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#1
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Resolution and print size
Hi ng,
Iīve a problem understanding digital camera resolution and max print sizes for files derived by those cameras. I take the Canon EOS-D60 as an example. The D60 has a pixel size of 7.4 microns, so there are 136 pixels/mm. However, that doesn't mean that the camera will actually resolve 136 lines per mm. The real useful resolution will be 70-80% of that, something like 105 lines per mm. Also, this is lines, while film and lens resolution is always given in line pairs, and it takes two lines to make a line pair. So the D-60 will actually resolve about 53 line pairs/mm at best. - I know that it makes no sense to compare resolution in lines/mm as the sensor and 35 mm film are different in size. Lines/picture height are better. For the D60 this means that itīs measured resolution limit of 1600 lines/picture height is equivalent to a 35 mm camera resolution of 1600 / 2 / 24 = 33 line pairs per mm. - Anyway, if I take those 53 lp/mm into the formula to calculate system resolution like 1/T = 1/l + 1/f = 1/400+1/53 = 1/0,0214 = 46,8 lp/mm and divide this value by the resolution limit of the eye for 10 inches (6,88 lp/mm), I reach a max magnification of x6,8. - I know that this formula gives only a rough approximation. - The sensor is 22.7 x 15.1 mm, so max print size should be 6 inches wide. Now I found a value based on experience that says that D60 images printed at 200 dpi (thatīs a full 10x15 inch print) look very good and sharp. Thatīs consistent with other statements I found for other cameras that all give values for max print size that are higher than can be expected from theoretical resolution alone. Itīs quite clear to me that our perception of sharpness is based on more than resolution alone, that grain/noise plays an important role as well and that a camera like the D60 produces images that are virtually noise free. But as resolution still matters can someone explain to me how those figures correlate or where I made a mistake in calculating them? Marc Wossner |
#2
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Resolution and print size
"Marc Wossner" wrote in message
ups.com... Hi ng, Iīve a problem understanding digital camera resolution and max print sizes for files derived by those cameras. I take the Canon EOS-D60 as an example. The D60 has a pixel size of 7.4 microns, so there are 136 pixels/mm. However, that doesn't mean that the camera will actually resolve 136 lines per mm. The real useful resolution will be 70-80% of that, something like 105 lines per mm. Also, this is lines, while film and lens resolution is always given in line pairs, and it takes two lines to make a line pair. So the D-60 will actually resolve about 53 line pairs/mm at best. - I know that it makes no sense to compare resolution in lines/mm as the sensor and 35 mm film are different in size. Lines/picture height are better. For the D60 this means that itīs measured resolution limit of 1600 lines/picture height is equivalent to a 35 mm camera resolution of 1600 / 2 / 24 = 33 line pairs per mm. - Anyway, if I take those 53 lp/mm into the formula to calculate system resolution like 1/T = 1/l + 1/f = 1/400+1/53 = 1/0,0214 = 46,8 lp/mm and divide this value by the resolution limit of the eye for 10 inches (6,88 lp/mm), I reach a max magnification of x6,8. - I know that this formula gives only a rough approximation. - The sensor is 22.7 x 15.1 mm, so max print size should be 6 inches wide. Now I found a value based on experience that says that D60 images printed at 200 dpi (thatīs a full 10x15 inch print) look very good and sharp. Thatīs consistent with other statements I found for other cameras that all give values for max print size that are higher than can be expected from theoretical resolution alone. Itīs quite clear to me that our perception of sharpness is based on more than resolution alone, that grain/noise plays an important role as well and that a camera like the D60 produces images that are virtually noise free. But as resolution still matters can someone explain to me how those figures correlate or where I made a mistake in calculating them? Marc Wossner Just take the # of pixels on the long side of the image, and divide by 300 dpi for high quality prints, 250dpi for good quality or 200dpi for fair quality, ect. to get the recommended max print size. Very basic and it has always worked for me. When you start splitting hairs with numbers, you have to consider lens sharpness and contrast, actual resolution of the printer, illumination levels of print to be viewed and so on. -S |
#3
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Resolution and print size
pairs per mm. - Anyway, if I take those 53 lp/mm into the formula to
