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Photo Forum / Film Photography / 35 mm / February 2010Digital noise
Scott W wrote: >BTW this is one of my scans, I believe that was Kodachrome >http://www.flickr.com/photos/36939621@N06/4309159530/sizes/o/in/set-7... >When viewed at that size it would be hard to tell that scan from a >digital shot, but viewed closer and I see the noise in the scan that >drives me nuts. Being a film guy, digital noise is one of the many concepts that is foreign to me. I do scan my slides and negs, so I would like to know what to look for and get some tips on correcting it. Can anybody post some examples or explain how it happens? Thanks in advance. On Jan 28, 8:47 am, "pbromag...@aol.com" <pbromag...@aol.com> wrote: > Scott W wrote: > >BTW this is one of my scans, I believe that was Kodachrome [quoted text clipped - 9 lines] > > Thanks in advance. When scanning film areas that should be smooth will often have a texture from the grain, or dye clouds. I in a lot of skies and in darker areas of the image. This is a good example of a lot of noise in the sky http://www.flickr.com/photos/36939621@N06/4313348614/sizes/o/ This is a pretty extreme case of noise in a scanned photo, the image captures pretty good detail but looks way soft due to all the grain. http://www.flickr.com/photos/36939621@N06/4312626605/sizes/o/in/set-721576232852 64902/ This is not really digital noise, it is noise in the film. Some scanners do better at limiting the level of the noise/grain, but it is still there. > This is not really digital noise, it is noise in the film. Some > scanners do better at limiting the level of the noise/grain, but it is > still there. Right, film grain I am very familiar with. I never thought to call it noise. Your 2nd pic reminds my of what my mom used to take with her instamatic. I checked a few of my slide scans (I usually use Velvia, a very hi-def film) and didn't see any cases of my scanner adding noise. Thank you for replying. On Jan 28, 1:47 pm, "pbromag...@aol.com" <pbromag...@aol.com> wrote: > Being a film guy, digital noise is one of the many concepts that is > foreign to me. I do scan my slides and negs, so I would like to know > what to look for and get some tips on correcting it. Can anybody > post some examples or explain how it happens? > > Thanks in advance. Here's a quick and dirty test pic I just made showing what it looks like. Note the noise in the sky in the 6400 ISO pic. http://bretdouglas.smugmug.com/Other/Misc-stuff/noisetest/777532168_RW2m6-O.jpg > On Jan 28, 1:47 pm, "pbromag...@aol.com" <pbromag...@aol.com> wrote: > [quoted text clipped - 10 lines] > > http://bretdouglas.smugmug.com/Other/Misc-stuff/noisetest/777532168_R... Also, no noise reduction was used in either of these pics. They were both shot in RAW mode and imported with NR set to zero. I wonder how a 6400 ASA film shot (if there is such a thing) could compare? On Jan 28, 1:47 pm, "pbromag...@aol.com" <pbromag...@aol.com> wrote: > Being a film guy, digital noise is one of the many concepts that is > foreign to me. I do scan my slides and negs, so I would like to know > what to look for and get some tips on correcting it. Can anybody > post some examples or explain how it happens? > > Thanks in advance. Here's a quick and dirty test pic I just made showing what it looks like. Note the noise in the sky in the 6400 ISO pic. http://bretdouglas.smugmug.com/Other/Misc-stuff/noisetest/777532168_RW2m6-O.jpg Obviously, the ISO 100 shot is cleaner, but the ISO 6400 shot is amazingly good, considering that it could have been taken at midnight.....:^) > Here's a quick and dirty test pic I just made showing what it looks > like. > Note the noise in the sky in the 6400 ISO pic. > > http://bretdouglas.smugmug.com/Other/Misc-stuff/noisetest/777532168_R... Ooooh. Thank you. Just what I was looking for. So digital noise is really just the digital equivalent of film grain at higher ISOs. It happens at image capture time and there really isn't anything much you can do about it once it's there. On Jan 31, 8:25 pm, "pbromag...@aol.com" <pbromag...@aol.com> wrote: > > Here's a quick and dirty test pic I just made showing what it looks > > like. [quoted text clipped - 6 lines] > happens at image capture time and there really isn't anything much you > can do about it once it's there. Almost correct. You can eliminate most of it via software or by simply cranking up the NR when you import the RAW file. This can soften the overall image, however, so one trick is to just use the noise reduction on selected areas such as the blue sky in my example. One other point needs to be made. Some people often mistake film grain for detail in a photo. For example, if you shoot a photo of a snow-covered yard (or any monochromatic smooth surface) with both digital and film and then blow up both pics, it might appear that the film image has more detail in the snow. However, on closer inspection you'll see that most of this faux detail is really just grain. At least that was my experience the last time I did that test. Too bad I don't have any film in stock this weekend as we finally had our biggest snow in 10 years .... a whopping 4 inches. > One other point needs to be made. Some people often mistake film > grain for detail in a photo. Often, this is a plus point. Perfectly sharp noise-free images usually look softer. Some have speculated that