Re: filmscanners: Sharpness of color chrome vs color negative.
Laurie asks: That's nice; but pardon my ignorance, what is an MTF spec? MTF is the modulation transfer function: it is a measure of how well small details are recorded or focused, and is expressed as a percentage for a given resolution (in line pairs per millimetre, usually) and contrast ratio (1.6:1, 1000:1, etc.). A MTF of 50% at 50 lp/mm means that about fifty percent of the contrast between black lines and the white spaces between them is preserved when their spacing is 50 line pairs (one black, one white) per millimetre. The MTF can never be higher than 100% for a lens, since at 100% the lens is transmitting 100% of the contrast in the target--perfect resolution. The MTF _can_ be higher than 100% for film, though, since some films will exaggerate contrast at some resolutions, causing the contrast to appear higher on film than it was in real life (this is called accutance). When you look at an MTF chart for film, the horizontal scale is usually lp/mm, and the vertical scale is modulation transfer in percent. The curve on the graph represents the percent of modulation transfer at a given resolution. It usually starts just above 100% for low resolutions, and gradually dips downwards for higher resolutions, eventually dropping below 30%, at which point most graphs stop. The 50% point is often considered the nominal resolving power of the film. For film, a MTF chart shows the curve for a specific contrast ratio in the target, usually 1.6:1 or 1000:1. Higher contrasts produce higher resolution figures, since they tend to show up better on film. When you look at an MTF chart for a lens, the horizontal scale is usually the distance from the center of the frame, and the vertical scale is again the percent of modulation transfer. There are usually four curves, representing resolutions of 5 lp/mm, 10 lp/mm, 20 lp/mm, and 40 lp/mm. The curves show how much of the resolution is retained as you move outward from the center of the image. The MTF is never higher than 100% for a lens, since a lens cannot show more contrast than what exists in the original scene. A good lens will show relatively flat curves that are quite high on the MTF scale all the way out to the edges of the frame. A poor lens will show a sharp drop in resolution as you move outward, and even in the center, the curves will start quite low, especially for the 40 lp/mm curve. The exact MTF for a lens depends on the aperture setting, focus setting, and focal length (for zooms); MTF is usually best for some intermediate aperture, like f/5.6.
Re: filmscanners: Sharpness of color chrome vs color negative.
On Thu, 30 Aug 2001 08:04:39 -0400 Austin Franklin ([EMAIL PROTECTED]) wrote: What do people have to say about the differences in sharpness between same ASA, same brand chrome vs color negative film? My experience shows that the chrome films are not as sharp as the negative films. I think I would agree, though it wasn't the case a few years ago, when ISO100 slide seemed to be much sharper than col.neg. I think both have improved, but neg has improved more. There isn't much in it though, and I'm limiting the verdict to Fuji, speed for speed. I have usually been less impressed by Kodak sharpness, though grain is sharper in their emulsions they seem to get more image diffusion - halation perhaps, or thicker emulsion layers, or just different grain technology?. All anecdotal and informal anyway, not measured or done with any rigour, and may be wrong. OTOH I have some old Kodachrome 25 slides which probably exceed any E6 or C41 film. Regards Tony Sleep http://www.halftone.co.uk - Online portfolio exhibit; + film scanner info comparisons
Re: filmscanners: Sharpness of color chrome vs color negative.
Tony writes ... On Thu, 30 Aug 2001 08:04:39 -0400 Austin Franklin ([EMAIL PROTECTED]) wrote: What do people have to say about the differences in sharpness between same ASA, same brand chrome vs color negative film? My experience shows that the chrome films are not as sharp as the negative films. I think I would agree, though it wasn't the case a few years ago, when ISO100 slide seemed to be much sharper than col.neg. I think both have improved, but neg has improved more. There isn't much in it though, ... Nikon's book Scanning Essentials (which came with my original LS-10) implies the reversal process for chrome processing has a tendency to reduce the definition and increase the contrast (reduce the latitude). They describe the reversal process as an intermediate step, when all steps have a tendency to increase contrast and lose definition. It goes on to say (keep in mind this text is 7 years old and doesn't take into account new films) ... In general, color negative films have the potential to scan with better results than transparencies, because they have a flatter gamma (lower contrast) and the Dmax is relatively low. Also, the mask colors help to improve color reproduction, the grain size has been diminished for the relative film speed, and the emulsions are considerably sharper ... The text does acknowledge the obvious benefits of trannies, as well as many applications which demand slides. shAf :o)
RE: filmscanners: Sharpness of color chrome vs color negative.
