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View Full Version : New Rebel underexposing. Why??



Jaxi
09-28-2004, 06:33 PM
My friend has a new Digital Rebel and most of her photos with flash EZ430 are underexposing. We've looked up in the book on exposure compensation and it states that option is not usable on manual mode???? This just doesn't sound right to me. Everytime you set the compensation, it balances the shot when the shutter is partially pressed. She plays around withthe film speed adn shutter speed to get a good exposure, but may have to take 4 shots. She uses a Seconic Light meter and shoots what the meter states. What is she doing wrong? I even shot a wedding a few weeks ago with it and it also underexposed for me. I have been shooting weddings for over 10 years and have never had my exposures off in so many shots. Any help would be greatly appreciated. I would very much like to buy this camera but not if there is so much work involved in getting the shots down pat. Too much work in shooting sports or children.

BryanMsi
10-24-2004, 05:29 PM
I've never seen a camera in 10 years that would consistently underexpose as badly as my Rebel (and I have had 2 Rebels - both had the same problem).

The true cause is a bit hard to nail down, but I think it has to do with the way Canon designed (crippled is a better word) the metering system on the Rebel. Basically, so as not to steal sales away from its $500 more expensive 10D, Canon took away your ability to do much with the meter. Its default mode biases the overall metering based on whatever is selected as an autofocus point.

So if you have an autofocus point on a light part of your image, the metering system thinks the whole scene is bright and adjusts the exposure accordingly - resulting in underexposed shots. Its almost like a spot meter tied to the autofocus point.

Of course, I could be totally off-base here, but this seems to match my experience and others who shoot with the Rebel.

I actually use a handheld light meter for shots that I really want to nail - I can't trust the Rebel to get it right.

For an interesting experiment, put your camera on a tripod and frame up a shot. Shoot one frame in full auto and another in Aperture Priority or Shutter Priority (don't move the camera or change any other setting). If the two shots differ much in overall exposure, your camera is a candidate for exposure problems.

Ant
10-26-2004, 10:58 AM
I wouldn't blame the poor digital rebel. I've got a Nikon D70 and I've heard lots of similar complaints about that, and the D100 before it.

I don't know what kind of metering the rebel uses but I'd be surprised if it wasn't some kind of full scene metering. Nikon calls it matrix metering, I can't recall what Canon call it.

Anyway, the problem is that digital has less contrast range than film. The upshot is that blown highlights from digtal are far more of a potential problem than film. Therefore digital SLRs tend to look at the whole scene and compensate for the brightest part. This can look underexposed, but really it's just a side effect of the linear tone resolution of digital. The theory is that it's a lot easier to bring detail out of shadow in post edit..but a badly blown highlight is irrecoverable and you've lost the shot.

The answer is that you just have to learn to work with the camera. Digtal isn't film, it's a different media. That's pretty much the same for most DSLRs, not just the rebel.

There's a number of options. Post edit in software seems to be the standard method. Most digital photographers who use DSLRs (though not all) will say that post editing is compulsory for a good photo.

Or you could simply permanantly dial in +ve exposure.

The other method...unfortunately not available to the rebel, is to spot meter.....hey, you should have bought a D70 instead :)

BTW there's also a firmware hack available on the web that enables a lot of the dormant 10D feaures on the rebel, one of which is flash compensation; which may help the OP. Not sure if it enables alternative metering methods.

BryanMsi
10-26-2004, 11:42 AM
I do blame the Rebel...none of my other digital cameras have had metering problems like the Rebel does, and I have a good friend who often shoots with me and his 10D shots are much more consistently exposed than my Rebel shots.

I think part of the challenge for dSLRs is that they can't use the sensor itself for metering and instead have to rely on some sort of matrix-based meter. That isn't ever going to be as accurate as using the sensor itself the way a digicam can. For the Rebel specifically, they seem to be using a center-weighted average metering with the focus point serving as the "center" and therefore biasing the overal exposure.

For most shots, I am sure this is fine but it occasionally (or regularly) goofs up a shot depending upon the type of photography you do.

There is a great article on the Luminous Landscape site explaining why you want to tend toward less underexposure on a digital sensor. It sure opened my eyes!

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

The trick is to expose as much as you can without blowing out the highlights.

jamison55
10-26-2004, 12:14 PM
Reading the manual should help you understand the exposure system of the DReb, which should help you use it more effectively. Basically it works this way: All of the "dummy" modes use the matrix metering previously discussed, the P, AV and TV modes use a quasi-spot metering system based upon the center focus point, and the M mode uses center weighted average metering. If you plan your shots according to the metering system you wish to use, the camera is usually pretty accurate.

For example, if you are shooting a portrait and want a shallow DOF, you have two metering choices. If you want to use the Matrix metering system, set the camera to the automatic portrait mode. If you want to spot meter on your subject, set the camera to the AV mode and choose a large aperture.

Not the best system, but they wanted to make sure serious amateurs would still buy the 10D at the time.

