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Thread: Resolution Comparison Between Films?

  1. #11

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    Re: Resolution Comparison Between Films?

    Could you speak a bit more to this point, Drew?


    Quote Originally Posted by Drew Wiley View Post
    Taming its cyan idiosyncrasy is a bit more involved, but doable with correct filtration at the time of the shot.

  2. #12

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    Re: Resolution Comparison Between Films?

    Quote Originally Posted by ClickCL View Post
    Hi, I'm curious if anyone has a resource or personal opinion on the resolution differences between films?
    See this document http://www.tmax100.com/photo/pdf/film.pdf

    Click image for larger version. 

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    You see that:

    1) Velvia is a sharper color film than Portra, and the sharpest with VR100 exception

    2) The sharpest color film mentioned is defunct VR100, a consumer color film manufactured since 1982 at 100lp/mm, while Portra sported 73lp/mm.


    Well, first film sharpness is a very complex matter as MTF depends on subject's "microcontrast" (unlike with optics). This is becasue film has halide crystals of different sizes that work or not in different situations, so depending on the test constrast ratings may change, not the same with 1.6:1 contrast than with 1000:1

    In the digital minilab era industry had a severe transformation: all color film was to be scanned instead optically enlarged, so today all color negative film datasheets say: "Optimized for scanning"

    One of the Optimizations was making the clouds of different color layers overlap better (larger clouds? less completing coupler in the color developer?) to avoid color noise for the scanning discretization, possibly this had an impact in sharpness, being lower. It is difficult to understand that 40 years ancient consumer VR100 was sharper than today's Pro color film !!!

    Instead you won't find "Optimized for scanning" in Velvia/Provia datasheets, slides are optimized for projection, not for scanning.

    Extreme sharpness capability of film is little seen in real photography, textures do not have 1000:1 microcontrast projected on film allowing those 180 lp/mm that TMX shows in a lab test, instead you may have 3:1 "microcontrast" in the many textures.

    1000:1 contrast situation, when TMX allows 180lp/mm is 10 stops!!! contrast projected in 180 line pairs for each mm !!! this is a situation you won't find in real photography.

    ... but anyway it explains why a silhouette shape can be very sharp, as the contrast to the background can be very high.

    _____________________________


    All that was theory that is not much relevant as with LF you have insane lots of Image Quality. In practice... what you should care is illumination quality to get a sound image, and learning the film sensitometric and spectral behaviour.

  3. #13
    Drew Wiley
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    Re: Resolution Comparison Between Films?

    That's interesting, Pere, but pre-Ektar and pre E100 chrome too. Lot's of other info is also somewhat out of date. With Kodak sheet film, "optimized for scanning" seems to have more to do with a slightly textured coating than anything pertaining to the dye clouds, other than the usual progressive improvements.

  4. #14

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    Re: Resolution Comparison Between Films?

    Quote Originally Posted by Drew Wiley View Post
    That's interesting, Pere, but pre-Ektar and pre E100 chrome too. Lot's of other info is also somewhat out of date. With Kodak sheet film, "optimized for scanning" seems to have more to do with a slightly textured coating than anything pertaining to the dye clouds, other than the usual progressive improvements.
    Yes - it was the supercoating of some films that had to be tweaked for scan compatibility - Fuji as well as Kodak. The rest of his claims about MTF (and muddling it up with ISO resolution testing) and dye cloud size are disconnected from the realities of imaging science.

  5. #15
    Drew Wiley
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    Re: Resolution Comparison Between Films?

