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#21
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Digital quality (vs 35mm): Any real answers?
I spent ages working out all the details. I came to the conclusion that if
you measured the area of a perfect print from a 35mm negative or 35mm slide in inches and then divided the dimensions by 150 you'd be able to work out the vertical/horizontal pixels of the image. Then simply multiply the two together to get megapixels. That's the theory anyway. In practice, how big is the biggest print you normally make? If your normal biggest print is 10x8 then 3 megapixels is all you ever need (two at a pinch). But the biggest limitation is your printer. How many of us can afford an A3 or greater printer or even the ink to make A3 prints? How many A4 prints can you hang on your wall? I decided to settle on 3 megapixels. It's adequate for my needs and as with slides, I ensure my photos are perfect before I squeeze the button. I claim 3 megapixels is the perfect equivalent of 35mm for most purposes. 6mp just eats up storage space for no visible advantage. -- Yours Zebedee (Claiming asylum in an attempt to escape paying his debts to Dougal and Florence) |
#22
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Digital quality (vs 35mm): Any real answers?
Zebedee wrote:
I spent ages working out all the details. I came to the conclusion that if you measured the area of a perfect print from a 35mm negative or 35mm slide in inches and then divided the dimensions by 150 you'd be able to work out the vertical/horizontal pixels of the image. Then simply multiply the two together to get megapixels. That's the theory anyway. In practice, how big is the biggest print you normally make? If your normal biggest print is 10x8 then 3 megapixels is all you ever need (two at a pinch). But the biggest limitation is your printer. How many of us can afford an A3 or greater printer or even the ink to make A3 prints? How many A4 prints can you hang on your wall? I decided to settle on 3 megapixels. It's adequate for my needs and as with slides, I ensure my photos are perfect before I squeeze the button. I claim 3 megapixels is the perfect equivalent of 35mm for most purposes. 6mp just eats up storage space for no visible advantage. I have 50x60 (cm) B&W photo paper which I use for the right pictures. I doubt 3 (or 6) megapixels will do the job... Chris |
#23
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Digital quality (vs 35mm): Any real answers?
Toralf wrote:
Hi. I'm still wondering about how good the image quality of modern digital cameras (especially SLRs) really is, in particular how it compares with 35mm film. I've seen many articles on the subject on the Net, but few of them seem to give you a lot of tangible information (I want to see the numbers, please), and I can't help feeling that tests they refer to are usually done to prove a point, i.e. that digital cameras are as good as 35mm, which is not the way you do proper research. The reality is that both film and direct digital offer some goods choice to produce images. I see them more as complimentary devices, rather than an either/or choice. To say a few words about myself, I'm working for a company that makes high-accuracy, large-format scanners, so I'm not particularly impressed when I hear e.g 6 million pixels (you need to talk about *billions* of pixels if I'm really going to listen), and the word "interpolation" leaves a bad taste in my mouth. But this also means I know that high resolution isn't everything, of course; parameters like geometric precision or signal-to-noise ratio also count a lot. Do you work for Creo? Be that as it may, some of the questions I'd like to have answered are these: 1. What is the resolution of a 35mm film anyway? I think I read somewhere that a colour negative is at least 3000dpi. Is that correct? How about black&white? (Yeah I know, a film doesn't have pixels in exactly the same sense as a digital image, but it *is* made up of discrete elements after all.) Okay, it is tough to find numbers that always tell an absolute. If you check the film data sheets (often in PDF format) from AGFA, Fuji, Ilford, and Kodak, you will find many films that are capable of 100 lp/mm resolution (or more), though those are from photographing test targets under controlled conditions. Similar test target photos as posted to DPReview seem to indicate just under 50 lp/mm for the near 35 mm sized imaging chips (such as the Canon 1Ds and Kodak 14n (also 14c). Some smaller digital chips seem to be able to resolve more detail than that, though those smaller chips are often just for P&S cameras, so I will leave those out of the discussion. Obviously, many of us choose 35 mm photography so we can do hand held shooting. If you place the camera on a tripod, you increase the captured resolution. If you use strobes, flash, or other controlled lighting, you can also increase the resolution. Again, not many of us do that all the time, which means that our choice of doing photography with a hand held camera will only reduce the maximum possible resolution. The same choice of use would affect the resolution of direct digital SLR imagery. If you only went by the test target lp/mm comparison, then it seems that film is capable of twice as much resolution, or more, than direct digital imaging. However, the resolution at the edges of the image seem to always suffer a bit more, though with the results from some direct digital images seem to indicate that the falloff at the edges is absent, or at least less severe. That would imply that direct digital imaging with some devices might give a more even resolution across an image. I also think that resolution is a very unfortunate choice of comparison. If you look at the colour response, then you will find that film is very different. Any digital imaging sensor using an RGB filter (Bayer pattern, or Foveon), will have limited response accuracy in colours approaching Cyan, or Yellow. There is also the problem that white balance seems to be variable in operation when comparing different systems. You should also read more about interpolation in imaging chip image processing. One resource that has some great technical papers about this is: http://www.fillfactory.com 2. What about the print? 