Tips for dealing with ISO graining

[zac510]

Hi guys can you give me some tips for post-processing images at higher ISO?

I find that almost anything above ISO200 on my Canon 30D just looks like sandpaper and it drives me mad.

Could it be my shooting style or a setting on my camera too? I'm willing to accept some blame

I always shoot in RAW and have played with the various settings in photoshop that are supposed to gut down on graining like sharpening and so forth.

Thanks!

[grantp]

Noise reduction tool is what you need. They can vary a lot. The more recently introduced the better, in terms of broader packages like PS bust otherwise there are some dedicated NR applications like Neat Image or Noise Ninja which can be applied to your output jpgs or, potentially I think, usind as plugins for PS and other packages.

I use an editor called LightZone (not to be confused with Adobe LightRoom) that provides some rather excellent adjustment for my Canon 400D et al, images especially from RAW files. Just don't overdo the adjustment.

There are 2 basic types of noise - Colour noise and Luminance noise - often referred to as Grain noise. It sound like it is mainly the grain noise you need to deal with ... unless your images tend to be underexposed by the camera settings and you are lightening them. In that case you may be seeing sensor electrical noise and there is not a lot you can do about that in my experience without some radical graphics editing.

Sensor noise shows up mainly in the darkest areas of images that are pushing the exposure boundaries.

Bear in mind that all noise reduction will affect the ultimate resolution available for the image and so represent a compromise - usually one that is worth trading for providing the result is not too extreme in its detail destruction.

[zac510]

I feared this might be something to do with my addiction to my polarising filter..

[andrewc]

Are you pixel-peeping?

I was never really disappointed with my 30D results unless you really examine the pictures closely at 100%. I regularly printed out pictures at ISO 1600 and they were fine.

If you are unhappy, then there are various noise reduction software packages - neat image, noise ninja, noiseware etc.,

[zac510]

What's pixel-peeping?

[andrewc]

Pixel-peeping is where you are viewing the image at 100% or more on a monitor. It shows up a lot of things which you simply don't see when the image is printed, even at pretty big sizes - eg A2.

[grantp]

Originally Posted by zac510

I feared this might be something to do with my addiction to my polarising filter..

Is it a linear of circular polarizer? (That refers to the way it polarizes not the shape of the filter. Just in case you were not aware that there was a difference.)

I spent some time yesterday with my elderly Canon Pro1 and a circular polarizer and there are certain observable differences in aaent noise levels for shots taken when the sun went in.

Now the problem is likely that the poor old Pro1, great though it can be, is not exactly the latest technology and is naturally quite noisy in some situations. The polariser will cost it somewhere between one and two stops of exposure and the metering and focus systems are probably compromised as well, especially if the light dips as a cloud passes.

On a Pro1 compensating by upping the ISO is not really an option, though as andrewc has pointed out, at typical print sizes (and provided one is not cropping the original too much before printing) you should be able to create something where the noise does not show. Unless you have had to go for an extreme adjustment somewhere along the way, as I mentioned before.

The circ-pol on my Canon 400D + 70-300 DO lens also introduced some dubious results, notably on motor sport focus matters, but then that would not be a surprise really given that the focus systems like to have something like at least f5.6 worth of light and that is the DO lens at full stretch BEFORE the filter is taken into account.

My conclusion to date is that the safest way to use a polarizer and get predictable results is going to be to set it up for a single shot and manually focus if necessary. That way you get consistent polarization effects and a known focus point and save some battery power as an added bonus.

Or it could be that my Cokin filter is not very good ...

[atky]

Sharpening an image will increase noise, the best advise to reduce noise is to nail the shot (good exposure, good sharp focus). While pore quality lenses don't increase noise the work required in photo shop to improve the quality of the image will. In short the less you have to do after the shot is taken the better.
I find it hard to believe noise is a problem at ISO 200.

[Tim the Grey]

I have no Pola issues, but then I run a Zuiko at f2.8 and a negabucks Hoya filter...
God bless the £-$ exchange rate being at 2 some years back!

Zac? I suspect it's the RAW conversion that may be causing your problems? In camera jpg is fine with my VERY Old Skool Olympus. I can find issues using CS4 to convert though.

Try it, see if it improves?

Tim

[zac510]

I might be pixel peeping, maybe subconsciously. The pics do look alright when I look at them on photobucket at 800x600 but what's the point of all of these megapixies if you're viewing at that resolution? I've never printed one of my pictures out.

Lens is 100-400 IS and it is a circular polariser (I think it's Hoya, regular spec). I'll try upping the exposure a bit next time I'm out and see what that brings me.

I am quite picky about my pictures though, I'd rather quality over quantity any day.

[Woolley]

The simple answer to noise is to shoot at the native ISO for the camera - either 100 or 200 depending on the model and get the shot right in the first place. If the polarizer is pushing the ISO up then the trade off is to lose what it does for you (saturation and lack of windscreen reflections) in order to maintain a lower ISO. Anything you need to remove in post processing will affect overall IQ.

[grantp]

With my 400D I really don't see a lot of noise until I get to ISO 1600 though at ISO800 the images will look OK but not if compared to ISO100 (for example). Not so much noiose as overall quality falls off as you would expect.

If I try extreme adjustments (over 1.5 stops) on very dark areas I may well since luminance graining.

By chance I read this today. It may be of interest. A noise reduction tool. Examples shown.

http://www.luminous-landscape.com/re...re/topaz.shtml