calculate system resolution like 1/T = 1/l + 1/f = 1/400+1/53 = 1/0,0214 = 46,8 lp/mm and divide this value by the resolution limit of the eye for 10 inches (6,88 lp/mm), I reach a max magnification of x6,8. - I know that this formula gives only a rough approximation. - The sensor is 22.7 x 15.1 mm, so max print size should be 6 inches wide. Now I found a value based on experience that says that D60 images printed at 200 dpi (thatīs a full 10x15 inch print) look very good and sharp. I think a better way of looking at your numbers is this: Up to 6" wide (or so), you get (almost) no increase in quality from more pixels, because the increase in resolution is beyond the resolving power of the human eye. However, equipment is not perfect, and if any stage of your workflow introduces fuzziness (which it surely does), you'll find the 6" figure growing. Suppose, for example (and this is probably true), that you use a printer that only prints at 200dpi. Then up to 10x15 or so you get (almost) no increase in quality from more pixels. It is also true, as you note, that we perceive sharpness based not only on resolution. This is why sharpening a low resolution image can make it look sharp, even at the expense of detail. Similarly, I have seen 3'x4' images printed on canvas from very low resolution images, and they look great. I suspect this has something to do with the coarse texture of the canvas, but I don't know for sure. -Joel ---------------------------------------------------------------------------- Free Tanach and Mishna printouts in Hebrew: http://liturgy.lashon.net/ ---------------------------------------------------------------------------- |
#4
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Resolution and print size
? "Marc Wossner" ?????? ??? ?????? ups.com... Hi ng, Iīve a problem understanding digital camera resolution and max print sizes for files derived by those cameras. I take the Canon EOS-D60 as an example. The D60 has a pixel size of 7.4 microns, so there are 136 pixels/mm. However, that doesn't mean that the camera will actually resolve 136 lines per mm. The real useful resolution will be 70-80% of that, something like 105 lines per mm. Also, this is lines, while film and lens resolution is always given in line pairs, and it takes two lines to make a line pair. So the D-60 will actually resolve about 53 line pairs/mm at best. - I know that it makes no sense to compare resolution in lines/mm as the sensor and 35 mm film are different in size. Lines/picture height are better. For the D60 this means that itīs measured resolution limit of 1600 lines/picture height is equivalent to a 35 mm camera resolution of 1600 / 2 / 24 = 33 line pairs per mm. - Anyway, if I take those 53 lp/mm into the formula to calculate system resolution like 1/T = 1/l + 1/f = 1/400+1/53 = 1/0,0214 = 46,8 lp/mm and divide this value by the resolution limit of the eye for 10 inches (6,88 lp/mm), I reach a max magnification of x6,8. - I know that this formula gives only a rough approximation. - The sensor is 22.7 x 15.1 mm, so max print size should be 6 inches wide. Now I found a value based on experience that says that D60 images printed at 200 dpi (thatīs a full 10x15 inch print) look very good and sharp. Thatīs consistent with other statements I found for other cameras that all give values for max print size that are higher than can be expected from theoretical resolution alone. Itīs quite clear to me that our perception of sharpness is based on more than resolution alone, that grain/noise plays an important role as well and that a camera like the D60 produces images that are virtually noise free. But as resolution still matters can someone explain to me how those figures correlate or where I made a mistake in calculating them? Hi, I printed a full-size A4 (larger than 8X10")with a cheapo Kodak CX 7300 and a Canon Pixma IP 4300 and looks perfect, much better than any B&W prints I did in my film era, save colour.(With some german glossy paper, 25 euros for 50 A4 sheets, compu color by Felix Schoeler).Surely you have a better camera than mine? Hope this helps, -- Tzortzakakis Dimitrios major in electrical engineering mechanized infantry reservist dimtzort AT otenet DOT gr |
#5
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Resolution and print size
Iīve a problem understanding digital camera resolution and max
print sizes for files derived by those cameras. I have historically used the 300 dpi guide, but find that with digital cameras, I can get pretty good results with a minimum of about 240 dpi - 250 dpi of resolveable detail, perhaps because with digital there is no grain or other such distorting factors to deal with. This depends on a number of factors, such as the quality of the camera / ccd / lens, the ISO level of the shot, lighting levels and type of object being shot. For outdoor nature shots, I can get away with as low as 200 dpi and still be somewhat satisfied, but for shots of people, anything below the 240-250 dpi range and I can start to notice things. A good 5mp camera like the Oly C5050 can give you great looking, 300+ dpi prints in 4x6 and 5x7 and still accommodate some cropping. But for 8x10's, I think 5mp can be stretching it for non-nature type shots, like portraits, etc. That's just my personal feeling though. I'm not trying to indicate that it's right for everybody - it is just what I have found to be my preferences over the years. |
#6
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Resolution and print size
As you all state the common dpi values is the traditional resolution measure of line pairs per mm or lines per picture with or picture height not relevant when calculating the resolution of a digital imaging system? - I still use silver film and try to figure out the theoretical foundations before I switch to digital. Marc Wossner |