300dpi? Any print can either make and image, or break an image. There are so many different printing technologies, that it is tough to put one number on any. If you have ever heard of an imagesetter, these devices output to film at 2400 or 2540 dpi, using laser technology. A different factor is Dot Gain, which is the spreading of ink. All inks spread a little, though desktop inkjet systems have the highest dot gain. If you are imaging to a desktop inkjet output, then many direct digital choices might be an easier path. It takes a great deal of knowledge to get the best results in printing, or at least lots of trial and error. 3. I know that the most common sensors are made up of individual elements for the read, green and blue channels, arranged in a special pattern, whose data is somehow interpolated into RGB pixels. But what exactly does e.g. 6 megapixels mean in that context? Does it mean that the sensor has (just) 6 million elements, or that data from a higher number (like 18 or 24 million) is combined into 6 million RGB pixels? A Bayer pattern is an array of Red, Green, or Blue pixels, often in a repeating pattern. Most of these Bayer pattern filters are arranged so that there are twice as many Green pixels as all others. The patent actually dates from around 1978 from Kodak, and the choice of Green dominance was determined then based on the human eye being able to resolve Green slightly better than Blue or Red. Again, check out the Fill Factory web site link for more technical information. Sony with their latest fourth colour Bayer pattern is trying out a different approach. While these variations have occurred in the past, the previous results often showed interpolation errors, especially at edges of objects in a scene. While the Sony attempt is a nice direction, it would seem to need more work. Read more by searching for "fringing" in Sony based images. The same question more bluntly put: When Canon/Nikon/Pentax is talking about 6MP, is that just a big a lie as the one about 10MP on Sigma cameras? (I'm hoping not, as I think the Sigma/Foveon way of counting really takes the cake.) Technically, photographing a mostly Green subject or scene, should show more detail than photographing something more Red, or more Blue. However, if you actually look at the largest file size, then the dimensions of the chip in millimetres, you can figure out the maximum potential resolution. Doing just that would seem to indicate that some direct digital SLRs are capable of 50 to 58 lp/mm, though they fall short of that. There is also an anti-alias (anti-moiré) filter, often and IR filter, microlens array (or similar diffraction layer), and the Bayer pattern to all reduce some of the maximum potential resolution. With the Foveon, the potential is that Green, Red, or mostly Blue scenes could be recorded equally high resolution. Foveon also interpolates the data striking the imaging chip, though it provides the potential to do better. This is really an attempt to get away from the Bayer pattern, though they do not have it quite figured out. Perhaps in another release in the future they may provide better results. Take a look at the file size and chip dimensions, then you know the limits currently. 4. Can the inaccuracy associated with the above mentioned interpolation be quantified and/or measured against e.g. the error introduced by scanning a negative with a film-scanner? And how does it compare with pixel interpolation in the scanning sense? A CCD film scanner uses a trilinear array, often with a fourth white array to correct all settings. What happens is that there is no colour interpolation of adjacent pixels, and a pixel value can be set for Red, Green, and Blue at any one pixel, without interpolation. Film scanners are actually much slower than direct digital cameras, so this approach works. Some of the high end scanning backs, or scanning cameras are capable of extremely high resolution and accuracy, though they were only useful for non moving subject matter. Try this article for mo http://www.adamwilt.com/TechDiffs/CCDColor.html Excellent overview of the technologies. Anyway, when you read a bit more about this stuff, then you realize that even getting accurate colour from a film scan could be tough. Also, since a computer monitor is RGB, even then the colour response of near Cyan, or near pure Yellow, is impossible to see. One needs to use a colour picker tool (eyedropper in PhotoShop) to tell if some colours are correct. So depending upon the scanner, skill of the operator, editing software, and monitor, some might find that scanned film does not offer an advantage over direct digital imaging. These skills might be tough to master, meaning that the best choice might be direct digital. 