Anyone got a rational explanation why Canon underexposes?

Does the histogram show a shift to the left?

Cosworth

I too suffer your frustration and I don't believe you'r doing anything wrong.

I too suffered perminate flash underexposure and so have many others too. I have used two 20D/580EX combinations and one 30D/580EX combination and they all expose flash the same (badly).

The secret, I believe, is that ETTL 2 is in perminant fill in mode and as such the darker it gets the more it underexposes ie the further away from fill in it is the worse job it does.

The way around this is to change CF-14 to average when it gets too dark to use the flash as a fill.

As a general rule only use ETTL 2 when outside under decent light or inside under abnormally bright light the rest of the time change CF-14 to average.

I have expressed these views before and got shot down for them so try it yourself and if it works then great. Personally I think ETTL 2 is the most overated camera system of all time as the subject/distance info used to "help" calculate the flashs output is completely useless unless you point the flash forward ( if it's not pointed forward the info is ignored anyway)and then use no diffuser is used. And who in there right mind would spend hundreds/thousands £/$ and then do that? All it does is complicate things and makes consitant flash exposure a lot more difficult.

It would make sense that your wide angle overexposes a bit but your telephoto lenses don't. The FOV increases and therefore the camera has to meter a lot more.

The cameras flash is only good for photos within one or two meters. If you want to use flash for longer distances, you need to get a stronger flash like the 430EX or the 580EX.

Also don't use the flash in automodes, since you can't control anything. For example if you use the the flash in aperture mode the camera will choose to expose your subject in "Slow sync":
http://photonotes.org …flash/index2.ht​ml#avflash
http://photo.net …rts/mirarchi/co​ncer_4.htm

Use manual mode and a large aperture to make sure, that your flash has enough power to be bounced against the ceiling or wall:
http://www.canon.co.jp …hniques/bounce/​index.html

roeddel wrote in post #2385138
It would make sense that your wide angle overexposes a bit but your telephoto lenses don't. The FOV increases and therefore the camera has to meter a lot more.

Actually my wide angle underexposes.

Henrik Ploug wrote in post #2385160
The cameras flash is only good for photos within one or two meters. If you want to use flash for longer distances, you need to get a stronger flash like the 430EX or the 580EX.

Also don't use the flash in automodes, since you can't control anything. For example if you use the the flash in aperture mode the camera will choose to expose your subject in "Slow sync":
http://photonotes.org …flash/index2.ht​ml#avflash
http://photo.net …rts/mirarchi/co​ncer_4.htm

Use manual mode and a large aperture to make sure, that your flash has enough power to be bounced against the ceiling or wall:
http://www.canon.co.jp …hniques/bounce/​index.html

I have a 580 and I get it to throw over13 metres easily with trapeze shots. I use M and ettl all the time. But I have to dial in FEC. The basis of my thread.

oops my bad! i mean underexpose ... but you get the idea

My 30D with kit lens seems to underexpose on AV all the time. Even if I overexpose byt 1 or 2 it still looks bad. Shoot manual mostly now to stop it. The historgram someone else was talking about earlier is always over to the left...

LOL.......not to start this whole thing again, but I hope you understand that by selecting the M mode does not do a damn thing for changing the exposure.......it's your metering mode that does that. It's going to give you the EXACT same results as TV or AV............that is unless you actually understand that one mark over the center point = +1/3, 2 over = +2/3.......and so on. But if your just lining up the arrows, your not going to get anything different than TV or AV. Knowning what metering mode to be in per situation, and knowing you camera is the key to proper exposures.......not just clicking it into M.

I normally shoot AV and my Mk2N is pretty much glued to +1/3. But to answer you question, it's as simple as..... you can't bring back blown out highlights. I think that pretty much sums it up as to why Canons under expose.

cosworth wrote in post #2384673
Hmm... maybe the metering system has a bit of trouble with polarizers.

Hmmm, possibility. I recall shooting a boat race last year with a polarizer. Most all shots were under by 2/3 of a stop. Could have been my choice of metering mode and my lack of forethought though. I didn't pre-meter or fire any test shots.

I"m used to Canon's flash being 1/3 to 2/3 under. On my 10D, I set it at +2/3 FEC and it worked well except with very dark or very light subjects. With the newer ETTL-2 cameras, I still set FEC at +2/3, though they do handle the wedding dress/dark suit situation better. I think it's pretty consistent.

You'll be able to get better flash results when you get away from full auto and P mode for flash.

Av and Tv will use the flash as a fill and will not meter to account for the flash.

Use the flash in M mode and adjust your shutter speed, appeture, iso, and FEC to get your desired exposure. Shooting RAW is always a big help and even moreso with flash.

Once again....YAY for hand-held meters and BOO to in-camera meters!

cosworth wrote in post #2384505
I notice that only certain lenses do it with my cameras. My new 70-200 F/4 L IS seems to NOT do it. My non-L lenses always need exposure comp. The non IS 70-200 I have seems ok.

This may have something to do with the fact that some lenses report distance to the camera and some don't. The distance data augments the flash power calculations when using direct flash.

My uncle once had a pickup truck that you had to turn the steering wheel 45 degrees to the left in order to drive straight. You just learn to adapt. The fact that E-TTL underexposes doesn't bother me so much as the fact that it only does it sometimes, and I never know when, or by how much!

I actually like using E-TTL outdoors. When the background is distant it doesn't seem to get confused so much. Indoors, I use my Sunpak 383 as a simple, effective, and consistent flash unit.

My 30D seems fairly accurate, if just slightly underexposing
My 1D on the other hand meters WAY under...

wouldn't underexposing let you save more of the detail than overexposing?
if answer is yet - then i'd rather underexpose than overexpose!

muscleflex wrote in post #2388131
wouldn't underexposing let you save more of the detail than overexposing?
if answer is yet - then i'd rather underexpose than overexpose!

No the exact opposite in fact. As long as the exposure isn't burnt out then overexposure is a good thing.

read some threads on exposing to the right ( on the histogram )