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While purchasing a DSLR which factors should be kept in mind if your aim is to zoom your photograph to 100%, frame it, and hang it on a wall?

At 100% there shouldn't be ANY noise.

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Hmmm. Would you rather have a 1 megapixel camera which could make images you could print at 100% with no noise, or a 24 megapixel camera where you could print at 50% with no noise? –  mattdm Dec 26 '11 at 4:33
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This question also gets into some technical details but should help you: Is there a general formula for image size vs. print size?. If the arithmetic makes your eyes glaze over, scroll down to the answer with a rainbow-colored chart. It's oversimplified, but maybe that'll be the most helpful to you at this point. –  mattdm Dec 26 '11 at 15:35
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@mattdm :) you said: How large of a picture do you really want to print Finally I gave it a thought and decided that the pictures I would print will be roughly of max size equal to a 19 inch LCD screen. I'll soon look up your linked questions too. –  TheIndependentAquarius Dec 30 '11 at 3:53
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A 19" wide-screen LCD is typically about 16"×10". That gives you some numbers to work with in looking at the other posts. –  mattdm Dec 30 '11 at 4:03
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It's not quite so simple when printing (see particularly jrista's answer linked to above), but very roughly: a 16 megapixel DSLR will produce images about 5000 pixels across. That means a little more than 300 pixels per inch, which in turn can roughly be considered "100%" if you are inspecting quite closely. –  mattdm Dec 30 '11 at 4:22

4 Answers 4

up vote 6 down vote accepted

Noise is like death and taxes, it is unavoidable.

Even the most expensive cameras produce noise and, although, it may only be visible at 100%. The base ISO, usually between 100 and 200 is almost noise-free, but you will still see noise in images, particularly in shadow areas.

What strikes me as odd about your request is that 100% scale can give you very different print sizes depending on the camera and print resolution. If you print an image at 300 DPI from a 8 MP DSLR, you will give a MUCH smaller print than an image from a 24 MP DSLR printed at 180 DPI.

What happens to noise is that it gets averaged-out and becomes visibly diminished when images are scaled down, so if you have extra pixels and can afford to scale down for the print size you want, you will be better off in terms of noise.

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You said: Noise is like death and taxes, it is unavoidable. But I have seen giant sized photographs with zero noise. Oh, so they use noise reduction filters? How many pixels are considered \enough? –  TheIndependentAquarius Dec 26 '11 at 3:55
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Ditto to the print-size consideration. Anisha, This seems like the wrong way to look at the problem. Instead, decide how large you want to print, how closely you expect the print to be examined (a billboard is large, but no one looks at it with a magnifying glass), and how much you can spend. Then, if the technology doesn't live up to what you need for all three of those, decide where you want to compromise. –  mattdm Dec 26 '11 at 3:55
    
The best way to get a noise-free image is to average out tons of pixels. You can make a panorama using dozens or even hundreds of images and they scale it down. That way the individual pixels get average out even if you print at 240-300 DPI which is considered dense enough not to see pixels at close viewing distances. –  Itai Dec 26 '11 at 3:59
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A) stand far away, as one normally does with a billboard, B) use an expensive medium-format camera, or C) take many, many images and merge/blend them with software as Itai suggests. But how big do you really want to print? –  mattdm Dec 26 '11 at 4:09
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@AnishaKaul 'I have seen giant sized photographs with zero noise' show us some examples of what you mean. I suspect that when you say noise it doesn't mean the same as when others say noise –  user7226 Dec 28 '11 at 14:43

There will always be noise - but you can minimize noise, you can remove it in post processing or you can understand that in most cases noise doesn't matter.

Minimize noise

To minimize noise you need lots of light, there will always be noise but if you have a bright image the image will be so much "stronger" than the noise you wont be able to notice it - so, the minimize noise you have to over expose your image just a bit (but not so much you blow the highlights) and avoid dark areas.

To do so turn on the histogram display on your camera and expose the picture so that the all the histogram data is on the right side (but without hitting the edge).

