Need to reduce noise / but not detail

Started 2 months ago | Discussions thread
tvstaff
OP tvstaff Senior Member • Posts: 2,628
Re: Need to reduce noise / but not detail

Mark Scott Abeln wrote:

tvstaff wrote:

Photo needs to be 8000px on long edge at 1200DPI for a client.

That camera can deliver images that are at most 5472 x 3648 pixels, and so anything wider than that is upsampled, interpolated detail. But that usually isn't a problem.

"Dots per inch" are pretty much meaningless with regards to digital image files. That is a value that describes how particular printers work. Each pixel is rendered as many dots of various colors, but the number of dots in the pattern varies between printer models and printer settings, none of which are encoded in the image file.

Perhaps they meant pixels per inch, but even if that were true, 1200 pixels per inch would be quite excessive, and I doubt that anyone could see the detail unless they examined the image under a magnifying glass. A better value is 300 pixels per inch. This would give us 4 dots per pixel, which is reasonable for some printers, but not all of them.

Under most circumstances, such as making images for the web or making prints using a desktop printer, I would recommend ignoring the pixels per inch setting altogether as being at best meaningless, and at worse misleading. In these cases, pixels alone are what's important.

Unfortunately, many page layout packages, such as Adobe InDesign, use inch dimensions for everything, and so images have to be tagged with a pixels per inch value in order for them to import at the correct inch size. It is easy for whomever is doing the layout to simply just change the pixels per inch value of the image, but that might get them upset at you. Of course, pixels per inch times inches is equal to pixels, so nothing really is different.

Is there is process outside of PS that will reduce noise but keep detail.

No, there is not. Some noise reduction software is better than others, but they all have to guess at what is noise and what is detail, and inevitably some detail will be lost along with the noise, and some of the noise will be retained as detail.

Or am I relegated to doing it by hand? Not lazy just looking to enhance workflow if possible.

As the others mentioned, this image is considerably oversharpened, and this image does not have a problem with noise; understand that sharpening enhances noise. I hope this wasn't done in-camera, but it looks that this was edited in Lightroom, and am hoping it was from a raw file.

What I'd do is reprocess this, but turn off sharpening upon import. I then would then save it as a 16 bit file, and import the image into Photoshop and then resize it to 8000 pixels wide at 300 pixels per inch.

I would move the image to 32 bit mode and then do sharpening there. The reason for this is that sharpening an image in either 8 or 16 bits tends to produce light haloes that are excessively strong, and dark haloes that are not strong enough, but 32 bits balances the strength of both, so you can eventually sharpen far more strongly without bad artifacts.

ASSUMING that the image will be printed at roughly 27 inches across (is this correct? Do you know the exact output dimensions?) then I would suggest using Smart Sharpen with a sharpening radius of approximately 1.5 pixels and an Amount of 100% to start. If you do see some noise being sharpened, you can adjust the tool for noise. You might have to stand back from the monitor a bit to give you a realistic view on the image. You want the image to look crisper but without visible artifacts, unless you unrealistically zoom way in.

Then you move the image to 8 bits using the Exposure and Gamma conversion without changing the sliders (don't use the default Local Adaptation method).

You may very well avoid sharpening the image altogether and then let the publisher know that they will have to sharpen the image to their taste.

Hi Mark, Thank you.   I'm going to try your workflow and a few others suggested. They did not specify the intended dimensions, just the request. Thank you for writing.

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