Fuji does provide MTF for both their positive and negative film, Provia 100 and Superia 100. There is also additional information besides the MTF provided, like resolving power and diffuse RMS granularity value. The problem I am having with the numbers provided, is I must not be understanding them completely. I know that the RMS granularity for chrome film has to be divided by 2.5...that would make them equal (Provia is 10, divided by 2.5 = 4, and Superia is 4. OK, so that's a wash... Then, the resolution shows that at 1000:1, Provia resolves 140 lines/mm and Superia 125. That would mean that Provia (positive film) has a HIGHER resolving power than Superia (negative film)...BUT, wait...there's more. The MTF for Provia falls off at around 60, and the MTF for Superia falls off at ~130. That, to me, means Superia is FAR superior at resolution than Provia OK, so why the discrepancy? Sharpness is determined by the 50% point and resolution is determined by just visible lines (typically 5% to 10%). If the 50% frequency (fc) is 60cycles/mm, the the 10% to 90% transition width of a white-black step will be 2.2/(2*pi*fc)=0.0058 mm. Mike Duncan
RE: filmscanners: Sharpness of color chrome vs color negative.
Thank You -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Anthony Atkielski Sent: Friday, August 31, 2001 3:20 AM To: [EMAIL PROTECTED] Subject: Re: filmscanners: Sharpness of color chrome vs color negative. Laurie asks: That's nice; but pardon my ignorance, what is an MTF spec? MTF is the modulation transfer function: it is a measure of how well small details are recorded or focused, and is expressed as a percentage for a given resolution (in line pairs per millimetre, usually) and contrast ratio (1.6:1, 1000:1, etc.). A MTF of 50% at 50 lp/mm means that about fifty percent of the contrast between black lines and the white spaces between them is preserved when their spacing is 50 line pairs (one black, one white) per millimetre. The MTF can never be higher than 100% for a lens, since at 100% the lens is transmitting 100% of the contrast in the target--perfect resolution. The MTF _can_ be higher than 100% for film, though, since some films will exaggerate contrast at some resolutions, causing the contrast to appear higher on film than it was in real life (this is called accutance). When you look at an MTF chart for film, the horizontal scale is usually lp/mm, and the vertical scale is modulation transfer in percent. The curve on the graph represents the percent of modulation transfer at a given resolution. It usually starts just above 100% for low resolutions, and gradually dips downwards for higher resolutions, eventually dropping below 30%, at which point most graphs stop. The 50% point is often considered the nominal resolving power of the film. For film, a MTF chart shows the curve for a specific contrast ratio in the target, usually 1.6:1 or 1000:1. Higher contrasts produce higher resolution figures, since they tend to show up better on film. When you look at an MTF chart for a lens, the horizontal scale is usually the distance from the center of the frame, and the vertical scale is again the percent of modulation transfer. There are usually four curves, representing resolutions of 5 lp/mm, 10 lp/mm, 20 lp/mm, and 40 lp/mm. The curves show how much of the resolution is retained as you move outward from the center of the image. The MTF is never higher than 100% for a lens, since a lens cannot show more contrast than what exists in the original scene. A good lens will show relatively flat curves that are quite high on the MTF scale all the way out to the edges of the frame. A poor lens will show a sharp drop in resolution as you move outward, and even in the center, the curves will start quite low, especially for the 40 lp/mm curve. The exact MTF for a lens depends on the aperture setting, focus setting, and focal length (for zooms); MTF is usually best for some intermediate aperture, like f/5.6.
RE: filmscanners: Sharpness of color chrome vs color negative.
Not totally (which should not surprise you); but we are getting there. :-) If I understand your requirements, each film should contain the same photograph of the same subject taken at the same time (so to speak) under the exact same lighting with the same or equivalent equipment. In addition; each film should be scanned by the same scanner in the same way under the same conditions and with the exact same settings; and each should be output to the same exact monitor for display and viewing upon which the evaluation will be based. Identical images, shot at the same time from the same angles etc. I got that much; what I was really asking was not the same lighting source at the time of the taking of the image but rather at the time of viewing the processed films. I think you got at this by suggesting both were to be scanned images as viewed via a monitor. If that is correct, you indirectly answered my inquiry; if not, than it remains open for further specification. Assuming my understandings are correct, all I can say is let the games begin. :-) However, I would respectfully submit that this may tell us more about which type of film scans and displays sharper than which is actually capable of capturing a sharper image on the film; and as such may not really be getting at the question you asked unless your concern is with scanned and monitor displayed images only. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Austin Franklin Sent: Thursday, August 30, 2001 2:53 PM To: [EMAIL PROTECTED] Subject: RE: filmscanners: Sharpness of color chrome vs color negative. Ok Austin, You have just openned a can of worms here. Are we talking about sharpness as seen through a loup, from a monitor, off a light table, photographic print or inkjet print? Seen through, say, a drum scanner...or a very high end CCD scanner. Take every factor out of it you can...so both are on equal footing and only the ability of the film to retain sharpness is at question here. Is the comparison based on each coming from the same type of source and under the same lighting; or are we comparing apples and oranges (e.g., projected chromes or light table chromes versus reflected light prints)? Identical images, shot at the same time from the same angles etc. I think if you are fishing for a set of comparable data and experiences to evaluate you will need to set out some very precise standards and conditions under which we are to analyze our experiences so as to produce comparable data worth evalauating. Assuming a very controlled scene, such that the only difference is in the actual ability of the film to maintain image sharpness. This SHOULD be a very very basic question, not related to anything but the film, assuming both are processed to the highest standards. What do people have to say about the differences in sharpness between same ASA, same brand chrome vs color negative film? My experience shows that the chrome films are not as sharp as the negative films. OK, Laurie, do you have an answer ;-)
RE: filmscanners: Sharpness of color chrome vs color negative.
