Re: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
Mikkel Høj [EMAIL PROTECTED] wrote: Just out of sheer interest; is it also this quality of film recorders that is used in the motion picture industry? This subject came up once before, and someone said that the recorders used for motion picture work were actually lower in resolution - 2048 lines - since the number of frames to process is much higher and the motion tends to make pixels less noticeable. Rob The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
RE: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
I don't know if its that bad. What optical density is to scanners; spot size is to film recorders. Everyone has there own method for determining it. In general the more money you spend on the base film recorder the better it is. A lot has to do with the film you are outputting on. 4x5 film is the absolutely the most stressful for a film recorder. In our line , to get the best 4x5 you need the ProPalette 8045 which has a MSRP ~$17500(~14000 recorder $3500 4x5 camera). If all you did was 35 mm the ProPalette 8000 at $10,000 would be great. You wouldn't notice much difference unless you images 4x5. -Original Message- From: Arthur Entlich [mailto:[EMAIL PROTECTED]] Sent: Thursday, September 28, 2000 5:44 AM To: [EMAIL PROTECTED] Subject: Re: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?) "Hemingway, David J" wrote: God I hate to allow the film recorder demons out of the bag but here goes. The actual resolving power of a HR6000 is probably along the lines of 1000 lines and with a totally white background probably less. Addressable resolution means you can hit the exact area on the CRT but because of design limitations that are directly related to money you are also illuminated a whole bunch of other pixels in the area. You absolutely need some pixel overlap to get a smooth image but the lower price units have much more pixel overlap than more expensive units. David David, You know that you are now going to have to have your memory totally erased, having revealed major trade secrets here. For a long time, I have wondered about film recorder specs, and why I couldn't see any reason (at least on the spec sheets) to justify paying 4-10 times more for one unit than another. You do realize in clarifying this matter, you now have triggered massive paranoia on my part about what to make of the specs film scanner manufacturers so comfortably use. And you also bring the issue of what trade selected specs really mean to the potential purchaser. This really explains the need for independent testing methods that places one manufacturer's model against another. Art The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest. The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
RE: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
Rob, In my first life here at Polaroid I am the film recorder expert. My gut says a film recorder might have some problems. 1- all film recorder specs are in addressable resolution not resolvable resolution. Polaroid makes film recorders that sell from $4000 - $1900, all of them image 4096 pixels but there is a significant difference in sharpness, particularly edge sharpness, as you go up the line. The other thing film recorders are not particularly good at doing black on white particularly when the white is the majority of the image. The edges soften. Thanks David I think David is right - I've been using a Polaroid HR6000 (the $4000 model) for a couple of years now. It works perfectly well for PowerPoint-type slides on coloured backgrounds, but I've always advised faculty and students to avoid black text on a white background. The text is never really black and small details fuzz out. In a way, David, I'm glad to hear you say that, because I've often wondered if my machine was out of adjustment. I figured it wasn't because it works fine otherwise, but now I know. By the way, I presume you meant "film recorders that sell for $4,000 - $19,000". Regards, Roger Smith The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
Re: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
Rob, Edmunds did make a USAF target exposed on emulsion. The $100 one (I think) is on glass chrome plate. In the eighties I built a series of autocollimators as a part of a research project and may have a spare one of these laying around somewhere but it probably is cut sown to a 1" diameter circle. If I can find it, maybe a contact exposure can be made on film. I believe there is an easier way to do a comparative resolution test. It won't give you any numbers but it will provide an objective comparison between the two scanners, each set to their max. optical resolution. If you can get a sharp black/white edge on film, take a look at the scans of this edge on each scanner. If, for example, the edge is diffused over a span of four pixels (from both the 2700 dpi and 4000 dpi scanners), then the 4000 dpi scanner has a higher resolution because there are simply more bits of information. If the 2700 dpi scan is showing four pixels across the edge and the 4000 dpi scan is six, then the resolution would be similar. Ideally there should be X Y edges. There are bullet holes in this type of test but I think it would be a quick way to get some idea as to the comparison of resolving capability. Meanwhile I will look for the glass target. Jim Sims Rob Geraghty wrote: Shough, Dean [EMAIL PROTECTED] wrote: I would be very leery of obtaining useful or repeatable results from a recorder. Why? It's 4096 lines, which is more than the scanner I want to test. It's an electronic device so it ought to