noise is actually a source of dither that improves our visual acuity - compare the way that a dither signal (noise) must be added to 24-bit digital audio before it is truncated to 16-bit CD audio. There is currently not enough evidence to turn the visual acuity hypothesis into science. Personally, I like the idea. > For example, if you shoot a photo of a snow-covered yard (or any > monochromatic smooth surface) with both digital and film and then blow [quoted text clipped - 4 lines] > this weekend as we finally had our biggest snow in 10 years .... a > whopping 4 inches. Digital noise is more annoying than dye clustering in film (grain) when the measured RMS noise is the same. Both the probability and spectral densities are quite different. The RMS value does not take visual acuity into account, again there is insufficient evidence to create a repeatable formula. Pete Annika1980 wrote,on my timestamp of 1/02/2010 3:42 PM: > For example, if you shoot a photo of a snow-covered yard (or any > monochromatic smooth surface) with both digital and film and then blow > up both pics, it might appear that the film image has more detail in > the snow. Brett: no one in his right mind wants to see "detail" in snow!... When are you gonna start taking *photos* instead of "statements of detail"? > Annika1980 wrote,on my timestamp of 1/02/2010 3:42 PM: > [quoted text clipped - 5 lines] > Brett: no one in his right mind wants to see "detail" in snow!... > When are you gonna start taking *photos* instead of "statements of detail"? Odd statement: Bret has posted more photos than anyone, and I sure haven't seen anything worthwhile from your sniping self.  Signaturejohn mcwilliams John McWilliams wrote,on my timestamp of 3/02/2010 3:00 AM: >> Annika1980 wrote,on my timestamp of 1/02/2010 3:42 PM: >> [quoted text clipped - 9 lines] > Odd statement: Bret has posted more photos than anyone, and I sure > haven't seen anything worthwhile from your sniping self. Rest... It's obviosuly all too much for your old mind. > John McWilliams wrote,on my timestamp of 3/02/2010 3:00 AM: >>> Annika1980 wrote,on my timestamp of 1/02/2010 3:42 PM: [quoted text clipped - 13 lines] > Rest... > It's obviosuly all too much for your old mind. Almost a week and you come up with this weak response? You've slipped to nu lo's. John McWilliams wrote,on my timestamp of 9/02/2010 4:13 AM: >>>> Brett: no one in his right mind wants to see "detail" in snow!... >>>> When are you gonna start taking *photos* instead of "statements of [quoted text clipped - 7 lines] > > Almost a week and you come up with this weak response? The truth hurts, doesn't it? > You've slipped to nu lo's. Nevertheless, I still look down on you. > Brett: no one in his right mind wants to see "detail" in snow!... First off, it's "Bret." I remember the last time it snowed here (2003, I think) and I posted some pics I took then comparing film to digital. A few of the film luddites complained that the digital shots smoothed out the texture of the snow into a white blob. So maybe that bolsters your point. Annika1980 wrote,on my timestamp of 3/02/2010 4:16 AM: > First off, it's "Bret." Er....... OK. > I remember the last time it snowed here (2003, I think) and I posted > some pics I took then comparing film to digital. A few of the film > luddites complained that the digital shots smoothed out the texture of > the snow into a white blob. So maybe that bolsters your point. Wanna bet all of those "film luddites" weren't? > this weekend as we finally had our biggest snow in 10 years .... a > whopping 4 inches. And here we've had less snow this season than in most years. (A "small" fall is about 4 inches, however). Signaturegmail originated posts are filtered due to spam. On Feb 5, 12:12 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca> wrote: > > this weekend as we finally had our biggest snow in 10 years .... a > > whopping 4 inches. > > And here we've had less snow this season than in most years. (A "small" > fall is about 4 inches, however). Snow? what is this snow stuff you guys keep talking about? Scott > On Feb 5, 12:12 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca> > wrote: [quoted text clipped - 5 lines] > > Snow? what is this snow stuff you guys keep talking about? It's that white stuff on the top of Haleakala, and select places on the Big Island.... Signaturejohn mcwilliams > > On Feb 5, 12:12 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca> > > wrote: [quoted text clipped - 8 lines] > It's that white stuff on the top of Haleakala, and select places on the > Big Island.... So that is what that stuff is, cool. Scott > On Feb 5, 12:12 pm, Alan Browne<alan.bro...