18MEGAPIXELS! resizes better?

I just ordered t3i which has an insane 18megapixel raw setting that cant be set lower

unlike my 40d and 5DII, i can set it to SRAW which gives me 10mp and 6mp. I only load 6mp photos to my iphoto.

So my question is, which gives a cleaner and sharper photo

1) 18MP raw resized to 6mp JPEG

2) 10MP raw resized to 6mp JPEG

I would say 18mp raw to 6mp jpeg since you start off with a higher resolution raw file than the 10mp file.

Have you done any tests? Any scientific tests around here thats been posted?

Anyway thanks. I do agree but I cant say for sure.

I see you have the t3i, how do you find the 18-55mm compared to the 18-135mm? I find the 18-135mm too delicate. Ive had my share of damaged lenses due to regular use.

aznlunatic wrote in post #12264212
I would say 18mp raw to 6mp jpeg since you start off with a higher resolution raw file than the 10mp file.

The contrary argument would be that with the 18mp file, you need to throw more information away to get it down to 6mp, so the 10mp file will produce a better image.

Don't know the real answer, just speculating.

If by cleaner you mean less noise, down-sampling reduces noise because a core area of pixels is examined and the RGB values that will be given to the new single pixel that will replace them are calculated. If in the sample area there is a divergent (noisy) pixel it's values will be averaged in with the others. If the down-sample is larger (18 > 6) the sampled area will be correspondingly larger. In an image that is not very noisy to begin with it could well be that in a sample area that is four times larger there still is only one noisy pixel which would then have only a quarter of the influence on the interpolated values. But in a noisier image a 4x area might have 4x noise pixels, so the relationship would be unchanged. In other words, the answer is, "It depends". There are two many variables to give a simpler answer.

Regarding sharpness, I'd say that downsizing causes a loss of sharpness and detail, more downsizing = more loss. Probably, the advantage the 18 MP had in resolving detail would be erased. And it would require stronger output sharpening, which is itself always destructive to a certain degree.

I doubt it'd make any difference in practice. Try it and see if you can spot any difference at all.

In the samples I've seen, there is no gain to the quality of mRaw or sRaw. Amd. in practice, you have more control over the full Raw processing.

As far as iPhoto goes, I've never heard of a "6 Megapixel limit" -- that doesn't sound right -- you might want to check on that. Cameras have been producing shots much higher than that for several years.

But all this is in the context of the fact that I've never done my own testing on sRaw or mRaw and I don't own a Mac!