Reducing Noise by Reducing Resolution

[Instinct]

Hi,

I'm using the Canon t1i\500D. I'll jump straight to the question:

Can you reduce high ISO noise by lowering the resolution (from 15MP to 8MP)?

Logic (and some simple tests by me) indicate it's possible - the less 'dense' the sensor is, the less noise it is bound to produce, the bigger the pixels are, etc.

What do you think? Have you tried this yourself? Can you direct me to any serious tests done online?

Thanks!

[bono]

Well, the pixel count of your sensor won't change. By reducing image size you lose information and this results in lower noise. But you could also just take the picture and reduce the size later or try using neat image or noise ninja for some noise reduction.

[Instinct]

But you could also just take the picture and reduce the size later or try using neat image or noise ninja for some noise reduction.

How do I do that, and what are those? Types of software?

[jdepould]

Originally Posted by Instinct

How do I do that, and what are those? Types of software?

Most photo software (Photoshop, GIMP, Lightroom, iPhoto, etc) can do resizing and noise reduction. There are standalone/plugin noise reduction tools (Neat Image, Noise Ninja) too.

What are you working with right now?

[Instinct]

What are you working with right now?

Mostly Photoshop Elements 8, Lightroom and even Nikon's NX2.

I don't want to reduce noise in post-production, but avoid it altogether.

To my first question - will reducing the mega-pixel count also reduce noise, or am I dreaming here?

[jdepould]

Originally Posted by Instinct

Mostly Photoshop Elements 8, Lightroom and even Nikon's NX2.

I don't want to reduce noise in post-production, but avoid it altogether.

To my first question - will reducing the mega-pixel count also reduce noise, or am I dreaming here?

You're dreaming if you think you can eliminate noise all together.

If you run around glued to base ISO, then yeah, you'll get clean images, but that puts a huge limit on what you can do with the camera.

[Instinct]

You're dreaming if you think you can eliminate noise all together.

If you run around glued to base ISO, then yeah, you'll get clean images, but that puts a huge limit on what you can do with the camera.

I meant, avoid the noise I would otherwise be eliminating with software (and also losing detail, as a result).

I am not going to use 100 ISO all of the time, and indoor, night pictures call upon 1600 ISO.. at which point, our old nemesis, noise, comes in. I want that bastard out! I don't want to post-process and fudge up my pictures (smoothed-over and blurred), but simply not see the noise in the first place. Noise-reduction in-camera does the same as post-processing does.

I've read that APS-C sensors with less MP count deal with noise better, and that makes sense. Will reducing the mega-pixels on my T1i sensor do the same?

[RichardTaylor]

Reducing the megapixel count, by using a different sensor, will help.

See the RAW noise graphs for the 500D (15MP) & 450D (12MP) here:
Canon EOS 500D / Digital Rebel T1i Review: 15. Photographic tests (Noise): Digital Photography Review

That is the closest comparison I can find using similar tests. The 8MP 350D noise graphs are from jpgs

However as a guide to when you can reduce the MP output from the camera you may find this enlightening (5DII)

Canon EOS 5D Mark II Review: 23. Photographic tests (Noise): Digital Photography Review

Reducing the MP (from the same sensor) doesn't help with noise.

[Instinct]

Reducing the MP (from the same sensor) doesn't help with noise.

Well, it seems I have been dreaming, then...

The 500D\T1i is quite noisy at ISO 1600 and up. I've read the newer T2i is less so.

[RichardTaylor]

Marginally better.

Canon EOS 550D / Rebel T2i Review: 14. Photographic tests (Noise): Digital Photography Review

Real world constraints like camera motion, subject motion, subject contrast, lighting (Especially low light) and DOF may influence image quality - so it is not just noise.