5. And how about those other parameters I mentioned briefly above - like different kinds of geometric distortions, noise, flat field bias etc.? Can those be compared with the ones of plain old film? Noise can be roughly compared to grain. However, a word of caution here; what you see on a monitor may never appear on a final print. While it may depend upon the printing technology in use, quite often there is not visible noise (or grain) on a print, when it seemed to be visible on a computer monitor. Okay, so obviously a chip should be flatter than a piece of film, especially as one goes larger than 35 mm. An imaging chip is actually three dimensional, with a type of well to capture the light striking each pixel. There are also dead areas between pixels, though microlens arrays and diffraction layers try to avoid problems with that. Film is not linear in construction, and the molecules and grain clumps overlap on many different layers within the film. Light could sensitize any particular point, and from really any angle of contact. Film grains are under 3µ in size. Film imaging chips have an optimum response at around 6.8µ to 8µ (microns) in size. Too small reduces sensitivity to light, while too large introduces noise. There are drum scanners that can image at about 3µ, though they are very new, and not very common. CCD film scanners are capable of much less than drum scanners. 6. And the chromic aberration effects? How serious are they these days? And are the full-frame sensors that are actually found in some high-end cameras now, in any way comparable to film in that respect? Sure. I suggest looking at the test images from DPReview. Obviously, it is tough to tell just by looking on a monitor, though you could try printing some of the images. Well, maybe some people will say I have a somewhat critical or conservative attitude towards digital cameras, but I actually think you ought to be a bit sceptical when something "new and wonderful" comes a long; new technology is too often introduced for technology's own sake, IMO. - Toralf I think the technology is improving all the time. Obviously, the gear available next year will be better than the gear there is today, and will be priced lower. I think we will see many more full 35 mm sized imaging chips in the near future, and I expect that to be the most common SLR in 2008. Film still offers some great choices, especially for those more concerned with colour (or B/W), than with outright resolution. Both methods still offer advantages, so I still think they are complimentary technologies. Ciao! Gordon Moat A G Studio http://www.allgstudio.com Updated! |
#24
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Digital quality (vs 35mm): Any real answers?
Toralf wrote:
Hi. I'm still wondering about how good the image quality of modern digital cameras (especially SLRs) really is, in particular how it compares with 35mm film. I've seen many articles on the subject on the Net, but few of them seem to give you a lot of tangible information (I want to see the numbers, please), and I can't help feeling that tests they refer to are usually done to prove a point, i.e. that digital cameras are as good as 35mm, which is not the way you do proper research. The reality is that both film and direct digital offer some goods choice to produce images. I see them more as complimentary devices, rather than an either/or choice. To say a few words about myself, I'm working for a company that makes high-accuracy, large-format scanners, so I'm not particularly impressed when I hear e.g 6 million pixels (you need to talk about *billions* of pixels if I'm really going to listen), and the word "interpolation" leaves a bad taste in my mouth. But this also means I know that high resolution isn't everything, of course; parameters like geometric precision or signal-to-noise ratio also count a lot. Do you work for Creo? Be that as it may, some of the questions I'd like to have answered are these: 1. What is the resolution of a 35mm film anyway? I think I read somewhere that a colour negative is at least 3000dpi. Is that correct? How about black&white? (Yeah I know, a film doesn't have pixels in exactly the same sense as a digital image, but it *is* made up of discrete elements after all.) Okay, it is tough to find numbers that always tell an absolute. If you check the film data sheets (often in PDF format) from AGFA, Fuji, Ilford, and Kodak, you will find many films that are capable of 100 lp/mm resolution (or more), though those are from photographing test targets under controlled conditions. Similar test target photos as posted to DPReview seem to indicate just under 50 lp/mm for the near 35 mm sized imaging chips (such as the Canon 1Ds and Kodak 14n (also 14c). Some smaller digital chips seem to be able to resolve more detail than that, though those smaller chips are often just for P&S cameras, so I will leave those out of the discussion. Obviously, many of us choose 35 mm photography so we can do hand held shooting. If you place the camera on a tripod, you increase the captured resolution. If you use strobes, flash, or other controlled lighting, you can also increase the resolution. Again, not many of us do that all the time, which means that our choice of doing photography with a hand held camera will only reduce the maximum possible resolution. The same choice of use would affect the resolution of direct digital SLR imagery. If you only went by the test target lp/mm comparison, then it seems that film is capable of twice as much resolution, or more, than direct digital imaging. However, the resolution at the edges of the image seem to always suffer a bit more, though with the results from some direct digital images seem to indicate that the falloff at the edges is absent, or at least less severe. That would imply that direct digital imaging with some devices might give a more even resolution across an image. I also think that resolution is a very unfortunate choice of comparison. If you look at the colour response, then you will find that film is very different. Any digital imaging sensor using an RGB filter (Bayer pattern, or Foveon), will have limited response accuracy in colours approaching Cyan, or Yellow. There is also the problem that white balance seems to be variable in operation when comparing different systems. You should also read more about interpolation in imaging chip image processing. One resource that has some great technical papers about this is: http://www.fillfactory.com 2. What about the print? 