High ISO Noise
Digital Noise Is The New Film Grain
Back in the days of film we may have steered away from using a high speed film like black & white Tri-X Pan or Kodacolor 400, due to its more noticeable grain. But since It was ASA 400, we could use it in lower light situations at hand held speeds. We just sort of accepted the fact that grain would be there and shot it anyway.

Even before the digital revolution took hold, the speed settings we knew as ASA (American Standards Association) became ISO (International Standards Organization) for labeling film speeds. And not to add even more confusion, I will just mention that there is also a 3rd way in which sensitivity was measured called DIN ( Deutsch's Institut für Normung).

Anyway.... to prevent me having to skip explanations about mathematical stuff and combinations of ways of measuring sensitivity, let's just say that ASA and ISO are pretty much the same. In fact if you never shot film or didn't learn photography with film, you most likely don't even know of the term "ASA".

Hopefully you know of the Exposure Value Triangle in which ISO, Shutter Speed and Aperture are all coincide with each other and if you changed one setting the others will have to be changed to correspond. Thats where cameras help you out with that aspect of making a photo by automatically making the changes to the exposure value according to the change in any of the three settings when using some variation of an automatic mode. Of course that whole mess of the triangle is another topic in itself...

Just as we have the grainy look to High ASA speed film images, we also have a similar effect that happens in High ISO images. And as digital cameras have progressed in development, one of the big factors that keeps improving is the amount of grain we see in High ISO images. In fact they don't even call it "grain" anymore since it's not about grains of silver, it is now known as "Noise".

Digital Noise Is The New Film Grain
My first DSLR was a Nikon D100 introduced in February of 2002 that had a native ISO range of 100-1600, which meant I could shoot the camera as if I had film in it up to a speed of 1600 ASA/ISO. Probably the biggest reason photographers don't accept digital noise like we did film grain, is because digital noise is ugly and not as natural looking as film grain seemed to be.

There are three basic types of noise (these are just my three picks, you will find an assortment of names for different types of noise throughout the Internet) you will encounter in digital photography...
Color Noise, which mostly will appears as red, green and blue random pixels.
Luminance Noise
contains pixels of varying brightness levels (black, white, and gray).
and JPEG Artifacts which make the image look like it's been divided into a pattern of 8x8 pixel squares.

Although personally I would put JPEG artifacts in it's own category since it is created by image compression and not from underexposure shadow recovery or high ISO.

Even the noise produced from shadow recovery of underexposed images is different than typical high ISO noise in properly exposed images. How you decide to treat them will vary from image to image depending once again on your final use of the image.

Pushing The Envelope
For the most part, you mostly will encounter noise when shooting at High ISO and recovering the shadow areas from underexposure and in the darker tones of the image. As DSLR's keep evolving, so do the demands for a cleaner and higher "native ISO" (I don't like to include the extended range ISO, since they are really just a setting that will capture an image but it certainly will be quite noisy and not salable or suitable for large prints.

In the Fall of 2013 I acquired a Nikon D600 that has a native ISO of 100-6400 with extended ranges that took it to 25,600. Those are ISO speeds hundreds of times higher than ever imaginable with film.

The D600 is also a "Full Frame" digital camera which means the sensor is the same size as 35mm film is, which in turn will produce a larger print than the "Crop Frame" DSLR's that were originally produced.

The native ISO keeps being pushed and pushed to a point where the even the very affordable Nikon D500 has a native ISO range of 100-51,200 with an extended range up to 1,640,000 equivalent. Even a more budget minded D5500 has native ISO from 100-25,600. Back in the day when I would "push" a roll of ASA 400 film to 800. would be pushing the usable limits, although you could push it to 1600 or 3200 ASA with some extreme amounts of graininess. The idea that one day it would reach ISO speeds of 25,000 and above would have been an insane idea.

Not All ISO's Are Created Equally
Just because a camera boast it may have a native ISO up to 6400, doesn't mean it is as equal to any camera with the same native ISO range. In this comparison at ISO 3200 from a Crop Frame D3100 (14MP), Full Frame D600 (24MP) and Full Frame D810 (36MP), you can see there are differences in the resulting images.

There are many photographers that claim you can get just as good of an image from mostly any DSLR as it is more about the photographer's knowledge than it is the cameras features. Yes... that is true in some respects but not when it comes to High ISO performance.

Whether or not you even need to concern yourself with the attributes of noise in your images also depends on your final use of the images you capture. If they stay on digital devices like computers, phones and tablets, then you really don't need to bother much with spending money to have less noise.

