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#11
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Film Q.
David Nebenzahl wrote:
On 3/3/2009 12:31 PM Michael Benveniste spake thus: "Annika1980" wrote in message ... Remind me again ..... I just got a few rolls of Kodak Ektar 100. Everything I read says to rate it at either 50 or 64 instead of 100. If Johnny tells you to jump off a cliff ... (I'd rate it at 80 myself). Doesn't the difference between ISO 50 and 64 fall well under the tolerance for inaccuracy in most camera's light meters? In other words, won't make any visible difference. For me, ISO 50 and 64 can be treated as identical for all practical purposes. Even 50 and 80 are pretty dang close (1 stop vs. ~2/3 stop difference). Calibration may be out a bit with any given meter, but the repeatability should be pretty accurate. You should always test a film against your meter to find the best setting for your camera, after which the meter should be as accurate as you want. Professional meters like the Sekonic range for example are guaranteed accurate to within 1/10 of a stop, provided it is used intelligently. Colin D. |
#12
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Film Q.
On 3/4/2009 9:17 PM Peter Irwin spake thus:
Michael Benveniste wrote: On Thu, 5 Mar 2009 01:51:17 +0000 (UTC), Peter Irwin wrote: It is going to take more than the listed results from filmscan.ru to convince me that Kodak is rating their films inaccurately. Then pick up some old film shootouts from the various photo magazines, or go shoot some and ask your lab to measure the densities for you, or talk to people who rate their own film, and see if they use the same EI for all films with the same ISO rating. That's another question entirely. What is optimum to use is a different question from whether or not films are rated accurately. Film manufacturers always tell users to find their own optimum EI by testing, and say the ISO rating is only a starting point. This whole exchange you two are having is very enlightening (what parts of it aren't whizzing over my head). Please don't stop. -- Made From Pears: Pretty good chance that the product is at least mostly pears. Made With Pears: Pretty good chance that pears will be detectable in the product. Contains Pears: One pear seed per multiple tons of product. (with apologies to Dorothy L. Sayers) |
#13
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Film Q.
"Peter Irwin" wrote"
That's another question entirely. What is optimum to use is a different question from whether or not films are rated accurately. Film manufacturers always tell users to find their own optimum EI by testing, and say the ISO rating is only a starting point. If ISO is as accurate as you claim, such tests would result in the same EI for all films of a given ISO. They don't. Cine negative film speeds are covered by a different ISO standard than still negative films. Both will be rated to the nearest standard value to the measured speed. And that standard is? For the 250D movie film, Kodak states: "Use these indexes with incident- or reflected-light exposure meters and cameras marked for ISO or ASA speeds or exposure indexes." So from this statement, we see that ISO for movie photography should equate to ASA, which covered both markets. You claim that ASA and ISO for still camera film are also equivalent. If A=B and B=C, then why doesn't A=C? One uses the same exposure meters and settings for movie or still photography. I haven't shot 250D in a film camera, but I have shot Fuji Eterna 500T. The "grain" was about the same as Fuji NPZ, but I found it was true to its 500 speed badging. I bet that difference is to gain more contrast on the Portra by putting more of the exposure off the toe. When I'm using a film like 160S, I'm not interested in gaining contrast. Within 1/6th of a stop for _all_ existing films? Not very likely. From _Photographic_Sensitometry_ by Todd and Zakia (1974 ed) p.162 You're confusing precision and accuracy. ASA defined one method of measurement, specifying a precision of 1/3rd of a stop. Yet under those methods, original Tri-X was marketed at either two or three different speeds. ISO also specifies a precision of 1/3rd of a stop, but requires different measurements. Both specs had and have plenty of slop. Neither B&H nor Adorama make film. I haven't seen anything actually from Kodak which claims 3200 as the ISO speed. Here's one such flyer: http://wwwca.kodak.com/HK/zh/consume...ireworks.shtml I haven't used Ektar 100 yet. I don't doubt that you saw what you describe. I do doubt that it had anything to do with overexposure. So inaccurate recording of color doesn't qualify as overexposure by your definition? Then we should agree to disagree. Then please feel free to provide your own data or test shots rather than stating generalities. My three generalities were useful, and were things I did not know when staring out. The site I referred to provided data from actual tests, which you claim are not meaningful. So please provide meaningful data to support your generalities. -- Michael Benveniste -- (Clarification required) Nid wif yn y swyddfa ar hyn o bryd. Anfonwch ar unrhyw waith i'w gyfieithu. |
#14
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Film Q.
