5d Mark III low iso poor performance.

Started Jun 20, 2012 | Discussions thread
gdanmitchell
gdanmitchell Veteran Member • Posts: 7,730
Re: Take it back

Alexandros Trichos wrote:

Hello , noise and banding from ISO100 on a nearly-flagship 3.5k product ???

Basically there are three possible explanations for what you are seeing. Let me list them in order of decreasing probability:

1. The cause can be traced to some aspect of your shooting technique, most likely underexposure with consequent radical adjustments to compensate in post. You can rule this out by setting your camera at the ISO 100 setting you mention, making an exposure in raw mode, and then checking the camera histogram display to make sure that the curve reaches all the way to the right edge of the display or else very slightly (a fraction of a stop) short of it. (It is a bit more complicated than that, but this is a fine way to start.)

If the histogram curve does not look like this - e.g., it is clustered in the lower/left half of the histogram display - you are underexposing. In order to get what looks like a normal image out of this underexposed image either your camera (if you shoot jpg) or your raw conversion software are making gross adjustments to a poor exposure... and you will get awful noise.

2. There could be something wrong with your particular camera - e.g. a manufacturing or other flaw in the single unit that you acquired. This is pretty unlikely considering the nature of the problem you describe, but it isn't quite impossible. If you do the test above - shooting at ISO 100 and obtaining a good histogram on the camera LCD display - and you still see gross noise in normal subjects then you might want to take the camera back to the vendor or send it to Canon for a look. Again, this is quite unlikely to be the problem.

3. There is an inherent flaw in the design of the 5D3 camera that makes in unable to produce good image quality at ISO 100. While people could argue the fuzzy edges of what "good image quality" means and point to very marginal differences between one camera and another, the odds that the 5D3 as a breed is simply so defective that one cannot produce a photograph at ISO 100 without really awful noise of the type you describe... is basically impossible.

What I think I notice in your posting sequence here is that you seem to be starting with the assumption that the least likely (indeed, virtually impossible) third explanation is the one to go with. I think you are barking very badly up the wrong tree here, and that this is going to be a very unproductive and futile approach for you to take to the problem.

The second option is slightly less unlikely that the nearly-impossible third option, but not utterly and completely out to the question. If you really think that you somehow picked up a lemon that expresses its inner "lemon-ness" by generating horrible levels of noise at ISO 100, then you should return it or send it to Canon for service since it you would have to assume that it is your camera rather than all 5D3 cameras with the potential problem.

In my experience, the far more likely (though I'll agree, not the only) explanation likely lies with how you are using the camera. Here is one scenario that I've seen quite a few times. A new DSLR owner makes some photographs, perhaps looking at the image (but not the histogram) on the read LCD and liking the darker rendition , or else not looking there much at all... and then brings the image into the computer for conversion in DPP or even Lightroom, etc. These programs often will default to using some automatic exposure adjustments that make your images look like they are exposed correctly - but they do this even when the underlying exposure is way off. For example, the shot might be underexposed by several or even many stops, but it looks correctly exposed to you in the conversion program because the program automatically and invisibly compensated for your error. When it makes this compensation it must take very, very poor image data - especially from shadow areas - and brighten it up, with the consequence being absolutely horrible noise - just like you describe.

There are two ways to see this. First, check that histogram at the time of exposure by viewing the histogram display on the camera back. Second, disable any automatic adjustment preferences that your raw conversion app may have, allowing you to see the "actual" raw image is it was captured.

What would make the exposures be so far off? There are several common culprits. It is not uncommon for people with new cameras (and sometimes older cameras!) to accidentally switch to a different exposure mode on the camera, perhaps accidentally moving the dial to the manual setting. Or, it is possible to not realize that the an exposure compensation setting has been dialed in - either you did it by accident or you did it on purpose and forgot to set the compensation back to neutral.

Also, for an earlier poster in this thread: There is virtually never any reason to post full size images in forum threads. They take forever to load and mess up the forum display! Please don't do this. Either post a small cropped section at 100% magnification to illustrate your point, or include a link to some other place where those who are actually interesting in full images can find them if they want.

Thanks,

Dan

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