    6X6. Let me just briefly reply to your question from a practical rather than sensotometric standpoint, lest the thread fall into an unnecessarily complicated tailspin. Ektar is not artificially warmed like ordinary color neg films oriented to skintone reproduction. With its higher contrast and greater overall saturation, it is capable of handling a variety of hues more accurately than previous CN films, but has an Achilles heel of potential cyan crossover at both ends of its native latitude. You need to carefully meter it, shoot it at box speed of 100, and realize that you get only about a stop extra, either over or under, of what you'd ordinarily get with a chrome film, before encountering problems. It's important to correct for color temp issues at the time of the shot because post-correction will either be difficult or impossible once the dye curves have begun crossing over. It's not just a matter of overall balance, but of how the three respective dye spikes maintain their individual integrity before mud starts getting mixed, and can't be unmixed. So I'd recommend carrying a light pink skylight filter for minor color balance correction, something like an 81A or KR1.5 for bluish overcast conditions, and something stronger like an 81C or KR3 for deep blue shade under intense open blue skies. The tricker question is how to handle mixed lighting with warm overall lighting, but deep blue shadows in the same scene. It is possible to pre-flash the film with a diffused amber warming filter and gray disc for around two stops below middle gray; but this requires a fair amount of testing to get right. There is also a new Tiffen 812 filter available coated which has a similar effect to combining an 81B warming filter plus 1B skylight. This is designed to correct overly blue shadows (which have an annoying cyan cast with Ektar), and if too warm, can be more realistically corrected during the printing step than no filtration at all. Hope this helps.

  6. #16

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    Re: Resolution Comparison Between Films?

    Thanks Drew for the exhaustive, informative and practical guidelines.

    Apropos Technicolor, the process you describe sounds similar to Kodachrome, which was one of my favorite films (along with Velvia, they complimented each other nicely depending on what/where I was shooting) before "mamma took my Kodachrome away" :-(

  7. #17

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    Re: Resolution Comparison Between Films?

    Quote Originally Posted by interneg View Post
    Yes - it was the supercoating of some films that had to be tweaked for scan compatibility - Fuji as well as Kodak. The rest of his claims about MTF (and muddling it up with ISO resolution testing) and dye cloud size are disconnected from the realities of imaging science.
    You are not well informed, please read for example the Ektar 100 datasheet:

    https://imaging.kodakalaris.com/site..._ektar_100.pdf


    It says: TECHNOLOGY: Micro-Structure Optimized KODAK T-GRAIN Emulsions >>>>> BENEFIT: Ideal for scanning



    The optimization for scanning relies in the micro-structure, so in the final dye clouds.


    Look, perhaps you are aware that a high production Frontier has an area sensor with a Bayer mosaic (not a linear one like flatbeds). If dye clouds of different colors do not overlap well you boost color noise in the discretization.

    Take a decent microscope and observe strips of the pre/post digital minilab dawn at 1000X, you will learn what happened. Weren't you aware?



    Of course manufacturers never mentioned the clouds because decreasing noise has an slight drawback in the sharpness, a bit like with OLPF in DSLRs.

    Kodak VR100 (since 1982) was incorporating Tabular T-Grain yet, probably T-Grain was developed to improve color films that were the vast majority of the business, T-Max BW films were a just sequel.

    Since 1996 all color films were re-engineered or replaced to deliver an optimal micro-structure for scanning in the digital minilabs, the big business. The supercoating modification is only some icing on the cake.
    Last edited by Pere Casals; 17-May-2020 at 05:40.

  8. #18
    Drew Wiley
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    Re: Resolution Comparison Between Films?

    Minilab "quality" was always on the awful side. Amateur consumers didn't care much about grain as long as Grandma's face didn't turn out green. That was pretty much determined by the character of dye clouds anyway. What was a huge incentive to T-grain R&D was the cost of silver during that era, in which Kodak found itself in direct competition with commodities brokers, and how to make the particles more efficient in thinner emulsions for actual black and white film use, while, at the same time, replacing multiple b&w films with fewer more versatile ones, more cost efficiently. Color film use far less silver, and T grain for color emulsions seems to be fairly recent. Otherwise, I don't scan, but do appreciate how the new supercoating helps to suppress Newton rings somewhat, though I still use AN glass too.

  9. #19

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    Re: Resolution Comparison Between Films?

