hagerman@nermal.DEC (06/21/85)
x Someone was wondering whether Kodachrome was really all that much more fine-grained than the other available color films. I went down to the local camera store and looked in a Kodak book called the Professional Dataguide (I'm too cheap to buy one), which lists film data for all of Kodaks color and black and white films. They break resolution (lines per milimeter) and graininess into groups and give the results by group, such as high, very high, etc. Without memorizing all the data, in the group with high resolution and extremely fine grain were Kodachrome 25 and 64, Kodacolor II (ASA 100: it must have been an edition from before the new color films), and Plus-X. Not included were any Ektachrome films. This kind of goes along with what you'd expect from technological and marketplace considerations: 1. Reversal films such as Ektachrome are inherently finer grained than the equivalent negative film, because in the negative film the image is made up of the larger grains of silver which pick up light better. In a reversal film, the image is made up of what's left after the large grains are removed in the reversal process, i.e. the smaller grains. 2. But market conditions are that most pictures are made with color negative film, therefore they put more effort into the negative films. An example is the new range of high performance print films. 3. Kodachrome has an advantage over Ektachrome because the emulsion is thinner. This is because the dye is added in during processing in the Kodachrome method. 4. Black and white film has the advantage of a very thin emulsion and no color filtering needed, so is finer grained for a given film speed. In regards to Mike Rosenlof's ranking of sharpness problems, anybody who has ever seen an 8x10 contact print knows that graininess is a big factor. One reason auto-focus cameras are so successful is because for the first time, the average snap-shooter now gets back prints that are in focus. Camera shake is a problem if you can get things focussed right. But back to reality, aren't the full-page spreads in Time, Sports Illustrated, etc, good enough? They're mostly taken with 35mm film, hand-held... Doug Hagerman
howard@sfmag.UUCP (H.M.Moskovitz) (06/24/85)
> Someone was wondering whether Kodachrome was really all that much > more fine-grained than the other available color films. I went > down to the local camera store and looked in a Kodak book called > the Professional Dataguide (I'm too cheap to buy one), which > lists film data for all of Kodaks color and black and white films. > > Not included were any Ektachrome films. > I have had an opportunity to work professionally in my spare time and have met and talked with some of New York's best professionals from the advertising world. The common factor that I've heard is that if you insist on shooting 35mm for magazines, they will only accept Kodachrome 25 or 64 and prefer the newer Professional emulsions (which have guaranteed optimal color balance). Ektachrome is out of the question for 35mm because it is relatively grainy and COOL. In general there is no 35mm film that can be reproduced and enlarged and still retain the sharpness and color SNAP that magazines require. If you want to use any other film (and mags generally only want slides, no negs), you are going to have to use a larger format and probably Ektachrome. Basically the rule of thumb that I've seen is: Fashion Kodachrome 35mm General Ads " " Portaits Medium format (2.25x2.25, 6x7, etc...) Vericolor prints Glamour Medium/Ektachrome or 35mm/Kodachrome Products Large format (4"x5", 8x10) and Ektachrome Weddings Medium and Vericolor prints I feel that the professional standards speak for themselves. Howard Moskovitz AT&T Info. Systems (& Phantasm Studios) attunix!howard
jer@peora.UUCP (J. Eric Roskos) (06/25/85)
Um, while I will agree with a lot of what you said [I posted the original article you are commenting on], a few of the statements aren't entirely accurate (though close):* > 1. Reversal films such as Ektachrome are inherently finer grained > than the equivalent negative film, because in the negative film > the image is made up of the larger grains of silver which pick > up light better. In a reversal film, the image is made up of what's > left after the large grains are removed in the reversal process, i.e. > the smaller grains. Kodachrome film does not use silver, I don't think. However, I believe other reversal films do. This is one reason why Kodachrome has better grain/sharpness. But, negative film does not leave behind the silver grains either. The silver grains produce "dye clouds" during development; but during the last step of the development process (the "Blix" step in 2- step processes), the silver grains are chelated out with EDTA, leaving only the dye behind. The main reason why negative film has a POTENTIAL for greater graininess is that negative-working paper has higher contrast, and consequently can make the graininess be exaggerated. The reason it has higher contrast is that print film has lower contrast than reversal film. The