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500 lines/mm sounds outrageous. All tests on lenses I have seen have the scale topped at 80 lines/mm. And with full stop it is sometimes 40-50 lines/mm especially on the edges.
Now we can argue how may pixels you need for a line, and I would say that two is a safe bet. So 160 dots/mm is what I would say a perfect film camera can produce.
Translating that to a 35 mm negative that would mean we need 5760*3850 which is about 20 megapixels, or 60 MB (8 bit colors).
However, I own one of the sharper 35 mm lenses on the market, Zeiss Planar 50 mm 1,7, and scanning the negatives in at 2400 dpi seems to be just about enough to get all the information in. Most color negative films especially start to show their grain quite strongly at that resolution.
For practical purposes I therefore tend to think that 6 megapix will be the sweet point of acheiving 35 mm film quality in digital, in normal conditions.
I have also had a chance to experiment with a Fuji 2,1 megapix camera, and I have to say I was quite impressed. The main difference, at immediate magnifications is the absolute lack of grain. The minus point is that usually you have to use too heavy compression to save space on your flash cards, and that shows especially on colored edges as artefacts. And then, of course, when increasing the magnification, you start to see the pixels.
As for the dpi of the picture for the printouts, of course you have to size the picture for the output medium before doing the actual output, otherwise you either waste storage space or see the pixelation. However, for your home prints with your home printer, defining the real dpi of your printer is not easy at all.
Especially the ink jet manufacturers talk about their 1440 dpi and 1200 dpi printers as that was the real output respolution on those printers. However, that number only shows how closely you can print dots of ink together. With that resolution you only can print the clean colors that come out of the ink cartridges, for all other colors the printer has to do dithering.
With ink jets the size of he dithered elements (the true "dot" in the true dpi) depends on the color and lightness to be printed.
So, how do you determine your dpi? My advice is to experiment with photos with different dpi, start with 75 or even 50, go to 300 or 600 and look yourself when the differences do not show up any more. (Well, what you actually see printed out with a dpi like 25 is the piels, When you increase the dpi of the picture, the printout get's smaller and the pixels are not visible anymore. When you start to lose detail, you have gone past your printers dpi, provided the picture used was "sharp").
You should not use a test pattern of e.g. adjacent lines of e.g. prime colors, as they are typically output with a better "real dpi".
Sorry for the long post, guys.
M.
[This message has been edited by Meek (edited 10 February 2000).]
[This message has been edited by Meek (edited 10 February 2000).]
Now we can argue how may pixels you need for a line, and I would say that two is a safe bet. So 160 dots/mm is what I would say a perfect film camera can produce.
Translating that to a 35 mm negative that would mean we need 5760*3850 which is about 20 megapixels, or 60 MB (8 bit colors).
However, I own one of the sharper 35 mm lenses on the market, Zeiss Planar 50 mm 1,7, and scanning the negatives in at 2400 dpi seems to be just about enough to get all the information in. Most color negative films especially start to show their grain quite strongly at that resolution.
For practical purposes I therefore tend to think that 6 megapix will be the sweet point of acheiving 35 mm film quality in digital, in normal conditions.
I have also had a chance to experiment with a Fuji 2,1 megapix camera, and I have to say I was quite impressed. The main difference, at immediate magnifications is the absolute lack of grain. The minus point is that usually you have to use too heavy compression to save space on your flash cards, and that shows especially on colored edges as artefacts. And then, of course, when increasing the magnification, you start to see the pixels.
As for the dpi of the picture for the printouts, of course you have to size the picture for the output medium before doing the actual output, otherwise you either waste storage space or see the pixelation. However, for your home prints with your home printer, defining the real dpi of your printer is not easy at all.
Especially the ink jet manufacturers talk about their 1440 dpi and 1200 dpi printers as that was the real output respolution on those printers. However, that number only shows how closely you can print dots of ink together. With that resolution you only can print the clean colors that come out of the ink cartridges, for all other colors the printer has to do dithering.
With ink jets the size of he dithered elements (the true "dot" in the true dpi) depends on the color and lightness to be printed.
So, how do you determine your dpi? My advice is to experiment with photos with different dpi, start with 75 or even 50, go to 300 or 600 and look yourself when the differences do not show up any more. (Well, what you actually see printed out with a dpi like 25 is the piels, When you increase the dpi of the picture, the printout get's smaller and the pixels are not visible anymore. When you start to lose detail, you have gone past your printers dpi, provided the picture used was "sharp").
You should not use a test pattern of e.g. adjacent lines of e.g. prime colors, as they are typically output with a better "real dpi".
Sorry for the long post, guys.
M.
[This message has been edited by Meek (edited 10 February 2000).]
[This message has been edited by Meek (edited 10 February 2000).]
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