My personal 400D's underexposure FAQ

Started Nov 13, 2006 | Discussions thread
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oriomenoni Contributing Member • Posts: 554
My personal 400D's underexposure FAQ

I hope that this can help to stop the irrational rumours that keep going on.
I am really tired of reading unaccurate things about this subject.
I put here what I learned from my personal experience.

Q.: So, does the 400D actually underexpose or not?

A: It seems to underexpose more or less constantly for most people using Evaluative mode. A minority of people only report some occasional underexposure, always with Evaluative mode.

Q.: Is this underexposure real, or does it come from the comparison with 300D and 350D (which are known to overexpose)?

A.: This is debated. Some people (the majority) claim that the underexposure is real and that it shows also from comparison with non-Canon SLRs. Some other people claim that the 400D meters correctly and that it's the 300D and 350D that meter wrong.

Q.: Does 400D only feature the Evaluative metering mode?

A.: No, it features three metering modes: Evaluative, Partial, and Centre-weighted.

Q.: Does the camera underexpose with the other metering modes?

A.: No. With the Partial and Centre-weighted modes, the 400D does not underexpose, on the contrary it shows the same results as the predecessors (300D and 350D), that is, some overexposure, ranging from +1/3 to +2/3, although in some cases I even got a +1 stop (compared with external Gossen MultiPro meter).

Q.: Is this Evaluative mode underexposure a hardware's fault? Is the sensor of 400D less sensitive to light? Are there other hardware components of 400D that are faulty and cause this underexposure?

A.: No, the use with Partial and Centre-weighted modes show that the sensor is not less sensitive than those of 300D or 350D. And neither are there problems with other hardware components of 400D. The underexposure with Evaluative mode is merely the result of a software calibration.

Q.: So where is this problem located?

A.: It is merely a matter of how much importance or "weight" the algorhythm of the Evaluative mode gives to the different measurement points. The Evaluative mode measurement seems to be somehow related to the location of the AF points. Let's not forget that the 400D has a different AF system than the 300D's and 350D's. Let's say you shoot a landscape with horizon in the middle, if the algorhythm "says" that the sky is more important than the land, you'll end up with a correctly exposed sky and a slightly underexposed land. Of course it is more complicated than this (and the 9 points location is not rectangular), but it can serve as an example.

Q.: Can a competent use of camera prevent that?

A.: YES! Too many people now expect to just point and shoot with a reflex. Then I say they have gotten the wrong type of camera. Reflex photography does not work like that. You have an assistance from the automation, but ultimately, it's about you the photographer knowing your camera and how to use it. GET TO KNOW YOUR CAMERA. Learn how to meter it. There is a useful button in your 400D, it's the Exposure Lock button. LEARN IT AND USE IT. Meter your scene by centering the view on the most sensible part of the scene, then press the AE button, recompose and shoot. Professionals do always meter accurately their scenes. You are not so much better than a professional, that you can skip that part and pretend to always get good pictures. Either shoot like professionals shoot, or sell your SLR and get a point-and-shoot camera.

Q.: So, if it's not a hardware problem, should I keep my 400D?

A.: Yes you should!! The 400D is an excellent camera that rewards you with quasi-professional images at a fraction of the price of a professional camera. To return it (or even worse, to send it to servicing) because of this supposed underexposure "problem" would be the most stupid thing that you could do.

Q.: Can I expect that a firmware update fixes the problem?

A.: In theory, yes: since this is obviously a software "problem", a firmware update may definitely fix it. But I doubt that such "fixing" firmware will ever be released.

Q.: Why?

A.: Because in my opinion, this "problem" or "fault" is not a problem or fault in Canon's engineer eyes, but an actual improvement on the metering performance of 400D compared to 300D and 350D. And I agree with them. If you use your 400D long enough to learn how it meters and works, it will turn out to be an advantage and not a feature. I personally rarely rely on the Evaluative mode, but when I do, I get significantly LESS thrash shots that I used to get with my 300D (by trash shots I mean shots that are unrecoverable even with RAW).

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