The sample images shown here are only 643 pixels wide and that may be within a couple hundred pixels of the extent of your image needs. As you scroll through the examples, you will be hard pressed to really see much of a difference in the apparent noise in any of these 3 images captured at ISO 3200.

Even the image from the budget price Crop Frame camera is very acceptable at ISO 3200 when used in this format. Even printed at small 5x7 size it will not be unacceptable due to noise. Since Color Balance, White Point, Shadows and other attributes of the image are purely subject to the desires of the photographer, you can indeed get just as good of an image from about any camera.

Buying a camera based on it's ISO range and level of noise should not be a part of the decision making unless your use for the images is dependent upon the clarity when viewed at larger sizes and most notable when in print. Since it's is estimated that only 15% of digital photographs captured are actually printed, then that makes the market need for High ISO capable cameras much smaller than the manufacturers would have you to believe.

Diving deeper into this set of example images, lets see how they look at much larger magnifications. Although in the small size uses of an image may not show any noise at all, you will have noticeable amounts when using the image for a larger presentation such as for prints and large format outputs.

One thing to keep in mind about this particular set of example images is that all 3 samples must be presented at different magnifications to display them at the same visual size. Meaning the 36MP image doesn't have to be magnified as much to make a 12x18 print as the other two do. And the same for the 24MP image needs less magnification than the 14MP image does.

So naturally if you are going to get a camera that has a higher mega-pixel count, you will see less noise at the same ISO than one of a smaller mega-pixel count. This is where sharpness and noise kind of go hand-in-hand with each other. The issue photographers are facing when it comes to figuring out the best camera for low noise, is also going to be one that will be slightly sharper in it's visual appearance, but mostly wen viewed at magnifications above 100% of the actual pixel size.

As a sort of Rule-of-Thumb... the more the camera cost, will also be one that produces less noise. The subject of noise seems to be the trend manufacturers are taking now that sharpness is pretty much reached an almost level playing field. Now the push is to see who can make a sensor with the highest possible ISO and the lowest possible amount of noise. The consumer grade camera has gotten so good that noise is not a problem except to those with specialized image needs or trying to correct an underexposed imaged by several stops.

Smooth Away The Noise
There are now many specialized applications and Photoshop filters designed to eliminate the noise in our digital images. While not so evident in the sample image shown here captured at ISO 12,800, you don't see the noise when viewed at the 800 pixel wide sample image.

Using Noiseless CK, one of the many assorted noise reducing filters & applications on this image did in fact remove the noise, but also with a loss of sharpness as a result.

You can remove noise within the Photoshop application using one of the built-in noise reduction filters or choose from an untold amount of Noise Reduction filters available, the end result is going to be quite similar no matter which one you use.

How To Choose To Leave It Be or Clean It Up
To repeat my response to most image quality questions, and many other photography questions it would be "It depends on the final use of the image". In my personal final uses of my images fall into two categories, being small JPEG images for social media and large format GiClee prints that are available from my website and galleries that represent me.

When it comes to social media images, I really don't care if there is visible noise or not, and when an image I want to make a gallery print out of has a visible amount of noise, then I am Ok with it if it resembles film grain and not colored noise. But... in certain images that I really like and want to print large but really need less noise, I will employ some method of noise reduction.

As in the case of the sample image shown here of "Uneven Crowns" that I produced from my 6MP Nikon D100 in June of 2004. In the original version which has been printed several times and a 22x28 still hangs in my home, I felt that the added softness worked well with this image and the tone down of the gritty noise look just is more appealing.

I used the "Extreme" setting in Noiseless CK for this image and you can see the actual difference side by side in the second image in the pop up window of these samples. I tested the same effect in Photoshop with it's built in filter and even tinkered with the resharpening slider. But like sharpening an image of any type you basically are just increasing edge contrast of pixels and thus making a harsher looking edge. When resharpening an image you have already smoothed out with a noise filter, you most likely will not like the results unless the final use will be only for computers or digital devices.

Just like any other topic in digital photography you will find a wide array of articles on how to get rid of noise...
Again, my advice to anyone who ask it to find out for yourself so you know what methods work best for you with the tools you have and yield the result you best like. Make your images suit you and don't make them to suit some other experts opinion.

Even in todays Hi-Tech times, people still buy photography that is visually appealing to them and not on how technically correct it may happen to be. The only photo critics are other photographers and they are not your target market and they shouldn't be the ones you shoot for to please.

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