Post Processing High ISO

[weepete]

Hi all,

I'm attempting to pp some shots I took recently using high ISOs and was looking for some advice, pointers or ideally if someone knew of a tutorial somewhere on how to get the best out of them particularly with noise reduction.

My shots have been taken on a canon 7D, large raw format, with all the in camera processing disabled, ISOs range from 5000 - 12800. Program wise I was hopeing to just use lightroom but I do have photoshop as well.

Can anyone help?

 

[EIngerson]

In lightroom I like to bump the luminance slider up to about 15-20 then slide the color to 100% You'd be surprised just how much smoother it looks with the color gone.

*edit* Although I have never used ISO's that high on my 7D. It just didn't handle noise good enough.

 

[KenC]

You can push the color (or chrominance) slider without any noticeable effect on the image quality, although I never pushed it all the way. The luminance is where you have to be careful, as noted above. You start to pay for it in image sharpness after a while. You have to decide how much the noise actually detracts from the image and balance that against the sharpness loss. Some have become so noise-averse that they consider any detectable noise unacceptable. This may be so in some images, but not in all.

 

[Ysarex]

Do as much as you can in Lightroom without compromising the detail in the image. Watch for the color noise to start creating a glow around objects and then back down till the glow is gone.

Eventually you have to move to an RGB image. You can often go an additional two steps using Photoshop's Reduce Noise filter. First get a good look at each separate channel and compare noise. You'll often find that the noise is worse in one channel versus the other two. In the Reduce Noise filter switch to the advanced mode and you can adjust the amount of noise reduction per channel leaning harder on the noisy one and backing off on the least noisy one. You'll also find that noise is worse in the shadow end. You can apply two different degrees of noise reduction. First pass for the entire image and then from the Select menu go to Color Range -- from the drop box select Shadows and then apply somewhat heavier noise reduction to just the shadows.

Joe

 

[weepete]

Thanks guys, I'll definatley be trying to take these on board and apply them to my images. Previously I've allways just played about with the liders until I thought my image was reasonable. Recently been reading up on it a bit more, but while there is loads of info on pp in general actual practical info on how to pp high iso shots seems thin on the ground. The couple I've tried already seem over processed to me so I will be trying again in the next couple of days to get it right

 

[bc_steve]

This is something I have been learning about lately as well, and I am finding the more I do it the more I start to notice the noise in my other pictures. The luminance slider in the raw-conversion window in photoshop is pretty effective but above 25 or so it usually starts to make the image look too soft. I will try playing with the colour slider more now that I have heard a few people recommend it.

One thing that bothers me is when I get the noise down only to reintroduce it when I do a little sharpening (sometimes I just avoid the sharpening altogether to avoid this). I definitely need to learn some better techniques to sharpen images without adding too much additional noise

weepete, not sure what kind of camera you shoot with, but if you are taking long exposures of 8 seconds or more there is an option in your camera for Long Exposure Noise Reduction (that's what Nikon calls it anyways). It's default setting is off. I guess after you take a picture (> 8 seconds) it does another exposure with the shutter closed and subtracts the noise in that image from the original picture that you took. I haven't had the opportunity to try it yet but if you're not aware of it it might be another thing to look into to keep the noise down.

 

[Big Mike]

The biggest thing to know (IMO) is that you don't want to increase the exposure/brightness. Sure, you can get away with a little bit here and there, but as you increase the brightness of the whole image, you are increase the brightness of the noise as well (it will show up more, especially in darker areas where the s/n ratio is lower).

You will also want to be wary of increasing things like contrast, clarity etc. Sharpening is a deeper subject to tackle, but you certainly have to be aware that too much sharpening will affect noise as well. But there is a good reason the sharpening and noise reduction are in the same section...they sort of go hand in hand.
If it suits the image, you could adjust the clarity to a negative value. That is usually not my cup of tea, but it will smooth out noise.

Also, make sure you are adjusting your noise reduction and sharpening while viewing at 100% (at least in the little window) so that you can clearly see what is happening, but don't forget to zoom out and get an 'overall' sense of what the image is looking like.

 

[bc_steve]

The biggest thing to know (IMO) is that you don't want to increase the exposure/brightness. Sure, you can get away with a little bit here and there, but as you increase the brightness of the whole image, you are increase the brightness of the noise as well (it will show up more, especially in darker areas where the s/n ratio is lower).

You will also want to be wary of increasing things like contrast, clarity etc. Sharpening is a deeper subject to tackle, but you certainly have to be aware that too much sharpening will affect noise as well. But there is a good reason the sharpening and noise reduction are in the same section...they sort of go hand in hand.
If it suits the image, you could adjust the clarity to a negative value. That is usually not my cup of tea, but it will smooth out noise.

Also, make sure you are adjusting your noise reduction and sharpening while viewing at 100% (at least in the little window) so that you can clearly see what is happening, but don't forget to zoom out and get an 'overall' sense of what the image is looking like.

Yes, and I find it's a good idea to use CTRL-Z (undo/redo) back and forth a few times to see if the change you made was a good one or a bad one.

I have heard a few people say that it is better to over-expose slightly than to under-expose. I have traditionally done the opposite because I worried about having blown out areas where the detail is unrecoverable but maybe this isn't the right approach? I hadn't realized until now that the reason to over-expose is to minimize noise. Thanks.