    Drew - T-grain's biggest advantages are that it allows drastically better sensitivity for a given amount of silver and with better 'coverage' (Bob Shanebrook, 2nd Edn, pg.18) - and with finer more densely packed flatter grains, coverage gets better - especially in complex multi-layer emulsions - which also improves scanning and darkroom performance. It's a misnomer propagated by the inept that scanning and darkroom printing of films have significantly different technical requirements overall. There have been attempts at making scan-only materials and they all failed to have any longevity. The major change with regards to minilabs which Pere's ahistoriscist claims get badly wrong, was the way that the entire Portra family was designed to print on the same 'channel'/ baseline colour correction (Shanebrook, 2nd edn, pp.45-48).

    The Bunker Hunt affair probably provided a convenient distraction from where a bigger need for higher resolution, better sensitivity films had come from - the Key Hole and Corona reconnaissance satellites. And if the first T-grain containing consumer market films launched in 1982, the product R&D (as opposed to the fundamental principles) had probably started at least 5 years earlier - likely straight after Kodacolor 400 had launched. The same satellite programmes seem to have been important in driving significant technological steps in the use of ESTAR base etc.

    According to Shanebrook, TMax 100 had to have an extra thick gelatin supercoat added to slow down the development speed to something more acceptably 'normal' compared to other films in the market - with SO variants for solar photography without the overcoating & protective 'gelatin rails' (Shanebrook, 2nd edn, pg.24).

  10. #20
    Drew Wiley
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    Re: Resolution Comparison Between Films?

    I don't know how far back T-grain research went, probably quite a ways. The Hunt brothers nearly obtained a complete monopoly on the silver trade in the late 70's; but several years before that I can recall the panic of photographers as good black and white papers were getting unaffordable, and it was inevitable that certain film and paper products were going to outright disappear. A substitute was particularly needed for Super-XX, which was a thick emulsion film with an exceptionally long straight line. The first version of TMax 100 appeared on the market in 1986 and I immediately started using it, and the earlier grittier version of Tmax 400 soon thereafter. I've salvage printed some of my own first 4x5 shots of both with the past few weeks. All of this was long before mini-labs and so forth digitally printed. Even the discontinuance of dye transfer supplies hadn't been announced yet, and optical Cibachrome printing was in its heyday. I don't remember if Ektar 25 adopted T-grain technology, but it had serious hue reproduction issues and never found the market niche which current Ektar 100 has.
    Estar base was necessarily used for any film requiring dimensional stability. Remember, most advanced printing skills still required mechanical registration, and still do for people like me who print exclusively darkroom-style. Acetate-based films are a horrible headache to deal with in that respect, though I had to do a lot of it. I don't know the detailed motives of how TMax films were overcoated. But one huge advantage is that it made them more robust in handling. The FP4 of that time (prior to FP4 plus) had a rather soft emulsion, and there was still interleafing paper between sheets in the box. The greater scratch resistance in handling and tray processing is still one of the premium features or advantages of TMax products. Due to their very carefully designed spectral qualities and curve flexibility, plus detail capacity, these films were introduced to replace several previous product lines, including the color separation tasks of Super-XX and Color Sep Film, the industrial and forensic applications of Tech Pan, the general usage of Tri-X, the studio usage of Plus X Pan. Longtime loyalists to certain favorite films weren't amused at having to switch to something fussier in exposure and development, so that made quite an opening for Ilford to expand their film selection. As far a aerial surveillance is concerned, I've seen a number of classified optical prints from the era with my own eyes; and I'm convinced that certain branches of the military and intelligence operations were fully twenty years ahead of anything on the public market. Equipment-wise, the public will never be able to afford the kind of photo gear they had. Some of it was made locally, and still is. Real film is still the best option for highly-detailed, intuitively assessed aerial reconnaissance. Satellites are better at telling you where to look, or for tracking specific changes in real time, but often require specialized analysts to interpret. Nothing is better than WWII style overlapping b&w stereo photos that you can view 3D with your own eyes under a stereoscope. It's awfully fatiguing to the eyes, however. I once used a lot of these for geological and archeological mapping, but the USGS had automated methods for making topo maps from precise sequential aerial photos.

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