be able to print the same image on the same film in a much more repeatable way than photographing a target, and it removes the distortions caused by a camera's lens system. What makes you think that it would be any better than the scanner you are trying to measure. See above - it's 4096 lines whereas my Nikon LS30 is 2700 dpi. The USAF target is available as chrome on glass from Edmund Industrial Optics ( http://www.edmundoptics.com ) for $100. Max resolution is 228 lines/mm. If you could find their OEM supplier, price might be around $50. Which translates to AUD$200+ including PP. I can't justify that sort of expense on something which I'm doing for interest's sake. I could buy ten rolls of Provia 100F for that price, which would be a whole lot more useful to me. Thanks for the pointer though. If I win lotto I'll buy one. :) I can use the film recorder for free (plus the cost of the film). The point of the exercise (again) wasn't so much getting a scientific measure of the scanner's resolution (although it may be possible), it was to get a clean image of a target to scan rather than having to use the somewhat complicated protocol I posted for use with a camera. What films I could use will be restricted by what films the recorder supports. Anyhow I'll try it - I've been wanting to try writing film scans back to film anyway. Rob The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
Re: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
One thing to remember is that the resolution charts were designed to be set up at a finite distance. The SMPTE target is 26X the lens focal length and 25X (I believe) for the 1952 USAF target. At his distance the resolution can be read directly off the image. The distance is based on the finite conjugates used in I agree, and those are the target to film distances. Peter The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
RE: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
Roger wrote: I think David is right - I've been using a Polaroid HR6000 (the $4000 model) for a couple of years now. It works perfectly well for PowerPoint-type slides on coloured backgrounds, but I've always advised faculty and students to avoid black text on a white background. The text is never really black and small details fuzz out. Does anyone have the means to edit the USAF target PDF to change the background colour? Maybe make it blue and the lines white instead? Rob Rob Geraghty [EMAIL PROTECTED] http://wordweb.com The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
RE: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
God I hate to allow the film recorder demons out of the bag but here goes. The actual resolving power of a HR6000 is probably along the lines of 1000 lines and with a totally white background probably less. Addressable resolution means you can hit the exact area on the CRT but because of design limitations that are directly related to money you are also illuminated a whole bunch of other pixels in the area. You absolutely need some pixel overlap to get a smooth image but the lower price units have much more pixel overlap than more expensive units. David -Original Message- From: Rob Geraghty [mailto:[EMAIL PROTECTED]] Sent: Tuesday, September 26, 2000 7:52 AM To: [EMAIL PROTECTED] Subject: Re: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?) Jim wrote: [snip] the design of general purpose lenses. Even so, the scanner resolution can be calculated but I do not have the equations in front of me. I will try to find them. That would be great! Thanks! The main thing is to get a good sharp image on the film. From what David is saying, this may not be possible. A different test image will probably be necessary where the dominant "colour" is not white. I have a really good one I downloaded off the net but I think I can't reproduce it for distribution. I also may not be able to get the PC with the recorder to *load* such a huge file. The PC doesn't have a lot of RAM. All this *may* be irrelevent depending on the result from the recorder. In any case from my perspective what I was interested in was a consistent image which was made without lenses that can then be scanned to get an idea of film grain on different film types. Rob Rob Geraghty [EMAIL PROTECTED] http://wordweb.com The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest. The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
Re: Measuring resolution (was Re: Real resolution of a 4000 dpiscanner?)
Jim wrote: [snip] the design of general purpose lenses. Even so, the scanner resolution can be calculated but I do not have the equations in front of me. I will try to find them. That would be great! Thanks! The main thing is to get a good sharp image on the film. From what David is saying, this may not be possible. A different test image will probably be necessary where the dominant "colour" is not white. I have a really good one I downloaded off the net but I think I can't reproduce it for distribution. I also may not be able to get the PC with the recorder to *load* such a huge file. The PC doesn't have a lot of RAM. All this *may* be irrelevent depending on the result from the recorder. In any case from my perspective what I was interested in was a consistent image which was made without lenses that can then be scanned to get an idea of film grain on different film types. Rob Rob Geraghty [EMAIL PROTECTED] http://wordweb.com The filmscanners mailing list is hosted by http://www.halftone.co.uk To resign, mailto:[EMAIL PROTECTED] with UNSUBSCRIBE FILMSCANNERS in the title, or UNSUBSCRIBE FILMSCANNERS_DIGEST if you are reading the Digest.
