Canon Line Offset Noise

Started Oct 20, 2009 | Discussions thread
OP John Sheehy Forum Pro • Posts: 22,808
Re: Let me just say...

JimH wrote:

Let me just say that as someone who has spent a lot of time on this forum over a number of years, I know whose technical expertise I respect.

And John is one of those people.

John: You won't win this argument and it's totally off topic anyhow. Don't waste your energy worrying about attacks on your "tone". Who cares?

You've clearly shown that it's relatively easy to reduce the vertical pattern noise in a 7D file. I have yet to see anyone offer a technical rebuttal to that.

"There are people who know more than you or I" is not a technical rebuttal?

It's amazing how creative people can be, and how wide open their imagination gets when they are conjuring ways of discrediting someone who is saying something that they don't like.

Sometimes discussions have to assume a certain amount, and a certain amount of understanding, and the important thing missing in a few people's understanding is the fact that if you did any subtraction of banding that was unnecessary or incorrect, it would show up as worse or redistributed banding; not as a texture without the banding! I did not randomly replace some pixels from other columns to get rid of the banding; I did exactly what the banding does; I altered the values of entire lines by the same amount. If that can't be accepted, an argument is hard to have. Apparently, some people don't seem to understand that these corrections can't ruin other tonal levels, even if they were wrong, because the correction are infinitesimal compared to signal levels and even the shot noise, as you move up from black in the tonal range. The only mistakes possible of any consequence are near black.

Anyway, I am now a 7D owner, so I will investigate sometime soon to see if the low-ISO vertical offset banding is basically the same in every RAW of the same ISO. For my hand-converted color, and B&W images (who needs a converter for B&W?), I should be able to get very good results. Once you subtract the vertical banding, the 7D ISO 100 RAWs look pretty good. Not nearly as good as the D3X, perhaps, but about as good as any recent Canon at the pixel level, and better than any 12 MP or less Canon at the image level. Maybe I'll actually be able to shoot with that extended negative ISO that the 7D gives, or use HTP in auto-ISO manual mode (since Canon has given metering instead of EC in that mode - a bad decision, IMO).

I took the 7D out last night, right after opening the box and taking a few quick shots at home, and I must say that as far as high-ISO is concerned, Canon has taken a big step forward here. Not only is the RAW data low in read noise, but the JPEG engine, with the defaults the camera comes in, gives very reasonable detail despite the NR used, and the medium quality of the embedded JPEG. It looks like when pushed to the limits, the camera is struggling against a fine - grained noise that originates almost completely at the photosites.

Shooting at "H", and even at 6400 with -5 EC, I can read fine text and see reasonable detail. Apparently, not only the quantity of read noise has decreased, even at the pixel level, but the quality or character of it at high ISOs also has taken a big step forward.

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John

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