Robert A. Staub, Jr |
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grain caused by camera resolution?
I have a Canon digital Rebel, the old one, with 6+ mpxl, shoots files at 12-bit.Lens: EF 100 macro. Shots taken during indoor live concerts at 400 ISO, aperature 2.8, shutter 1/125 sometimes come out ok sometimes turn out very grainy(at the exact same settings) Could this be due to the 12 bit limit? Would a 24 bit newer Rebel, or 36 bit 30D solve the problem? I am looking to invest in new equipment, and was looking to a new lens, but perhaps a new body would be better? Thanks in advance for your attention! Rob
January 03, 2008
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Ariel Lepor |
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Exactly how much grain do you see? 400 ISO is a bit high. A lot of pixels squeezed into a smaller area often results in more noise.
January 02, 2008
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Alan N. Marcus |
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Hi Robert Happy New Year! Noise:
We want our cameras to faithfully record thus we are disappointed when image defects creep in. To explain noise we revert to the particle theory (we effortlessly switch between wave theory, particle theory, and occasionally unified theory of light). In this case, the surface of the light capturing chip (CCD or charged coupled device) is covered with an array of light sensitive sites. When the shutter winks, umpteen billions light particles called photons are focused by the lens and caused to bombard the chip’s surface. A particular sight must receive multiple photon hits to cause it react and record. The higher the ISO setting, the less hits required. Time is of the essence, the hits are not instantaneous, they accumulate all the time the shutter is open. To make matters worse, we require that the sights differentiate between red – green – blue photons. To accomplish, we cover each sight with a strong red or green or blue filter. The filter is so strong that it restricts light passage by more than 66%. To compensate we must turn up the sensitivity of the sight (kind of like a volume control). This amplification opens up the door to generate more noise. Noise is random and unwanted false positives. We want to record only the correct the red – green – blue photon hits. Sadly we record bad information as well. First defects in the optical system and internal reflections bombard the chip with a high percentage of stray photon hits. Secondly, we have never been able to shield the chip from stray radiations. The sights additionally record heat, and x-ray and gamma ray etc. Heat is a real problem and is responsible for oodles of false positives. The size of the sight is an important factor. The larger the sight, the more likely it will receive a photon hit. Thus larger sights are naturally more sensitive (higher ISO). Since there is an abundance of accurately target photons, as compared to wrongly targeted energies, the larger the sight, the less likely it will be triggered by a false positive hit. Noise is more prevalent in smaller chips with smaller sights. The more sights on a chip the smaller they must be. The more we turn up the volume the more likely it will record a false positive. The camera heats up as it operates. Noise is more likely later on, in a session, as the heat generated causes false positives. Noise in the final image may go unnoticed if the subject is made up of random patterns. Noise is most noticeable if the subject contains expanses of mundane (uniform) areas. Hope springs eternal. Newer CCD’s will incorporate a pattern whereby a quantity of sights will be unfiltered. This greatly increases light sensitivity. Kodak’s research allows camera software to identify by adjacent sights what color photon hit should have hit an unfiltered sight. Look for this technology in all makes and models. This paves the way for smaller chips with higher sensitivity and less noise. Alan Marcus (marginal technical gobbledygook)
ammarcus@earthlink.net
January 03, 2008
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Robert A. Staub, Jr |
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Thanks Alan! That is a terrific scientific explanation; however how does it relate to the resolution of the device? The sensors are all the same overall size, until the 5D with a full frame sensor, but differ in resolution. Would the higher resolution produce less noise at the same settings for the same image? If it would, then I will invest in a new body; if not, then I will invest in new lenses. . . Thanks!!
January 04, 2008
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Alan N. Marcus |
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Hi again Robert, First I need to tell you that gobbledygook is a synonym for nonsense or stated another way; there are many others who can provide far more reliable data on this subject. That being said, here goes another attempt to throw some baloney. A larger chip sizes permit larger light sensitive sights. Larger sights are less likely to spawn noise. When a smaller than native resolution is chosen via camera setting, camera software, transparent to the user, chooses which sights are to be discarded and which to include Hopefully, the camera software enhances via filtering-out and interpolating and thus rejecting some of the noise. Likely newer camera software and newer chip designs slip in improvements. Consider that the display logic will cast out pixels and interpolate. Might display logic also play a big part in this? Also the graphic software program in-use encompasses noise reduction logic. Lenses with large apertures, approaching f/1, are best for concerts as they are able to throw brighter image thus noise is reduced as noise is worsened by under exposure. This is your best option. Hope others will shed light on this subject. Regards, Alan Marcus
January 04, 2008
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Robert A. Staub, Jr |
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Thanks! I use a 100mm f/2.8 lens; I have yet to see a faster lens at the focal length I need, besides the 50mm lenses. It seems that I need a better camera body, or I need to start shooting film!
January 08, 2008
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Alan N. Marcus |
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I think a zoom with a maximum aperture of f/2.8 is about it. Likely there are faster lenses but it’s just as likely the price is astronomical. I advise you to stick with what you have for now. You can always use noise reduction software. This is your best bet for now. Meanwhile, the Consumer Electronics show is now in full swing followed by Photo Marketing International in February. PMA is generally where the camera makers and lens makers display new models although CES is gaining ground. It’s no secret, Kodak Engineering has devised a new digital chip that will escalate ISO. Likely it will appear incorporated into several name brand bodies. Likely such a breakthrough sparks the paying of royalties or the circumventing patents. Alan Marcus
January 08, 2008
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Peter K. Burian |
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One entirely different suggestion. Take care not to underexpose your images. When we underexpose, and use software to lighten up the image, the digital noise is definitely more obvious. Use + exposure compensation as required when shooting to make well exposed images. (Is f/2.8 at 1/125 sec. the best exposure for *every* shot at a concert? Regardless of the lighting or the type of outfits the performers are wearing? probably not.) At ISO 400, you should NOT be having any serious complaint about digital noise. The newer Digital Rebel cameras do produce better quality at ISO 300 but the original Rebel was not bad! Cheers! Peter K. Burian
January 18, 2008
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Pete H |
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Hello Robt, Without delving into particle physics...here's the lowdown. "It seems that I need a better camera body, or I need to start shooting film!" It's not the body, it's the sensor.
Larger sensors generally have less "noise." That being said, most "noise" issues are due to the scene being photographed.
Dark areas are your major culprits. Most of us know the latitude of film exceeds the average digital camera. Technology is rapidly closing the gap in this area. No..You don't need to go back to film. I considered that avenue about a yr ago, and came to the conclusion that the restrictions on editing film are far too great for me. Think about it: First you need to expose it perfectly or as close as you can get. No preview as with digital.
Next; you will want a way to scan them to digital..and I am NOT talking about a flatbed, but a dedicated film/transparency scanner. Time consuming to say the least. Finally you are ready to edit etc... Whew! No Thanks! Out of curiousity;I did have a few medium format negs scanned by a company who does Hi-Res scans..cost me 2 bucks per neg! I was not impressed enough to run out and buy a dedicated scanner. By my math, by the time you purchase a decent scanner to handle the full dynamic range of a 35mm neg and a good 35mm camera..You may as well have bought yourself the Nikon D-3.
all the best,
Pete
January 19, 2008
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