reason for THAT is that print film has a greater "exposure latitude" -- a wider range of luminance produces different densities in the film than in reversal film, because reversal film has the constraint that the densities produced in the film are those used to actually view the image. Along with the wider range of exposure latitudes comes a smaller relative difference in densities between two luminances (in the linear portion of the characteristic curve), since there is only a certain density range that is usable, for practical purposes. This is a design decision in the manufacture of negative film. Just as B&W negative film doesn't give the same densities in the negative (e.g., there is a visibly-grey base+fog density, Dmin) that appear in the print, so you can adjust the appearance of your print by varying the exposure of the paper, so also color negatives do likewise. > 2. But market conditions are that most pictures are made with > color negative film, therefore they put more effort into the negative > films. An example is the new range of high performance print films. Actually, it's not "market conditions". I wrote a letter to Kodak about this a long time ago, asking "given the fact that you make negative film specifically for making prints, why is it that people claim the quality of reversal film (for prints) is so much better? Why don't you optimize the negative film for making prints, and the reversal film for making slides?" Kodak wrote back (just recently) and said, in essence, "we do. It's just that some people prefer high-contrast prints and saturated colors. We make the negative film to suit what are considered normal print properties by professionals in the industry. It's just a matter of what the individual prefers." > 3. Kodachrome has an advantage over Ektachrome because the emulsion > is thinner. This is because the dye is added in during processing in > the Kodachrome method. This is true. Despite my dogmatic Realism-based opposition to people's obsession with Kodachrome, actually it is very good film, for slides. However, print film has another interesting advantage that is not related to emulsion thickness -- most of the print films have 2 emulsions in each color, one faster (but coarser) than the other. This is why many people overexpose VPS film (which is rated at ASA 160) by exposing it at ASA 100; it exposes the finer emulsion more, and gives a finer grain. You can do this with print film because of the above exposure latitude. > But back to reality, aren't the full-page spreads in Time, Sports > Illustrated, etc, good enough? They're mostly taken with 35mm film, hand- > held... Well, except that they are usually printed through a halftone-screen, which introduces a severe "grain" of its own! ... actually Audobon Magazine experimented with printing without halftone screening about 8 years ago. This produced very beautiful prints, although many of them had flaws where the dye didn't go on uniformly. But I haven't seen many magazines that do that (and I really don't know how Audobon did it, either). --------- *Of course, venerable and more experienced photographers in here may well find errors in my statements, too! -- Shyy-Anzr: J. Eric Roskos UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!peora!jer US Mail: MS 795; Perkin-Elmer SDC; 2486 Sand Lake Road, Orlando, FL 32809-7642 "Erny vfgf qba'g hfr Xbqnpuebzr."
hyder@tekecs.UUCP (Paul Hyder) (06/27/85)
For the record the Kodachrome will always be sharper.
The primary difference between Kodachrome and Ektachrome is the
method of dye production. The dye is present in Ektachrome in
colorless form and is converted to colored form in processing.
The dye molecules are large and sharpness suffers. Speed increases
also can degrade the sharpness by requiring larger silver crystals
but the new technology is reducing this factor reapidly. The other
problem is that the extra dye is not removed in processing of
Ektachrome, it just stays there in colorless form. As Ektachrome
ages these residual couplers can become colored and cause color
shifts in the images, N.B. this is in addition to any "fade".
Kodachrome is a multi layer black and white emulsion with coupling
sites but no dye molecules. The quality control is easier and
the sharpness improves. Processing involves linking dyes
in the chemistry to the correct sites (Yep, three color developers).
This results in a sharper image without residual colorless
dyes waiting to change. You do have to put up with the speed being
slow and the fact that you can't process it yourself. (Well, you
can't process it yourself easily. The chemical control lab costs
would drive most people under, the chemistry doesn't come in easy
to use boxes.)
I use Kodachrome unless speed is a factor.
Paul Hyder { ...tektronix!tekecs!hyder }
[Guess 5 years as a Tech Rep in the Photo Industry
wasn't a waste after all.]cjn@calmasd.UUCP (Cheryl Nemeth) (06/28/85)
How much difference does the ISO rating make in the grain? I realize that very fast (1000+) are going to be very grainy, but is there much difference between 100, 200, and 400?