#7
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Resolution and print size
Marc Wossner wrote: As you all state the common dpi values is the traditional resolution measure of line pairs per mm or lines per picture with or picture height not relevant when calculating the resolution of a digital imaging system? - I still use silver film and try to figure out the theoretical foundations before I switch to digital. An interesting aside, Marc - my video projector has a basic 1440 x 1080 pixels resolution, but it displays video at fantastic resolution at a 10 foot wide screen size. To my eye, I can't imagine having any more detail in some of the images I'm seeing on a good broadcast. My thought is that all that matters is how big the resultant image is in your eye. If I sat 5 feet away from my screen, it wouldn't fare as well. So I sit about 20 feet back, and it is impressive and amazing. I have also seen very large paper prints from various digital (and film) cameras at exhibitions and shows. I guess the proof is in the pudding, so try various outrageous sizes and see at what point it breaks down. Probably doable anywhere above 100 DPI. Gary Eickmeier |
#8
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Resolution and print size
"Marc Wossner" wrote: As you all state the common dpi values is the traditional resolution measure of line pairs per mm or lines per picture with or picture height not relevant when calculating the resolution of a digital imaging system? - I still use silver film and try to figure out the theoretical foundations before I switch to digital. Forget the theory: look at the images. This guy complains about moiré and fine text in street signs getting messed up, but it sure looks to me that the 5D and 645 (actually, 6x6 cropped to slightly smaller than 645) are pretty much equivalent for prints 17x26" and smaller. http://www.shortwork.net/equip/review-1Ds-SQ-scantech/ David J. Littleboy Tokyo, Japan |
#9
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Resolution and print size
On 25 Jan., 15:29, "David J. Littleboy" wrote:
"Marc Wossner" wrote: As you all state the common dpi values is the traditional resolution measure of line pairs per mm or lines per picture with or picture height not relevant when calculating the resolution of a digital imaging system? - I still use silver film and try to figure out the theoretical foundations before I switch to digital. Forget the theory: look at the images. Not so easy if something keeps nagging your mind. But I agree with you: Image quality of the 5D is absolutely stunning. This guy complains about moiré and fine text in street signs getting messed up, but it sure looks to me that the 5D and 645 (actually, 6x6 cropped to slightly smaller than 645) are pretty much equivalent for prints 17x26" and smaller. http://www.shortwork.net/equip/review-1Ds-SQ-scantech/ So thereīs the question again: How can you print that large from the resolution the 5D gives? When you calculate 4368 pixels * 0,7 = 3057,6 lines / 2 = 1529 line pairs / 35,8 mm you reach 42,7 lp/mm. I donīt know the true resolution of the lens, but as itīs a prime lens letīs assume 100 lp/mm. Taking it into account like this 1/T = 1/43 + 1/100 makes it a system resolution of 30 lp/mm worst case. The images presented are printed at 17x26" so thatīs a magnification of x18. Divide the 30 lp/mm by the 2 lp/mm that are necessary for that diagonal you get a max magnification of x15. But the guy shows clippings that appear sharp from 10" and for that distance you need 6,88 lp/mm to have a sharp impression. Note that those figures are all based on "normal" 20/20 vision or max resolvable detail of 1 minute of an arc (see Norman Korenīs site for the calculation: http://www.normankoren.com/Tutorials/MTF.html). As I know that you are quite knowledgeable from various other threads David, can you explain me how this is possible, or better, where my possible misconception is? Marc |
#10
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Resolution and print size
I hate math... lol...
So thereīs the question again: How can you print that large from the resolution the 5D gives? When you calculate 4368 pixels * 0,7 = 3057,6 lines / 2 = 1529 line pairs / 35,8 mm you reach 42,7 lp/mm. I donīt know the true resolution of the lens, but as itīs a prime lens letīs assume 100 lp/mm. Taking it into account like this 1/T = 1/43 + 1/100 makes it a system resolution of 30 lp/mm worst case. The images presented are printed at 17x26" so thatīs a magnification of x18. Divide the 30 lp/mm by the 2 lp/mm that are necessary for that diagonal you get a max magnification of x15. But the guy shows clippings that appear sharp from 10" and for that distance you need 6,88 lp/mm to have a sharp impression. Note that those figures are all based on "normal" 20/20 vision or max resolvable detail of 1 minute of an arc (see Norman Korenīs site for the calculation: http://www.normankoren.com/Tutorials/MTF.html). As I know that you are quite knowledgeable from various other threads David, can you explain me how this is possible, or better, where my possible misconception is? Marc |
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