300dpi? Any print can either make and image, or break an image. There are so many different printing technologies, that it is tough to put one number on any. If you have ever heard of an imagesetter, these devices output to film at 2400 or 2540 dpi, using laser technology. A different factor is Dot Gain, which is the spreading of ink. All inks spread a little, though desktop inkjet systems have the highest dot gain. If you are imaging to a desktop inkjet output, then many direct digital choices might be an easier path. It takes a great deal of knowledge to get the best results in printing, or at least lots of trial and error. 3. I know that the most common sensors are made up of individual elements for the read, green and blue channels, arranged in a special pattern, whose data is somehow interpolated into RGB pixels. But what exactly does e.g. 6 megapixels mean in that context? Does it mean that the sensor has (just) 6 million elements, or that data from a higher number (like 18 or 24 million) is combined into 6 million RGB pixels? A Bayer pattern is an array of Red, Green, or Blue pixels, often in a repeating pattern. Most of these Bayer pattern filters are arranged so that there are twice as many Green pixels as all others. The patent actually dates from around 1978 from Kodak, and the choice of Green dominance was determined then based on the human eye being able to resolve Green slightly better than Blue or Red. Again, check out the Fill Factory web site link for more technical information. Sony with their latest fourth colour Bayer pattern is trying out a different approach. While these variations have occurred in the past, the previous results often showed interpolation errors, especially at edges of objects in a scene. While the Sony attempt is a nice direction, it would seem to need more work. Read more by searching for "fringing" in Sony based images. The same question more bluntly put: When Canon/Nikon/Pentax is talking about 6MP, is that just a big a lie as the one about 10MP on Sigma cameras? (I'm hoping not, as I think the Sigma/Foveon way of counting really takes the cake.) Technically, photographing a mostly Green subject or scene, should show more detail than photographing something more Red, or more Blue. However, if you actually look at the largest file size, then the dimensions of the chip in millimetres, you can figure out the maximum potential resolution. Doing just that would seem to indicate that some direct digital SLRs are capable of 50 to 58 lp/mm, though they fall short of that. There is also an anti-alias (anti-moiré) filter, often and IR filter, microlens array (or similar diffraction layer), and the Bayer pattern to all reduce some of the maximum potential resolution. With the Foveon, the potential is that Green, Red, or mostly Blue scenes could be recorded equally high resolution. Foveon also interpolates the data striking the imaging chip, though it provides the potential to do better. This is really an attempt to get away from the Bayer pattern, though they do not have it quite figured out. Perhaps in another release in the future they may provide better results. Take a look at the file size and chip dimensions, then you know the limits currently. 4. Can the inaccuracy associated with the above mentioned interpolation be quantified and/or measured against e.g. the error introduced by scanning a negative with a film-scanner? And how does it compare with pixel interpolation in the scanning sense? A CCD film scanner uses a trilinear array, often with a fourth white array to correct all settings. What happens is that there is no colour interpolation of adjacent pixels, and a pixel value can be set for Red, Green, and Blue at any one pixel, without interpolation. Film scanners are actually much slower than direct digital cameras, so this approach works. Some of the high end scanning backs, or scanning cameras are capable of extremely high resolution and accuracy, though they were only useful for non moving subject matter. Try this article for mo http://www.adamwilt.com/TechDiffs/CCDColor.html Excellent overview of the technologies. Anyway, when you read a bit more about this stuff, then you realize that even getting accurate colour from a film scan could be tough. Also, since a computer monitor is RGB, even then the colour response of near Cyan, or near pure Yellow, is impossible to see. One needs to use a colour picker tool (eyedropper in PhotoShop) to tell if some colours are correct. So depending upon the scanner, skill of the operator, editing software, and monitor, some might find that scanned film does not offer an advantage over direct digital imaging. These skills might be tough to master, meaning that the best choice might be direct digital. 5. And how about those other parameters I mentioned briefly above - like different kinds of geometric distortions, noise, flat field bias etc.? Can those be compared with the ones of plain old film? Noise can be roughly compared to grain. However, a word of caution here; what you see on a monitor may never appear on a final print. While it may depend upon the printing technology in use, quite often there is not visible noise (or grain) on a print, when it seemed to be visible on a computer monitor. Okay, so obviously a chip should be flatter than a piece of film, especially as one goes larger than 35 mm. An imaging chip is actually three dimensional, with a type of well to capture the light striking each pixel. There are also dead areas between pixels, though microlens arrays and diffraction layers try to avoid problems with that. Film is not linear in construction, and the molecules and grain clumps overlap on many different layers within the film. Light could sensitize any particular point, and from really any angle of contact. Film grains are under 3µ in size. Film imaging chips have an optimum response at around 6.8µ to 8µ (microns) in size. Too small reduces sensitivity to light, while too large introduces noise. There are drum scanners that can image at about 3µ, though they are very new, and not very common. CCD film scanners are capable of much less than drum scanners. 