> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Alex Z > Sent: Wednesday, June 18, 2003 11:50 AM > To: EOS mailing list > Subject: EOS ETTL flash metering > > > This sounds to be quite interesting issue to discuss. > I'm a member on several Canon-related lists (such as Fred Miranda's one > and Rob Galbraith Forums) and recently came upon certain topic that > thrilled me. The issue is related to ETTL flash metering people tend to > lament about a lot. Though it was originally related to digital bodies > (mostly 1D and 1Ds), but since certain popular film bodies are also > featured by that (such as EOS-3 I'm using) I thought it may be related > to these also. > It is known that ETTL is heavily biased on active AF point producing > precise flash exposure for particular piece of the subject that is > covered by tiny AF point (out of 45 of 1V/EOS-3 and their digital > siblings). > So far I was mostly impressed by the precision of the ETTL flash > exposures, especailly for fill-flash that is usually recognized as the > most difficult for camera system, however, the case raised on Rob's > Forum may impact the reliability of ETTL in certain situations. > The issue is more related to shooting subjects featured by high > contrast sweep such as weddings (bride+ groom portrait, for instance). > In this case, I would aim the particular AF point on subject's eyes to > ensure proper flash exposure for the face, but then may end up with > severely overexposed bride's dress (that is usually shiny white) or > underexposed groom's black suit. In such case, more balanced (perhaps > more averaged) flash metering would be desired (aka, center-weighted > averaging). This way the are chances more contrast range will be > preserved in the image. > Word of caution: I haven't yet tested this myself, so just passing the > info. > > The cure for this potential problem would be to configure CF 4 > (available on EOS-3/1V/1D and 1Ds) to define the * button for AF while > AE is still triggered by release. Then, once AF is achieved and > confirmed, releasing this button just prior to releasing the shutter > would force ETTL to measure over entire 45 sensors AF field producing > some kind of averaging over the entire area. This is supposedly to take > into account the wide spread pf contrast over the image and is expected > to produce more balanced flash exposure preserving more or less overall > image contrast range. > > I would be glad to hear user opinions about this issue, especially > those who shoot weddings or similar events with either EOS-3, 1V > coupled to 550EX. > > Regards, Alex > >
Hi Alex, In your example with the bride and groom for a high contrast image you cannot solve the limited dynamic range (contrast range), of film (or digital sensor for that matter), by changing the exposure. That's not how it works. To solve this problem you have to use a low contrast film and/or darkroom manipulation during print making. For a digital body you can take two exposures, one for the highlights and one for the shadows and merge the images in PS. Exposure cannot overcome the limited range of film or sensors. At some point there should be a way to capture high contrast images digitally through improving the range of the sensors and by using higher resolution A/D converters which are capable of full range resolution. Cheers/Chip * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