Of course, nothing in life is free - if you do it too much you will get low-contrast washes out images too little and you get noise

What's better, a boring washed out noiseless image or an interesting image with some noise?

Noise reduction in post processing

Every software that is designed to handle photos has a noise reduction feature - some are better than others but they all basically work by hiding small details and blurring the picture a bit, the stronger the noise reduction the more blur you get.

What's better, a blurred photo without noise or a crisp photo with some noise?

Understand that noise is fine

Normal people (that is, not photographers or graphic designers) will never look at a 100% crop of your photos, also, the bigger you print the farther away from the picture they will go to look at it - so they will never see the noise.

Normal people also don't notice noise, unless you have extreme noise people just won't notice it - they look at your subject, expressions on faces (if any), they notice color and contrast but their brain is ignoring the noise and they just won't see it unless someone points it out for them (unless the noise is so extreme it's hiding important details of the photo).

What's better, a photo people like when they look at it or a picture that is technically perfect in ways your audience will never notice?

Summary

Bright images have less noise, if you have little bit of noise you can remove it in post processing and, most importantly, unless you are shooting stock photos or most of your viewers are members of camera clubs (or other types of "pixel peepers") some noise doesn't matter at all.

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Noise reduction doesn't necessarily mean blur -- it depends how good the algorithm is. Wavelet algorithms aren't particularly good at preserving detail when the noise reduction gets aggressive, but wavelet isn't the only technique out there. Some types of detail (more textures than details) may be nearly indistinguishable from noise -- but then, you wouldn't notice the noise, would you? –  user2719 Dec 26 '11 at 8:23
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@StanRogers - it's true that there are better and worse algorithms, but at the end of the day the computer has no way of knowing if a slightly brighter pixel is slightly brighter because of noise or because something you photographed and any aggressive noise reduction will remove some details (but the details that are removed will vary by algorithm). –  Nir Dec 26 '11 at 12:36
    
At the risk of sounding like a shill (I'm not -- just a huge fan), you've really got to try interactive manually-adjusted noise removal in Topaz DeNoise (not the presets). But don't take my word (or Topaz's marketing's word, or even John Cavan's (see photo.stackexchange.com/questions/5019/… )) for it; check the review at Luminous Landscape: luminous-landscape.com/reviews/software/topaz.shtml . Then try the trial yourself. –  user2719 Dec 26 '11 at 18:06
    
@StanRogers - the example pictures on the topaz site look too good to be true and the pictures in the review you linked to also look amazing, unfortunately I don't have the budget to buy this plugin right now (saving up for lighting equipment) but fortunately, I really don't feel the need for noise reduction in anything other then my cell-phone pictures, so I don't need to buy it - I'll just take your word on it (and I will check it out if I ever really need to reduce noise). –  Nir Dec 26 '11 at 21:49
    
There's a 30-day free trial if you get the urge to check it out -- same as with most of the better plug-ins. (It's also useful if there are a few images you need to rescue and can't actually afford to buy it -- there are no restrictions on the trial except for the thirty-day thing. Tag all of your noisy-but-good images as they accumulate, then tackle them when there are enough to make it worthwhile.) And it's worth watching the tutorial on YouTube before using it, because although it's very simple once you know what you're doing, there are a lot of controls to learn. –  user2719 Dec 26 '11 at 22:05

I don't understand what you mean by zoom your image to 100%.

Do you mean print it at whatever size allows you to print at 300 dpi (assuming that's your printer's native output?)

Looking at your photo at 50% on screen is a good way of approximating what it will look like when printed.

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At 100% there shouldn't be ANY noise

This is a poor assumption. The world of film cameras (and pre-digital movies) had tons of 'noise' due to the way film is constructed and processed. A grainy picture can often be better than a smooth one.

Texture is important in photographs and part of the texture is the 'noise', a texture free photograph would actually be more like a cartoon or those horrendously overdone 'airbrushed' covers on magazines.

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