Has anybody had problems with 20D flash underexposure?

[Jonathan19610]

Has anybody had problems with 20D flash underexposure?

I am on my second 20D having returned the first for underexposure problems especially with the onboard flash. This second camera seems to be suffering a similar problem albeit slightly better than the first one. The images taken with the onboard flash seem to be up to 1 stop underexposed in all modes. I am using the 17-85 EFs lens.

Has anyone any advice?

[slin100]

Yes, this is a well-known behavior. Consider using +2/3 or +1 FEC.

[Jonathan19610]

Thank you for your reply.
Do you know if Canon have acknowledged this problem if so what do they suggest?
Is the 350D any better do you know?

[robertwgross]

First, understand a few things.

1. If the built-in flash were perfect, then nobody would need to buy the big external flash units, so Canon would make less profit.
2. The built-in flash is not intended to light up a concert hall. It is only for short-range purposes since it has such a small guide number.
3. If Canon had made the built-in flash too strong, then everybody would be bitching about how it was too strong and the highlights were blown out, thereby ruining every flash shot. Instead, they keep it maybe a half stop low, so the shots are much less likely to be blown.
4. You can overcome some of your problem with exposure compensation and flash exposure compensation. That's what they are there for.

---Bob Gross---

[slin100]

Thank you for your reply.
Do you know if Canon have acknowledged this problem if so what do they suggest?
Is the 350D any better do you know?
Canon hasn't ackowledged a problem. They do, however, ackowledge that their design decision for flash exposures may differ from one's desires. It has nothing to do with the built-in flash. Even EX flashes behave similarly. Canon's suggestion has been to use FEC.

[EDIT: Here's is Canon's position stating the above:]

The 'correct' level of flash exposure, especially for fill-flash, is often a matter of personal taste. If you don't like the default settings, then by all means experiment until you get the result you're after. If it ends up being +2/3 stop or +1 stop, or even higher, compared to the camera's recommendation, that doesn't automatically mean you have an equipment problem.
Complete text found here (http://www.cps.canon-europe.com/kb/detail.jsp?faqId=1021).

I don't expect the 350D to perform any differently. Flash underexposure has been reported on every Canon DSLR.

[Bob_A]

Thank you for your reply.
Do you know if Canon have acknowledged this problem if so what do they suggest?
Is the 350D any better do you know?

I have had emails from Canon Tech Support stating that the 20D has been designed to slightly underexpose to help ensure that you don't blow the highlights. It is much easier to correct for underexposure than overexposure.

For me, I dial in +1 stop then check the histogram after I shoot. Sometimes I need + 2/3 and sometimes + 1 1/3. How much flash compensation you need is also a matter of taste. So ... this really isn't a bug that needs to be fixed, it's a "feature".



Regards,

Bob

[scottbergerphoto]

This is discussed ad nauseam in the EOS Flash Sticky.

[Jonathan19610]

Thank you for your advice and the links. Very, very useful!
I have just upgraded from a G3 to the 20D and it initially appeared Canon had made a backward step in terms of flash exposure or at worst the camera was faulty.
However I am very interested to learn that all Canon DSLRs have had flash underexposure 'problems' reported in the past. I am also comforted by this and the fact that this under exposure could be considered a feature so that the highlights are not blown out and that this is the way they have been set up.
Kind regards
Jon
Birmingham, England

[Tudordoc]

I am new to digital photography and I too was disappointed with my recent flash shots using both the built-in and also a 420EX on my 350D. Can Bob_A tell me how he reads the histogram to judge the exposure. If it has been dealt with elsewher please could you point me in the right direction

TudorDoc
London UK

[Maureen Souza]

I only use the built-in flash for fill-flash outdoors. It does great in the shade or when the subject is a position with shade hitting them. Other than that, I use my 420EX.

[Bob_A]

I am new to digital photography and I too was disappointed with my recent flash shots using both the built-in and also a 420EX on my 350D. Can Bob_A tell me how he reads the histogram to judge the exposure. If it has been dealt with elsewher please could you point me in the right direction

TudorDoc
London UK

The following article on the Luminous landscape website may help:

http://www.luminous-landscape.com/tutorials/expose-right.shtml

For flash exposures (using my 420EX ... I don't use the onboard flash) I've been having success with starting with 1 stop FEC then checking the histogram to see if it tapers off to the bottom within the last quardarnt. However, I also check picture beside the histogram on the camera LCD screen to ensure that nothing is flashing (no blown highlights).

If something flashes in the picture you have to decide if this is something you would expect such as a reflection or a pure white surface. If what is flashing has some detail to capture then you need to back off a bit with the FEC even if it places the histogram further from the right.

So, I try to add as much FEC as I can get away with without having the Histogram pile up at the right or having the overexposure warning flash on areas of the picture. If you underexpose by quite a bit you can often correct the picture with digital exposure compensation during post processing, but it can add a lot of noise to your image.

Note that there may be some scenes where the histogram should pile up on the right (lots of backlighting) ... or taper off well before the right hand side. But for "around the house" simple candids using flash the way I've approached using FEC and the histogram seems to work well.


Just my $0.02 ... I hope this helps!


Bob

[mwinog2777]

The flash on the camera is not meant to be a full service flash, as alluded to by several other of the posts.

To do any serious photography, need external flash. Even then, have to continuously check every picture's histogram as its done. Flash is easy only for the point and shooters.