each film should be scanned by the same scanner in the same way under the same conditions and with the exact same settings; You can't use the same settings for scanning positive film, then negative film... I got that much; what I was really asking was not the same lighting source at the time of the taking of the image but rather at the time of viewing the processed films. I think you got at this by suggesting both were to be scanned images as viewed via a monitor. If that is correct, you indirectly answered my inquiry; if not, than it remains open for further specification. Yes, viewed on a monitor, in PhotoShop, actual pixels or even higher magnification...just to see if there is a noticeable sharpness difference. However, I would respectfully submit that this may tell us more about which type of film scans and displays sharper than which is actually capable of capturing a sharper image on the film; and as such may not really be getting at the question you asked unless your concern is with scanned and monitor displayed images only. I don't think that's going to be the case... Then hell, make a 20x30 print from each and compare the prints ;-)
RE: filmscanners: Sharpness of color chrome vs color negative.
Not totally (which should not surprise you); but we are getting there. :-) If I understand your requirements, each film should contain the same photograph of the same subject taken at the same time (so to speak) under the exact same lighting with the same or equivalent equipment. In addition; each film should be scanned by the same scanner in the same way under the same conditions and with the exact same settings; and each should be output to the same exact monitor for display and viewing upon which the evaluation will be based. Identical images, shot at the same time from the same angles etc. Kodak and Fuji publish MTF specs on their films. Check their web sites. Mike Duncan
RE: filmscanners: Sharpness of color chrome vs color negative.
Kodak and Fuji publish MTF specs on their films. Check their web sites. Fuji does provide MTF for both their positive and negative film, Provia 100 and Superia 100. There is also additional information besides the MTF provided, like resolving power and diffuse RMS granularity value. The problem I am having with the numbers provided, is I must not be understanding them completely. I know that the RMS granularity for chrome film has to be divided by 2.5...that would make them equal (Provia is 10, divided by 2.5 = 4, and Superia is 4. OK, so that's a wash... Then, the resolution shows that at 1000:1, Provia resolves 140 lines/mm and Superia 125. That would mean that Provia (positive film) has a HIGHER resolving power than Superia (negative film)...BUT, wait...there's more. The MTF for Provia falls off at around 60, and the MTF for Superia falls off at ~130. That, to me, means Superia is FAR superior at resolution than Provia OK, so why the discrepancy?
RE: filmscanners: Sharpness of color chrome vs color negative.
You can't use the same settings for scanning positive film, then negative film... I should have been clearer. I meant a raw scan in which such things as levels, curves, gammas, unsharp mask , etc. settings were the same (i.e., uncorrected and unadjusted). Obviously, there might be some reversal of the negative image from negative to positive (although technically that would not really be necessary) and removal of the orange color mask from the color negative. I don't think that's going to be the case... Then hell, make a 20x30 print from each and compare the prints ;-) I don't know either which is why I raised the possibility. As for making a 20 x 30 print from each, is that an inkjet, Lightjet, LaserJet, or traditional enlarger prints; and how do we account for the differences in the paper media between Ilfochrome and C Print materials if we select the traditional enlarger avenue? Moreover, a non-enlarger (e.g., digital file based print) does not avoid the issue of whether the differences in the sharpness of the two types of films are being represented or the quality of scan that each might produce is being reflected. If one is trying to determine the sharpness of the film in capturing an image, one needs to eliminate scans and other digital intervening variables; however, if one is looking at not the comparative sharpness of the film's capacity to capture sharp images but at the films ability to be scanned and produce a sharp image, then that is a different question where one does not have to eliminate the digitalizing variable only control for it. As I initially said, you may have opened up a can of worms. :-) Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Austin Franklin Sent: Thursday, August 30, 2001 10:17 PM To: [EMAIL PROTECTED] Subject: RE: filmscanners: Sharpness of color chrome vs color negative. each film should be scanned by the same scanner in the same way under the same conditions and with the exact same settings; You can't use the same settings for scanning positive film, then negative film... I got that much; what I was really asking was not the same lighting source at the time of the taking of the image but rather at the time of viewing the processed films. I think you got at this by suggesting both were to be scanned images as viewed via a monitor. If that is correct, you indirectly answered my inquiry; if not, than it remains open for further specification. Yes, viewed on a monitor, in PhotoShop, actual pixels or even higher magnification...just to see if there is a noticeable sharpness difference. However, I would respectfully submit that this may tell us more about which type of film scans and displays sharper than which is actually capable of capturing a sharper image on the film; and as such may not really be getting at the question you asked unless your concern is with scanned and monitor displayed images only. I don't think that's going to be the case... Then hell, make a 20x30 print from each and compare the prints ;-)
