EOS20D - Flash pictures not bright enough

[kevinma]

I'm using a 20D and find that with the pop up flash, pictures (taken at distances of 6, 8, 10 feet etc) are a little on the dull side. I am not sure if this is a white balance issue or a brightness issue. I am new to this camera and to DSLRs. Any suggestions as to how to go about dealing with this would be appreciated. Kevin.

[phili1]

It depends on what your shooting at. Raw has to be post processed for everyting. Jpg when I use the buit in flash if has a tendency to be dark but levels in photoshop brings it back to what I want. It also depends on how you focus. If your using multi point it might select a subject nera which is its tendency and that makes the background darker.

One way to eliminate this is focus on an object near the subject hit the *AE lock button that locks exposure re focus on your subject. This is not good for spontanious pictures, so I put my focus on center pointfocus on my subject re compose and shoot the shot. Try that and see if it is any better.

[kevinma]

Thanks. I was shooting jpgs. Levels in Photoshop does indeed make a big difference - it's just frustrating that I would have to do the post-exposure manipulation when I didn't have to with my previous (inferior) camera. The pictures were taken on Auto - maybe I should also try using P with exposure compensation? Could the camera require calibration?

[phili1]

Actually you can get an exposure increase. go to flash comp and increase by 1 stop 1+ and see if you like it. Pro cameras are meant for people who like to decide what they want so the Cameras are set neutral. You can go into menu and set new parameters, exampl my 20 D has parameter 1 and 2, one gives more contrast and sharpens and then you can adjust Color and saturation as well. Exposure is done with the EV setting. You Camera should have one for the flash and one for exposure.

[scottbergerphoto]

I'm using a 20D and find that with the pop up flash, pictures (taken at distances of 6, 8, 10 feet etc) are a little on the dull side. I am not sure if this is a white balance issue or a brightness issue. I am new to this camera and to DSLRs. Any suggestions as to how to go about dealing with this would be appreciated. Kevin.
It's easy to tell if your picture is underexposed. Look at the histogram and see where the right most part of the graph is. If is is far away from the Rt most point (255), your picture is underexposed. The simplest way to adjust this in ETTLII is to use FEC(flash exposure compensation). Dial in +1/3 stop at a time until you get what you like. Canon cameras tend to underexpose the flash a little. It is always better to get a correct exposure then to try to recover the shadow detail later. Usually shadow detail is hard to recover and you get alot of noise when you apply levels correction.
If you think the camera is being fooled by a highly reflective object in the picture causing the flash to turn off too soon, try FEL(flash exposure lock). This is usually not needed with ETTLII, as very bright and very dark areas are excluded from the flash calculation in Evaluative Flash Mode, which is the default.
Scott

[Aylwin]

Actually, I've noticed the same flash "feature" on my 20D. Shots are a bit under-exposed. I believe a few others have also noticed this. For me, I now have flash exposure compensation on +1 stop by default.

Probably has to do with ETTL-II or my lack of knowledge on how to use it properly. :roll:

[drisley]

Actually, I've noticed the same flash "feature" on my 20D. Shots are a bit under-exposed. I believe a few others have also noticed this. For me, I now have flash exposure compensation on +1 stop by default.

Probably has to do with ETTL-II or my lack of knowledge on how to use it properly. :roll:
This also tended to be the same with the DRebel, and the 10D if I'm not mistaken. It's done that way to preserve highlights.
Like Aylwin, I always leave my FEC at +1 for normal flash and bounced flash. I usually turn it down to 0 for fill flash.

[kevinma]

Thank you all for your help. The images are under-exposed as shown by the histogram. Changing the FEC has helped.
Kevin.

[John_T]

Kevin, the underexposure you are having is more likely to be a factor of the lenses you are using than the camera itself. A slower lens will need more light to give you an acceptable shutter speed and a good shot.

You can compensate somewhat for a slower lens by raising the ISO, though be aware that the higher the ISO, the higher the noise. The 20D is better than many cameras in this respect, but you will still need to find a happy medium to get what you want.

The 20D with lenses is likely to be a different game from your previous camera so you probably can't make a valid comparison or use the same parameters for shooting. Likewise, it is good if you tell us what lens you are using as that is an important factor.

For example, if I'm using an f4-5.6 lens, generally the pop up flash just won't cut it, so I use a more powerful external flash to get a good quality image at a low ISO. Does that make sense?

[evilenglishman]

I have to say that one of the things that has impressed me most about the 20D is the flash.

I haven't adjusted anything on this image, flash was set to +1 though.
17-40L. 1/15th F4

http://www.electricvenus.com/dump/ettl2.jpg

I think this looks quite nice except for the shadow under the curtain.

[Aylwin]

I haven't adjusted anything on this image, flash was set to +1 though.
Exactly. If most people need to set FEC +1 most of the time then why didn't Canon just use that reference as 0?

By the way, it seems to me that my 10D exposes more than my 20D whether using the built in flash or a mounted one. I guess it's because of the different algorithms used. :roll:

[phili1]

John T you had me going until I read you last sentence. I will agree that the onboard flash has limitations but it should be compensating for the lens aperature if the Camera reads the lens properly. The only thing with the onboard flash will be when you get into a larger room, its power will peak and you will get dark shots but that is flash photography. If you set your flash at F8 for a small room and go into a larger one you will need more light to the sensor so you will have to open it lets say 1 stop to F5.6. Thats is what manual and EV is for, I think. In any event do what Drisley said 1+ ev as default, even the better flash units fall below the mfg specs.

[scottbergerphoto]

You can use the following formula to determine if your flash is able to cover a particular distance at a particular f stop.