Peter Irwin wrote:
Michael Benveniste wrote: You're right on Kodak's spec sheets, although they've been less precise in consumer ads. In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as ISO 3200 films. Adorama does the same. Neither B&H nor Adorama make film. I haven't seen anything actually from Kodak which claims 3200 as the ISO speed. Just grabbed a box out of the fridge - here is what it says: Front: Kodak Professional T-MAX P3200 FILM P3200TMAX Black & White Negative Film Film Negatif Noir Et Blanc Schwarzweiss Negativ Film Pelicula Negativa En Blanco Y Negro End: Kodak Professional T-MAX P3200 FILM P3200 TMAX Black & White Negative Film Film Negatif Noir Et Blanc 135-36 P3200TMZ The other end is the same except in foreign language. Top Kodak Olympic Sponsor Symbol. T-Max P3200 Film P3200TMAX Bottom 36 EXP 24x36mm CAT 151 6798 Made In USA Finished in Mexico for EASTMAN KODAK COMPANY Rochester NY 14650 www.kodak.com/go/professional Back: Limitation of Liability: blah blah blah Expiry Date... EXPIRY 05/2007... FLAMIN HELL!!! I bought a pack just before my youngest kid was born to do some nice grainy baby photos. He's now 2-1/2, and the pack is untouched. Time to get some batteries for the film camera and start snapping I think. I hope my developer and fixer are still good. In answer to the original discussion, there is nothing on the box that actuall says "ISO 3200", although it is certainly inferred by the repeated use of "P3200". The DX coding on the film is 3200, if that means anything. I've always shot it at 3200, because I like the look that it gives at that speed. I don't know and don't care what the true ISO rating of the film is - 3200 gives results that I like. If I didn't want the look that P3200 gives at 3200, I'd shoot something else. |
#15
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Film Q.
Peter Irwin wrote:
Michael Benveniste wrote: In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as ISO 3200 films. Adorama does the same. Neither B&H nor Adorama make film. I haven't seen anything actually from Kodak which claims 3200 as the ISO speed. As responsible vendors B&H and Adorama do post the specifications of the products they sell, which was Michael's point, I'm sure. As to 3200 ISO, yes indeed, Kodak make that too. |
#16
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Film Q.
Michael Benveniste wrote:
"Peter Irwin" wrote" That's another question entirely. What is optimum to use is a different question from whether or not films are rated accurately. Film manufacturers always tell users to find their own optimum EI by testing, and say the ISO rating is only a starting point. If ISO is as accurate as you claim, such tests would result in the same EI for all films of a given ISO. They don't. There seem to be several issues packed together here. - Are ISO ratings the nearest standard value to what the film actually was tested at? (Yes) - Are the ISO ratings of negative films a valid indicator of the useful response of the film in the toe, so that two films of the same rating will have about equal shadow detail for the same exposure? (I think yes) - Do the two points above mean that you can determine the exposure which will get the results you want entirely from the ISO speed rating? (No) Cine negative film speeds are covered by a different ISO standard than still negative films. Both will be rated to the nearest standard value to the measured speed. And that standard is? I was wrong about this. There is no ISO speed for cine negative films. There seems not to be a standard on purpose. (The standard for reversal films covers both still and cine films, but the standards for negative films specify still films only.) Kodak's cine negative films all carry an EI rating in their datasheets. I haven't been able to find out what Kodak's rules are for rating cine negatives, but they seem generally to be 2/3 of a stop under what the ISO speed rating would be if they were still films. Thus Plus-X cine negative is rated at EI 80, but is the same speed (though not exactly the same film) as Plus-x 125 for 35mm still cameras. The EI 250 cine films seem to be about the speed of ISO 400 still negative films. For the 250D movie film, Kodak states: "Use these indexes with incident- or reflected-light exposure meters and cameras marked for ISO or ASA speeds or exposure indexes." So from this statement, we see that ISO for movie photography should equate to ASA, which covered both markets. You claim that