6. And the chromic aberration effects? How serious are they these days? And are the full-frame sensors that are actually found in some high-end cameras now, in any way comparable to film in that respect? Sure. I suggest looking at the test images from DPReview. Obviously, it is tough to tell just by looking on a monitor, though you could try printing some of the images. Well, maybe some people will say I have a somewhat critical or conservative attitude towards digital cameras, but I actually think you ought to be a bit sceptical when something "new and wonderful" comes a long; new technology is too often introduced for technology's own sake, IMO. - Toralf I think the technology is improving all the time. Obviously, the gear available next year will be better than the gear there is today, and will be priced lower. I think we will see many more full 35 mm sized imaging chips in the near future, and I expect that to be the most common SLR in 2008. Film still offers some great choices, especially for those more concerned with colour (or B/W), than with outright resolution. Both methods still offer advantages, so I still think they are complimentary technologies. Ciao! Gordon Moat A G Studio http://www.allgstudio.com Updated! |
#25
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Digital quality (vs 35mm): Any real answers?
"Chris Loffredo" wrote in message ... Zebedee wrote: I have 50x60 (cm) B&W photo paper which I use for the right pictures. I doubt 3 (or 6) megapixels will do the job... 50cm = 19.7 inches 60cm = 23.6 inches 19.7 x 150 = 2955 pixels 23.6 x 150 = 3540 pixels 2955 x 3540 = 10.4607 megapixels It could be a little stretch for a 6mp camera or you could even use the Kodak 14mp SLR Having said that, it's a really unusual size and more suited to medium format than for 35mm. -- Yours Zebedee (Claiming asylum in an attempt to escape paying his debts to Dougal and Florence) |
#26
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Digital quality (vs 35mm): Any real answers?
"Chris Loffredo" wrote in message ... Zebedee wrote: I have 50x60 (cm) B&W photo paper which I use for the right pictures. I doubt 3 (or 6) megapixels will do the job... 50cm = 19.7 inches 60cm = 23.6 inches 19.7 x 150 = 2955 pixels 23.6 x 150 = 3540 pixels 2955 x 3540 = 10.4607 megapixels It could be a little stretch for a 6mp camera or you could even use the Kodak 14mp SLR Having said that, it's a really unusual size and more suited to medium format than for 35mm. -- Yours Zebedee (Claiming asylum in an attempt to escape paying his debts to Dougal and Florence) |
#27
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Digital quality (vs 35mm): Any real answers?
And unless you take your film to a professional photo lab the processing lab will likely print it out of focus anyway. You're absolutely right about this point. I tried 4 labs and only the most expensive one gave me prints that I was satisfied with and were worth the discipline and cost of using film rather than digital. The budget labs were crap. Out of focus, off-color, scratched negatives... just crap. But using the most expensive was not really a practical option for routine, regular photography. I think this is an advantage of digital that's not often mentioned; is that you free yourself from the sometimes unpredictable results of someone else processing your images. If you process film yourself and are experienced enough to get the result you want, and most importantly, have the time and inclination to do it, then its another matter. |
#28
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Digital quality (vs 35mm): Any real answers?
And unless you take your film to a professional photo lab the processing lab will likely print it out of focus anyway. You're absolutely right about this point. I tried 4 labs and only the most expensive one gave me prints that I was satisfied with and were worth the discipline and cost of using film rather than digital. The budget labs were crap. Out of focus, off-color, scratched negatives... just crap. But using the most expensive was not really a practical option for routine, regular photography. I think this is an advantage of digital that's not often mentioned; is that you free yourself from the sometimes unpredictable results of someone else processing your images. If you process film yourself and are experienced enough to get the result you want, and most importantly, have the time and inclination to do it, then its another matter. |
#29
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Digital quality (vs 35mm): Any real answers?
And there's also a question of whether it looks *right* (based on whatever you take a photo of), which is not the same thing as looking good. What does looking *righ* mean? |
#30
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Digital quality (vs 35mm): Any real answers?
And there's also a question of whether it looks *right* (based on whatever you take a photo of), which is not the same thing as looking good. What does looking *righ* mean? |
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