Flash exposure is a different subject all together. First off, the 430EZ flash is not compatible with the E-TTL system of the DReb. Your friend should give a try to the 420EX or 550EX and see if it solves some of her woes. I suspect it will a little, but the DReb will still underexpose using a flash (it does so consistently with my E-TTL Sigma 500 DG Super). In that case either use the FEC option on the flash (not available on the 420EX), or install the Russian Firmware Hack, which enables the on-camera FEC. Bump the FEC up a stop or so, and see if you like the results a little better.

The 10D was also prone to underexpose using a flash. Most folks blame the E-TTL system that the two cameras share. Prelim reports are that the 20D's E-TTL2 system is much better.

Ant
10-26-2004, 12:21 PM
I do blame the Rebel...none of my other digital cameras have had metering problems like the Rebel does

Were your other cameras DSLRs or P&Ss? My Olympus C750 exposes totally differently to my D70. I don't consider either of them to have a problem, they just work differently.


I have a good friend who often shoots with me and his 10D shots are much more consistently exposed than my Rebel shots.

So learn to work with the camera you've got or buy a 10D


I think part of the challenge for dSLRs is that they can't use the sensor itself for metering and instead have to rely on some sort of matrix-based meter

Sorry but I have no idea what you mean by this.


For the Rebel specifically, they seem to be using a center-weighted average metering with the focus point serving as the "center" and therefore biasing the overal exposure.

Maybe you're right. I have no experience of the DRebel, but again you seem to have two choices: Learn to work with the camera you've got or get a 10D.


For most shots, I am sure this is fine but it occasionally (or regularly) goofs up a shot depending upon the type of photography you do.

Cameras don't goof up shots...photographers do. Sorry to be blunt but the camera is doing what it's supposed to do, you just haven't learned to work with it.

I used to use an Olympus C750 (and still do for plenty of stuff) but it wasn't fast enough for what I wanted to do, so I spent a fair chunk of money buying a Nikon D70. When I took my first experimental pics I was all prepared to be blown away by the quality of a DSLR...as I'd read in many articles and web sites.......What a disappointment. I actually preferred the shots I got out of my P&S Olympus. I'd just paid all this money for a camera that gave me worse shots that the one I'd already got :mad:

I read as much info as I could about DSLRs, and the D70 in particular, on the internet and various magazines and discussion forums, and I eventually learned that I just had to get used to the way the camera worked and learn to use it accordingly.

Now, several months later, I'm pretty familiar with my D70 and I can get shots that my Olympus never could and I now realise the power of a DSLR over a P&S....but there's more hard work involved too.

I don't know your experience so I'm not sure if what I'm saying is valid or not but from what I can see, as I said, you've essentially got two choices: Learn to use the rebel or get a different camera.

I've read lots of stuff from people who own the Drebel and they all seem very happy with it.

BryanMsi
10-26-2004, 10:48 PM
"Cameras don't goof up shots...photographers do. Sorry to be blunt but the camera is doing what it's supposed to do, you just haven't learned to work with it."

When 2 cameras are side by side, pointing at exactly the same subject, reading exactly the same light, using the same settings and one consistently gets the exposure wrong and the other doesn't its hard to blame the photographer.

And if you read the Canon reviews, you find a small (but non-trivial) number of people with the same problems, so it isn't just me.

The thing about metering is that it isn't really a relative relationship between shutter speed, ISO, and aperture...the relationships are fairly well established. Camera's can be different but not dramatically so.

I can use my light meter and manually set the exposure and produce a breathtaking shot. I've done it many times on many photo trips. Its what I did with my film cameras of the past, and I'm comfortable with that. I understand 18% gray and keep a sunny 16 card in my camera bag. I have even begun seriously trying to use hyperfocal distance guides.

Part of my struggle with the Canon is that the exposure is different between the modes and the center-weighted semi-spot seems to miss as often as it hits. I find that with the Rebel, I can't consistently put the camera in dummy mode and fire off a shot that turns out well. Its not too much to ask that the Canon handle "snappy shots" as well as a digicam. In fact, I expect it.

And what I meant by the sensor metering is this: in a dSLR the mirror obscures the sensor until the shot is actually taken so no light hits the sensor between shots. This prevents actual sensor data from being used by the camera's metering system. In a digicam, the onboard processor can actually read the data coming from the sensor and use that data to adjust exposure since the sensor is always "live."

I'll be the first to admit I am always learning to use my camera better, but having had both film experience as well as Fuji s602, Nikon 5700, and the Panasonic to compare to the Rebel, I'm pretty sure the problem isn't just me.

:D

Ant
10-27-2004, 02:06 AM
If you've just got the camera recently maybe you can still take it back.

Since the release of the 20D I've heard that 10D prices are really coming down, you may be able to pick one up for a good deal.

John_Reed
10-27-2004, 11:31 AM
In this (http://www.dcresource.com/forums/showthread.php?t=1760) post by Brian on the Panasonic board. Just a suggestion! :)

BryanMsi
10-27-2004, 09:24 PM
I'm thinking this might be a great time to pick up a 10D... :)