ASA and ISO for still camera film are also equivalent. If A=B and B=C, then why doesn't A=C? The meters are the same. Exposing cine negatives at the rating system used for still negative camera films would give you degraded blacks. You have probably noticed that reversal films of a given speed rating tend to be much better at picking up shadow detail. Kodachrome 64 will give you a bit better shadow detail at box speed than ISO 100 colour negative film shot at EI64. If you are going to make a transparency for projection from negative film shot at the ISO speed rating, you will probably find the film underexposed for that purpose. ISO speed for negative films is supposed to be the minimum exposure required to produce a reflection print rated as excellent. The same exposure is probably inadequate for making a transparency for projection. One uses the same exposure meters and settings for movie or still photography. I haven't shot 250D in a film camera, but I have shot Fuji Eterna 500T. The "grain" was about the same as Fuji NPZ, but I found it was true to its 500 speed badging. Interesting, how did you do the subjective comparison? If my belief is correct about cine films being rated conservatively then Eterna 500T should be more than 1 stop faster than NPZ+80A conversion filter. If it is only equal to ISO 500 then it should be less than one stop faster than ISO 800 speed negative plus an 80A filter. Note that if you are shooting tungsten balanced negative film or daylight film plus an 80A then you need a little extra exposure with 2800K household incandescents to get enough blue on the film. Neither B&H nor Adorama make film. I haven't seen anything actually from Kodak which claims 3200 as the ISO speed. Here's one such flyer: http://wwwca.kodak.com/HK/zh/consume...ireworks.shtml It does seem that Kodak got it wrong on a Chinese language webpage. Thanks for pointing that out. It would seem to indicate that it is something that Kodak promotional material very rarely gets wrong. Peter. -- |
#17
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Film Q.
"Peter Irwin" wrote:
There seem to be several issues packed together here. - Are ISO ratings the nearest standard value to what the film actually was tested at? (Yes) I'm not sure what you're saying here. The ISO rating is a summary statistic of a test, but that doesn't speak to the accuracy of that test. - Are the ISO ratings of negative films a valid indicator of the useful response of the film in the toe, so that two films of the same rating will have about equal shadow detail for the same exposure? (I think yes) The ISO standard says nothing about the shape of the curve, and the ASA measurement specifically ignored the toe when rating a film. But to test your claim, compare the curves for Fuji Reala 100 and Fuji Superia 100. The manufacturer, exposure and methods and resulting ISO ratings are the same; the toes are markedly different. http://www.fujifilm.com/products/con..._datasheet.pdf http://www.fujifilm.com/products/con..._datasheet.pdf Thus Plus-X cine negative is rated at EI 80, but is the same speed (though not exactly the same film) as Plus-x 125 for 35mm still cameras. The EI 250 cine films seem to be about the speed of ISO 400 still negative films. Ah, Plus-X. Initially marketed as an ASA 80 film, it then changed to an ASA 160 film, and finally settled in at 125. But Kodak 5231/ 7231 and PXP are the same stuff -- only the aerial stuff is different. If you're willing to load it yourself in a changing bag or darkroom, you can often buy "short ends" of Kodak 5231 for under $0.20 a foot. Then shoot and process normally. Once again we find that in other markets, Kodak does refer to 5231/7231 as an ISO 80 film: http://motion.kodak.com/DE/de/motion...ilms/index.htm But here the difference in recommended shooting speeds is easily explained. Kodak recommends EI 80 for D-96 developer. D-96 has less metol and hydroquinone than D-76, so it isn't surprising that the output is different. There's no such discrepency between ECN-II and C-41 chemistry. The Aerecon version has extended red sensitivity and gets yet a different rating (200) on yet a different ISO scale (ISO-A) for a different developer. I've never tried it, and with a minimum order of 500' in 70mm I'm not likely to. But I have tried Agfa Aviphot N400, which is a C-41 film. That film was rated at 400 via both the ISO-A and ISO methods, and did well in my Pentax 645 at rated speed. I certainly wouldn't rate it any