). The second photo was the same, except I used FEL on my Elan IIE, centered on the dark green shirt. The slide done with FEL had signficantly greater flash exposure than the basic ETTL photo. I assumed this was because the FEL exposure was more strongly biased to the dark green sheet in the center of the photo than standard ETTL.
Is this positive proof that FEL uses partial meter(or spot meter on the 3 & 1v)? I'm not sure, but the test slides certainly does suggest it. At $.10 per photo bribe to my 6 year old (now 8 year old), photography does get expensive.
-- kenneth katz (email@example.com), November 17, 2001.
With the Elan IIe you have to use custom function #8 to tie the the partial meter and FEL to the active AF point. Otherwise it uses the central area, not the focus area you select.
-- Jim Strutz (firstname.lastname@example.org), November 24, 2001.
Just re-read you comment/question Kenneth. My last response doesn't answer your question or deal with your results, since both shots were done with the subject dead center. Actually I have no answer, but Canon has stated that their flash system never uses partial/spot metering in conjunction with E-TTL or any other metering scheme.
-- Jim Strutz (email@example.com), November 24, 2001.
I have also been trying to understand how the flash system works on the EOS 300.I e- mailed Canon and received the following reply
When an EX series Speedlite is used, the flash metering system is always evaluative, regardless of what exposure / metering mode is selected (controls the subject exposure.) If partial or centre weighted metering on the camera is selected with the Speedlite in use, this may alter the degree of background (ambient) exposure only and will not affect the subject exposure
I then replied pointing out that partial metering cannot be selected with the speedlight fitted as the partial metering button becomes a FEL button.I then received the following reply
Flash Exposure Lock allows a partial flash exposure reading to be taken. With the EOS 300, this area is the central 9.5 % of the viewfinder. This allows a selective flash exposure reading to be made, rather than all areas of the scene evaluated. This however still has no bearing on any metering selection made on the camera. Flash exposure and 'ambient' exposure are two separate metering methods.
I have experimented with the camera(without film) using a very slow ASA setting and using FEL on subjects of black and white and the fact that the the lightning symbol changes from steady to flashing when on the black object suggests that the second e mail is correct(ie partial metering does work)I shall now do some real testing and hopefully confirm this
-- rod barnett (firstname.lastname@example.org), November 27, 2001.
Rod, thank you for your valuable response
However, even if we know that FEL takes only a selective area for flash metering, my original question is still not solved. That is....Will FEL perform an auto flash reduction?
-- Jason Poh (Jasonpgc@yahoo.com), November 27, 2001.
According to all the posts I have read on this forum and photo.net the auto flash reduction is dependant only on the ambient lighting (ie EV 10 or above)As the method of flash metering does not change the ambient lighting I would expext the auto flash reduction to work no matter how FEL works.If I find out different by testing I will post my results.
-- rod barnett (email@example.com), November 28, 2001.
One question I have in my mind is that...When we say that the EV level is above 10, are we talking about the EV level measured by the metering mode or is it the EV level we've set for the ambient?
For Example, Is you Use Av, Tv or P mode, the evaluation mode takes over, this means that...the exposure if not compensated, will be the same EV level suggested by the meter.
On the other hand, When we use M mode, we set both the Aperture and Shutter Speed, therefore we are determining the EV level for the Ambient Exposure.
As such, for M mode, even if the scene has a lot of bright light and fool the meter to assume a high EV level, yet we are setting a low EV combination for it. Does it means that the auto flash reduction will still be performed regardless of my manual setting?
-- Jason Poh (firstname.lastname@example.org), November 30, 2001.