@FreelunchVideotron.ca> > wrote: [quoted text clipped - 6 lines] > > Snow? what is this snow stuff you guys keep talking about? Solid phase dihydrogen-monoxide. Signaturegmail originated posts are filtered due to spam. >> Snow? what is this snow stuff you guys keep talking about? > > Solid phase dihydrogen-monoxide. Sounds poisonous. Pete >>> Snow? what is this snow stuff you guys keep talking about? >> [quoted text clipped - 3 lines] > > Pete Not poisonous, but is is an asphyxiant and a good solvent. You may be more familiar with the common drink, hydrodgenol. -Jim >>>> Snow? what is this snow stuff you guys keep talking about? >>> [quoted text clipped - 5 lines] > Not poisonous, but is is an asphyxiant and a good solvent. You may be more > familiar with the common drink, hydrodgenol. Is that the drink I call tapolene by any chance? Much cheaper than buying in bottled form. My deranged mind is now attempting to think of a name for the result of combining the good solvent dihydrogen-monoxide with washing up liquid - for the purpose of turning the processes of washing-up into a fun exercise. Any help would be more than appreciated, if only for the sake of my dishwasher - it has so far managed to avoid having things shoved into it that are not supposed to go there, but it's living on borrowed time. Pete >>> Snow? what is this snow stuff you guys keep talking about? >> >> Solid phase dihydrogen-monoxide. > > Sounds poisonous. It's all over the place, mostly unregulated. Food companies use it in processing and as an ingredient. The human body can die for lack just enough or just a little too much. Must be very careful around it. Signaturegmail originated posts are filtered due to spam. >>>> Snow? what is this snow stuff you guys keep talking about? >>> [quoted text clipped - 7 lines] > > Must be very careful around it. In its solid phase I can't walk on it - the opposite of metal and most other reasonable materials. Obviously it should be banned outright. I'm waiting for the day when the annual motor vehicle test includes dihydrogen-monoxide in the list of exhaust gasses. Being serious for once, I do sometimes dilute my dihydrogen-monoxide intake with a little alcohol, so I think I'm on safe ground. When the ground becomes unsafe I've learnt to adjust the ratio for next time. Thanks for the humour Alan, Pete >>>>> Snow? what is this snow stuff you guys keep talking about? >>>> [quoted text clipped - 10 lines] > In its solid phase I can't walk on it - the opposite of metal and most other > reasonable materials. Obviously it should be banned outright. I walk on it all the time. It compacts into a more resilient packed form. You can also wear solid phase di-H monox shoes to decrease your load over the surface. Whether compact or not, various sports are practiced on it, occasionally leading to injury or death. > I'm waiting for the day when the annual motor vehicle test includes > dihydrogen-monoxide in the list of exhaust gasses. > > Being serious for once, I do sometimes dilute my dihydrogen-monoxide intake > with a little alcohol, so I think I'm on safe ground. When the ground > becomes unsafe I've learnt to adjust the ratio for next time. Too much of the later and the ground might rise up and smite thee. > Thanks for the humour Alan, Humour? Signaturegmail originated posts are filtered due to spam. >> Thanks for the humour Alan, > > Humour? It's very serious- I found this info via a quick Google: "BAN DIHYDROGEN MONOXIDE – THE INVISIBLE KILLER! Dihydrogen monoxide is colorless, odorless, tasteless, and kills uncounted thousands of people every year. What are the dangers of Dihydrogen Monoxide? Most of these deaths are caused by accidental inhalation of DHMO, but the dangers of dihydrogen monoxide do not end there. Prolonged exposure to its solid form causes severe tissue damage. Symptoms of DHMO ingestion can include excessive sweating and urination, and possibly a bloated feeling, nausea, vomiting and body electrolyte imbalance. For those who have become dependent, DHMO withdrawal means certain death. Dihydrogen Monoxide Facts Dihydrogen monoxide: is also known as hydric acid, and is the major component of acid rain. contributes to the Greenhouse Effect. may cause severe burns. contributes to the erosion of our natural landscape. accelerates corrosion and rusting of many metals. may cause electrical failures and decreased effectiveness of automobile brakes. has been found in excised tumors of terminal cancer patients." SignatureJohn McWilliams > Dihydrogen Monoxide Facts > Dihydrogen monoxide: [quoted text clipped - 7 lines] > brakes. > has been found in excised tumors of terminal cancer patients." Yes, it is a very serious issue. In the s/w US they can't get enough of it; in parts of Asia they get far too much. I just heard that there is a major dihydrogen-monoxide attack on Washington DC and much of the eastern seaboard. Terrorists? If Bush were still in power he would certainly raise the threat level three notches to: "Beyond all doubt, we're at war. Break out the non-negotiated support contracts!" Signaturegmail originated posts are filtered due to spam. >> Dihydrogen Monoxide Facts >> Dihydrogen monoxide: [quoted text clipped - 17 lines] > level three notches to: "Beyond all doubt, we're at war. Break out > the non-negotiated support contracts!" There was a time when GW seemed to feel he could walk on the liquid form. Some say his successor may eventually accomplish that feat. I suspect there must be a change in the laws of physics before such a thing can come to pass. SignatureFrank ess >> Here's a quick and dirty test pic I just made showing what it looks >> like. [quoted text clipped - 4 lines] > Ooooh. Thank you. Just what I was looking for. So digital noise is > really just the digital equivalent of film grain at higher ISOs. They are not at all the same. Higher ISO film grain takes more surface area as the dye spreads are larger in x,y (surface of the film) which contributes a softening as well as a noisy look. Digital noise is always constrained to its pixel regardless of ISO. They characterize much differently in the final image