lower. The meters are the same. Exposing cine negatives at the rating system used for still negative camera films would give you degraded blacks. By "degraded blacks," do you mean loss of shadow detail? Underexposing would make the blacks even blacker. In the past, several labs offered a service to create slides as well as negatives from C-41 film. Dale labs still does. While such slides suffer from the usual "2nd generation" issues, loss of shadow detail was not a significant problem. Nor does the difference in workflow explain the difference in recommendations. When movies shifted from using optical intermediate films to a digital intermediate process, the EI of camera films didn't change at all. One uses the same exposure meters and settings for movie or still photography. I haven't shot 250D in a film camera, but I have shot Fuji Eterna 500T. The "grain" was about the same as Fuji NPZ, but I found it was true to its 500 speed badging. Interesting, how did you do the subjective comparison? I compared grain by scanning both films with a Canon FS4000US. I determined exposure by bracketing and verifying incident light with a Minolta V light meter. The grain comparison was against NPZ shot in daylight -- I gave up on trying to use 80A filters long ago. I've shot the 500T under 3200K photofloods, stage lighting, and room lighting. It's a bit warm under room lighting, as expected. I've still got about 100' left of the stuff in the freezer, so I can spool up some more if you want to give it a try. -- Michael Benveniste -- (Clarification required) Nid wif yn y swyddfa ar hyn o bryd. Anfonwch ar unrhyw waith i'w gyfieithu. |
#19
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Film Q.
Harold Gough wrote:
In the pre-digital days the rule of thumb was to slightly under-expose reversal film and to slightly over-expose print film. To me, that would mean 1/3 to 1/2 stop and no more. Slightly under-exp reversal means 1/3 to 1/2 stop. Slightly over-exp negative means 1/2 to 1 stop. Don't top post. Do trim attribution to what's relevant. -- -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. -- usenet posts from gmail.com and googlemail.com are filtered out. |
#20
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Film Q.
On Tue, 10 Mar 2009 09:47:29 -0700 (PDT), Annika1980
wrote: And therein lies the main difference between film and digital! The digital shooters want high Megapixels, low noise, and anything else that will give them the best shot. The film shooters worry about the shape of the toes on the film curves. Digital shooters get to worry instead about birefringence in micro lenses, sensor bloom, light-angle induced falloff, banding and a whole set of different issues. They also have to worry about paying for that latest and greatest camera every 2 years or so. Been there, still doing that. The funny thing is that I _don't_ worry about curves, toes, and the rest except in one rare circumstance. Once or twice a year, I'll shoot slow black-and-white film outdoors in medium or large format and do the quasi-zone system thing. Otherwise, I just grab the film I want, set the EI to my preferred value, load up and go. Yeah, once in a great while, I have to *gasp* go out and shoot a test roll to rate a new film, or at least one new to me. Such a burden! In most typical shooting situations, you can shoot at the manufacturer's suggested speed and get reasonably good results. You make decide you like the "look" of a different EI, but that's purely a subjective call. Don't let anyone else make it for you, whether you crank that difference in via EI or exposure compensation. But when the lighting gets both interesting and challenging, whether you are shooting digital or analog, you're going to have to make some tough choices. If you have the luxury of a static subject, a sturdy support, and sufficient shooting time, you can use HDR techniques. If you're not that lucky, then there isn't a generality in the world that can help you. My point in this thread is that the manufacturer's speed ratings on film, even when marked as an ISO rating, is a compromise between the engineers and the marketeers for a particular market. It doesn't tell you anything about exposure latitude, contrast, color shifts or any of the other non-linear response characteristics you see when you push the envelope. -- Mike Benveniste -- (Clarification Required) Amo conventum instituti. -- Artifex Hannibal |
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