At ISO 100 the Maximum Distance = Guide Number of Flash / F stop
For ISO 200 Multiply by 1.4
For ISO 400 Multiply by 2
The Guide Number for the 20D internal flash is in the manual.
The 420EX is 42 Meters and the 550EX is 55 Meters.

As long as you are within the Maximum Distance, your flash will adequately cover the subject.

Scott

[John_T]

Yes Phil, I was adding to what everybody else had said from different perspectives, feeling that perhaps Kevin was using his previous camera as a reference which could be misleading him on the 20D. What I might have added is that bouncing with an external flash will also be less harsh, something you can't do with the pop up.

[kevinma]

John_T, I am using the EFS 18-55 lens (3.5-5.6) and wouldn't have thought that this lens should impede the flash's performance. Anyway, FEC+1 is working well over here! Kevin.

[scottbergerphoto]

John_T, I am using the EFS 18-55 lens (3.5-5.6) and wouldn't have thought that this lens should impede the flash's performance. Anyway, FEC+1 is working well over here! Kevin.
It doesn't matter which lens you use, It's the f stop! :roll:
Scott

[John_T]

Scott put it right. The prime factor is the speed of the lens you mount on the camera, not the camera. If the camera gives you the function to compensate for the lens speed, that's the camera. In your initial post you had sounded like you were disappointed in the 20D over this issue, therefore the point I was making. Glad you are happy now! :)

I am very happy with the 20D, and I am particularly happy over it's ability to use slower lenses without getting into noise or focus problems, especially with the EF-S 17-85 f4-5.6 and the EF 70-300 DO f4.5-5.6.

[scottbergerphoto]

I wish I knew how to make this clearer, but I don't. The maximum speed of the lens is irrelevant. The flash coverage for "flash X "using a 20D and a 24-70 f/2.8 or a 70-200 f/4 is the same when both lenses are set for the same f stop. Each of those lenses at f/5.6 will allow for the same flash coverage. A 550EX with either lens set at f/11 at ISO 100 will cover 55/11= 5 Meters.
Using the lens mentioned above, the 18-55 f/3.5-5.6, using a 550EX, the maximum distance would be in a range of 55/5.6 to 55/3.5 or 10-15 Meters at ISO 100.
A faster lens has the advantage of having a couple of wider f stops that a slower lens doesn't. That only comes into play when you have maxed out the flashes ability to cover distance using the f stops available on a slower lens based on the formula above.
Scott

[John_T]

That's pretty clear Scott. I think the thread started of on a non-technical basis and now you've set it on track.

[Aylwin]

That's pretty clear Scott. I think the thread started of on a non-technical basis and now you've set it on track.

Actually, I think the issue is... or at least my issue is :wink: ... given the same lens and same settings, the 20D will produce under-exposed shots compared to the 10D. Setting FEC to +1 stop fixes this problem.

It could be argued though that the 20D is correct while the 10D over-exposes. However, in Kevin's case, he's not comparing the 20D with any other camera. He's simply stating that his photos are a bit under-exposed when using the flash. And now, using FEC at +1 stop produces better results.

To me, this supports the theory that the 20D does, in fact, under-expose by default.

Yes, given a certain focal length, aperture setting and ISO setting we can determine the effective coverage distance of the flash. That doesn't explain though why the 20D will decide to output X intensity from the flash while the 10D will output Y lumens where X < Y. What would interest me is a technical explanation of why this is the case.

[scottbergerphoto]

The issue of underexposure with Canon cameras and flash is not new. This has been reported ad infinitum with the 1D Mark II and 550EX combination. Part of the problem is that in Av and Tv there is an automatic fill flash reduction that can't be turned off. In P mode, the camera decides whether to use it or not based on ambient lighting. The only way to avoid it for sure is to put the camera in M Mode and use the flash in ETTLII. Then there is no automatic reduction of the flash. As long as the amount of underexposure is consistent it isn't an issue. Just use the same FEC each time. It is believed that Canon has chosen to set the flash exposure a little on the dark side to avoid blown highlights.
You will find this thread addresses this issue in detail:
http://www.robgalbraith.com/ubbthreads/showflat.php?Cat=&Number=247684&page=&view=&sb=5&o =&fpart=all&vc=1
Scott

[Aylwin]

Thanks, Scott! You hit the head right on the nail! :D

This has been reported ad infinitum with the 1D Mark II and 550EX combination. Sorry, I missed that discussion. :oops: I suppose the 20D takes after the 1D MKII being DIGIC II, newer technology and all, huh? :roll: I does make sense though trying to avoid blow outs. I can see why Canon would decide to be a bit conservative with flash intensity.

[scottbergerphoto]

Thanks, Scott! You hit the head right on the nail! :D

This has been reported ad infinitum with the 1D Mark II and 550EX combination. Sorry, I missed that discussion. :oops: I suppose the 20D takes after the 1D MKII being DIGIC II, newer technology and all, huh? :roll: I does make sense though trying to avoid blow outs. I can see why Canon would decide to be a bit conservative with flash intensity.
No need to apologize. There is a wealth of information in the archives of this forum and at www.robgalbraith.com that can be accessed using the Search function. Unfortunately, once it leaves the first page, it's like it never happened.
Scott

[drisley]

The issue of underexposure with Canon cameras and flash is not new. This has been reported ad infinitum with the 1D Mark II and 550EX combination.
Don't forget, this also has been reported on the 300D (http://host.whereuhiding.com:9080/canon/FEC_TEST/Canon_Rebel_FEC_Test.htm) as well. That is why people used both the firmware hack, and the FEC hack, to set the default FEC to +2/3.
The 20D's flash response is exactly like the 300D's in this respect, in that they require a +2/3 to +1 FEC to give a histogram that is more centralized than "to the left".
However, as others have mentioned, the 1DMKII/20D's ETTL-II works much better than ETTL in almost every situation.