which is why digital generally looks so clean, even at moderately high ISO. Signaturegmail originated posts are filtered due to spam. On 1/28/2010 10:47 AM pbromaghin@aol.com spake thus: > Scott W wrote: > [quoted text clipped - 8 lines] > what to look for and get some tips on correcting it. Can anybody > post some examples or explain how it happens? Digital noise is a pretty deep subject; techincally, it's a thermodynamic phenomenon, and the physics that explains it is way above all our heads. To simplify, noise in digital photos is basically errors in conversion from analog to digital (known as "quantization error"). Remember that while everything downstream of the CCD in a digital camera is digital, the sensor is an analog-to-digital converter. While it works fairly well, at higher sensitivities (higher ISO settings), more errors occur in the conversion process. Since the errors are more or less random, the result is the specking effect visible as "noise". The same thing happens with film, of course. You'll see similar types of speckling in shots made on high-speed film. (This is entirely separate from grain, which is the result of actually seeing the grains that make up a photographic image; kind of the film equivalent of pixels.) I'm no expert on the subject. I do know that one proven way to avoid digital noise is to shoot at lower ISO settings (like using slower film). SignatureYou were wrong, and I'm man enough to admit it. - a Usenet "apology" > Digital noise is a pretty deep subject; techincally, it's a thermodynamic > phenomenon, and the physics that explains it is way above all our heads. The effect of thermal noise in the photosite amplifiers is being reduced all the time. Canon have brought it down to a very low level. > To simplify, noise in digital photos is basically errors in conversion > from analog to digital (known as "quantization error"). Remember that [quoted text clipped - 3 lines] > conversion process. Since the errors are more or less random, the result > is the specking effect visible as "noise". ISO is increased via the amplifier gain, therefore thermal noise is increased by the same amount. The output of the amplifier goes to the analog to digital converter, which does have some quantization error (as you stated) - this error is not affected by ISO setting. Technology is continually reducing this error. The dominant source of noise is photon shot noise (unless the camera is very poor). When the number of photons is fairly large, the signal to noise ratio is proportional to the square root of the number of photons accumulated by the photosite. Large photosites can accumulate more photons before they become full (saturate) thereby increasing signal to noise ratio - under the same shooting conditions as a small photosite. Doubling the area of a photosite allows it to capture twice as many photons while the shutter is open (and allows it to accumulate twice as many before it saturates) - this increases the signal to noise ratio by 1.4. Looked at another way: it allows the shutter to be open for half the amount of time (same signal to noise ratio) therefore we get a doubling in ISO sensitivity. One of the reasons for having two green photosites in a Bayer CFA RGGB detector is to reduce noise in the green channel - the eye is most sensitive to green light. > The same thing happens with film, of course. You'll see similar types of > speckling in shots made on high-speed film. (This is entirely separate > from grain, which is the result of actually seeing the grains that make up > a photographic image; kind of the film equivalent of pixels.) Film "grain" is actually dye clustering, it looks completely different from the thermal and shot noise in digital photography. The magnitude of dye clustering is indicated by its RMS granularity (hence the name "grain"). Kodak did tremendous work to reduce the annoyance of dye clustering then produced their T-grain emulsions. Bravo. > I do know that one proven way to avoid > digital noise is to shoot at lower ISO settings (like using slower film). Yes. Pete Scanning at a high resolution to capture all the details will also capture grain of the film. There is no way around it. Here is a good site which tells you more than you ever need to know about scanning; http://www.scantips.com/ A good grain reduction software which I use is Digital Gem. By Kodak. It has settings for noise reduction as well as fine grain removal. http://www.asf.com/ I use the stand alone program more than the Gem that came with my Nikon film scanner software because it gives me more controls for suppression. Michael...... >Scott W wrote: > [quoted text clipped - 10 lines] > >Thanks in advance. > Scanning at a high resolution to capture all the details will also capture grain > of the film. There is no way around it. Here is a good site which tells you [quoted text clipped - 23 lines] > >what to look for and get some tips on correcting it. Can anybody > >post some examples or explain how it happens? One addition to what everyone has said to date, whether your image source is scanned film or from a digital camera, always, always keep the original image, before noise reductions. You might well find a number of years from now you have better noise reduction software available and it would be a shame to have only saved the noise reduced image. |
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